Chapter  32:  Treatment of Degenerative Lumbar Spinal Stenosis Volume 1: Evidence Report: Evidence Report/Technology Assessment Number 32

Searches in MEDLINE^®, EMBASE^®, CINAHL^®, Current Contents^®

(presented in PubMed syntax)

• Lumbar spinal stenosis literature key words: Spinal stenosis, sciatica, backache, spinal diseases, ischialgia, compressive neuropathy, spinal claudication, neurogenic claudication, intermittent claudication, nerve root entrapment, nerve root compression, osteoarthritis, spondylosis, spondylolisthesis, cauda equina, spinal osteophytosis, stenosis (lumbar, exit zone, nerve root canal, foraminal)

• Spinal canal measurement literature key words: Spinal canal/anatomy, histology, spine, anthropometry, spinal (column, canal, diameter, measure)

Searches in PsycINFO^®

(presented in DIALOG^® syntax)

• Key words: Back pain (chronic), cauda equina (syndrome, compression), sciatica, lumbago, spondylolisthesis, spinal osteophytosis, stenosis (spinal, lumbar, foraminal, nerve root canal), intermittent neurogenic claudication

Searches were restricted to studies examining human subjects. Case reports were excluded.

Our literature searches were geared to seeking out articles on a broad range of conservative treatments. These included physical therapy, management of symptoms with drugs, rigid brace, bed rest, epidural injection of steroids and/or anesthetics, injection of calcitonin, acupuncture, trigger point treatment, electrical stimulation of nerves or muscle, facet joint injections of steroids or anesthetics, chiropractic manipulation, and multidisciplinary approaches. We also searched for studies on a broad range of surgical treatments. These included total radical laminectomy, standard wide decompressive laminectomy, standard wide decompressive laminectomy with fusion, standard wide decompressive laminectomy with fusion and instrumentation, partial laminectomy (hemilaminectomy), laminotomy, and foraminectomy.

Our searches yielded 4,788 items that were evaluated for this project.

To prevent potential biases in this evidence report, we adopted specific a priori criteria for determining whether we would retrieve any article identified by our literature searches. Separate criteria were developed for studies of conservative treatment, studies of surgical treatment, and studies of diagnostic modalities. Disputes were always resolved in favor of retrieving the full article.

Because the different key questions of this report could be answered using different kinds of data, we adopted slightly different criteria to select articles relevant to answering questions about natural history, treatment, and diagnosis. Our criteria were, in general, very broad in order to ensure that we did not overlook any relevant information.

Patient groups less than 20 years of age were excluded to ensure that degenerative lumbar spinal stenosis and not congenital lumbar spinal stenosis was being examined. We abstracted only the data on degenerative conditions when these data were reported separately.

To answer questions about the natural history of lumbar spinal stenosis, we retrieved all published studies that contained (or purported to contain) measurements of the spinal canal among patients with lumbar stenosis and all trials that contained (or purported to contain) measurements of the spinal canal in normal healthy patients or patients with back pain, regardless of cause. To be retrieved, studies relevant to the natural history of spinal stenosis had to contain more than 10 patients; or, if the study contained more than 1 patient group, it had to contain more than 10 patients per group.

Only two general criteria were applied for retrieving articles on diagnosis of spinal stenosis. First, the article had to be on a diagnostic, and second, it had to be on patients with degenerative lumbar spinal stenosis.

In general, we employed the following criteria for determining whether an article on conservative treatments or surgery would be retrieved:

• We retrieved any controlled trial, regardless of whether the trial was randomized or concurrently controlled.

• In addition to controlled trials, we also retrieved any clinical study of surgical treatment for lumbar spinal stenosis.

• Only studies with at least 10 patients in each arm of the trial were retrieved.

• Studies of patients with degenerative spondylolisthesis, also called pseudospondylolisthesis, were included.

Once an article was retrieved, we evaluated the comparability of the patients in its different groups, the reporting of data, whether results from more than one type of treatment were combined, and whether results from patients with different disorders or conditions were combined. Trials that combined data from different procedures or from patients with different conditions were not considered further.

Data from all articles that met our inclusion criteria were abstracted using electronic data abstraction forms.

Our analysis of the literature comprised questions for which we were able to combine evidence from different studies and questions with evidence that did not permit such combination. We employed quantitative methods to answer both types of questions.

For parts of questions 1 and 2, we found data that permitted us to combine evidence, and we performed meta-analyses to address them.

Our quantitative analyses of those questions with data that did not permit combination consisted of performing de novo statistical analyses of the data published in the relevant articles wherever possible. Such statistics were either computed from raw data presented in the article or from figures contained in the article. In some cases, we computed effect sizes based on the published data.

Disk Degeneration

Figure 2. Etiology of Lumbar Spinal Stenosis (more...)

   Figure 2. Etiology of Lumbar Spinal Stenosis

Radicular pain (radiculopathy): disorder of the peripheral nerves due to compression of the nerve roots where they emerge from the spinal cord; responsible for leg pain. Patients have intense sciatica that may persist upon sitting. Nocturnal pain may become a predominant symptom.

Neurogenic intermittent claudication: radiating pain to the thighs and calves associated with compression of the caudea equina. Burning, cramping, numbness, tingling, and dull fatigue in the thighs and legs are classic clinical presentation for lumbar spinal stenosis. These symptoms appear or worsen with the onset of walking, or the severity increases with standing only; both are promptly relieved by sitting, bending, or lying down. The patient may also have urinary incontinence and sphincter dysfunction.

Figure 2

In susceptible individuals, disk degeneration can lead to pain and damage to the spinal nerves. Whether joint degeneration leads to pathologic consequences depends upon the characteristics of the individual patient (Jane, Jane, Helm et al., 1996).

Osteoarthritis in the Spine

Incremental microdamage in the lower disks of susceptible patients ultimately results in venting and loss of pressure in the disk nucleus (Rowe, 1969). As the disk degenerates, it narrows, decreasing the distance between vertebrae. The distribution of forces in the joint is altered. The ligaments connecting the vertebrae become lax, destabilizing the joint. Instability and altered force distribution lead to mechanical stress, which in turn can cause osteoarthritic changes in the articular processes (Fast and Greenbaum, 1995). Consequently, the vertebral facets become enlarged, the vertebral pedicles thicken, and the ligamentum flavum thickens. Type II collagen replaces elastic tissue (Jane, Jane, Helm et al., 1996; Schrader, Grob, Rahn et al., 1999), and calcium crystals are deposited (Schrader, Grob, Rahn et al., 1999). Hyalinization of the collagen fibers and proliferation of chondrocytes also contribute to the ossification of the ligament. Facet hypertrophy, thickening of the pedicles, and ossification of the ligamentum flavum lead to narrowing of the central spinal canal. Traction spurs may develop. These spurs can also impinge on the spinal canal or the nerve roots.

Eventually, vertebral stability may be regained as scarring occurs across the nuclear compartment (Rowe, 1969). Osteoarthritic changes may also lead to increased stability or even fusion between two vertebrae (Postacchini and Perugia, 1991; Rosenberg, 1975).

In susceptible individuals, the degenerative changes in the facet joints lead to two overlapping pathological and clinical entities: central and lateral stenosis. The two conditions may not be distinguished by their symptoms (Amundsen, Weber, Lilleas et al., 1995). The extent to which the degree and location of stenosis correlates with the nature, intensity, and location of symptoms is unclear. Individuals are frequently observed to have marked stenosis and no symptoms (LaRocca and Macnab, 1969; Nagler and Bodack, 1993; Postacchini and Perugia, 1991; Splithoff, 1953). Among patients with symptoms, long periods of remission are thought, at least by some, to be common (Rosenberg, 1976). However, the incidence and duration of these periods of remission are not well studied.

Degenerative Central Lumbar Stenosis

Lumbar spinal stenosis can be separated into three broad categories, specifically central stenosis, lateral stenosis, and spondylolisthesis. We have used these categories in our analysis to organize the literature and assist in combining evidence. Specific consideration of the etiology of the stenosis is important because different conservative and/or surgical treatments may be more or less effective depending on the nature of the stenosis.

Figure 3. Top View of a Normal Lumbar Vertebra (more...)

   Figure 3. Top View of a Normal Lumbar Vertebra

Figure 5. Oblique View of the Normal L3 to (more...)

   Figure 5. Oblique View of the Normal L3 to L5 Lumbar Vertebrae

Figure 6. Pathology Associated with Lumbar (more...)

   Figure 6. Pathology Associated with Lumbar Spinal Stenosis

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Degenerative Lateral Stenosis

Entrapment and compression of the nerve root in its pathway through the spine, referred to as the nerve root canal, is termed lateral stenosis (Gunzburg and Szpalski, 1999; Jenis and An, 2000; Postacchini, 1999; Woolsey, 1986). The nerve root canal begins where the nerve root exits the dura and ends where the nerve root leaves the intervertebral foramen. The nerve root canal is bordered by the pedicle of the vertebra above and the pedicle of the vertebra below. The anterior side of the canal is formed by the vertebral body and vertebral disk. The posterior side of the canal is formed by the facet joint structures of the vertebrae above and below (see Figures 3, 4, and 5). Lateral stenosis occurs when the spinal nerve is compressed within the nerve root canal and/or the vertebral foramina (Fritz, Delitto, Welch et al., 1998). As the disk narrows, the pedicle may move in an inferior direction, narrowing the lateral recess and pinching the spinal nerve (Jane, Jane, Helm et al., 1996; Mirkovic, Garfin, Rydevik et al., 1992). MacNab (1977) originally described this entrapment and compression of the nerve root between a diffuse lateral bulge of the disk and the pedicle above as pedicular kinking. Narrowing of the lateral recess can also be the result of facet hypertrophy or enlargement and ossification of the ligamentum flavum. Radiculopathy, or decreased function of a nerve root, is commonly observed with lateral stenosis. Impingement of the disk into the lateral recess is considered a separate condition (Amundsen, Weber, Lilleas et al., 1995) and is beyond the scope of this evidence report.

Degenerative Spondylolisthesis

Figure 7. Spondylolisthesis Showing Entrapment (more...)

   Figure 7. Spondylolisthesis Showing Entrapment of Spinal Canal and Nerve Roots

Figure 7

Disk degeneration may lead to spinal instability. Decreased disk height and degenerative changes in the angles of the facet joints contribute to this instability (Mirkovic, Garfin, Rydevik et al., 1992; Postacchini and Perugia, 1991; Rowe, 1969). This can lead to spondylolisthesis, or displacement of the vertebrae. Lumbar vertebrae have a tendency to be displaced forward due to their normal anterior curve and the action of gravity, muscular force, and other forces (Kim and Lee, 1995). As the vertebra slips forward, the medial edge of the superior facet may encroach on the central canal (Postacchini and Perugia, 1991). Distal to the slipping vertebra, the dural sac becomes trapped between the intervertebral disk and the posterosuperior angle of the underlying vertebral body on one side and the advancing neural arch of the slipping vertebra on the other. This is most commonly observed at the L4-5 level (Herkowitz, 1995; Newman, 1976). The anatomical reasons for the greater likelihood of degeneration at L4-5 have been described by MacGibbon and Farfan (MacGibbon and Farfan, 1979). Lateral stenosis may also result from spondylolisthesis when the nerve root becomes compressed between the inferior facet of the superior vertebra and the vertebral body of the inferior vertebra (Newman, 1976).

Further remodeling of the articular processes may eventually limit the vertebral slippage (Postacchini and Perugia, 1991). The degree of slippage usually does not exceed 20 percent to 30 percent of the width of the inferior vertebra (Herkowitz, 1995; Postacchini and Perugia, 1991; Rosenberg, 1975).

Spinal Stenosis and Spondylolisthesis in the Asymptomatic Population

Table 4. Spinal Stenosis in Asymptomatic Adults

Table 4. Spinal Stenosis in Asymptomatic Adults

Study	n	Selection	Patient Characteristics	Image and Interpretation	Stratification	Frequency of Lumbar Stenosis	Comments
Healy, Healy, Wong et al., 1996	19	Long-time highly active male athletes over age 40, currently free of pain or physical limitations (some were symptomatic with low back pain in past)	All male; mean age 53 yr (range 41 to 69)	MRI Readers: 2 blinded, 1 not; no significant differences in interpretation; small differences resolved by consensus	None	Stenosis 5% (1/19) Neural foraminal narrowing 16% (3/19)	One patient was considered to have "marked spinal stenosis"; only 16% had "normal" MRIs; 79% had abnormal disks
Jensen, Brant-Zawadzki, Obuchowski et al., 1994	98	Volunteers recruited by advertising among hospital staff; no previous back pain for longer than 2 days	51% male, 49% female; mean age 42.3 yr (range 20 to 80)	MRI 2 readers: blinded by randomly adding 27 abnormal scans (22% of total); differences resolved by consensus	None	Stenosis 7% Neural foramen stenosis 7%	Stenosis criteria: obliteration of epidural fat and thecal sac flattening; foramen criterion: obliteration of perineural fat; 64% had abnormal disks
Parkkola, Rytokoski, and Kormano, 1993	60	Healthy volunteers randomly selected from Finnish national insurance roll; matched by sex, age, employment, and profession with a cohort of chronic low back pain patients	55% male, 45% female; "middle aged," Million index1 mean (SD): males 6 (±11), females 7 (±12)	MRI 2 readers; intraobserver kappa = 0.93 and 1.0, p >0.001; interobserver kappa = 0.33 and 0.85, p <0.05	None	Central stenosis 3% (2/60)	Disk bulging in 15% of healthy patients; 40% of the 3 lowest disks were degenerated
Boden, Davis, Dina et al., 1990	67	Volunteers recruited with newspaper ads with no history of back pain of greater than 1 day and no history of sciatica or neurogenic claudication	45% male, 55% female; mean age 42 yr (range 20 to 80)	MRI 3 readers: blinded by randomly adding 33 abnormal scans (33% of total); ratings were averaged	Total, n = 67 20-39 yr n = 35 40-59 yr n = 18 60-80 yr n = 14	5% 1% 0 21%	Stenosis criteria: nondisk loss of signal in epidural fat with compression of neural tissues within canal; 24% had herniated disks
Wiesel et al., 1984	52	Volunteers with no history of back pain or sciatica	33% male, 67% female; mean age 40 yr (range 21 to 80)	CAT 3 readers: blinded by randomly adding 6 abnormal scans (10% of total); ratings were averaged; some scans rejected as inadequate	Total n = 48 <40 yr n = 22 >40 yr n = 26	5% 0 9%	Stenosis criteria: facet arthritis or bulging anulus and loss of epidural fat and compression of neural tissues

1 Million index scale: 0 = perfect back health, 100 = unable to manage daily activities due to back pain.

Although the presence of apparent stenosis in the asymptomatic population raises a question about whether stenosis per se causes symptoms, those with more severe symptoms are more likely to have stenosis. In one study, stenosis was observed by imaging in 50 percent (5/10) of patients with severe low back pain, 11 percent (4/38) of patients with less severe low back pain, and 3.3 percent (2/60) of asymptomatic controls matched to the back pain patients by sex, age, employment, and profession (Parkkola, Rytokoski, and Kormano, 1993).

Table 5. Spondylolisthesis in Asymptomatic Older Adults (more...)

Table 5. Spondylolisthesis in Asymptomatic Older Adults

Study	n	Selection	Patient Characteristics	Image and Interpretation	Stratification	Frequency of Degenerative Spondylo-listhesis	Comments
Kauppila, Eustace, Kiel et al., 1998	477	Surviving participants in Framingham Heart Study who had lateral lumbar radiographs and no chronic back pain or stiffness	35% male, 65% female; mean age 79 yr	Radiographs (lateral) Readers: slippage identified by one researcher blinded to demographic variables and symptoms; slippage measured by same and additional radiologist; only slippage >3 mm according to both readers was counted	None	17.6% 1 (84/477)	Spondylolisthesis criteria: degenerative slippage of >3 mm, not including spondylolytic spondylolisthesis

1 Our calculation from the reported data

The presence of stenosis and slippage in spinal images of asymptomatic people indicates that treatment must be based on the convergence of symptoms and image evidence rather than on either type of evidence alone. And in spite of the relationship between image evidence and more severe symptoms, the possibility exists that, even in more severe cases, treatment based on the image and symptoms may actually address a coincidental condition without eradicating the actual cause of symptoms.

History and Physical Examination

Katz et al. (1995) examined the value of the history and physical examination in the diagnosis of degenerative lumbar spinal stenosis. In this study, 93 patients over 40 years of age with symptoms of low back pain were examined by attending physicians who were then asked the extent to which they were certain the patient had lumbar spinal stenosis. The diagnostic impressions of expert clinicians and imaging, when available, were used as a reference standard to evaluate the attending physician's diagnosis. Severe lower extremity pain, absence of pain when seated, a wide-based gait, thigh pain following 30 seconds of lumbar extension, and neuromuscular deficits were all strongly associated with patients with lumbar spinal stenosis. No pain when seated and wide-based gait had the highest specificity, 93 percent and 97 percent, respectively. The highest sensitivity came from age greater than 65 (77 percent), pain below buttocks (88 percent), and no pain with flexion (79 percent) (Katz, Dalgas, Stucki et al., 1995).

Fritz et al. (1997) have developed a treadmill test as a clinical diagnostic tool for the differentiation of neurogenic claudication due to lumbar spinal stenosis from other pathologies that may produce similar symptoms. Spinal extension and weight bearing that occur during walking narrow the spinal canal and exacerbate the symptoms of lumbar spinal stenosis. Spinal flexion or nonweight-bearing postures that occur while sitting increase the dimensions of the spinal canal and reduce symptoms. The treadmill test involves having the patient walk on a level surface and an inclined surface. The time until onset of symptoms, total walking time, and time until symptoms return to baseline are recorded for each surface. Walking on an inclined plane produces spinal flexion and may be better tolerated by patients with lumbar spinal stenosis. The treadmill test was evaluated using 45 subjects with low back pain of varying etiologies and self-reported limitations in walking. Diagnostic images with MRI or CT were used as the gold standard for diagnosis. Twenty-six of the subjects were diagnosed by imaging as being stenotic. Self-reported sitting to relieve symptoms was significantly related to diagnosis. The sensitivity of this self-reported measure was 88.5 percent (95 percent confidence interval [CI] of 76.2 to 100), but specificity was 38.9 percent (95 percent CI of 16.4 to 61.4). For the treadmill test, earlier onset of symptoms with level walking, greater total walking time during inclined walking, and prolonged recovery after level walking were significantly related to a diagnosis of lumbar spinal stenosis. The sensitivity and specificity for earlier onset of symptoms with level walking were 68.0 percent (95 percent CI of 49.7 to 86.3) and 83.3 percent (95 percent CI of 66.1 to 100), respectively; for larger total walking time during inclined walking, they were 50.0 percent (95 percent CI of 37.5 to 62.5) and 92.3 percent (95 percent CI of 77.8 to 100), respectively; and for prolonged recovery after level walking, they were 81.8 percent (95 percent CI of 5.7 to 97.9) and 68.4 percent (95 percent CI of 47.5 to 89.3), respectively. The authors concluded that a two-stage treadmill test might be more useful in the differential diagnosis of lumbar spinal stenosis compared to patients' self-reports of posture (Fritz, Erhard, Delitto et al., 1997).

Use of the treadmill-bicycle test for the differential diagnosis of neurogenic claudication was also examined by Tenhula et al. (2000). In this study, 32 patients with documented lumbar spinal stenosis were evaluated before and after surgery. Patients were found to have a significant increase in their symptoms from the start to the end of the treadmill test but fewer patients were found to have significant symptoms on bicycle testing. Two years after surgery, patients had an improvement in their walking ability on treadmill testing, but showed no improvement in their ability to bicycle. The authors believe the treadmill-bicycle test may be a useful tool for the differential diagnosis of neurogenic claudication (Tenhula, Lenke, Bridwell et al., 2000).

Imaging examinations appear to be used primarily in a second diagnostic stage. At this stage, some surgical intervention is usually under consideration, so the imaging examination is as much for surgical planning as it is for confirmation of the preliminary diagnosis. In chiropractic care, a plain x-ray image may initially be obtained to aid in chiropractic therapy even if surgery is not planned (DuPriest, 1993).

In clinical practice, the imaging results help to confirm the diagnosis of spinal stenosis after the history and physical indicate the likelihood of spinal stenosis. Clinical trials interchangeably use myelogram, CT, or MRI results for confirmation of the diagnosis. This is partly because spinal stenosis is defined in terms of the anatomy displayed in the images. Also, there is no other means of verifying the results, short of measurement of the spinal canal during surgery. As discussed in the next section, plain film radiography is not considered a definitive standard for use in diagnosing lumbar spinal stenosis (Widelec, Bacq, and Peetrons, 1999). Because no independent means is available to confirm that imaging results are right or wrong, assessment of the performance of any of the imaging modalities for diagnosis of lumbar spinal stenosis is not possible in the same way we usually assess diagnostics. This is particularly true for negative cases, in which there would not be subsequent surgery on the spine.

Diagnostic Imaging Modalities

Radiography

Figure 4. Lateral View of a Normal Lumbar (more...)

   Figure 4. Lateral View of a Normal Lumbar Vertebra

The first imaging modality used to diagnose and evaluate lumbar spinal stenosis was radiography: film-based x-ray imaging, colloquially known as "plain film." The typical lumbar spine examination consists of AP (anteroposterior: front to back), lateral (side to side; see Figure 4), and oblique (diagonal; see Figure 5) views (Widelec, Bacq, and Peetrons, 1999). Film radiography has excellent spatial resolution for displaying small anatomic details but has several characteristics that limit its value in diagnosing spinal stenosis. First, it is a projection method: small anatomic details may be obscured by overlapping structures. Obtaining multiple views can sometimes resolve those structures. Second, the soft-tissue contrast of radiography is relatively low. Bones are depicted very clearly on plain radiographs, so they are frequently used to rule out vertebral fracture, if it is suspected.

Plain radiographs depict the spinal canal well enough for measurement of its diameter. The lateral radiograph is also useful for diagnosing spondylolisthesis, forward/backward displacement of a vertebra (Sackett, 1994; Wood, Popp, Transfeldt et al., 1994). For measuring displacement, radiography is considered the gold standard.

Myelography

Intradural contrast-enhanced radiography of the spine is known as myelography. To obtain a myelogram, a radiopaque contrast agent is injected into the spinal canal, and x-ray images are taken. The contrast agent diffuses through the spinal canal, outlining it quite clearly on the myelogram, but if stenosis causes a complete blockage of the spinal canal, no contrast agent will flow below (inferior to) the stenosis. Modern contrast agents for myelography are water soluble and contain iodine. Some patients are sensitive to iodine and may have an allergic reaction to the contrast material. Myelography is contraindicated in these patients. Adverse side effects are common in myelography. About half of patients experience head or neck pain, and 15 percent experience nausea or dizziness. Nearly all patients find myelography uncomfortable and will not be able to resume some normal activities, like driving, until the day after the procedure (American College of Radiology. 1999; Mitchell, 2000; Ramsbacher, Schilling, Wolf et al., 1997).

Table 17. Surgical Trials Reporting Imaging Results (more...)

Table 17. Surgical Trials Reporting Imaging Results

Authors and year	Imaging results reported	Signs and symptoms	Clinical results
Herno, Partanen, Talaslahti et al., 1999	Stenosis grade (four-point scale)	None	Correlation not reported
Hurri, Slatis, Soini et al., 1998	AP distance (<7 mm or >7 mm)	Correlation not reported	Success
Airaksinen, Herno, Turunen et al., 1997	AP distance (CT or myelogram, five-point scale)	None	Oswestry score, return to work
Nishizawa and Fujimura, 1997	Stenosis grade (myelogram; 3-point scale); stenosis grade (enhanced CT; - point scale)	None	Change in JOA score
Sato and Kikuchi, 1997	One-level or two-level stenosis	Symptoms	Success
Kawauchi, Yone, and Sakou, 1996	Myeloscope; degree of adhesive arachnoiditis	None	Success
Rompe, Eysel, Hopf et al., 1995	AP distance (CT; 2-point scale)	Characteristis	Confounded by disk disease
McCullen, Bernini, Bernstein et al., 1994	Degree of scoliosis, percent of slip	None	Turner score
Silvers, Lewis, and Asch, 1993	Complete block or no block (myelogram)	None	Pain relief (short-term and long-term)
Satomi, Hirabayashi, Toyama et al., 1992	Stenosis grade (myelogram 3-point scale)	Symptoms	Confounded by age
Johnsson, Uden, and Rosen, 1991	Complete or partial block (myelogram)	Symptoms	Success
Jalovaara, Lahde, Iikko et al., 1989	Marked or moderate stenosis (myelogram)	None	Success
Young, Veerapen, and O'Laoire, 1988	Stenosis grade (myelogram)	None	Stenosis grade at surgery
Surin, Hedelin, and Smith, 1982	Marked or moderate stenosis (myelogram)	None	Success
Johnsson, Willner, and Pettersson, 1981	Complete or partial block (myelogram)	Symptoms	Success
Tajima, Fukazawa, and Ishio, 1980	Exclude; method not reported
Verbiest, 1977	Type of stenosis and disk involvement	Symptoms	Success
Paine, 1976	AP distance		Success
Shenkin and Hash, 1976	Specific myelogram findings, level of stenosis	Symptoms	Correlation not reported

Spinal stenosis is traditionally defined by its appearance on a myelogram. Complete blockage is as described above. Partial blockage is a stenosis where the film shows a complete interruption of the column of contrast agent at the point of focal narrowing (i.e., the stenosis), but enough contrast agent gets through the stenosis to opacify the spinal canal below (inferior to) the stenosis. Stenoses of lesser degree are defined by the diameter of the contrast agent column at the stenosis. This is usually measured in the AP dimension, as viewed on the lateral film. The threshold measurement used to define stenosis varies from investigator to investigator (see Table 17 and Question 7 in Chapter 3).

The myelogram has long been considered a gold standard for imaging spinal stenosis and helping to confirm the diagnosis, but it has been supplanted by the cross-sectional modalities CT and MRI. Recent clinical handbooks now recommend MRI rather than plain films or myelography as the primary imaging modality in cases of suspected spinal stenosis. Myelography is now rarely done in routine clinical practice (Eisenberg and Margulis, 2000b; Grossman, Katz, Santelli et al., 1994; Gundry and Heithoff, 1999; Mitchell, 2000).

Computed Tomography

Because it is a three-dimensional modality, CT avoids the overlapping-structure problem of film-based radiography. But CT is still an x-ray modality, and bones will appear more distinct than soft tissue on a CT scan. CT is limited to axial images (cross sections as viewed from the patient's head to toe; see Figure 3), but all currently available CT scanners have tilting gantries that allow the imaging plane to be tilted 20° to 30° in each direction (ECRI. 1999). For many patients, this permits acquisition of images parallel to the disks, so the entire disk is in one image, although the vertebral column is not straight up and down.

CT scans can be acquired following administration of contrast agent, just like radiographs. Because the three-dimensional images resolve overlapping structures, there is less need for contrast agent in CT scans of the spine. Also, smaller quantities of the contrast agent are necessary with CT, but CT can be done following a myelogram with its larger contrast agent dose.

Magnetic Resonance Imaging

While it depicts anatomy in cross-section as CT does, MRI is based on completely different physical principles. A full explanation of how MRI works is beyond the scope of this report. Briefly, MRI derives contrast primarily from differences in the T1 and T2 relaxation times of hydrogen nuclei in the body. Those differences stem from differences in the chemical environment of water in different types of cells. Parameters for magnetic resonance (MR) image acquisition ("pulse sequences") can be varied to emphasize T1 or T2 or to base contrast on some combination of the two. Usually, MR examinations comprise several sets of images using several different pulse sequences. As with all other MRI applications, some pulse sequences are more effective than others for imaging the spine (Ramsbacher, Schilling, Wolf et al., 1997). Because technical characteristics of different MR scanners are different, the pulse sequences that are ideal for one scanner may not be ideal for another scanner.

Besides the advantage of soft-tissue contrast, MRI has the advantage of being able to acquire images in any user-selected plane. Sagittal sections (cross sections as viewed from the patient's left to right; see Figure 4) are particularly useful in spine imaging, and it is quite easy to select axial image planes parallel to the disks. Contrast-enhancement agents are also available for MRI, but instead of containing iodine or other atoms of high atomic number like x-ray contrast agents, MR contrast agents contain paramagnetic ions like gadolinium. Because MR images inherently provide good contrast of the spine and its contents, contrast agents are not usually necessary in MRI of the spine. Studies described as "MR myelography" do not necessarily involve contrast agents (Ramsbacher, Schilling, Wolf et al., 1997).

The chief disadvantage of MRI is that its spatial resolution is not as good as that of film radiographs (Ramsbacher, Schilling, Wolf et al., 1997). MRI can also be susceptible to spatial distortions that would cause errors in quantitative measurements of the vertebrae, but adherence to routine quality assurance procedures at the imaging center will minimize distortions.

Imaging of the Spine in Typical Practice

Recent textbooks and clinical handbooks of radiology identify an important shift in clinical practice for diagnosis of spinal stenosis, herniation of the disks, and other conditions of the lumbar spine. The cross-sectional modalities, particularly MRI, are now considered the primary imaging tools for diagnosis of spinal stenosis (Eisenberg and Margulis, 2000a; Eisenberg and Margulis, 2000b; Grossman, Katz, Santelli et al., 1994; Gundry and Heithoff, 1999; Kirkaldy-Willis and Bernard Jr, 1999; Mitchell, 2000; Spengler, 2000; Widelec, Bacq, and Peetrons, 1999; Wilmink, 2000). Reasons cited for the shift include multiplanar imaging capabilities, better ability to show bulging or fragmentation of the disks, and the risks and discomfort of myelography. These books should not be considered evidence based. They represent "conventional wisdom" among radiologists, which is shaped in part by clinical trials and other evidence. In fact, Wilmink notes the absence of conclusive evidence that MRI is the most effective modality for diagnosing spinal stenosis (Wilmink, 2000).

Official guidelines developed by professional specialty societies like the American College of Radiology (ACR) and the Canadian Association of Radiologists (CAR) are also based on a mix of scientific evidence and expert opinion. CAR states that "CT and MRI have replaced myelography as the examination of choice for the above [spinal stenosis and other myelographic] indications" (Fontaine, Lee, Maloney et al., 1996). Myelography would still be an appropriate choice if the patient cannot be imaged by CT or MRI due to unavailability of a scanner, metal implants, or patient size or noncompliance. Appropriateness criteria from the ACR do not specifically address diagnosis of spinal stenosis, but for various types of nontraumatic myelopathy, MRI is considered very appropriate (8 on a scale of 1 to 9), and CT and myelography are considered less appropriate (usually 4 on the same scale) (American College of Radiology, 1998).

Plain films still have a role in diagnosis of spinal disorders; they may be all that is necessary to diagnose vertebral fracture and/or spondylolisthesis (Crosby and Brant-Zawadzki, 1994; Grossman, Katz, Santelli et al., 1994), and they are capable of measuring the diameter of the spinal canal (Sackett, 1994). Plain radiographs are considered "appropriate" by ACR in some clinical circumstances (6 or 7 on a 9 point scale) (American College of Radiology, 1998).

All the imaging modalities are adversely affected by surgical hardware and other metal objects implanted in the body. These objects are radiopaque; so they obscure overlapping structures in plain x-rays and myelograms. The effect is heightened in CT scanning, where the metal objects cause artifacts that can affect the entire image. Metal objects also affect MR scans, although most orthopedic devices are nonmagnetic and do not completely contraindicate MRI. Metal causes susceptibility artifacts: there is no signal from the object itself, and portions of the image near the object may be distorted or lose signal. The magnitude of this effect depends on the size and placement of the object and its composition (Fredrickson, 2000). Since diagnosis among patients who already have had surgery is outside the scope of this report, the studies we examined for this technology assessment did not deal with artifacts from metal implants.

All imaging modalities are subject to variation in image quality and diagnostic effectiveness and variation in interpretation by the radiologist. We located one study that addresses how variations in image quality affect the diagnosis of spinal stenosis. Jarvik et al. (2000) examined variations in the quality of lumbar spine MR images, and attempted to correlate them with characteristics like the magnetic field strength of the scanner and the ownership and siting of the scanner. Three readers rated the quality of 69 examinations from 17 centers. Readers were blinded to identifying information on the images, including information that could identify the center or the type of scanner used. The readers graded each examination on a four-point scale for the sharpness with which each of seven clinically important structures was depicted. They also assigned an overall quality score to each examination, using the same scale. The average overall quality rating for each center ranged from 1.96 to 3.56, while the average rating of the seven structures from each center ranged from 2.25 to 3.82 (Jarvik, Robertson, Wessbecher et al., 2000).

Jarvik et al. (2000) found that image quality was significantly decreased by the following characteristics: low magnetic field strength (less than 1.0 tesla), location of the scanner outside a hospital, and for-profit ownership of the scanner. The number of radiologists interpreting images at a center and the percentages of images reviewed by a physician before the patient was dismissed had smaller but still statistically significant effects on study quality. The authors note that they were unable to measure some characteristics that would be expected to affect study quality, such as training and experience of the radiologists. However, the results of this study are consistent with the idea that the quality of diagnostic imaging examinations, especially complicated ones like MRI, should not be taken for granted.

Finally, image quality should not be mistaken for diagnostic effectiveness, although poor image quality can impede effective diagnosis. While one modality may be able to depict structures with more detail and more contrast than another, the modality of lesser "quality" may still depict the anatomy clearly enough to permit a correct diagnosis. For this reason, we base our evaluation of diagnostic imaging modalities on their diagnostic results, not on subjective or objective measurements of image characteristics.

Surgical Planning

Imaging data are also necessary for planning surgical treatment. The surgeon needs to determine the extent of decompression, identify the bony anatomy, and measure the extent of the stenosis (Gunzburg and Szpalski, 1999). Accurate location of the stenosis is essential to avoiding operation at the wrong lumbar level. Identification of vertebral defects, anatomic landmarks, and other bone anatomy is necessary to minimize complications (Bernard and Yong-Hing, 1999). Selection of the correct type, size, and placement of orthopedic hardware is aided by preoperative imaging studies (Visarius, 2000). Both plain x-rays and CT or MRI are often needed in surgical planning (Lazennec, Ramare, Arafati et al., 1999); the specific combination of modalities varies from surgeon to surgeon and from patient to patient. There is no single preoperative imaging plan that is appropriate for all spinal stenosis patients.

Assessment of this indication for spinal imaging is complicated by the absence of any clinical trials measuring the effectiveness of the various imaging modalities in surgical planning.

Summary

Diagnostic imaging data are essential in planning for surgical treatment for lumbar spinal stenosis and related conditions. No one procedure or combination of procedures is right in every case, and multiple imaging modalities are used in most cases. Images obtained at the time the diagnosis of the patient's condition is confirmed are usually sufficient for surgical planning, in part because part of the purpose of those imaging examinations is surgical planning. No clinical evidence is currently available on the effect of any particular imaging modality on surgical outcomes.

Focus and Refinement of Topic

In order to focus, refine, and arrive at the key questions addressed by this assessment, the research team held telephone conversations with 11 experts in the field of lumbar spinal stenosis and one patient representative. These individuals were invited to comment on a document prepared by the research team charged with preparing the present evidence report. This research team consisted of five experts in technology assessment. The document comprised a preliminary evidence model (evidence models are discussed below) and written descriptions of the specific issues depicted in this model. Conversations with the experts and the patient representative clarified that the evidence report was to cover primarily lumbar stenosis in adults and that congenital stenosis or stenosis resulting from trauma was beyond the scope of the present evidence report. Upon receipt of the comments of the experts and the patient representative, the research team met to ensure that the evidence model was refined to incorporate the comments of the experts and the patient representative.

Evidence Model

The evidence model developed for this report is a graphic that depicts the relationships between the diagnostics and treatments of spinal stenosis and the benefits and harms that result from their use. These relationships are denoted by links (represented by arrows). The important links in the model were used to generate the key questions addressed in this report. Because of the complexity of the topic, we divided the evidence model into two sections. The first section portrays the questions on the natural history of lumbar spinal stenosis, and the second section portrays the questions on the diagnosis and treatment of lumbar spinal stenosis.

Key Questions on the Natural History of Lumbar Spinal Stenosis

Figure 9. Evidence Model Depicting the Natural (more...)

   Figure 9. Evidence Model Depicting the Natural History of Lumbar Spinal Stenosis

The evidence model for the natural history of lumbar spinal stenosis addresses three questions that relate patient characteristics to patient signs, symptoms, and conditions (see Figure 9). The three questions are:

1. What is the relationship between each relevant patient characteristic and the presence and/or intensity of each of the patient signs, symptoms, and conditions of lumbar spinal stenosis?

2. Which relevant patient characteristics are correlated with an increased likelihood of focal narrowing of the spinal canal?

3. What is the relationship the degree of stenosis and the presence and/or intensity of each of the signs, symptoms, and patient conditions?

Key Questions on the Diagnosis and Treatment of Lumbar Spinal Stenosis

Figure 10. Evidence Model Depicting the Diagnosis (more...)

   Figure 10. Evidence Model Depicting the Diagnosis and Treatment of Lumbar Spinal Stenosis

The evidence model for the diagnosis and treatment of lumbar spinal stenosis addresses five questions that relate to the connection between the signs and symptoms of lumbar spinal stenosis and the results of conservative treatment, the imaging examination, and the results of surgical treatment (see Figure 10).

• 4

  What is the relationship between the signs and symptoms and other features of the history and physical and the results of the imaging examination? Implicit in this question is an examination of the criteria for diagnosis of spinal stenosis.

• 5

  What is the relationship between the signs and symptoms and other features of the history and physical and results of conservative treatment and what is the relationship between the type of conservative treatment, and patient outcomes? Implicit in this question is whether any particular patient subgroup benefits from medical management of spinal stenosis.

• 6

  What is the relationship between the signs and symptoms and other features of the history and physical and the success or failure of surgical treatment? Implicit in this question is whether any particular patient subgroup benefits from surgical treatment of spinal stenosis and whether some patients might benefit more from surgery than from medical management.

• 7

  What is the relationship between the results of the imaging examination and the success or failure of surgical treatment? Implicit in this question is whether it is possible to predict that a certain patient subgroup will benefit from surgery.

• 8

  What is the relationship between the type of surgery received and patient outcomes?

Hand Searches of Journal and Nonjournal Literature

To further ensure that our searches allowed for comprehensive identification of information, we searched Current Contents^© -- Clinical Medicine on a weekly basis and routinely reviewed more than 1,600 journals and supplements maintained in our collections. Nonjournal publications and conference proceedings from professional organizations, private agencies, and government agencies were also screened.

Finally, to further ensure the comprehensiveness of our identification of relevant literature, we reviewed bibliographies/reference lists from peer-reviewed and gray literature. (Gray literature includes reports and studies produced by local government agencies, private organizations, educational facilities, and corporations that do not appear in the peer-reviewed literature.)

World Wide Web Searches

Searches of the World Wide Web were also conducted using various resources and search engines, including (but not limited to) AltaVista, NorthernLight, and Google. Selected Internet resources include:

American Academy of Orthopedic Surgeons (AAOS) http://www.aaos.org/

American Back Society http://www.americanbacksoc.org/home.htm

Centre for Clinical Effectiveness http://www.med.monash.edu.au/publichealth/cce/

Development Evaluation Committee http://www.hta.nhsweb.nhs.uk/rapidhta/main.htm

GICD Online http://www.gicd.org/index.html

HCUPnet http://www.ahcpr.gov/data/hcup/hcupnet.htm

Mecqa (benchmarking data) http://www.mecqa.com/consumer/frame.htm

Medscape http://www.medscape.com

NHS Centre for Reviews and Dissemination http://www.york.ac.uk/inst/crd/welcome.htm

North American Spine Society http://www.spine.org

Spinal Disorders http://www.spinaldisorders.org/index.html

SUM Search http://sumsearch.uthscsa.edu/searchform4.htm

The Spinal Foundation http://www.spinal-foundation.org/home.htm

TRIP Database http://www.ceres.uwcm.ac.uk/section.cfm?section=trip

MEDLINE^®, EMBASE^®, CINAHL^®, Current Contents^® (presented in PubMed syntax)

Range of Searches for Surgical Treatments

We also searched for studies on a broad range of surgical treatments. The terminology for surgical procedures is inconsistent in the literature. Therefore, items in the following list of surgical procedures are general in nature. Specific modifications or refinements of these techniques appear in many publications, and these specific modifications were located by our searches.

1. Total radical laminectomy (all of the facet joints are removed)

2. Standard wide decompressive laminectomy

   • Single or multiple levels

3. Standard wide decompressive laminectomy with fusion (arthrodesis)

   • Single or multiple levels

4. Standard wide decompressive laminectomy with fusion and instrumentation (pedicle screw fixation)

   • Single or multiple levels

   • Instrumentation may be bilateral or unilateral

5. Partial laminectomy, hemilaminectomy

6. Laminotomy

   • Single or multiple levels

7. Foraminectomy

   • Unilateral or bilateral

Patient Populations Included

Few restrictions were placed on the patient populations in clinical trials of conservative or surgical treatments that were retrieved for this analysis. All patients, or a separately reported subset of patients, had to be diagnosed specifically with lumbar spinal stenosis. Groups of patients less than 20 years of age were excluded to ensure that degenerative lumbar spinal stenosis and not congenital lumbar spinal stenosis was being examined. However, several publications mixed congenital conditions with degenerative conditions. We abstracted only the data on degenerative conditions when these data were reported separately.

Years Included

For all aspects of this evidence report, publications from 1960 to the present were retrieved.

Criteria for Retrieving Articles on Conservative Treatment

We employed the following criteria for determining whether an article on conservative treatments would be retrieved:

1. We retrieved any controlled trial, regardless of whether the trial was randomized or concurrently controlled.

2. Only studies with at least 10 patients in each arm of the trial were retrieved.

3. Studies of patients with degenerative spondylolisthesis, also called pseudospondylolisthesis, were retrieved.

Criteria for Retrieving Articles on Surgical Treatments

The following inclusion criteria were used to determine whether articles on surgical treatments were retrieved:

1. Providing that the article met the two inclusion criteria listed below, we retrieved all controlled and uncontrolled trials, regardless of whether they were prospective or retrospective and, if controlled, regardless of whether the controls were historical or concurrent, and regardless of whether patients were randomly assigned to groups.

2. Only studies with at least 10 patients in one arm of the trial were retrieved.

3. Studies of patients with degenerative spondylolisthesis (also called pseudospondylolisthesis) were retrieved.

Criteria for Retrieving Articles on Diagnostics

Only two general criteria were applied for retrieving articles on diagnosis of spinal stenosis. First, the article had to be on a diagnostic, and second, it had to be on patients with spinal stenosis. Surgical trials included in the analysis were reviewed for image-related data.

Criteria for Retrieving Articles on the Natural History of Lumbar Spinal Stenosis

To answer questions about the natural history of lumbar spinal stenosis, we retrieved all publications that contained (or purported to contain) measurements of the spinal canal among patients with lumbar stenosis and all trials that contained (or purported to contain) measurements of the spinal canal in normal healthy patients or patients with back pain, regardless of cause. Studies reporting spinal measurements in cadavers or skeletons were retrieved, but were not used because they did not include information describing the health status of the subjects before death. To be retrieved, studies relevant to the natural history of spinal stenosis had to contain more than 10 patients, or if the study contained more than one patient group, it had to contain more than 10 patients per group.

Approaches to Evaluating and Combining Evidence

Our analysis of the literature comprises questions for which we were able to combine evidence from different studies, and questions with evidence that did not permit such combination. We employed quantitative methods to answer both types of questions.

Parts of questions 1 and 2 had data that permitted us to combine evidence, and we performed meta-analyses to address them. These data came from observational studies and not randomized controlled trials (RCTs). Therefore, caution is needed in interpreting these data. In these two questions, we were interested in the difference between spinal canal sizes of patients with and without certain symptoms. To perform meta-analyses on such data, we converted the mean canal size difference between groups to the effect size, Hedges' d (Hedges and Olkin, 1985). This effect size is determined by expressing the difference between two groups in standard deviation units. A 95 percent confidence interval around the effect size indicates the range into which, if the experiment were repeated a large number of times, the effect size would be 95 percent of the time. If this interval does not include zero, the effect is considered statistically significant. In some cases, a very large effect size may be considered clinically significant even if it is not statistically significant, and vice versa. We employed a fixed effects model for all of our meta-analyses.

To check the validity of the summary statistic of these models, we used two tests for heterogeneity, the Q test and each study's standardized residual. A standardized residual of >1.96 was taken to indicate that a study's effect size was heterogeneous with respect to the other studies in the meta-analysis. Results of our meta-analyses are graphically displayed in Forrest plots. In this type of plot, each effect size (including the summary statistic) is depicted as a point, surrounded by bars illustrating the 95 percent confidence interval around each study's effect size and around the summary statistic.

To further assist in interpreting the results of our meta-analyses, we depicted the results of our meta-analyses in plots that show a pair of normal curves. One of these curves represents the distribution of nondiseased (or, where appropriate, asymptomatic) patients. The mean of this curve was arbitrarily set to zero. The second curve in each plot represents diseased (or, where appropriate, symptomatic) patients. The difference between the mean of this curve and the mean of the former curve represents d, the effect size. Perhaps more importantly, the curves depict the degree of overlap in the normalized distributions of the canal sizes of the two groups of patients that are being compared in the meta-analysis. We quantified the degree of this overlap using the statistics described by Cohen (Cohen, 1988). More specifically, we computed the ₁ statistic, which is the percentage of nonoverlap of the two normal curves. We then subtracted this number from 100 percent to obtain the percentage of overlap between the two curves.

As a final way of facilitating interpretation of the results of our meta-analyses, we expressed their results in terms of a binomial effect size display, or BESD (Rosenthal, 1991). This display depicts the results of a meta-analysis as a 2 by 2 table in which there are 100 patients in each of the two groups being compared. The BESD also artificially dichotomizes the dependent variable and sets the number of patients in each category of this variable to 100. As such, the BESD illustrates the proportion of patients in each group who do or do not have a certain characteristic.

Some minor differences exist between the results derived from the statistic and those illustrated by the BESD. These differences have not been explored in the statistical literature, but they do make it important to display the results of both statistical procedures. We stress that these differences are minor, and one would arrive at the same conclusions using either one of these methods alone.

Our quantitative analyses of those questions with data that did not permit combination consisted of performing de novo statistical analyses of the data published in the relevant articles wherever possible. Such statistics were either computed from raw data presented in the article or from data read off of figures contained in the article. In some cases, we computed effect sizes based on the published data. For computation of effect sizes derived from dichotomous outcomes, we employed the odds ratio and natural log transformation as described by Hasselblad and Hedges (Hasselblad and Hedges, 1995). We used the method of Torgerson (1958) to analyze data from rating scales that comprised more than two categories and transformed the result of this statistic into Hedges' d. We also conducted additional de novo statistical analyses using a variety of standard tests. Because these tests are quite varied, we describe each of them in the text when used (Torgerson, 1958).

Previous Meta-analyses of Treatments for Lumbar Spinal Stenosis

Prior meta-analysis has been performed on clinical studies of treatments for lumbar spinal stenosis (Niggemeyer, Strauss, and Schulitz, 1997; Turner, Ersek, Herron et al., 1992), degenerative lumbar spondylolisthesis (Mardjetko, Connolly, and Shott, 1994), and degenerative lumbar spondylosis (Gibson, Grant, and Waddell, 1999). These meta-analyses differ in approaches to the pooling of data from across studies and in the interpretation of results. Important differences exist between our approach to the meta-analysis of lumbar spinal stenosis and these other meta-analyses. None of these meta-analyses attempted to evaluate conservative therapy for lumbar spinal stenosis or spondylolisthesis.

Turner et al. (1992) looked at the literature concerning outcomes of surgery for spinal stenosis from 1966 to 1990. Studies were included if they were original studies of patients undergoing decompressive laminectomy for lumbar spinal stenosis and appeared in English-language journals. Studies were excluded when spinal stenosis patients could not be separated from other diagnoses, outcome data were not reported, sample size was less than six, and there were no data concerning patient preoperative characteristics. Seventy-four articles met the inclusion/exclusion criteria. The authors noted the wide variation in outcome measures and created their own definitions for the outcome categories of good-to-excellent, fair, and poor. For actual analysis, the outcomes were dichotomized into good-to-excellent versus fair and poor. Thirty-one studies reported outcomes that allowed the recoding according to this good-to-excellent versus fair and poor rating scale. Studies were included regardless of study design, presence of a control group, or patient characteristics that would preclude combining data across studies. Only three studies had prospective designs. A chi-square test was used to determine whether the proportion of good-to-excellent versus fair and poor outcomes varied significantly across studies. This test was highly significant (p <0.0001), indicating significant heterogeneity of outcomes across studies. The average proportion of good-to-excellent outcomes among the studies was 64 percent, but the range was 26 percent to 100 percent. No standard deviations or confidence limits were calculated. The authors used regression analysis to examine whether specific predetermined variables could explain the large variation across studies. No significant associations between outcome and patient variables such as age, gender, neurogenic claudication, number of levels of laminectomy, or prior back surgery were found. The authors concluded that the poor scientific quality of the literature, especially major deficits in study design, analysis, and reporting, prevented the construction of a proper meta-analysis. In particular, the lack of comparative trials, especially randomized controlled trials, prohibited any attempt at addressing the question of efficacy of various therapies through meta-analysis (Turner, Ersek, Herron et al., 1992).

There are difficulties in interpreting the Turner et al. (1992) analysis. The authors do not provide a detailed description of their methods and, in particular, do not state how (or whether) they calculated effect sizes for each study. Therefore, it is not at all clear that they used meta-analytic methods to perform their analysis. Failure to use such methods could severely compromise their findings. Consequently, we will not assess their findings.

Niggemeyer et al. (1997) conducted a meta-analysis of surgical treatments for lumbar spinal stenosis, again using their own definitions for good, fair, and poor outcomes. Studies published between 1975 and 1995 in English, French, or German were included if the studies reported cases of degenerative lumbar spinal stenosis with no prior back surgery and had a minimum of seven patients. Thirty articles met the inclusion criteria. As in the meta-analysis by Turner et al., studies were included regardless of study design, presence of a control group, or patient characteristics that would preclude combining data across studies. The authors calculated a pooled weighted proportion for each of the three outcome categories within each of three surgical approaches: decompression alone, decompression plus fusion, and decompression with fusion and instrumentation. Proportions for each outcome category were then compared across surgical approaches using a Z score and pooled variance. This resulted in the calculation of nine separate Z scores (3 categories by 3 surgical comparisons). None of the Z scores were significantly different from zero. The use of uncontrolled trials in this analysis compromises its validity. The study was further compromised by the lack of any test of heterogeneity. Therefore, one cannot determine whether the trials were, in fact, combinable. Consequently, we do not discuss this analysis further (Niggemeyer, Strauss, and Schulitz, 1997).

Mardjetko et al. (1994) performed a meta-analysis of studies examining decompression and fusion for treating degenerative lumbar spondylolisthesis. Studies were included if they enrolled patients with degenerative spondylolisthesis with radicular leg pain or neurogenic claudication, were published in English between 1970 and 1993, had at least four patients, and reported primary outcomes specifically for the spondylolisthesis patients. Twenty-five papers met the inclusion criteria, and of these, 21 were classified as retrospective, nonrandomized, and uncontrolled. Outcomes were reassigned into satisfactory or unsatisfactory categories, and pooled weighted proportions were calculated. Z scores were then calculated for comparisons of decompression without fusion to decompression with fusion and decompression with fusion and instrumentation. Significant Z scores were found in favor of fusion increasing patient satisfaction and instrumentation increasing fusion rates. The authors commented on the serious methodological flaws, such as poorly defined outcome measures, lack of blinded outcome assessment, failure to provide adequate patient demographics, and lack of stratification of outcomes by diagnosis, that led to a poor meta-analysis. The meta-analysis method allowed data from poorly designed studies to dilute the data from better-quality studies. Like the Niggemeyer et al. (1997) analysis, this analysis does not provide a test of heterogeneity. For these reasons, we do not consider the results of this analysis (Mardjetko, Connolly, and Shott, 1994).

In 1999, Cochrane Review published a discussion of the difficulties of conducting a meta-analysis of randomized controlled trials on surgery for degenerative lumbar spondylosis (Gibson, Grant, and Waddell, 1999). Their analysis addressed the questions of what evidence exists concerning the clinical effectiveness of lumbar spine surgery and what evidence exists concerning alternative forms and techniques of lumbar spine surgery. All randomized and quasirandomized controlled trials identified between 1966 and 1998 and pertaining to degenerative lumbar spondylosis and the associated pathologies or clinical syndromes of back pain, instability, spinal stenosis, and degenerative spondylolisthesis were included. Fourteen RCTs for degenerative lumbar spondylosis were retrieved. Many of the trials had major defects of design, such as including heterogeneous pathologies and clinical syndromes, and the subgroups were often too small to give meaningful results. The authors mentioned that clinical outcomes were mainly crude ratings on a three- or four-point scale. The reader should note that spondylosis is a large category of spinal pathology. Differences in the number of RCTs mentioned in the present analysis and the Cochrane Review are due to separating out the specific pathologies of lumbar spinal stenosis and spondylolisthesis, as well as not including studies that did not report outcomes separately for these conditions. The Cochrane Review found no RCTs dealing with the efficacy of surgical decompression for degenerative lumbar spondylosis or spinal stenosis or of surgical fusion for degenerative spondylosis and back pain. A meta-analysis of fusion rates in trials of instrumented fusion versus fusion alone was performed. This analysis suggested that solid fusion was more likely if instrumentation was used. However, the significant heterogeneity among the trials prevented the drawing of conclusions about the results of instrumented fusion for any particular pathologic condition or about any particular instrumentation system. The authors concluded that there is a serious lack of scientific evidence supporting surgical management for degenerative lumbar spondylosis. The authors go on to say that "there is no scientific evidence on the effectiveness of any form of surgical decompression or fusion for degenerative lumbar spondylosis compared with natural history, placebo, or conservative management."

A meta-analysis of the accuracy of CT, MRI, and myelography was published in 1992 (Kent, Haynor, Larson et al., 1992). The authors wished to evaluate what was known about the diagnostic accuracy of these imaging tests for the diagnosis of lumbar spinal stenosis in adults without prior surgery. Studies were included if they contained cases of canal, lateral recess, or foraminal stenosis. Cases with entirely acute-onset radiculopathy, where all cases had herniated disk, or with fewer than 10 cases of lumbar spinal stenosis were excluded. The contribution of plain film to diagnosis was not reviewed. One hundred and sixteen articles from 1986 to 1991 were read, and only 14 were retained for analysis. A series of quality criteria were developed based on the technical quality of study procedures (index test quality, reference test quality, application of reference test) and on the proper selection of patients and unbiased interpretation of information (independence of interpretations, clinical description, cohort assembly, and sample size). Based on these criteria, an overall rating from A (best) to D (worst) was assigned to each article. All studies received a C or D rating. C studies had poor clinical descriptions but had intermediate ratings in all other categories. Studies failing the C rating received a D. The authors calculated sensitivities of 0.81 to 0.97 for MRI (four studies), 0.70 to 1.0 for CT (nine studies), and 0.67 to 0.78 for myelography (four studies) and specificities of 0.72 to 1.0 for MRI (three studies), 0.80 to 0.83 for CT (four studies), and 0.7 for myelography (one study). Based on their review of the literature, the authors concluded that any estimates of sensitivity or specificity must be considered imprecise, since the estimates are based on small sample sizes and on studies with serious methodological flaws. In particular, the imaging literature for spinal stenosis failed to provide independent corroboration with a reference standard for the diagnosis. Thirty articles were excluded due to the lack of a proper reference standard. Failure to assemble a representative cohort and failure to maintain independence between image reading and reference standards were also common problems. The applicability of these cases to general practices was reduced by a selection of patients referred for surgery. These patients will tend to have the most severe disease and increase the frequency of true-positive diagnosis. The variation in study design prevented the pooling of sensitivity and specificity estimates.

Our current assessment of studies examining the diagnostic accuracy of MRI, CT, and myelography for lumbar spinal stenosis also concludes that these studies have one or more flaws in design or reporting that adversely affect the reliability or applicability of the results.

Relationship Between Spinal Canal Diameter and the Presence of Back Pain, Claudication, or Radicular Pain/Sciatica

Although it is commonly believed that the development of the symptoms of lumbar spinal stenosis are related to the size of the spinal canal (Clark, 1969; Postacchini and Perugia, 1991), very little evidence is available to support this belief. While more severe degeneration and degree of slippage are often associated with more severe symptoms, the extent of neural deficit may depend more on the degree of neural compression (Postacchini and Perugia, 1991). If the canal is wide and the stenosis is mild, there is relatively little or no compression of the dural sac. When the spinal cord is normally sized, stenosis may lead to compression of the dural sac. If the spinal canal is smaller than normal, the sac may be severely compressed even if there is only slight narrowing or vertebral slippage. When the canal is small, a developing stenosis may tend to become symptomatic earlier and is likely to present more severe deficits than in a wider canal (Clark, 1969).

There is an important distinction between canal size and stenosis. Canal size refers to the size of the healthy, nonstenotic canal. On the other hand, stenosis refers to a focal narrowing. When canal diameter is reported for stenotic patients, the measurement generally refers to canal size at the narrowest point. When canal size is described in epidemiologic or anthropologic studies such as those described in this section of this report, it refers to canal size at predefined levels. Although the spinal canal tends to narrow with age (Twomey and Taylor, 1988), the point at which normal narrowing becomes stenosis is imprecise.

The spinal canal is usually measured in one of three ways. The most common is to measure the midsagittal (anterior-posterior) diameter (Panjabi, Duranceau, Goel et al., 1991). This is the simple diameter of the canal at the widest point of the sagittal plane, and is measured in centimeters or millimeters. The sagittal diameter is the smallest dimension of the canal (Alvarez and Hardy Jr, 1998). The interpedicular distance, which is the diameter of the canal in the frontal plane, is usually considerably wider. Midsagittal diameter averages approximately 13.4 to 20.4 mm, while interpedicular distance is normally 19 to 27 mm (Postacchini, Pezzeri, Montanaro et al., 1980a). These measurements vary by spinal level as well as by the age, race, and size of the individual patient.

In some cases, the cross sectional area of the canal is measured. This may be a more informative measure if stenosis is occurring primarily in the lateral recesses. Finally, some researchers report the canal size in a ratio with the size of the vertebral body (Jones and Thomson, 1968). This ratio takes into account the observation that differently sized people have different sizes of canal. This reflects an attempt to define a "normal" canal size in relation to the size of the subject. It is not known whether a small person with a correspondingly small canal is less susceptible to spinal stenosis than a large person with a canal of similar size.

Spinal measurements are normally expressed individually for one or more discrete spinal levels. Spinal canal measurements of patients with stenosis may convey information about the global narrowing associated with degenerative changes on the spinal canal, but may not reflect the extent of focal narrowing in the stenotic area of the canal. When an osteophyte or an enlarged ligamentum flavum impinges on a spinal canal, the canal size at this point may be considerably less than in the surrounding area of the canal. This focal narrowing may not be reflected in the published measurements of canal size. The precise area of stenosis that is responsible for the patient's symptoms may be difficult to determine from diagnostic visualization (see section on Diagnostic Tests).

To investigate the relationship between spinal canal size and symptoms of stenosis, we conducted a series of meta-analyses of studies that compared spinal canal sizes among patients with back pain, claudication, or radicular pain to those of asymptomatic age-matched controls. The methods we used for our meta-analysis are described in the section entitled "Approaches to Evaluating and Combining Evidence" (see Chapter 2).

Table 6. Spinal Measurements in Patients with Symptoms (more...)

Table 6. Spinal Measurements in Patients with Symptoms of Stenosis

Study	Patient description	Units	n	Measurement
Back Pain
Hamanishi, Matukura, Fujita et al., 1994	Healthy controls age 42±15	Cross-sectional area of the dural tube (mm2)
	L2		11	213±48
	L2/L3		29	170±39
	L3		16	192±39
	L3/L4		31	157±39
	L4		20	170±43
	L4/L5		36	153±42
	L5		22	153±54
	L5/S1		32	129±55
	S1		15	98±53
	Low back pain patients age 44±17
	L2		4	168±51
	L2/L3		32	144±31
	L3		5	189±39
	L3/L4		37	135±45
	L4		21	143±67
	L4/L5		50	130±51
	L5		21	130±66
	L5/S1		47	113±52
	S1		15	103±62
Hultman, Saraste, and Ohlsen, 1992	Healthy controls	L3 sagittal diameter, mm	18	15.9±1.6
	Patients with acute back pain		34	15.6±1.9
	Patients with chronic back pain		21	15.1±1.9
	Healthy controls	L3 canal area, mm2	18	240.4±42.8
	Patients with acute back pain		34	240.7±48.8
	Patients with chronic back pain		21	231.4±52.3
Anderson, Adcock, Chovil et al., 1988	Healthy controls	Oblique parasagittal diameter at L5-S1, cm	33	1.72±0.23
	Patients who have missed work because of back pain		16	1.60±0.25
Drinkall, Porter, Hibbert et al., 1984	Controls with no history of back pain	Sagittal diameter, cm	132
	L1			1.52±0.079
	L2			1.49±0.077
	L3			1.47±0.078
	L4			1.44±0.078
	L5			1.44±0.074
	Patients with back pain		193
	L1			1.48±0.073
	L2			1.46±0.072
	L3			1.43±0.074
	L4			1.40±0.075
	L5			1.41±0.073
Macdonald, Porter, Hibbert et al., 1984	Coal miners who have taken various amounts of time off work because of back pain	Sagittal diameter, cm
	No time off		16
	L1			1.55±0.08
	L2			1.50±0.07
	L3			1.49±0.07
	L4			1.47±0.06
	L5			1.50±0.08
	8-16 weeks off		20
	L1			1.53±0.07
	L2			1.50±0.09
	L3			1.46±0.08
	L4			1.43±0.06
	L5			1.45±0.08
	16-24 weeks off		17
	L1			1.56±0.07
	L2			1.52±0.07
	L3			1.46±0.09
	L4			1.43±0.09
	L5			1.46±0.09
	26-52 weeks off		17
	L1			1.51±0.08
	L2			1.47±0.08
	L3			1.43±0.09
	L4			1.39±0.09
	L5			1.39±0.10
	>52 weeks off		4
	L1			1.45±0.05
	L2			1.44±0.04
	L3			1.41±0.03
	L4			1.36±0.04
	L5			1.37±0.06
Claudication
Hamanishi, Matukura, Fujita et al., 1994	Healthy controls age 62±11	Cross-sectional area of the dural tube (mm2)
	L2		6	194±41
	L2/L3		12	169±38
	L3		7	174±46
	L3/L4		13	148±33
	L4		10	165±39
	L4/L5		14	144±35
	L5		10	157±57
	L5/S1		13	139±40
	S1		7	101±57
	Patients with intermittent claudication age 62±12
	L2		13	119±38
	L2/L3		38	104±35
	L3		19	106±52
	L3/L4		41	79±28
	L4		31	96±41
	L4/L5		52	61±28
	L5		29	83±41
	L5/S1		46	59±34
	S1		21	47±38
Uden, Johnsson, Jonsson et al., 1985	Control age 71±7	Sagittal diameter (mm)	11
	L3			18.3±2.8
	L4			15.9±4.1
	L5			16.0±3.3
	Claudication age 68±5		23
	L3			15.6±7.2
	L4			10.8±6.5
	L5			14.0±5.6
Radicular Pain/Sciatica
Hamanishi, Matukura, Fujita et al., 1994	Healthy controls age 42±15	Cross-sectional area of the dural tube (mm2)
	L2		11	213±48
	L2/L3		29	170±39
	L3		16	192±39
	L3/L4		31	157±39
	L4		20	170±43
	L4/L5		36	153±42
	L5		22	153±54
	L5/S1		32	129±55
	S1		15	98±53
	Patients with radicular pain age 45±16
	L2		12	193±58
	L2/L3		35	131±29
	L3		19	166±50
	L3/L4		51	128±40
	L4		45	147±62
	L4/L5		79	116±59
	L5		51	133±54
	L5/S1		75	107±65
	S1		35	91±54
Uden, Johnsson, Jonsson et al., 1985	Control age 71±7	Sagittal diameter (mm)	11
	L3			18.3±2.8
	L4			15.9±4.1
	L5			16.0±3.3
	Sciatic pain age 67±6		33
	L3			18.4±3.3
	L4			14.2±4.5
	L5			14.9±4.3

For the sake of clarity, the measurements used in the meta-analyses are indicated with boldface type.

Many of the relevant studies provided spinal canal measurements at more than one level or in more than one set of units. If a study provided more than one unit of measurement, sagittal diameter was preferentially used in our meta-analyses. Similarly, if a study provided canal size at more than one level, then we used the size at L4 in our meta-analyses. This level was reported by all studies that reported multiple levels and is between L3 and L5, each of which was the only level reported by two studies (Anderson, Adcock, Chovil et al., 1988; Hultman, Saraste, and Ohlsen, 1992). Thus, L4 is the most commonly reported level. If canal measurements were given for more than one patient group, then we used the patient group with the most severe symptoms in our meta-analyses, as long as that patient group included at least 10 patients. For the sake of clarity, the measurements used in the meta-analyses are indicated with boldface type.

Table 7. Summary of Meta-Analysis of Differences in (more...)

Table 7. Summary of Meta-Analysis of Differences in Spinal Canal Diameter Between Patients With and Without Back Pain

Author	Year	Group 1 1 n	Group 2 n	d	Lower CL	Upper CL	p-value	Standardized Residual
Hamanishi, Matukura, Fujita et al., 1994	1994	21	20	−0.468	−1.089	0.153	0.140	0.243
Hultman, Saraste, and Ohlsen, 1992	1992	21	18	−0.443	−1.080	0.194	0.173	0.315
Drinkall, Porter, Hibbert et al., 1984	1984	193	132	−0.524	−0.749	−0.298	<0.0001	0.270
Anderson, Adcock, Chovil et al., 1988	1988	16	33	−0.499	−1.104	0.106	0.106	0.143
Macdonald, Porter, Hibbert et al., 1984	1984	17	16	−1.014	−1.739	−0.289	0.006	−1.321
	Q	p-value of Q		Overall d	Lower CL	Upper CL	p-value of d
	1.82	0.769		−0.541	−0.726	−0.357	<0.0001

1

Group 1 denotes patients with back pain, and Group 2 denotes those without back pain.

Figure 11. Forrest Plot of Differences in Spinal (more...)

   Figure 11. Forrest Plot of Differences in Spinal Canal Diameter in Patients With and Without Back Pain

Figure 11

Figure 12. Overlap of the Distributions of (more...)

   Figure 12. Overlap of the Distributions of Normalized Canal Diameters in Patients With and Without Back Pain

Table 8. Binomial Effect Size Display: Canal Size in (more...)

Table 8. Binomial Effect Size Display: Canal Size in Patients With and Without Back Pain

	Small Canal	"Normal" Canal
No Pain	37	63
Back Pain	63	37

Figure 12

We caution that even the modest effect obtained in our meta-analysis may be an overestimate of the magnitude of the relationship between pain and canal size. This is because the studies in this analysis may not distinguish a congenitally narrow canal from focal narrowing of the canal. It is possible that some of the patients in these studies had focal spinal stenosis. If the spinal canal measurements in these patients were taken at the level of stenosis, this would lead to a smaller mean canal size for that patient group. If patients with back pain are more likely to have stenosis than those without back pain, this would introduce bias toward finding smaller canals in the pain patients. The relationship between stenosis and back pain is discussed in question 3 ("What is the relationship between degree of stenosis and the presence and/or intensity of each of the signs, symptoms, and patient conditions?").

The fact that patients with back pain tend to have small canals does not allow one to conclude that patients with small canals are more prone to have back pain. This is because, as with all case control studies, the authors were forced to artificially set the prevalence of pain during the enrollment of patients into these studies (this artificiality is typically required to ensure there are enough cases and controls in the study to obtain appropriate statistical power). One probable consequence of this is that the proportion of patients in these studies with back pain is probably much higher than it is in the general population. This means that calculations of predictive values or relative risks cannot be performed on these data, which, in turn, means that it is not possible to use these data to determine whether patients with small canals are prone to have back pain.

This caution also applies to the BESD; although it is in the form of a 2 by 2 table, one cannot use the data in it to compute prevalence. This caution concerning the BESD is reinforced by the fact that this display artificially sets the prevalence of pain to be 50 percent.

Table 9. Summary of Meta-Analysis of Differences in (more...)

Table 9. Summary of Meta-Analysis of Differences in Spinal Canal Diameters of Patients With and Without Claudication

Author		Group 1 1 n	Group 2 n	d	Lower CL	Upper CL	p-value	Standardized Residual
Hamanishi, Matukura, Fujita et al., 1994		31	10	−1.669	−2.468	−0.870	0.00004	−1.467
Uden, Johnsson, Jonsson et al., 1985		23	11	−0.850	−1.597	−0.104	0.026	1.467
	Q	p-value of Q		Overall d	Lower CL	Upper CL	p-value of d
	2.15	0.142		−1.232	−1.777	−0.686	0.00001

1

Group 1 denotes patients with claudication, and Group 2 denotes those without claudication.

Figure 13. Forrest Plot of Differences in Spinal (more...)

   Figure 13. Forrest Plot of Differences in Spinal Canal Diameters in Patients With and Without Claudication

Figure 13

Figure 14. Overlap of the Distributions of (more...)

   Figure 14. Overlap of the Distributions of Normalized Canal Measurements in Patients With and Without Claudication

Table 10. Binomial Effect Size Display: Canal Size (more...)

Table 10. Binomial Effect Size Display: Canal Size in Patients With and Without Claudication

	Small Canal	"Normal" Canal
No Claudication	24	76
Claudication	76	24

Figure 14

Similar to the preceding analysis, data on the prevalence of neurogenic claudication are not available. Therefore, these data cannot be used to determine whether canal size predicts the development of claudication.

Examination of these two studies revealed that both had difficulties with experimental designs that would have made the results of a meta-analysis difficult to interpret. In both studies, patients with different symptoms were divided into different mutually exclusive groups. In the study by Hamanashi, 16 of 53 patients with radicular pain also had claudication (Hamanishi, Matukura, Fujita et al., 1994). Some or even many of the patients in the claudication group in the study by Uden may also have had radicular pain. By stratifying patients in this manner, patients with claudication (which, as shown above, is associated with smaller canal diameters) and radicular pain were eliminated from the sciatica groups, leading to bias in favor of the radicular pain groups having larger canals. For this reason, additional studies are necessary to quantify the relationship between canal size and radicular pain.

Relationship Between Patient Age and Symptoms of Spinal Stenosis

Next, we examined the relationship between patient age and symptoms of lumbar stenosis. Due to a lack of extensive research, our approach to determining the relationship between age and symptoms is, by necessity, a narrative review. Epidemiological surveys show that in the United States, low back pain is most prevalent between the ages of 55 and 64 (Deyo and Tsui-Wu, 1987). The proportion of this pain that is due to stenosis is not known. Initial onset of pain is most commonly reported in the second decade and remains high through the fourth decade, after which it declines (Deyo and Tsui-Wu, 1987). Lumbar instability, which correlates with back pain, is significantly higher among patients under the age of 45 (Friberg, 1989).

A 1998 report states that disability as assessed using the Oswestry index (a measure of disability from back pain, a score of 100 meaning the patient is completely disabled) correlates significantly with age among patients with stenosis (Hurri, Slatis, Soini et al., 1998). Patients between the ages of 41 and 55 years had a mean Oswestry index of 29.7, while patients aged 56 and higher had a mean score of 41.3. This index may include other disabilities that may relate to age but not to spinal stenosis.

Relationship Between Patient Sex and Symptoms of Spinal Stenosis

Although the incidence of disk degeneration in men and women is similar (Lawrence, 1969), men tend to have more severe degeneration. The same survey reports an association between extent of lumbar disk degeneration and severity of back, leg, and hip pain and incapacity. Presence of spondylolisthesis was associated with increased likelihood of back pain in women (p = 0.044), but not in men (Virta and Ronnemaa, 1993). A significant interaction was found between spondylolisthesis and sex, suggesting that the association between spondylolisthesis and back pain is sex dependent (Virta and Ronnemaa, 1993). This association is not explained by the slightly greater degree of spondylolisthetic slip found in women in this study.

Relationship Between Presence of a Herniated Disk and Symptoms of Spinal Stenosis

Spinal stenosis is frequently the result of disk degeneration. Herniated disks are also a result of disk degeneration. For this reason, it is not surprising that herniated disks are often found among patients with spinal stenosis. Of the 35 studies retrieved that reported this information, 692 out of 2,327 (29.7 percent) patients treated for lumbar spinal stenosis also had herniated or protruding disks (see Evidence Table 25^*). The range of disk abnormalities among these studies was rather broad; 2.9 percent to 100 percent of stenosis patients also had disk abnormalities (studies that used the presence of herniated disks as part of their inclusion or exclusion criteria were not included in this calculation). While we can conclude that there is an association between herniated disks and spinal stenosis, current data do not permit us to provide a precise estimate of the magnitude of that association or to provide evidence that one causes the other. Narrowing of the spinal canal due to herniated or protruding disks is considered a separate entity from spinal stenosis (Amundsen, Weber, Lilleas et al., 1995) but may contribute to the overall symptomology of the condition.

Summary

Patients with back pain or claudication tend to have narrower spines than asymptomatic patients. This suggests, although it does not prove, that patients with congenitally narrow spines may be more prone to developing symptoms of stenosis, especially back pain and claudication. Increased patient age and the presence of herniated disks may also contribute to the development of back pain and other symptoms of stenosis. The strength of these relationships and the exact ages at which patients are most likely to develop symptoms cannot be determined from the information available. There is some evidence that women with spondylolisthesis are more likely to experience pain than are men.

Relationship Between Nonstenotic Canal Diameter and Development of Focal Spinal Stenosis

Table 11. Spinal Measurements of Patients With Stenosis (more...)

Table 11. Spinal Measurements of Patients With Stenosis and in Control Subjects

Study	Patient description	Units	n	Measurement
Prasartritha, Suntisathaporn, Vathana et al., 1997	Controls with no back pain	Midsagittal diameter (Range includes all spinal levels)	23	Mean 15.67 Range 13.4-17.55
	Patients with stenosis 1		23	Mean 13.88 Range 11.6-16.7
				"Overall" midsagittal diametersignificantly different between the two groups, p<0.05
Kim and Lee, 1995	Healthy controls	L4-5 sagittal diameter, mm	25	20.3±1.8
	Isthmic apondylolisthesis		55	20.3±1.8
	Degenerative spondylolisthesis		48	19.2±1.8
Yoshida, Shima, Taniguchi et al., 1992	Herniated disk patients mean age 20.2	Cross sectional area at the level of the L4-5 facet joint	10	356.7±90.8
	Central stenosis		23	262.8±62.8
	Lateral stenosis		3	302.9±72.4
	Spondylolisthesis		7	223.6±71.4
	Mean age for all stenosis patients 63.8
Schonstrom, Bolender, and Spengler, 1985	Healthy controls	Sagittal diameter of the dural sac, mm
	L2-L3		5	14.6±1.2
	L3-L4		7	13.9±1.6
	L4-L5		10	14.6±1.5
	L5-S1		5	16.4±3.1
	Average		27	14.8±3.1
	Patients with surgically confirmed central stenosis 2		24	9.1±3.3, range 4.7-19.0
	Healthy controls	Transverse area of the dural sac, mm 2
	L2-L3		5	177±31
	L3-L4		7	176±53
	L4-L5		10	171±38
	L5-S1		5	193±73
	Average		27	178±50
	Patients with surgically confirmed central stenosisb		24	89.6±35.1, range 35-163

1

Symptomatic stenosis was defined as a clinical entity including back pain, intermittent claudication, sensory parasthesia, and weakness in the lower extremities. It is unclear whether all patients had all symptoms. All 23 patients had surgery for stenosis. Imaging criteria, if any, was not stated.

2

Seven stenotic patients were described as stenotic when in fact they had a protruding disk. Ten additional patients were excluded because no scans were available. N indicates number of measurements at different lumbar levels, not number of patients. There were 13 control subjects and 24 patients with stenosis.

Numbers used to calculate effect sizes appear in bold type.

Table 12. Summary of Meta-Analysis of Differences in (more...)

Table 12. Summary of Meta-Analysis of Differences in Canal Diameter Between Patients With and Without Stenosis

Author	Year	Group 1 1 n	Group 2 n	d	Lower CL	Upper CL	p-value	Standardized Residual
Prasartritha, Suntisathaporn, Vathana et al., 1997	1997	23	23	−0.587	−1.177	0.003	0.051	0.045
Kim and Lee, 1995	1995	48	25	−0.605	−1.098	−0.111	0.016	−0.045
	Q	p-value of Q	Overall d	Lower CL	Upper CL	p-value of d
	0.002	0.964	−0.597	−0.976	−0.219	0.002

1

Group 1 denotes patients with stenosis, and Group 2 denotes those without stenosis.

The 1995 study by Kim and Lee had two groups of patients with spondylolisthesis. Because isthmic spondylolisthesis is outside the scope of this assessment, the spinal measurements of patients with degenerative spondylolisthesis were used (Kim and Lee, 1995).

Prasartritha et al. (1997) did not provide a measure of dispersion among measurements of sagittal diameter (Prasartritha, Suntisathaporn, Vathana et al., 1997). Because of this, an exact effect size cannot be calculated. However, the report stated that the mean canal size was significantly different (p <0.05) between groups by t-test. Because the number of patients in each group was known, we were able to calculate the value of Student's t, assuming a p-value of 0.049. This translates to an effect size of at least −0.587. If the actual p-value was smaller (as it may well be), Student's t, and therefore Hedges' d, would be larger. The overall effect size calculated here is therefore a minimum value. How much further it may actually be from zero cannot be determined from the data provided.

Figure 15. Forrest Plot of Differences in Spinal (more...)

   Figure 15. Forrest Plot of Differences in Spinal Canal Between Patients With and Without Spinal Stenosis

Figure 15

When data from all groups were combined, the test of heterogeneity was not statistically significant (Q = 0.002, p = 0.964, standardized residuals = ±0.045), and the summary statistic, −0.597, was statistically significant (p = 0.002).

Figure 16. Overlap between Normalized Canal (more...)

   Figure 16. Overlap between Normalized Canal Measurements in Patients With and Without Stenosis

Table 13. Binomial Effect Size Display: Canal Size (more...)

Table 13. Binomial Effect Size Display: Canal Size in Patients With and Without Stenosis

	Small Canal	"Normal" Canal
No Stenosis	36	64
Stenosis	64	36

Figure 16

Relationship Between Nonstenotic Canal Cross-Sectional Area and Development of Focal Spinal Stenosis

Besides canal diameter, other aspects of the spinal canal may make an individual patient more prone to develop spinal stenosis. A well-documented anatomical variation known as the trefoil-shaped canal may predispose the patient to problems associated with lateral stenosis (Epstein, Epstein, and Lavine, 1962; Schatzker and Pennal, 1968). This variation is characterized by a smaller sagittal diameter and deeper lateral recesses. The association between trefoil canal and spinal stenosis may be merely coincidental (Eisenstein, 1980). A study of trefoil canal in South African skeletons found that while stenosis and trefoil canal may coexist in the same skeleton, they are often present at different vertebrae. Other attempts have been made to identify spinal characteristics that are predictive of future stenosis (MacGibbon and Farfan, 1979). No information is available quantifying the accuracy of these predictions.

Relationship Between Patient Age and Development of Focal Spinal Stenosis

Disk degeneration, spinal instability, and hypertrophy of the facet joints accompany the aging process (Prescher, 1998; Twomey and Taylor, 1988). Degeneration normally begins in the second decade (Mirkovic, Garfin, Rydevik et al., 1992), and its prevalence increases with age (Powell, Wilson, Szypryt et al., 1986). By the age of 40 years, 80 percent of male and 65 percent of female disks are moderately degenerated (Mirkovic, Garfin, Rydevik et al., 1992). Increasing age also correlates with increasing spinal osteoarthritis (Magora and Schwartz, 1978). While increased disk degeneration and spinal osteoarthritis implies increased stenosis, this has not been specifically demonstrated.

A 1988 study of cadavers found a decline in lumbar spinal canal anterior-posterior diameter with age that is significant in males (t = 3.95, df = 4, p <0.01) but not in females (Twomey and Taylor, 1988). This study looked at lumbar spines of men and women age 25 to35 and > 65. Our meta-analyses indicate an association between canal size and back pain, claudication, and stenosis. A narrower spinal canal may render the patient more vulnerable to developing symptomatic stenosis in cases of minor additional trauma or pathology (Clark, 1969; Twomey and Taylor, 1988). The narrowing of the canal with age may therefore contribute to the development of symptomatic stenosis.

There is a correlation between presence of calcium deposits and decreased elastic/collagenous fiber ratio in the ligamentum flavum and age among patients with degenerative stenosis (Schrader, Grob, Rahn et al., 1999). Patients under the age of 60 had 0.032 percent calcification, while patients between the ages of 70 and 75 had 0.336 percent calcification. This correlation was statistically significant (p <0.05) by the Mann-Whitney-Wilcoxon test. Few patients without degenerative stenosis had these changes. No correlation was reported between degree of change and degree of stenosis or symptoms.

Relationship Between Patient Weight and Development of Focal Spinal Stenosis

A 1976 survey indicates that increased weight correlates with increased incidence of spinal osteoarthritis (Magora and Schwartz, 1978). Only 53 percent of slim patients (weight in kg less than height in cm minus 110) had spinal osteoarthritis, compared to 59 percent of average patients (weight in kg equal to height in cm minus 90-110), 69 percent of heavy patients (weight in kg equal to height in cm minus 80 to 90) and 94 percent of very heavy patients (weight in kg more than height in cm minus 80). Overweight patients may also be more likely to have disk degeneration than normal patients (Parkkola, Rytokoski, and Kormano, 1993). A 1991 survey stated that body mass index is a predictor of disk degeneration according to univariate and multivariate analyses, but did not provide a description of the statistical analysis utilized to reach this conclusion (Symmons, van Hemert, Vandenbroucke et al., 1991). The clinical significance of these findings is unclear. Disk degeneration is a common precursor to stenosis, but it occurs in all patients to some extent, and does not inevitably lead to stenosis. No direct evidence in support of a link between body weight and development of stenosis is available.

Relationship Between Osteoarthritis and Development of Focal Spinal Stenosis

Among patients with severe osteoarthritis of one or both hips, there may be an increased frequency of moderate or severe degenerative changes as noted on radiographs in the lumbar spine. Among patients aged 40 to 59, 36 percent of patients with osteoarthritis of the hips had such changes, compared to only 4 percent of control patients matched for age, sex, and occupation. Among patients aged 60 to 69, 53 percent of those with osteoarthritis had moderate or severe degenerative changes of the lumbar spine, compared to 27 percent of matched control patients (Brewerton, 1983). No mention was made of presence or absence of stenosis or back pain, claudication, or other symptoms. In the seven studies giving this information, 42 out of 903 (4.7 percent) patients with lumbar spinal stenosis had osteoarthritis or other hip disease (see Evidence Table 25). Underreporting of this important comorbidity restricts our ability to determine its prevalence or clinical relevance. Whether hip and spine problems are both parts of a larger disease or whether mechanical changes resulting from hip disease lead to spinal degeneration is not known.

Relationship Between Diabetes and Development of Focal Spinal Stenosis

Although some skeletal defects may be more prevalent among patients with diabetes than in the general population, we were unable to locate any evidence on whether patients with diabetes are more prone to developing lumbar spinal stenosis. A cross-sectional epidemiological study published in 1994 found no significant difference in the prevalence of spondylolisthesis between diabetic and nondiabetic adults (Virta, Ronnemaa, and Laakso, 1994).

Relationship Between Type of Patient Employment and Development of Focal Spinal Stenosis

A 1993 report found no correlation (r= 0.07, n = 46) between work index (0-8 scale based on amount of lifting required in four categories of motion) and degree of spondylolisthesis (Virta and Ronnemaa, 1993). No numerical data were provided in support of this statement. In contrast, Lawrence found that coal miners and men doing outdoor or heavy manual work had earlier and greater degrees of disk degeneration than did business, professional or textile workers (Lawrence, 1969). Fifty percent of miners and 40 percent of outdoor workers aged 35-44 had disk degeneration of grade 2 or higher, compared to 14 percent of business and professional workers. Total incidence of disk degeneration for all age groups was significantly lower (p <0.01) in business, professional, and textile workers than in industrial, manual, trade, and outdoor workers or miners. The statistical test used was not stated. No such differences were found in women. Extent of degeneration as indicated by height of the intervertebral space (p = 0.003, n = 46) is associated with a greater degree of spondylolisthetic slip (Virta and Ronnemaa, 1993).

Summary

Patients with spinal stenosis tend to have narrower spines than asymptomatic patients. This suggests, although it does not prove, that patients with congenitally narrow spines may be more prone to developing focal stenosis. The shape of the patients' spinal canal may also contribute to the development of focal narrowing of the canal and symptomatic stenosis, but the evidence for this is weak. There is some evidence that disk degeneration, narrowing of the spinal canal, and degenerative changes in the spinal ligaments contributing to stenosis and instability increase with age. However, the strength of this relationship and the age at which stenosis is most likely to occur cannot be determined from the available information.

Heavier patients may be more likely to develop the degenerative changes leading to stenosis. Similarly, patients with osteoarthritis of the hips as well as patients who perform heavy labor tend to have more disk degeneration than other patients. While these data suggest a relationship between these characteristics and the development of stenosis, there is no direct evidence of a causal relationship. We located no evidence indicating a relationship between diabetes and spinal stenosis, and we located a single study giving evidence against the existence of such a link.

Relationship Between Degree of Stenosis and Back Pain

Three studies note a lack of association between degree of stenosis and back pain (Amundsen, Weber, Lilleas et al., 1995; Friberg, 1989; Virta and Ronnemaa, 1993). In two cases, no data were presented in support of this observation. The third study is discussed below.

This 1993 study found that presence of spondylolisthesis was associated with increased likelihood of back pain in women (p = 0.044), but not in men (Virta and Ronnemaa, 1993). Degree of slip was associated with extent of disk degeneration, but not with pain intensity (r= 0.14 in all subjects, r = 0.20 in symptomatic subjects) (Virta and Ronnemaa, 1993).

Table 14. Relationship Between Back Pain and Spondylolisthesis (more...)

Table 14. Relationship Between Back Pain and Spondylolisthesis

Study	Patients	n	Degree of Maximal Slip (mm)	Translatory Instability (mm)
Friberg, 1989	Symptomatic (back pain)	50	7.6±3.7	6.7±3.7
	Asymptomatic	29	8.1±5.7	1.9±2.0

Relationship Between Degree of Stenosis and Leg Pain

A study of clinical and radiological features of stenosis reported that bilateral leg pain is slightly more frequent among patients with central stenosis than in those with lateral stenosis (Amundsen, Weber, Lilleas et al., 1995), but the study presented no data or statistical analysis of this observation.

Relationship Between Degree of Stenosis and Neurogenic Claudication

A 1991 report observed that claudication is associated with severe stenosis of the entire canal (Postacchini and Perugia, 1991). No data were presented to support this observation. Claudication may be more common with spondylolisthesis of the L4 vertebra than the L5. Again, no data were provided in support of this observation (Postacchini and Perugia, 1991).

Relationship Between Degree of Stenosis and Reduced Physical Function and Activities of Daily Living

A 1998 report states that disability as assessed using the Oswestry index (a measure of disability from back pain; a score of 100 means the patient is completely disabled) correlates significantly with severity of stenosis (Hurri, Slatis, Soini et al., 1998). Patients with moderate stenosis had a mean Oswestry index of 28.0, while patients with severe stenosis had a mean score of 39.0.

Relationship Between Degree of Stenosis and Disability and Dependency

A 1993 study reported that use of medical facilities and likelihood of receiving a disability pension were no different for men or women with or without spondylolisthesis (Virta and Ronnemaa, 1993). Disabling back symptoms necessitating bed rest at the expense of work or hobby activity were more commonly reported in men without spondylolisthesis (70 percent) than in men with spondylolisthesis (38 percent; p = 0.026) (Virta and Ronnemaa, 1993). No information was provided on the presence of other back problems in the control subjects.

Relationship Between Multilevel Stenosis and Symptoms

A 1992 study reported that neurogenic claudication was generally associated with at least two levels of stenosis (Porter and Ward, 1992). In this study, 49 patients with neurogenic claudication were examined by myelography and CT and found to have stenosis in the central and/or root canal. Average patient age was 58.8 years (SD of 8.1). L4-5 was the level most commonly affected by central stenosis. Thirty-nine patients (80 percent) had multilevel central canal stenosis. Root canal stenosis was found in 37 patients. In all, 94 percent of patients had either a two-level or multilevel central stenosis or a one-level central stenosis and associated root canal stenosis. The authors concluded that neurogenic claudication is uncommon in the absence of multilevel stenosis.

Figure 17. Association Between Percentage of (more...)

   Figure 17. Association Between Percentage of Patients Reporting Neurogenic Claudication and the Mean Number of Stenotic Levels

The data for this figure were taken from 49 separate patient groups reported in 39 clinical studies. Data on the mean number of stenotic levels are contained in Evidence Table 10, and data on the number of patients with neurogenic claudication are contained in Evidence Table 11.

Figure 17

Summary

Very little evidence exists correlating degree of narrowing of the lumbar spine with the presence or severity of the signs, symptoms, or conditions associated with stenosis. Difficulties associated with finding such correlations include the presence of large numbers of patients with spinal narrowing and no symptoms; variations in canal size throughout the population; and lack of an accepted system for quantifying the degree of narrowing. Many asymptomatic patients have been shown to have stenosis or spondylolisthesis upon diagnostic imaging. Lumbar spinal stenosis is a condition that includes both a focally narrowed spinal canal and the associated symptoms. The extent of narrowing is also likely to change with the posture of the patient. Extension significantly decreases the canal area, whereas flexion has the opposite effect (Inufusa, An, Lim et al., 1996; Willen, Danielson, Gaulitz et al., 1997). Therefore, a static image of the canal dimension may not be predictive of a patient's symptoms. In current clinical practice, the course of treatment depends on the severity of the symptoms, not on the degree of narrowing.

Two studies have provided numerical evidence of a lack of association between severity of stenosis or spondylolisthesis and severity of back pain. There was, however, some evidence of a relationship between degree of spinal instability and back pain. Another study found that among patients with symptomatic stenosis, those with more severe stenosis tended to have more disability. However, other studies have indicated that patients with spondylolisthesis make the same use of medical resources and miss less work due to back pain than patients without spondylolisthesis. While neurogenic claudication is believed to be associated with more severe stenosis, we located no numerical evidence in support of this hypothesis.

Quality of the Diagnostic Studies

Diagnostic Imaging Studies

Table 15. Excluded Diagnostic Imaging Studies

Table 15. Excluded Diagnostic Imaging Studies

Authors and year	Year	Reason for exclusion
Berlemann, Jeszenszky, Buhler et al., 1999	1999	No diagnostic data
Maher and Henderson, 1999	1999	Fewer than 10 patients
Kuroki, Tajima, Hirakawa et al., 1998	1998	No diagnostic data
Rankine, Gill, Hutchinson et al., 1998	1998	Primarily disk disease
Zwarts, 1998	1998	Test not used in routine practice
Carragee and Kim, 1997	1997	No spinal stenosis patients
De Haan and Eward, 1997	1997	Published as abstract only
Vergauwen, Parizel, van Breusegem et al., 1997	1997	No diagnostic data
Carey and Garrett, 1996	1996	Acute disease
Elkayam, Avrahami, and Yaron, 1996	1996	No diagnostic data
Healy, Healy, Wong et al., 1996	1996	Asymptomatic patients
Jarvik, Deyo, and Koepsell, 1996	1996	Study incomplete
Khandelwal, Takhtani, Malik et al., 1996	1996	No diagnostic data
Dullerud and Johansen, 1995	1995	Examined only disks
Modic, Ross, Obuchowski et al., 1995	1995	Acute disease
Videman, Battie, Gill et al., 1995	1995	Asymptomatic patients
Simmons and Simmons, 1992	1994	Postsurgery
Gunzburg, Servais, and Verhas, 1994	1994	Acute disease
Lusins, Elting, Cicoria et al., 1994	1994	No control group
Tallroth, Ylikoski, Landtman et al., 1994	1994	No diagnostic data
Wood, Popp, Transfeldt et al., 1994	1994	No diagnostic data
Djukic, Vahlensieck, Resendes et al., 1992	1993	Postsurgery
Jinkins, 1993	1993	Fewer than 10 patients
Pai, 1993	1993	No diagnostic data
Antti-Poika, Soini, Tallroth et al., 1990	1990	Examined only disks
Boden, Davis, Dina et al., 1990	1990	Asymptomatic patients
Stanley, McLaren, Euinton et al., 1990	1990	Postsurgery
Stockley, Getty, Dixon et al., 1988	1989	Postsurgery
Deyo, Diehl, and Rosenthal, 1987	1987	No diagnostic data
Waddell, 1987	1987	Disk prolapse only
Downing, Schnitzlein, Clarke et al., 1986	1986	Technically suboptimal
Morris, Di Paola, Vallance et al., 1986	1986	Disk prolapse only
Osborn and Knight, 1986	1986	Postsurgery
McCutcheon and Thompson, 1986	1985	Acute disease
Tait, Charlesworth, and Lemon, 1985	1985	No spinal imaging
Firooznia, Benjamin, Kricheff II et al., 1984	1984	Examined only disks
Frymoyer, Newberg, Pope et al., 1984	1984	Asymptomatic patients
Hindmarsh, Ekholm, Kido et al., 1984	1984	No diagnostic data
Wiesel, Tsourmas, Feffer et al., 1984	1984	Asymptomatic patients
Crouzet, Vasdev, and Chirossel, 1983	1983	No diagnostic data
Gehweiler and Daffner, 1983	1983	Acute disease
Omojola, Vas, and Banna, 1981	1983	Obsolete methods
Postacchini and Pezzeri, 1981	1981	Obsolete equipment
Postacchini, Pezzeri, Montanaro et al., 1980b	1981	Obsolete equipment
Scafuri and Weinstein, 1981	1981	Obsolete equipment
Sandhu, Lakhanpal, and Gupta, 1976	1976	No diagnostic data
Torgerson and Dotter, 1976	1976	Acute disease

Note: Some articles could be excluded on multiple grounds; only one of those grounds for each article is listed in the table.

We begin our discussion of the validity of diagnostic imaging studies by first describing the reasons for excluding studies from our analysis. We retrieved 52 articles that were described as diagnostic imaging studies. Each of them was reviewed to see if they contained any evidence relevant to questions 4 or 7. Most of these articles (45) had to be excluded from our analysis. These excluded articles, and the reasons for their exclusion, are shown in Table 15. Note that some of the excluded articles met more than one criterion for exclusion, but only one criterion is shown in the table. Therefore, the proportion of articles excluded for a specific reason will underestimate the number of articles that actually have that particular flaw.

The most frequent reason for exclusion was a lack of diagnostic data in the article. This lack of data typically arose because it was the intention of the article to provide a description of the imaging of spinal stenosis and related conditions. Thus, while such articles might report the percentage of images that exhibited a particular feature, no relationship between these features and the patient's diagnosis would be made. These articles are as much tutorials as they are evaluations of the effectiveness of the technology. Typically, they show images that demonstrate normal and abnormal patients, show the features by which a diagnosis can be made, and show examples of how one modality can demonstrate an abnormality while another does not. These examples of cases diagnosed by one modality but not by another do not provide valid evidence on the effectiveness of either modality. There is no guarantee that the cases presented in the article are a representative sample of all cases encountered in clinical practice.

Another common reason for study exclusion was a lack of data on spinal characteristics. Several trials reported only imaging findings related to the intervertebral disks. Other studies were excluded because of the patient populations they studied: some studied asymptomatic patients, some studied patients who had already had back surgery, and some studied few (five or less) or no patients with spinal stenosis.

Table 16. Diagnostic Trials Meeting Preliminary Inclusion Criteria (more...)

Table 16. Diagnostic Trials Meeting Preliminary Inclusion Criteria

Authors and year	Imaging results reported	Signs and symptoms	Clinical results
Eberhardt, Hollenbach, Tomandl et al., 1997	Degree of stenosis (myelogram and MRI)	None	None
Muto, De Maria, Izzo et al., 1997	Size of spinal canal (CT, MRI in selected cases)	None	None
Ramsbacher, Schilling, Wolf et al., 1997	No quantitative data reported	None	None
Wood, Popp, Transfeldt et al., 1994	Amount of intervertebral motion	None	None
Phillips, Howe, Bustin et al., 1990	Abnormal or normal spinal motion	Physical exam findings	None
Modic, Masaryk, Boumphrey et al., 1986	Presence or absence of stenosis (MRI, CT, myelography)	None	Surgical findings
Bell, Rothman, Booth et al., 1984	Presence or absence of stenosis (CT, myelography)	None	Surgical findings

Seven articles (see Table 16) remained from this group after the preliminary inclusion/exclusion criteria were applied, but passing these criteria did not mean that valid conclusions could be drawn from the data in those articles. The studies are discussed in detail and the data is analyzed elsewhere in the report in specific sections pertaining to validation of the imaging modalities and to clinical questions 4 (Can clinical signs and symptoms predict imaging results?) and 7 (Can imaging results predict surgical results?).

Validation of Imaging Results

In the preceding two sections, we discussed how we arrived at the set of studies used to evaluate whether the relevant diagnostic modalities produced accurate measurements of spinal stenosis. In this subsection, we now consider those data. Because imaging findings are usually considered a reference standard for diagnostic tests in published studies of spinal stenosis, validation of the results of available studies is difficult. This is because validation requires an independent reference standard to which one can compare the imaging results. The only reference standard that would meet this criterion would be physical confirmation of stenosis during surgery.

Six trials report just such a comparison. Ramsbacher et al. (1997) compared MRI results to surgical findings. They determined that "the results of MRM [MR myelography] were identical to those of conventional myelography and corresponded to the surgical findings." However, this report provides no explanation of which imaging and surgical findings were compared: specific measurements of the spine and spinal canal, localization of abnormal disks, or the differential diagnosis between spinal stenosis and other conditions. Furthermore, there are no data presented in the paper to allow us to confirm the authors' conclusions. Although the authors intended to measure sensitivity and specificity of MRI in this study, we cannot use this trial to assess the efficacy of MRI (Ramsbacher, Schilling, Wolf et al., 1997).

The same difficulties affect the article by Muto et al. (1997). These investigators sought to evaluate the sensitivity and specificity of both CT and MRI, and found that CT evaluated the size of the spinal canal "perfectly." However, they do not report what reference standard they used, whether it was surgery, myelography, or some other test. Therefore, we cannot use this trial to validate CT or MRI. Furthermore, this study also has a patient selection bias affecting the MRI results. Only patients with polyradiculopathy or with imaging findings (modality not specified) that disagreed with the preliminary clinical diagnosis were referred for MRI, so the MRI results reflect only difficult cases, not a representative sample of all cases. Therefore, the sensitivity and specificity of MRI would be underestimated by any calculations performed on this data. The article includes examples of selected cases that were correctly or incorrectly diagnosed by CT and MRI, but we are not certain that these cases are a representative sample (Muto, De Maria, Izzo et al., 1997).

An early study validating MRI of the lumbar spine was reported by Modic et al. (1986). The study design was not subject to the difficulties of the other studies, surgical results to use as an independent reference standard were available for most patients (note that no quantitative definition was given for spinal stenosis), but the MR scanner used is now obsolete and technically inferior to scanners in routine use today. Gradient-echo techniques, now considered standard practice, were not available when Modic et al.'s patients were studied. Therefore, results from this study should be considered minimum levels of sensitivity for MRI. Calculation of specificity from the published results is not possible because no negative results were found on surgery. In this series, MRI alone detected 23 of 30 vertebral levels with spinal stenosis (sensitivity = 77 percent), while CT alone (combining studies done with and without contrast material) detected 19 of 24 stenoses (sensitivity = 79 percent), and myelography alone detected 13 of 24 stenoses (sensitivity = 54 percent). When results of both imaging examinations were used together, MRI and CT detected 23 of 24 stenoses (sensitivity = 96 percent) (Modic, Masaryk, Boumphrey et al., 1986).

Relatively current MRI techniques were used by Eberhardt et al. (1997). All 80 patients in their study underwent surgery, but the definition of stenosis used in the surgical reference standard was not reported. Nerve root compression appears to be their diagnostic criterion. There is a discrepancy in the percentages reported by Eberhardt et al. (1997) for the sensitivity of MRI in diagnosing stenosis. For diagnosing severe stenosis, they report 95 percent sensitivity, but with 50 cases of stenosis, this percentage is not possible. This percentage is also inconsistent with the percentage obtained from subtracting results for mild stenosis from results in all stenoses. To take a conservative approach to computing the sensitivity of MRI, we will assume the lower figure (the figure we calculated by subtraction) is correct. Making this assumption, the sensitivity was 100 percent for both x-ray myelography and MRI in diagnosing mild stenosis. For severe stenosis, we found the sensitivity of MRI was 88 percent and the sensitivity of myelography was 72 percent (Eberhardt, Hollenbach, Tomandl et al., 1997).

Validation of CT and myelography was the objective of a study reported by Bell et al. (1984). Their multicenter study compared imaging results to surgical findings. Details of the CT methods were not reported, other than the fact that they did not use contrast agents, so we cannot determine whether the CT scanners used in this study (reported in 1984) are now obsolete. However, these data are nearly 20 years old, and technical improvements have been made in CT scanners, so it is reasonable to assume now that current scanners are more effective in diagnosing spinal stenosis (Bell, Rothman, Booth et al., 1984).

Rather than expressing their findings as quantitative results for stenosis measurement and differential diagnosis, Bell et al. (1984) used descriptive words, "strong," "firm," and "weak," to describe the agreement between test results and surgical findings. For purposes of this evidence report, we will only consider "strong" agreements to be correct diagnoses. This requires both a correct diagnosis of the vertebra as normal or abnormal, and a correct differential diagnosis between disk herniation and spinal stenosis (or both). Based on these data, we calculated that the CT scan made both diagnoses correctly in 55 of 76 cases of disk herniation (72 percent) and 62 of 93 cases of spinal stenosis (67 percent). The myelogram made both diagnoses correctly in 63 of 72 disk herniation cases (83 percent) and 63 of 93 spinal stenosis cases (68 percent). The myelogram correctly diagnosed the presence of disk herniation a significantly greater percentage of the time (p <0.005, McNemar test), but the two modalities were not significantly different for diagnosing spinal stenosis. Unfortunately, the categories used by Bell et al. (1984) do not allow one to distinguish between false positive and false negative results, so their data cannot be expressed as sensitivity and specificity.

While the study by Young et al. (1988) was primarily a report on a new surgical procedure, it did include data validating myelography results by comparison to surgical findings. According to the myelograms, there were 70 stenosed vertebrae in the 32 patients in this series. However, six additional levels of stenosis were found at surgery. Assuming the surgical results to be the reference standard, this means that the sensitivity of myelography was 92 percent. Only seven patients in this study were imaged by CT, and the CT results were not reported (Young, Veerapen, and O'Laoire, 1988).

Summary

All of the clinical trials that report data validating MRI, CT, or myelography for diagnosis of spinal stenosis had one or more flaws in design or reporting that adversely affected the reliability or applicability of the results. Each of the five trials that studied CT or MRI found that the sensitivity of the cross-sectional modality is equal to or better than the sensitivity of myelography. None concluded that myelography was superior to the cross-sectional modalities. None of the trials attempted to validate the quantitative measurements of the spinal canal made by any imaging modality.

Signs, Symptoms, Patient History, and Physical and the Results of Imaging Exams

In this section, we address the fourth key question of this evidence report, "What is the relationship between the signs and symptoms and other features of the patient history and physical and the results of the imaging examination?" In considering our discussion of this question, it is important to bear in mind the conclusion of the previous subsection: there is little evidence that proves how well the modalities used to image spinal stenosis perform.

In answer to this fourth key question, we assess evidence related to whether there is a relationship between patient signs and symptoms the findings of the imaging examination. If such relationships exist, it may be possible to expedite proper diagnosis and treatment of the condition. The evidence base for this question consists of seven trials that retrospectively reported the number of patients with and without a few signs and symptoms among groups of patients with moderate or severe stenosis. In all of these trials, difficulties with patient selection and confounding variables, including disk herniation, could cause apparent associations between clinical signs and symptoms and imaging results in clinical trials. Therefore, trials of better quality are needed to adequately address this question. Nevertheless, currently available data do exhibit some patterns.

Only one of these trials was a diagnostic trial. Phillips et al. reported a study of "stress x-rays" (radiographs taken with the patient bending one way or another) (Phillips, Howe, Bustin et al., 1990). Angles between vertebrae were measured, and motion of the spine during these movements was described as normal or abnormal by the person reading the images. The investigators tried to correlate these descriptions with clinical information such as age, sex, previous history of injury or surgery, participation in sports, and discomfort. No statistically or clinically significant correlation was found with these variables or with physical exam findings like range of motion and palpation results. The authors conclude that the value of these x-rays is questionable. Accordingly, no other published studies report using this technique.

The remaining trials answering the present question were surgical trials that additionally reported imaging results. Sato and Kikuchi (1997) sought to determine whether there was a relationship between the number of stenosed levels and patients' symptoms. To accomplish this, they stratified their report of patients' symptoms by the number of vertebral levels where stenosis was found by myelography. Rates of radicular pain were the same in the two groups: 82 percent (23/28) of the patients with two stenosed levels and 83 percent (44/53) of the patients with one stenosed level. Cauda equina symptoms were present in 75 percent (21/28) of patients with stenosis at two levels but were present in only 53 percent (28/53) of patients with stenosis at one level. According to tests performed by the authors, this difference was not statistically significant (Sato and Kikuchi, 1997).

Rompe et al. (1995) studied the frequency of 13 different symptoms and patient characteristics among patients found to have absolute stenosis (AP diameter of spinal canal 10.0 mm or less as measured by CT) and relative stenosis (diameter 10.1 to 12.0 mm). Statistical tests performed by the authors found that rates of most of these characteristics were not significantly different between absolute and relative groups. Only ankle reflex differed significantly, with 72 percent of the absolute stenosis group having decreased reflex response, and 13 percent of the relative stenosis group having it. The ability of reflex abnormality to predict degree of stenosis was not discussed by the authors, nor is it examined in any other clinical trial (Rompe, Eysel, Hopf et al., 1995).

A pair of studies by Johnsson et al. (1981) compared the rates of major symptoms among patients with different degrees of stenosis. Their article included five patients with normal myelogram results and divided the abnormal results into complete block (n = 7) and partial block (n = 15) of the spinal canal. Our statistical calculations found no significant difference in degree of stenosis between patients with claudication and those with back and leg pain without claudication (χ² = 0.277, df = 2, p = 0.87) (Johnsson, Willner, and Pettersson, 1981).

The report by the same group (Johnsson, Uden, and Rosen, 1991) appears to include the patients included in the earlier report, along with subsequent surgical patients, as well as a group of patients who were not operated on. Symptoms were categorized as claudication and radiculopathy. Patients who underwent surgery were categorized as having complete stenosis (n = 14) or moderate stenosis (n = 30). The "not operated" group (n = 19) may have included some patients without stenosis, but it also included patients with stenosis who either refused surgery or were considered unacceptable surgical candidates. As in the previous study, we found no significant differences in the proportion in each stenosis group between the two symptom groups in this report (χ² = 0.398, df = 2, p = 0.82).

Verbiest's case series (Verbiest, 1977) reported measurements of the lumbar canal made during surgery. Therefore, using this data to answer the present question requires one to assume that the presurgical imaging findings accurately determine the degree of stenosis. Verbiest categorized the spinal findings as "absolute stenosis" (spinal canals with diameters of 10 mm or less), "relative stenosis" (spinal canal diameters between 10 and 12 mm), and "mixed stenosis" (some narrowed portions 10 mm or less and some between 10 and 12 mm). To analyze these results, we pooled the "absolute" and "mixed" groups, so that all patients with any spinal measurement of 10 mm or less would be in this severe stenosis group, and all spinal measurements in the patients in the mild stenosis group would be greater than 10 mm. These findings may be confounded by disk herniation. Most of the patients in the group with mild stenosis had disk herniation (29/32: 91 percent), while less than half the patients with severe stenosis had disk herniation (33/84: 39 percent, p <0.001, Fisher's exact test, as per our calculation). Therefore, we computed the correlation between the reported symptoms and the anatomic findings. Sciatica was significantly correlated with disk herniation (r = 0.143, p = 0.027) but not correlated with stenosis (r = 0.000, both calculations performed by us). While the correlation of sciatica with disk herniation was statistically significant, the correlation coefficient was relatively low, so it may have limited clinical significance. We found that sciatica was significantly correlated with disk herniation (r = 0.219, p = 0.004), but the correlation with stenosis was not statistically significant (r = −0.076, p = 0.095). Data for the correlation between intermittent claudication and disk herniation was not reported by Verbiest, so we cannot determine whether claudication correlates more with disk herniation or with stenosis. From this analysis, we can conclude that symptoms like sciatica and lumbago are not predictive of stenosis.

Summary

Clinical signs and symptoms do not appear to predict whether the results of imaging tests will show severe stenosis. The major symptoms of radiculopathy and cauda equina do not predict degree of stenosis. Lumbago and sciatica are significantly associated with disk herniation but not with stenosis. However, no trial that was relevant to the present question was prospective in design, and results of some of the trials are difficult to interpret because some patients had disk herniation. Therefore, a conclusive answer to this question awaits the results of trials of better design.

Factors That Could Potentially Predict the Success of Conservative Treatment

This part of the analysis addresses whether there are any signs or symptoms that predict the outcome of conservative treatment. Does the initial status among patients have a prognostic before receiving conservative treatment? To answer this question within a single study, there must be individual patient data on the initial signs and symptoms and the outcome of conservative treatment. Alternatively, the outcome must be stratified according to initial status. For these reasons, our inclusion criteria for this question were any trial with a conservative treatment arm that had either individual patient data for initial status and their final outcome or that stratified final outcome by initial status.

We examined every study that had a conservative treatment series, either as a control arm or as a single series. We identified one study that provided individual patient data for treadmill walking distance at the start of conservative treatment and after three months (Eskola, Pohjolainen, Alaranta et al., 1992). We also found one study that stratified patients according to outcome of conservative treatment (improved, same, worse) and reported the mean AP canal diameter for each group before treatment (Johnsson, Uden, and Rosen, 1992). We also located two recent publications that addressed this issue.

Eskola et al. (1992) provided plots portraying individual patient treadmill walking distances before conservative treatment and after three months. This trial had parallel arms, one of which received placebo, and one which received calcitonin. During the 3 month period for which individual patient data was reported, the calcitonin had a nonsignificant effect on treadmill walking distance (we calculated for t-test of difference: p = 0.23; t-test on ratio: p = 0.55). Therefore, we combined the arms to approximate a single series of 38 patients that received conservative treatment. This trial also provided individual patient data for resting pain; however, this is not a major factor in spinal stenosis. Furthermore, the calcitonin treatment had a significant effect in preventing resting pain in those who had it, and so the treatment groups could not be combined, greatly limiting the statistical power for our purposes. Therefore, we did not analyze this outcome (Eskola, Pohjolainen, Alaranta et al., 1992).

Figure 18. Initial vs. Final Walking Distance (more...)

   Figure 18. Initial vs. Final Walking Distance Computed from Eskola, Pohjolainen, Alaranta et al., 1992

Table 18. Regression Analysis of Treadmill Walking (more...)

Table 18. Regression Analysis of Treadmill Walking Distance Before and After Three Months of Conservative Treatment

Comparison	Correlation Coefficient	P-value
Initial distance vs. final distance (Figure 18)	0.92	<0.001
Initial distance vs. difference (Figure 19)	0.47	0.003
Initial distance vs. ratio (Figure 20)	−0.12	0.48

Calculated by us from Figure 6 in Eskola, Pohjolainen, Alaranta et al., 1992.

Figure 18

The second phenomenon observed in this analysis is that patients with poorer half in terms of initial status were more likely to stay the same or become worse (to be on or below the diagonal) than patients with more favorable half initially. For the half of the patients with the worst initial walking ability (below 520 m), 4 of 18 points were below the diagonal, and 8 of 18 points were on the line, for a total of 12 of 18 points. For the group with more favorable initial status, 2 of 18 points were below the line, and 4 of 18 points were on the line, for a total of 6 of 18 points. This is 67 percent the same or worse for the group with poorer initial status, and 33 percent the same or worse for the group with more favorable initial status. Our statistical analyses of these data show that this is an absolute difference of 33 percent (95 percent CI, 1 to 58) and a relative difference of 2.0 (95 percent CI, 0.96 to 4.15). One result is statistically significant, and the other is not. Thus, whether the trend observed is statistically significant in these data appears to depend on how one analyzes the data.

Figure 19. Initial vs. Difference in Walking (more...)

   Figure 19. Initial vs. Difference in Walking Computed from Eskola, Pohjolainen, Alaranta et al., 1992

Figure 19

Figure 20. Initial vs. Ratio of Change in Walking (more...)

   Figure 20. Initial vs. Ratio of Change in Walking Distance Computed from Eskola, Pohjolainen, Alaranta et al., 1992

Figure 20

Whether the regression on change as a difference or as a ratio is more informative is not immediately clear. The fact that the correlation goes from statistically significant and positive for regression on the difference to statistically nonsignificant and negative for regression on the ratio indicates that both types of regressions should be considered. In this regard, the proportional assessment of improvement is more like the way many surgery studies measured outcomes. Typically patients are categorized as being worse, the same, or improved following treatment. Frequently the same and improved categories are further categorized into fair (eg., those patients with 0 to 50 percent improvement), good (50 to 75 percent improvement), and excellent (>75 percent improvement), or similar categories. These categories demand proportional judgments. This expression of results obscures the influence on outcome of the initial status and assumes that, for example, a 50 percent improvement from poor initial status to mediocre status is equivalent to a 50 percent improvement from mediocre status to good status. This may be the case, but studies in this field have not acknowledged or addressed this assumption.

Figure 20

Table 19. Mean Change in Treadmill Walking Distance (more...)

Table 19. Mean Change in Treadmill Walking Distance before and after Three Months of Conservative Treatment Stratified by Initial Status

	Initial Distance (m)	Final Distance (m)	Difference (m) (95% CI)	Ratio
Whole Cohort	662	827	164 (58 to 270)	1.31 (1.09 to 1.53)
Worst Initial	204	247	43 (−18 to 104)	1.39 (0.97 to 1.79)
Best Initial	1129	1433	304 (122 to 486)	1.27 (1.09 to 1.45)
Strata Difference (best initial minus worst initial)			261 (54 to 468) t-test p = 0.016	−0.12 (−0.59 to 0.34) t-test p = 0.59

Calculated by us from Figure 6 in Eskola, Pohjolainen, Alaranta et al., 1992.

Table 20. Change Category Frequencies for Treadmill (more...)

Table 20. Change Category Frequencies for Treadmill Walking Distance After Three Months of Conservative Treatment Stratified by Initial Status

	Worse <0.75 Change (95% CI)	Same 0.75 to 1.25 Change (95% CI)	Improved >1.25 Change (95% CI)
Whole Cohort	0 % (0 to 9.6%)	61% (44% to 75%)	39% (25% to 55%)
Worst Initial	6% (1/18) (1% to 26%)	61% (11/18) (39% to 80%)	33% (6/18) (16% to 56%)
Best Initial	0 % (0% to 18%)	56% (10/18) (34% to 75%)	44% (8/18) (25% to 66%)
Strata Difference (best initial minus worst initial)	−6% (−26% to 13%)	−6% (−34% to 25%)	11% (−19% to 39%)	Somers' d −0.14 p = 0.38

Calculated by us from Figure 6 in Eskola, Pohjolainen, Alaranta et al., 1992.

Looking at the proportion of patients in each group that were improved (ratio >1.25), the same (ratio between 0.75 and 1.25), or worse (ratio <0.75), 44 percent (8/18) of the group with the most favorable initial status improved, 56 percent (10/18) were the same, and none were worse. In the group with the poorest initial status, 33 percent (6/18) of patients improved, 61 percent (11/18) remained the same, and one patient was worse (Somers' d −0.114, p = 0.38). Thus, with this frequency comparison, the best initial group had slightly more patients improved, although the difference was not statistically significant, nor does it appear to have much clinical significance. This crude and arbitrary categorization did not capture the fact that both groups actually had some patients with a change for the worse (4/18 in the group with the poorest initial status, and 2/18 in the group with the most favorable initial status), as was demonstrated in the above regression analyses.

Although this was a small study with only moderate statistical power (18 patients in each group), we conclude from this analysis that there was no substantial difference between the mean proportional improvement of the groups with best and worst initial status in terms of treadmill walking distance. However, a group of the worst initial patients (67 percent or 12/18 in the regression analysis) appears to remain the same or continue to get worse with conservative treatment. But because of the wide distribution of results in the patients with the worst initial status, in this trial the initial status for treadmill walking distance had little prognostic value in terms of predicting the outcome of conservative treatment for individual patients.

Table 21. Initial Stenotic Canal Diameter Stratified (more...)

Table 21. Initial Stenotic Canal Diameter Stratified by Outcome of Conservative Treatment

Visual Analog Scale Results	n	Mean AP Diameter Range)
Worse	4	4.7 mm (0 to 9 mm)
Same	19	6.8 mm (0 to 11 mm)
Improved	4	8.2 (7 to 10 mm)

Adapted from Johnsson, Uden, and Rosen, 1992.

Simotas et al. (2000) examined the effects of nonoperative treatment on 49 patients with lumbar spinal stenosis over a 3 year period. Although this study did not contain a surgical arm for comparison, this trial is mentioned here because of the long followup time and the information provided on those patients that eventually needed surgery. Conservative treatment consisted of bed rest for the first 1 to 2 weeks, followed by a physical rehabilitation program with a physical therapist. Patients performed flexion-based lumbar stabilization exercises. Patients with significant radicular symptoms received oral corticosteroids on a 7 day tapering schedule. Epidural steroid injections were used to treat patients who did not achieve adequate symptom control. Many patients had a recurrence of symptoms that required reinjection during the 3 year study period. The average age was 69 years (range 53 to 87). Radiographic severity of the stenosis was judged to be mild in 12 percent of patients, moderate in 43 percent of the patients, and severe in 45 percent of the patients. Nine patients required surgery within a mean of 13 months (range 2 to 41 months). These patients had more serious pretreatment averages for back and leg pain and a greater degree of stenosis. Among the 40 remaining nonoperated patients, only age seemed to be related to outcome variables, with older patients having worse scores for improvement in pain. Older patients had significantly greater radiographic severity, greater levels with at least moderate stenosis, and more frequently had scoliosis. If the patients with scoliosis were removed from the analysis, the relationship between increased age and worse outcomes was not significant.

Amundsen et al. (2000) divided their patients into three groups: patients with severe symptoms who were treated with surgery (n = 19), patients with pain considered too moderate to justify surgery and treated with conservative methods (n = 50), and the remaining patients whose severity of pain did not indicate surgery or conservative treatment (n = 31). The patients in this latter group were randomized to surgical (n = 13) or conservative treatment (n = 18). Over the course of the 10 year followup period, 20 percent of conservatively treated patients with mild pain needed surgery, and 56 percent of conservatively treated patients with moderate pain needed surgery. No convincing associations between any clinical feature, such as age, gender, type of work, duration of pain, and physical findings, and treatment results were observed by the authors. In addition, no convincing associations between any radiologic feature, such as degenerative changes, spondylolisthesis, type of stenosis, degree of narrowness, and measures of different dimensions of the spinal column, were observed. However, the sample size in this trial was small and the study may not have had sufficient statistical power to detect association between patient characteristics and treatment results.

Summary

Few studies have examined the question of the relationship of initial signs and symptoms to the final status or amount of change following conservative treatment. The one study, Eskola et al. (1992) which reported individual patient data indicated that with conservative treatment, some patients improve, some stay the same, and some get worse. Simotas et al. (2000) suggest that the patients with the highest degree of pain are more likely to have unsuccessful conservative treatment and go on to surgery. In Simotas et al. (2000), this was 19 percent of patients over three years. Amundsen et al. (2000) preselected those patients with the highest pain for surgery, but among the mild and moderate pain groups of conservatively treated patients, 20 percent and 56 percent, respectively, eventually required surgery over a 10 year period. This calls into question studies of conservative treatment or surgery that do not have parallel control groups. This also calls into question the usefulness of means in treatment comparisons. Reporting only the mean value for final status or amount of change can obscure the fact that substantial numbers of patients may differ greatly from the mean. The study by Eskola et al. (1992) indicated that for treadmill walking ability (a measure of neurogenic claudication), a moderate positive correlation may exist between initial status and amount of improvement measured as a difference (final status − initial status). However, no substantial correlation was found between initial status and improvement measured as a ratio (final status : initial status). The wide dispersion of results for the difference and ratio indicates that any correlations are not very useful for prognostication for individual patients. Johnsson et al., (1992) suggested some positive correlation between canal size at the point of focal narrowing and the outcome of conservative treatment. Simotas et al. (2000) also suggested that the degree of stenosis was related to the failure of conservative treatment and the need for surgery. Amundsen et al. (2000) found no association between spinal canal dimensions and treatment outcomes; however, the small sample size in this study may have prevented the detection of any significant association.

Comparison of Conservative Treatment Methods

Table 22. Disposition of Publications on Conservative Treatments (more...)

Table 22. Disposition of Publications on Conservative Treatments

Documents	Number	Percentage
Retrieved from literature searches	4,788	100%
Conservative treatment trials examined for lumbar spinal stenosis patients	178	3.71% of literature retrieved from searches
Conservative treatment trials rejected due to lack of control group, too few patients, failure to report outcomes separately for each spinal disorder, or failure to diagnosis specific lumbar spinal stenosis patients	174	98% of conservative trials
Conservative treatment trials that met inclusion criteria	4	2% of conservative trials

Table 24. Randomized Controlled Trials of Patients (more...)

Table 24. Randomized Controlled Trials of Patients Receiving Conservative Treatments

First Author and Year of Publication	Patient Group		N	Treatment	Outcomes Measured	Followup Period
Trials examining surgical patients with central or lateral lumbar stenosis (type of stenosis unspecified or includes both types of stenosis)
Fukusaki, Kobayashi, Hara et al., 1998	1	16		Epidural saline	Walking capacity (walking distance that provoked intolerable leg pain)	1 week, 1 month, and 3 months
	2	18		Epidural anesthetics
	3	19		Epidural anesthetics and steroids
Eskola, Pohjolainen, Alaranta et al., 1992	1	20		Calcitonin injections	Back pain (0-100 visual analog scale), Walkingcapacity (maximum distance on treadmill)	1, 3, 4, 6, and 12 months
	2	19		Calcitonin injections
Cuckler, Bernini, Wiesel et al., 1985	1	20		Epidural anesthetics and steroids	Global assessment (subjective improvement of 75% or more as judged by the patient)	24 hours and 13 to 30 months
	2	17		Epidural anesthetics
Patients with degenerative spondylolisthesis
Sinaki, Lutness, Ilstrup et al., 1989	1	29		Exercise/flexion	Ability to work, back pain (no pain, mild, moderate, and severe), global ssessment (patients were asked if they were recovered)	3 months and 3 years
	2	19		Exercise/extension

Eskola et al. (1992) examined the use of calcitonin injections as a treatment for lumbar spinal stenosis. This trial was previously discussed with regard to factors that may predict the success of conservative treatment. Patients received calcitonin or placebo injections every other day for 4 weeks. The injection period was followed by a 2 month washout period, and then patients crossed over to the other injection. Walking distance on a treadmill was measured before treatment and 1, 3, 4, 6, and 12 months after treatment. Walking capacity at baseline, approximated from published graphs, were the following: Group 1, 710 ± 20 m; Group 2, 550 ± 20 m (means and standard deviations). The authors do not statistically compare data across treatments at each time point, but evaluated only the changes between measurement periods. In the case of walking distance, both Group 1 patients (calcitonin then placebo) and Group 2 patients (placebo then calcitonin) showed significant increases in walking capacity compared to pretreatment values 1 month and 3 months after the first treatment. The increase in walking capacity continued through the crossover period until 6 months after the first treatment. After 6 months, both groups showed a significant decline in walking capacity so that at 12 months, Group 1 patients averaged 800 m and Group 2 patients averaged 475 m. From the data presented by the authors, no conclusions can be drawn as to whether the calcitonin, the placebo treatment, or some other aspect of the treatment process was responsible for the increase in walking capacity. All patients seem to respond during the treatment period regardless of the order in which they received calcitonin or placebo. Therefore, this trial cannot be used as evidence that calcitonin reduces the symptoms associated with lumbar spinal stenosis.

Cuckler (1985) examined the effects of epidural steroid injections on patient-perceived improvement in symptoms both at 24 hours and at 13 to 30 months later. The ability to evaluate the long-term effects of the injections was compromised by a study design that allowed all patients (placebo or steroid) to receive the steroid injection 24 hours after the first injection if symptoms did not improve. Therefore, few patients, 3 of 17 (17.6 percent), were left in the control group of this trial after 24 hours. Since this trial cannot be considered a controlled trial for evaluation of long-term effects of epidural steroid injections, we attempted no further analysis of its data.

Sinaki et al. (1989) examined the effect of two exercise regimens on patients with lumbar spondylolisthesis. Patients were randomized to different physiatrists, who then assigned the exercise regimen, resulting in 29 patients prescribed flexion exercises and 19 patients prescribed extension exercises. The assignment of exercise programs was therefore not random. Consequently, the pretreatment pain classification was very different between the patient groups. All 26 patients in the flexion group were considered to have moderate or severe pain, while in the extension group 12 patients had moderate or severe pain and 6 patients had no pain or mild pain. The lack of true randomization of the patients caused us to exclude this study from further analysis.

Table 23. Analysis of Walking Capacity Data from Fukusaki, Kobayashi, (more...)

Table 23. Analysis of Walking Capacity Data from Fukusaki, Kobayashi, Hara et al., 1998

Patient Group	Walking Distance that Provokes Neurogenic Claudication (Meters, Mean ± Standard Deviation)				Effect Size (Hedges ` d )and Confidence Limits Compared to Pretreatment Value
	Pre treatment	1 week	1 month	3 months	1 week	1 month	3 months
Saline n = 16	10 ± 8	23 ± 19	18 ± 13	11 ± 8	0.869 0.144 − 1.594 p = 0.019	0.723 0.007 − 1.438 p =0.048	0.122 −0.572 − 08155 p = 0.731
Mepivacaine n = 18	11 ± 9	92 ± 66	28 ± 24	13 ± 7	1.681 0.921 − 2.442 p = 0.000015	0.917 0.230 − 1.604 p = 0.0089	0.243 −0.413 − 0.898 p = 0.468
Mepivacaine plus methylprednisolone n = 19	9 ± 7	87 ± 58	26 ± 23	10 ± 8	1.849 1.089 − 2.608 p = 0.000002	0.979 0.306 − 1.652 p = 0.0044	0.130 −0.506 − 0.767 p = 0.688

Summary

Many conservative methods have been proposed for treating patients with lumbar spinal stenosis (Fritz, Delitto, Welch et al., 1998). Our search of the literature has uncovered only one well-designed randomized controlled trial that compared a conservative treatment to placebo treatment specifically in lumbar spinal stenosis patients. That study, Fukusaki et al. (1998), indicates that local anesthetic block provides temporary relief from neurogenic claudication for about 1 month. Conclusions about effectiveness beyond 3 months cannot be made.

Evidence for the efficacy of other conservative treatments in lumbar spinal stenosis patients is lacking. However, the lack of evidence for effectiveness does not prove that these treatments are not effective. The lack of evidence is an indication of the failure to design adequate clinical trials to show effectiveness.

Relationships Between Patient Characteristics and Surgical Outcomes

We addressed this question by performing a systematic narrative review of each study. In this review, we calculated, wherever possible, each study's effect size. The following analysis is subgrouped according to the type of lumbar spinal stenosis and the patient characteristics that were correlated with the outcomes of surgical treatment. Only studies that stratified surgical treatment outcomes by patient characteristics or used a regression analysis to compare patient characteristics to outcomes or used a regression analysis to compare patient characteristics to outcomes were considered to have evidence that could be used to answer question 6.

Table 25. Controlled Trials of Patients with Central (more...)

Table 25. Controlled Trials of Patients with Central Lumbar Spinal Stenosis

Authors and Year of Publication	Type of Lumbar Spinal Stenosis	Type of Surgical or Conservative Treatment	Patient Group	Number of Patients	Outcomes Measured	Followup Period
Herno, Saari, Suomalainen et al.,1999a	Central lumbar stenosis no post-surgery stenosis	Mixed ecompression techniques	1	35	Back pain, leg pain, walking, global, Disability	Mean of 47 months
	Central lumbar stenosis post surgery stenosis	Mixed decompression techniques	2	57
Herno, Partanen, Talaslahti et al., 1999b	Central lumbar stenosis post surgery stenosis	Standard wide decompressive laminectomy	1	41	Walking, global, disability	Between 113 and 157 months
	Central lumbar stenosis no post surgery stenosis	Standard wide decompressive laminectomy	2	15
Hanakita, Suwa, and Mizuno, 1999	Central lumbar stenosis younger than 64 years	Standard wide decompressive laminectomy	1	59	Back pain, leg pain, walking, global	Between 12 and 96 months
	Central lumbar stenosis older than 64 years	Standard wide decompressive laminectomy	2	61
	Central lumbar stenosis	Partial laminectomy or hemilaminectomy	3	16
	Central lumbar stenosis	SWDL with fusion (arthrodesis)	4	20
Thomas, Rea, Pikul et al., 1997	Central lumbar stenosis	Standard wide decompressive laminectomy	1	12	Walking	Pretreatment and 24 to 62 months
	Central lumbar stenosis	Laminotomy	2	14
Yone, Sakou, Kawauchi et al., 1996	Central lumbar stenosis	SWDL with fusion and istrumentation	1	10	Back pain, leg pain, walking, global	Between 24 and 68 months
	Central lumbar stenosis	Laminotomy	2	17
Grob, Humke, and Dvorak, 1995	Central lumbar stenosis	Partial laminectomy or hemilaminectomy	1	15	Back pain, back pain relief, leg pain relief, walking, global	Pretreatment and 24 to 32 months
	Central lumbar stenosis single level	Partial laminectomy with fusion and instrumentation	2	15
	Central lumbar stenosis multiple segments	Partial laminectomy with fusion and instrumentation	3	15
Johnsson, Uden, and Rosen, 1991	Central lumbar stenosis	Conservative-not described	1	20	Back pain, walking, global, work	Between 7 and 51 months
	Central lumbar stenosis moderate stenosis	Standard wide decompressive laminectomy	2	30
	Central lumbar stenosis severe stenosis	Standard wide decompressive laminectomy	3	14
Ray, 1982	Central lumbar stenosis	Standard wide decompressive laminectomy	1	48	Global	Mean of 10 and 13 months
	Central lumbar stenosis	Partial laminectomy or hemilaminectomy	2	17
Surin, Hedelin, and Smith, 1982	Central lumbar stenosis marked stenosis	Standard wide decompressive laminectomy	1	15	Global	Between 14 and 70 months
	Central lumbar stenosis moderate stenosis	Standard wide decompressive laminectomy	2	7
Tajima, Fukazawa, and Ishio, 1980	Central lumbar stenosis	Mixed decompression techniques	1	13	Global	Unkown post operative time
	Central lumbar stenosis and disk lesion	Mixed decompression techniques	2	14

In addition to these studies, the prospective single arm surgical trials of Katz et al. (Katz, Stucki, Lipson et al., 1999) and Jonsson et al. (Jonsson, Annertz, Sjoberg et al., 1997), and the retrospective single arm surgical trial of Thomas et al. (Thomas, Rea, Pikul et al., 1997) also examined the relationship between patient characteristics and surgical outcome.

Effect of Extent of Stenosis on Surgical Outcomes Among Patients With Central Stenosis

Table 26. Analysis of Walking Capacity in Meters from Johnsson, (more...)

Table 26. Analysis of Walking Capacity in Meters from Johnsson, Uden, and Rosen, 1991

Patient Group	Pretreatment Mean ± SD	At Followup Mean ± SD	Mean Difference at Followup	Hedges' d at Followup	95% Confidence Limits at Followup
Severe stenosis; n = 14	120±114	2,373±4,142	2,253	0.747	−0.020 1.513
Moderate stenosis; n = 30	186±203	1,453±2,935	1,267	0.601	0.080 1.120
Mean Difference between Patient Groups	66	920
Hedges' d between Patient Groups	−0.360	0.269
95% Confidence Limits between Patient Groups	−0.998 0.279	−0.368 0.906

Table 27. Analysis of Walking Capacity According to (more...)

Table 27. Analysis of Walking Capacity According to a Three-Level Scale from Johnsson, Uden, and Rosen, 1991

Patient Group	Walking Capacity			Effect Size at Followup	Confidence Limits at Followup
	Worse	Unchanged	Improved
Severe stenosis; n = 14	3	0	11	0.636	0.406 0.998
Moderate stenosis; n = 30	7	8	15

Johnsson et al. (1991) stratified patients receiving standard wide laminectomy according to the extent of pretreatment stenosis. A partial block at myelography indicated moderate stenosis (30 patients, mean and standard deviation of the AP diameter was 7.9 ±2.3 mm), and a total block indicated severe stenosis (14 patients, diameter = 0). The mean ages and their standard deviations were 62 ±9 years in the moderate group and 69 ±8 years in the severe group. Walking capacity was evaluated at a mean followup time of 50 ±32 months in the moderate group and 58 ±32 months in the severe group. The original walking data and our calculations of effect size are presented in Table 26. At baseline, the walking capacity was similar between groups, and both groups showed large increases in walking capacity at followup (>1,200 m). However, only the moderate stenosis group showed a statistically significant effect size when pre- and posttreatment values were compared. The large standard deviations at followup in both patient groups, approximately twice the mean, indicate a large variation in individual improvement in walking capacity. Our analysis of walking capacity based on the three level scale data reported by Johnsson et al. (1991) (worse, unchanged, improved) indicated only a small effect in favor of the severe stenosis group (Hedges' d effect size = .636, confidence levels of 0.406 and 0.998 (see Table 27). The data from this trial seem to suggest that a select group of patients benefited from surgery more than others. However, the degree of stenosis did not seem to determine who these patients would be, and insufficient information is presented in the trial to determine which patients might make up the group that benefits.

Surin et al. (1982) also stratified outcomes by degree of stenosis, but the moderate stenosis group (AP diameter between 11 and 14 mm) contained only seven patients, while the marked stenosis group (<10 mm) contained 15 patients. The sample size < 10 in the moderate stenosis group prevents a reliable comparison of the data between patient groups. The average followup examination after surgery was 29 months, but the range was 14 to 70 months. The small sample size and the large range in followup times prevent the use of data from this study in our analysis.

Herno et al. (1999a) and Herno et al. (1999b) retrospectively examined surgical outcomes based on the presence of stenosis at postsurgical followup. Herno et al. (1999a) reported on patients treated surgically for the first time between 1982 and 1984. Herno et al. (1999b) reported on patients who underwent surgery between 1985 and 1987. The stenosis was found at the original surgical site or an adjacent vertebral level. The mean patient ages were between 50 and 55 years at the time of surgery. Since these are retrospective trials, no pretreatment scores were reported for the outcome measures. Without baseline scores, the extent of patient disability before treatment cannot be judged or compared to patients in other studies. In addition, the degree of improvement over baseline conditions cannot be determined. This makes the results of these studies difficult to interpret. Baseline clinical features were reported. In Herno et al. (1999b) the nonstenosis group (15 patients) had a significantly greater baseline mean cross-sectional area of the dural sac compared to the stenosis group (41 patients) (145 mm² vs. 95 mm², p <0.0001, Mann-Whitney test). Laminectomy, extended laterally to decompress the nerve roots, was performed on all patients. After a mean followup time of 10.2 and 11.1 years for the nonstenosis and stenosis groups, respectively, no statistically significant differences were found in the mean Oswestry score (a measure of back pain disability) (28.7 v. 31.2, Kruskal-Wallis test) and walking capacity (15 minutes on a treadmill) (515 m v. 470 m, Kruskal-Wallis test).

Herno et al. (1999a) reported similar baseline clinical characteristics among the 35 patients with no stenosis postsurgery and the 57 patients with postsurgery stenosis. After a mean followup time of 3.5 years, no statistically significant differences were found in the mean Oswestry score (28.4 vs. 26.4, p = 0.755, Kruskal-Wallis test) and walking capacity (706 m vs. 602 m, p = 0.178, Kruskal-Wallis test). In these two studies, the presence of postsurgery stenosis was not correlated with surgical outcomes as measured by disability from back pain and walking capacity at the time of followup. The lack of pretreatment scores prevents any assessment of the actual effect of surgery on these patient groups, and the study does not provide evidence for a correlation between patient characteristics and the success or failure of surgery.

Jonsson et al. (1997) used a logistic regression analysis to correlate patient characteristics with favorable outcomes. In 105 patients with an average age of 65 years (range of 37-83 years), patients with an AP diameter of <6 mm had the most favorable outcomes at 5 years after surgery. No statistical information (p values, correlation coefficients) was reported to support these conclusions.

Effect of Herniated Disks on Surgical Outcomes Among Patients With Lateral Lumbar Stenosis

Table 29. Analysis of Global Success Data from Kirkaldy-Willis, (more...)

Table 29. Analysis of Global Success Data from Kirkaldy-Willis, Wedge, Yong-Hing et al., 1982

Patient Group	Global Success at Followup				Hedges' d Effect Size	Confidence Intervals
	Greatly Improved	Slightly Improved	No Improvement	Worsening
Lateral stenosis and Lateral and central stenosis patients; n = 33	14	9	10	0	−0.600 p = 0.006	−1.028 −0.171
Lateral stenosis plus herniated disk and lateral and central stenosis plus herniated disk patients; n = 44	34	7	2	1

Calculation of an effect size from dichotomous data was performed using an odds ratio and the natural log transformation. To calculate the odds ratio, the number of patients in the greatly improved group were considered successes and the number of patients in the remaining three categories were combined and considered unsuccessful.

The study by Kirkaldy-Willis et al. (1982) was a retrospective case series in which patients were selected if they had one of the following four conditions: lateral stenosis, lateral stenosis with disk herniation, lateral and central stenosis, and lateral and central stenosis with disk herniation. The average age for the entire group of patients was 46 years (range of 41 to 52 years). Between 12 and 120 months after partial laminectomy, these patients were asked to assess the degree of improvement in their condition. We analyzed these categorical data to determine if disk herniation in combination with lateral stenosis was detrimental to patient recovery compared to lateral stenosis alone (see Table 29). Based on patient reporting of general improvement after surgery, the patients with herniated disks in addition to stenosis experienced greater improvement (Hedges' d = −0.600, confidence intervals of −1.028 to −0.171). Improvement after surgery is based on the patient's perception of their pain and disability before treatment. The patients with herniated disks may have experienced more pain or disability before surgery, but in this retrospective study, no pretreatment measures of pain or disability are provided to judge each group's relative condition before surgery. Therefore, this study does not help us in determining if the pretreatment condition of patients with lateral lumbar stenosis influences their response to surgery.

Effect of Patient Characteristics on Surgical Outcomes Among Patients With Degenerative Spondylolisthesis

Table 30. Controlled Trials of Patients with Degenerative Spondylolisthesis (more...)

Table 30. Controlled Trials of Patients with Degenerative Spondylolisthesis

Authors and Year of Publication	Type of Lumbar Spinal Stenosis Disorder	Type of Surgical or Conservative Treatment Received by Patient Group	Patient Group	Number of Patients	Outcomes Measured	Followup Period
Plotz and Benini, 1998	Degenerative spondylolisthesis	Decompressive surgery without fusion	1	17	Back pain relief, leg pain relief, global success	9 to 120 months
	Degenerative spondylolisthesis	Decompressive surgery with fusion and translaminar screw fixation	2	18
	Degenerative spondylolisthesis	Decompressive surgery with fusion and AO internal fixator	3	71
Fischgrund, Mackay, Herkowitz et al., 1997	Degenerative spondylolisthesis	SWDL with fusionand instrumentation	1	40	Back pain, Leg pain, global success	24 to 36 months
	Degenerative spondylolisthesis	SWDL with fusion (arthrodesis)	2	35
Thomsen, Christensen, Eiskjaer et al., 1997	Degenerative spondylolisthesis	Partial laminectomy with fusion and instrumentation	1	20	Quality of life, mental status, Physical function and activities of daily living	12 and 24 months
	Degenerative spondylolisthesis	Partial laminectomy and fusion	2	21
Yuan, Garfin, Dickman et al., 1994	Degenerative spondylolisthesis	Fusion and pedical screw fixation	1	2177	Back pain relief, leg pain relief, physical function and activities of daily living	23 to 51 months
	Degenerative spondylolisthesis	Fusion	2	456
Bridwell, Sedgewick, O'Brien et al., 1993	Degenerative spondylolisthesis	Partial laminectomy or hemilaminectomy	1	9	Walking	34 to 45 months
	Degenerative spondylolisthesis	Partial laminectomy and fusion	2	10
	Degenerative spondylolisthesis	Partial laminectomy with fusion and instrumentation	3	24
Satomi, Hirabayashi, Toyama et al., 1992	Degenerative spondylolisthesis	Fusion and instrumentation	1	27	Back pain, Leg pain, Walking, Global success	approximately 36 months
	Degenerative spondylolisthesis	Mixed decompression techniques	2	14
Herkowitz and Kurz, 1991	Degenerative spondylolisthesis	Standard wide decompressive laminectomy	1	25	Back pain, leg pain, global success	29 to 48 months
	Degenerative spondylolisthesis	SWDL with fusion (arthrodesis)	2	25
Lombardi, Wiltse, Reynolds et al., 1985	Degenerative spondylolisthesis	Standard wide decompressive laminectomy	1	20	Global success	24 to 84 months
	Degenerative spondylolisthesis	SWDL with fusion (arthrodesis)	2	21
Fitzgerald and Newman, 1976	Degenerative spondylolisthesis	Rigid brace	1	29	Global success	6 to 216 months
	Degenerative spondylolisthesis	Mixed decompression techniques	2	14
Rosenberg, 1976	Degenerative spondylolisthesis	Partial laminectomy or hemilaminectomy	1	11	Global success	Soon after treatment to 120 months
	Degenerative spondylolisthesis	Standard wide decompressive laminectomy	2	15
	Degenerative spondylolisthesis	Conservative-not described	3	170

Four randomized controlled trials and six controlled trials examined surgical treatment of degenerative spondylolisthesis (see Table 30). The randomized controlled trial of Thomsen et al. (1997) included patients with isthmic spondylolisthesis, secondary degenerative spondylolisthesis, and primary degenerative spondylolisthesis, and reported surgical outcomes separately for each of these groups. However, when reporting on surgical outcomes according to patient characteristics, such as duration of symptoms and number of levels fused, all three types of spondylolisthesis were combined. Therefore, this study does not report evidence specific to primary degenerative spondylolisthesis to address the question of patient characteristics and benefit from surgery. The randomized controlled trials of Fischgrund et al. (1997), Bridwell et al. (1993), and Herkowitz and Kurz (1991) did not stratify or analyze data based on patient characteristics. In the controlled trials of Plotz and Benini (1998), Yuan et al. (1994), Satomi et al. (1992), Lombardi et al. (1985), Fitzgerald and Newman (1976), and Rosenberg (1976) data within the surgical treatment groups was not analyzed or reported in relation to patient characteristics. Therefore, these studies cannot be used to address the connection between patient characteristics and surgical outcome.

Summary

Poor study quality, especially the lack of pretreatment measurements of patient condition, reduce the usefulness of available data to answer the question of whether patient signs, symptoms, and other characteristics determine the success of surgery for degenerative lumbar stenosis. The few studies that do stratify outcomes by patient characteristics, especially those that examined degree of stenosis, did not find a connection between successful treatment and specific patient characteristics. The data from these trials seem to suggest that a select group of patients benefited from surgery; however, insufficient information is presented in the trials to determine which patients make up this group. Regression analysis from two studies suggests that patients in poor health due to comorbidity may have inferior outcomes after surgery compared to healthier patients.

Table 28. Controlled Trials of Patients with Lateral (more...)

Table 28. Controlled Trials of Patients with Lateral Lumbar Spinal Stenosis

Authors and Year of Publication	Type of Lumbar Spinal Stenosis Disorder	Type of Surgical or Conservative Treatment Received by Patient Group	Patient Group	Number of Patients	Outcomes Measured	Followup Period
Lee and deBari, 1986	Lateral lumbar stenosis	SWDL with fusion (arthrodesis)	1	12	Global success	Between 12 and 72 months
	Lateral lumbar stenosis	SWDL with fusion and instrumentation	2	12
Kirkaldy-Willis, Wedge, Yong-Hing et al., 1982	Lateral lumbar stenosis	Partial laminectomy or hemilaminectomy	1	20	Leg pain, global success, ability to work	Between 12 and 120 months
	Lateral lumbar stenosis with disk herniation	Partial laminectomy or hemilaminectomy	2	32
	Lateral and central lumbar stenosis	Partial laminectomy or hemilaminectomy	3	21
	Lateral and central lumbar stenosis with disk herniation	Partial laminectomy or hemilaminectomy	4	21
Mikhael, Ciric, Tarkington et al., 1981	Lateral lumbar stenosis	Standard wide decompressive laminectomy	1	35	Global success	Between 12 and 40 months
	Healthy control	Control/placebo/none	2	50

Comparison of Surgical Versus Conservative Treatment

Table 31. Trials Comparing Surgery and Conservative Therapy (more...)

Table 31. Trials Comparing Surgery and Conservative Therapy

Authors and Year of Publication	Study Design	Patient Selection	Match Conservative versus Surgery		Treatment	n	Comments
Amundsen T, Weber H, Nordal HJ et al., 2000	Patients were diagnosed as having severe, moderate, or mild symptoms; severe patients received surgery, mild patients received conservative treatment, and moderate patients were randomized to conservative or surgical treatment	Sciatic pain in the leg (s), with or without back pain; radiologic signs of stenosis and compression of the clinically afflicted nerve roots; no bulging or herniated disk or previous surgery of the back	Age: 21-40: 2 41-60: 9 61-70: 6 >71: 1 Sex: 39% M Severity: 100% moderate Pain: light: 0 moderate: 5 severe: 13	Age: 21-40: 2 41-60: 7 61-70: 4 >71: 0 Sex: 69% M Severity: 100% moderate Pain: light: 0 moderate: 5 severe: 13	Nonsurgery brace, rehabilitation, physiotherapy,	18	Only study to randomly assign patients to either conservative or surgical treatment
					Laminectomy: no fusions	13
Mariconda, Zanforlino, Celestino et al., 2000	Unmatched observational comparison within cohort: all indicated for surgery; nonsurgery, 3 had contraindicating comorbidity, 14 refused surgery (appears to correlate with milder disease)	age >40, radicular pain, central stenosis (degenerative or combined), dural area <130mm2, indicated for surgery, no previous back surgery	Straight leg-raise:		Nonsurgery	17	Evaluator blinded for initial exam, questionnaire for followup exams; no dropouts reported Beaujon score (0 = worst, 20 = normal): neurogenic claudication, leg pain at rest, leg pain at exertion, low back pain, neurological deficit (motor or sensor), medications, QOL
			47%	45%	Laminectomy; diskectomy if necessary; no fusions or instruments	20
			Neurological deficits:
			47%	70%
			Stenosis:
			78 mm2	68 mm2
			Multiple levels:
			65%	70%
			Initial Beaujon score:
			11 (±2.4 SD)	8.1 (±2.7)
Hurri, Slatis, Soini et al., 1998	(1) Unmatched comparison of 57 patients. who had surgery and 18 treated conservatively for unreported reasons (2) comparison of Oswestry means adjusted (general linear model) for age, sex, body mass, severity of stenosis (radiographic)	Myelography diagnosis of LSS (<11 mm diameter) in years 1978-82 (134 patients) and able to be traced and interviewed by phone (86 still alive, 75 interviewed)	Age:		Conservative	18	Oswestry Disability Index (0 = normal, 50 = worst): pain, personal care, lifting, walking, sitting, standing, sleeping, sex life, social life, traveling
			Mean 47	Mean 50	Majority got laminectomy, some disk surgery, some foraminotomy, no fusions	57
			Sex:
			66% M	56% M
			Severe (<7.0 mm):
			33%	46%
			Sciatic (knee or below):	82%
			72%
			Neurological deficit:	67%
			44%	21%
			Previous surgery:
			22%	26%
			Early retirement:
			44%
Swezey, 1996	(1) Unmatched comparison; only the 23% (11/47) not improved by conservative treatment were treated surgically (2)Crossover with repeated measures: 11 patients who had unsatisfactory improvement with conservative therapy during first period were given surgery during second period	47 consecutive patients in 1986-7, 43 with >mild LSS by CT or MRI; 18 also had spondylolisthesis; 4 had no CT or MRI but had spondylolisthesis by x-ray; all available for phone interview, and 31 examined	Conservative treatment improved 56%, left 39% unchanged, 5% worse	None improved by conservative treatment; "greater preponderance" of moderate (7/11) or severe (4/11) neurogenic claudication	Conservative: instruction in ergonomics and flexion exercises, analgesics, NSAIDs; 23% had traction, 28% had epidural corticosteroid injections	36
					Conservative then surgery: all had wide laminectomies, 1 also had foraminectomy, 1 also had fusion	11
Herno, Airaksinen, Saari et al., 1996	Retrospective matched-pair	57 LSS patients from 1980-87 who had myelography and no surgery; from 310 not previously operated on patients with LSS and myelography, 54 were manually matched	Matched on age, sex, myelographic findings (block, subtotal block, AP diameter <10 mm, AP diameter 10-12 mm), major symptoms (claudication, leg pain, mixed), and duration of symptoms	Matched on age, sex, myelographic findings (block, subtotal block, AP diameter <10 mm, AP diameter 10-12 mm), major symptoms (claudication, leg pain, mixed), and duration of symptoms	Conservative (not systematic)	54	Patients not operated on for these reasons: 69% pain was bearable, 19% refused surgery, 5.6% were retired, 9% other reasons, 4% insufficient data
					Surgery: standard wide laminectomy with partial or whole facetectomy if needed	54
Atlas, Deyo, Keller et al., 1996	Prospective unmatched observational comparison within cohort	LSS by neurogenic claudication and radiographic findings of stenosis, including herniated disks; at least 2 weeks of unsatisfactory improvement with conservative treatment; no prior lumbar spinal surgery, cauda equina syndrome, developmental deformity, fractures, infection, tumor, inflammation, pregnancy; age >17	Straight leg positive:		Conservative: various types	58	Commonly known as the Maine Lumbar Spine Study 4-year followup outcomes were recently published in Atlas, Keller, Robson et al., 2000
			12%	28%	Surgery: 88% laminectomy, 9% diskectomy only, 4% fusion and laminectomy	72
			Radiographic normal or mild:
			33%	18%
			Radiographic severe:	28%
			10%
			Extreme low back pain:	59%
			39%	79%
			Extreme leg pain:
			32%	20%
			Disabled, in bed:
			11%
Nagler and Bodack, 1993	Retrospective unmatched observational comparison within cohort; patients receiving surgery were a "select group with fewer concomitant medical problems,"(i.e., a de facto pseudo-randomization to the extent comorbidities are independent)	100 patients with LSS symptoms (pain, numbness, weakness in back and legs that was worse with standing or walking and was relieved by sitting or lying) and positive CT and/or myelogram; not predominantly disk caused; 80 able to be interviewed by phone at 1 year	Age:		Conservative: combinations of analgesics, electrical stimulation, ice, heat, hydrotherapy, ultrasound, muscle relaxation techniques, stretching and strengthening exercises, treadmill training	41
			56.4 mean (range 26 to 82)	57.4 mean (range 28 to 78)	Surgery: laminectomy, with or without foraminectomy	39
			More comorbidities	Fewer comorbidities
(Johnsson, Uden, and Rosen, 1991)	Unmatched (retrospective?) observational comparison within cohort; 2 untreated patients had contraindicating cardiovascular disease; 17 refused surgery	Patients with <12 mm diameter on myelography but not total block, no previous spinal surgery, no impaired circulation in legs (i.e., any claudication was neurogenic)	Age:		Untreated (details not reported)	19
			60±9 (range 42 to 80)	62±9 (range 45 to 78)	Surgery: laminectomy and facetectomy; no fusion	30
			Symptom duration:
			22±24 months (range 4 to 96 months)	3±35 months (range 4 to 96 months)
			Observation after myelography:
			31±12 months (range 7 to 51 months)	50±32 months (range 5 to 109 months)
			Neurogenic Claudication:
			84% (16/19)	77% (23/30)
			Radicular pain:
			11% (2/19)	17% (5/30)
			Mixed symptoms:
			5% (1/19)	7% (2/30)
			AP diameter (myelography):
			8.6±1.7 SD	7.9 ±2.3 SD
			Walking capacity:
			1,355 (±3,081 SD)	186 (±203 SD)

Johnsson et al. (1991) compared 44 patients treated surgically for lumbar spinal stenosis with 20 patients not surgically treated. The nonsurgery patients refused surgery (19 patients) or the anesthesiologist refused to administer anesthesia because of advanced cardiovascular disease (2 patients). To obtain comparable groups for analysis, one patient in the nonsurgery group with severe stenosis was removed from the analysis, and the surgery patients were divided into severe stenosis (30 patients) and moderate stenosis (14 patients). Thus, we are concerned with the comparison of the conservatively treated moderate-stenosis group with the surgically treated moderate-stenosis group. The smallest AP diameter had a mean and standard deviation of 7.9 ±2.3 mm in the moderate-stenosis surgery group and 8.6 ±1.7 mm in the nonsurgery group. The mean ages were 60, 62, and 69 years for the nonsurgery, moderate-stenosis, and severe-stenosis groups, respectively. Neurogenic claudication was diagnosed before treatment in 84 percent, 77 percent, and 86 percent of patients in the nonsurgery, moderate-stenosis, and severe-stenosis groups, respectively. The signs and symptoms of lumbar spinal stenosis and the extent of stenosis seen by myelography are the only evidence reported that indicate that the nonsurgery and moderate-stenosis groups are comparable. Followup exams were performed, on average, 31 months after treatment in the nonsurgery group and 50 months after treatment in the moderate-stenosis surgery group.

Table 32. Analysis of Neurogenic Claudication Comparing Nonsurgical (more...)

Table 32. Analysis of Neurogenic Claudication Comparing Nonsurgical Patient to Surgical Patients from Johnsson, Uden, and Rosen, 1991

Patient Group	Number of Patients with Neurogenic Claudication Before Treatment	Number of Patients with Neurogenic Claudication at Followup	Odds Ratio and 95% Confidence Limits	Hedges' d and 95% Confidence Limits
Moderate stenosis; n = 30	23	11	1.76 0.50 to 6.22 p = 0.858	0.323 −0.395 to 1.040 p = 0.378
No surgery; n = 19	16	10

Table 33. Analysis of Walking Capacity in Meters Comparing Nonsurgical (more...)

Table 33. Analysis of Walking Capacity in Meters Comparing Nonsurgical Patient to Surgical Patients from Johnsson, Uden, and Rosen, 1991

Patient Group	Pretreatment Mean ± SD	At Followup Mean ± SD	Mean Difference after Treatment	Hedges' d	95% Confidence Limits
Moderate stenosis; n = 30	186 ± 203	1,453 ± 2,935	1,267	−0.601 p = 0.023	−1.119 −0.084
No surgery; n = 19	1,355 ± 3,081	2,342 ± 4,069	987	−0.268 p = 0.411	−0.906 0.371
Mean Difference between Patient Groups	1,169	889
Hedges' d	−0.599 p = 0.045	−0.256 p = 0.384
95% Confidence Limits	−1.186 −0.012	−0.833 0.321

Nagler and Bodak (1993) retrospectively analyzed the recovery from symptoms of 41 conservatively treated patients and 39 patients who received laminectomies. The degree of improvement, based on a ratio of the original symptoms to those at one year, was similar between groups (54 percent of conservative-treaatment patients and 56 percent of surgery patients had >50 percent improvement; X² = 0.06114, p = 0.804689, according to our calculations). The actual numbers of patients with each symptom before and after treatment were not reported. Without these data, we cannot determine the comparability of the patient groups before treatment. The authors suggest that the surgery patients represent a selected group with fewer concomitant medical problems. Therefore, the data in this study cannot be used to conclusively determine if patients with comparable levels of lumbar spinal stenosis do better with conservative treatment or surgery.

A recently published randomized controlled trial does provide a comparison of a nonsurgical control group with a surgery group with the same baseline patient characteristics (Amundsen T, Weber H, Nordal HJ et al., 2000). In this study, randomization was considered ethical only among patients whose severity of pain did not indicate to the physician that either surgery or conservative therapy was the indicated treatment. The physicians selected surgery for 19 patients with severe symptoms and conservative treatment for 50 patients with mild symptoms. The remaining 31 patients were randomized: 13 patients received surgery (laminectomy without fusion) and 18 patients received conservative therapy (a brace and rehabilitation for one month, followed by an additional 2 months with the brace, and physiotherapy).

Table 35. Examiner Assessment Data from Surgically (more...)

Table 35. Examiner Assessment Data from Surgically and Conservatively Treated Patients with Lumbar Spinal Stenosis from Amundsen T, Weber H, Nordal HJ et al., 2000

Patient Group	Time Post Treatment	Examiner Assessment of Patient Condition Following Treatment
		Excellent	Fair	Unchanged	Worse
Surgical treatment Nonrandomized n = 19, 2 dropouts by the 10th year	6 month	7	8	2	2
	1 year	9	8	2	0
	4 year	11	5	2	1
	10 year	7	5	4	1
Conservative treatment Nonrandomized n = 50, 9 dropouts and 10 surgery by the 10th year	6 month	18	17	5	10
	1 year	18	14	6	12
	4 year	17	11	8	14
	10 year	15	8	6	21
Surgical treatment Randomized n = 13, 2 dropouts by the 10th year	6 month	4	8	1	0
	1 year	5	4	1	3
	4 year	8	3	1	1
	10 year	5	5	0	1
Conservative treatment Randomized n = 18, 1 dropout and 9 surgery by the 10th year	6 month	3	4	1	10
	1 year	3	3	2	10
	4 year	2	6	0	10
	10 year	3	5	0	10

The numbers of patients in each category were extracted from histograms published in Amundsen et al. (2000). Any conservatively treated patient who was crossed over to surgery was considered a treatment failure and placed in the worse category for conservative treatment.

The trial by Amundsen et al. (2000) represents an attempt to randomize patient treatment between conservative and surgical approaches and thereby resolve an important clinical question. Will lumbar spinal stenosis patients with moderate symptoms benefit more from surgery or from conservative treatment? The data as presented by the authors suggest that surgery may be more beneficial. However, several design and reporting problems reduce the strength of this conclusion. Even the authors acknowledged that "because the situation was observational, the existence of hidden confounders and selection bias made it mandatory for the authors to be descriptive and noninferential." Our assessment of these potential hidden confounders and selection bias follows.

The criteria for assignment to the mild-, moderate-, or severe-symptom groups are not clearly stated. The authors assert that intensity of patient pain was the most important reason for selection to the severe-symptom group which received immediate surgery. However, several pieces of evidence indicate that physicians may have underrated the pain and severity of condition in some patients, resulting in these patients' inclusion in the moderate group as opposed to the severe group. First, the median time lag to crossover to surgery was 3.5 months, with a range of 3 to 27 months. This means that perhaps half of the conservatively treated moderate patients switched to severe patients within 3 months of entering the trial. If the original diagnoses had been correct, one would not have expected that half of the crossovers would have occurred by 3.5 months. Individual or subgroup data on when crossovers occurred were not reported.

Second, while 14 of 19 severe-symptom patients (74 percent) reported having severe pain at the start of the trial, 20 of 31 moderate-symptom patients (65 percent) and 24 of 50 mild-symptom patients (48 percent) also reported severe pain at the start of the trial. This indicates that severity of pain was not the only determining factor in how the physicians allocated patients to the treatment groups. Supporting this notion is that larger proportions of older patients appear in the mild-symptom group than in the other two groups. Nine of the 12 patients (75 percent) older than 71 years appear in the mild group (moderate: 8 percent, severe: 17 percent). Older patients may have been selected for conservative treatment because they would be expected to have a poorer prognosis after surgery. Although this is appropriate clinical judgment, this allocation introduces a bias into the trial that could favor surgery.

Third, there appears to be a difference between how physicians and patients rated symptoms. This difference manifests itself as an underrating by the physician. Thus, the authors report of the agreement between physician and patient yields a kappa statistic of 0.59 at 6 months and smaller kappas at later followup periods. This degree of agreement between patients, and examiner is moderate to small, with patients reporting more in the worse category than examiners (6 vs. 3). Such underrating of patient pain by medical personnel has also been observed in other studies (Choiniere, Melzack, Girard et al., 1990; Daniel, Long, Murphy/Kores et al., 1983). Because of physician underrating, patients may have been assigned to the randomized (moderate) group when they should have been assigned to the surgical (severe) group. If randomized to conservative treatment, these patients would be more likely to have unsuccessful results and be crossed over to surgery. The effect of misclassification is to artifactually reduce the reported effectiveness rate of conservative treatment, because patients who are crossed over are considered failures by intent-to-treat analysis. Misclassification increases the apparent difference in effectiveness between surgery and conservative therapy. Further, the size of this apparent difference increases as more patients are misclassified into the moderate group.

We can make one of two conclusions from our analysis of the patients in the Amundsen et al. (2000) trial. First, surgery is superior to conservative treatment for patients with moderate symptoms. As discussed above, the data are confounded and this conclusion lacks support. The second possible conclusion is that the apparent superiority of surgery in moderate patients is an artifact caused by inclusion of severe patients in the moderate-symptom group who then fail conservative therapy. In which case, this is evidence that surgery is superior to conservative treatment among patients with severe symptoms. Another trial, with more carefully designed patient selection and characterization into mild, moderate, and severe groups, will allow us to determine the actual extent to which surgery or conservative treatment benefits these groups.

Amundsen et al. (2000) provide three measures by which the efficacy of surgery compared to conservative therapy can be judged. The first outcome measure is the number of patients needing surgery after first receiving conservative treatment. In the mild-symptom group, only 20 percent of patients eventually needed surgery, indicating that conservative treatment may be justified in this group. In the moderate-symptom group, 54 percent of patients needed surgery. However, as discussed above, this number may be inflated by physician underrating of patient condition and judging severe patients as moderate. Therefore, conservative treatment is more likely to fail in these patients.

The second outcome measure is the examiner assessment of "overall treatment result." This was described as a subjective global assessment based on the following components: (1) a patient-reported scale of "better," "unchanged," or "worse" compared to their condition at the start of the trial; (2) pain; (3) working ability; (4) walking ability; (5) level of physical activity; and (6) the opinion of the examining physician. We would expect pain to be the major component of this scale because pain influences patient working, walking, and physical activity. Examiners were not blinded to treatment. As mentioned above, the agreement between examiner assessment and patient assessment is moderate to poor.

Table 36. Patient Reported Pain Data Compared to Examiner Assessment (more...)

Table 36. Patient Reported Pain Data Compared to Examiner Assessment Data from Surgically and Conservatively Treated Patients with Lumbar Spinal Stenosis from Amundsen T, Weber H, Nordal HJ et al., 2000

Original Diagnosis of Patient Condition	Treatment	Crossover	4-year Outcome Data			10-year Outcome Data
			n	Patients with no pain	Patients rated as excellent	n	Patients with no pain	Patients rated as excellent
Mild symptoms n = 50	Conservative	Surgery n = 10	10	3	4	10	3	4
		No crossover n = 40	40	13	17	32	12	15
Moderate symptoms n = 31	Randomized to conservative n = 18	Surgery n = 10	9	1	2	9	2	2
		No crossover n = 8	8	1	2	8	2	3
	Randomized to surgery n = 13	---	13	5	8	11	5	5
Severe symptoms n = 19	Surgery	---	19	6	11	17	8	7
Wilcoxon Signed Ranks Test results			Z = −2.23, p = 0.026			Z = −1.13, p = 0.257

Atlas et al. (1996) reported on o1 year outcomes of patients in the Maine Lumbar Spine Study, a prospective, observation cohort study of patients with spinal stenosis treated surgically (81 patients) or nonsurgically (67 patients). This trial has three design features that make its results more reliable than the Amundsen et al. (2000) trial. First, Atlas et al. (1996) used an objective scoring system for classifying patients' severity of disease. Therefore, misclassification of patients with severe disease into the moderate category was less likely. Second, there were no crossovers from conservative to surgical treatment. Therefore, the effect of surgery was not exaggerated. Third, study outcomes were based on patient ratings and not on physician ratings. Therefore, results were not skewed by the observer.

In this trial, laminectomy was performed in 88 percent of the surgery patients. Nonsurgery patients received mostly bed rest (29 percent), back exercises (39 percent), physical therapy (23 percent), spinal manipulation (23 percent), narcotic analgesics (21 percent), and epidural steroids (18 percent). Extensive patient information reported in the article showed that the severity of symptoms and the degree of disability because of pain were significantly greater in the surgically treated patients. These patients reported more frequent and severe leg and back pain and poorer functional status, but had greater improvement than patients treated nonsurgically. Because patient preference was the most common reason for not choosing surgery, the nonsurgery group may have selected conservative treatment because their symptoms were less severe than those patients who chose surgery. Therefore, the entire pool of data in this study cannot be used to determine if patients with comparable levels of lumbar spinal stenosis do better with conservative treatment or surgery.

However, a subgroup of 54 patients (31 surgery and 23 nonsurgery patients) reported moderate symptoms before treatment. Results from this group are useful for comparing conservative and surgical treatments. Patients receiving surgery were significantly improved compared to patients who did not receive surgery.

Table 34. Effect Sizes for One and Four Year Outcomes (more...)

Table 34. Effect Sizes for One and Four Year Outcomes of Patients with Moderate Symptoms at Baseline from Atlas, Deyo, Keller et al., 1996 and Atlas, Keller, Robson et al., 2000

Patient Groups	Major Symptom Much Better or Completely Gone		Overall Results of Treatment		Patient Satisfied with Treatment
1-Year Outcome Data	Actual Case	Worst Case	Actual Case	Worst Case	Actual Case	Worst Case
Surgery; n = 31	19 Yes 12 No	19 Yes 23 No	20 Yes 11 No	20 Yes 22 No	21 Yes 10 No	21 Yes 21 No
No surgery; n = 23	3 Yes 20 No	3 Yes 20 No	7 Yes 16 No	7 Yes 16 No	5 Yes 18 No	5 Yes 18 No
Effect size: Hedges' d 1	1.55	0.93	0.75	0.40	1.14	0.70
Lower limit of 95% confidence intervals	0.46	0.18	0.08	−0.19	0.32	0.06
Upper limit of 95% confidence intervals	2.64	1.68	1.42	0.99	1.95	1.34
p value for effect size	0.005	0.015	0.028	0.19	0.006	0.03
4-Year Outcome Data	Actual Case	Worst Case			Actual Case	Worst Case
Surgery; n = 29	24 Yes 5 No	24 Yes 18 No			21 Yes 8 No	21 Yes 21 No
No surgery; n = 22	12 Yes 10 No	13 Yes 10 No			6 Yes 16 No	7 Yes 16 No
Effect size: Hedges' d	0.75	0.01			1.06	0.45
Lower limit of 95% confidence intervals	0.07	−0.55			0.37	−0.14
Upper limit of 95% confidence intervals	1.46	0.58			1.74	1.04
p value for effect size	0.04	0.96			0.003	0.14

1

Hedges' d was calculated as described by Hasselblad and Hedges (1995).

Swezey (1996) retrospectively evaluated the progress of 47 patients diagnosed with neurogenic claudication 5 years earlier. At the time of diagnosis, the patients' average age was 76 years. Forty-three of these patients had moderate to marked lumbar spinal stenosis. The authors do not report how patients were judged to be mild, moderate, or severe with regard to stenosis. No spinal canal measurements were reported. All patients were started on conservative treatment (exercise, use of a cane, analgesic and nonsteroidal anti-inflammatory drugs). Thirteen patients received epidural steroid injections when other measures did not provide relief from neurogenic claudication. During the 5-year period, 11 patients were given laminectomy to relieve symptoms. This group was considered to have a greater proportion of moderate to severe neurogenic claudication, and all were considered improved after surgery. However, the lack of data on spinal canal diameters reduces the usefulness of this data in predicting who will benefit from conservative treatment and who will need surgery. Of the other 36 patients, 20 reported improvement in symptoms, 14 reported no change, and two reported a worsening of symptoms. This is one of the few trials that follows patients from diagnosis through conservative treatment and then to surgery. Although the numbers may be too small to provide a reliable estimate of the success of conservative treatment, this study indicates that 72 percent of patients (34 of 47) that begin conservative treatment will improve or remain the same, while 23 percent of patients (11 of 47) will eventually receive surgery for relief of symptoms. Those patients that receive surgery will tend to have greater stenosis.

Herno et al. (1996) attempted to generate comparable treatment groups by retrospectively matching surgical patients to a group of 57 nonsurgical patients. Patients were matched according to sex, age, myelographic findings, major symptoms, and duration of symptoms. Fifty-four matched pairs were constructed. Total spinal block and subtotal block occurred in only one and three matches, respectively. The remainder of the matches had AP diameters of <12 mm (31 patients) or had lateral stenosis (19 patients). The followup periods were 4.3 and 4.1 years for the nonsurgery and surgery groups, respectively. At followup, measures of disability and functional status were similar between groups. The authors caution that an important shortcoming of this retrospective study is the lack of knowledge about starting pain level and disability in either group and that patients with more pain are likely to have selected surgery over conservative treatment. This precludes any reliable comparison of surgery and medical treatment.

Hurri et al. (1998) retrospectively assessed the outcomes of surgery and conservative treatment 12 years after treatment began. Among the 57 patients in the surgery group, 26 (46 percent) were considered to have severe stenosis (<7.0 mm sagittal diameter of the canal), while in the nonsurgery group, 6 of 18 patients had severe stenosis. The authors report that there were no statistically significant differences in the percentage of patients improved (63 percent surgery vs. 44 percent conservative) or worse (18 percent vs. 11 percent) after 12 years. Although long followup periods are, in general, desirable, the authors suggest that after such a long period, any current patient problems may be caused by factors other than the original stenosis and that this could obscure the efficacy of treatment. This, however, is a difficult hypothesis to test. A study with multiple followup times would seem to be needed, as well as an accounting of the length of time that symptoms are relieved and the number of patients who received relief but later had a return of symptoms. Therefore, this study was not used in our analysis.

The study by Mariconda et al. (2000) consisted of 20 patients who received surgical treatment (standard wide decompressive laminectomy) and 17 patients who did not receive surgery. This latter group consisted of 14 patients who refused surgery and three patients who were not considered for surgery due to advanced cardiopulmonary disease. The treatment given to the patients who did not receive surgery was not described. All patients were older than 40 years, and the mean for the most stenotic dural sac cross-sectional area was 68 mm² in surgical patients and 78 mm² in conservatively treated patients. Baseline characteristics were different between the groups. The nonsurgery group had a better functional status as determined by the overall Beaujon scoring system (mean and standard deviation of 11 ±2.4 v. 8.1 ±2.7, p <0.05, t-test), the Beaujon score for leg pain at exertion (0.8 ±0.7 v. 0.25 0.6, p <0.05, t-test), and the Beaujon score for neurological deficits (3.3 ±1.0 v. 2.3 ±1.0, p <0.05, t-test). In the Beaujon scoring system, the overall score goes from 0 (worst) to 20 (normal), the leg pain at exertion score goes from 0 (severe) to 2 (none), and the neurological deficit score goes from 0 (major or sphincter dysfunction) to 4 (none).

Figure 21. Beaujon Score from Mariconda, Zanforlino, (more...)

   Figure 21. Beaujon Score from Mariconda, Zanforlino, Celestino et al., 2000

The Beaujon Scoring System goes from a worst possible functional score of 0 to a normal functional score of 20.

Figure 22. Leg Pain at Exertion Score from (more...)

   Figure 22. Leg Pain at Exertion Score from Mariconda, Zanforlino, Celestino et al., 2000

The Beaujon Scoring System for leg pain exertion goes from a score of 0 (severe) to 2 (no pain).

Figure 23. Beaujon Score for Neurological Deficit (more...)

   Figure 23. Beaujon Score for Neurological Deficit from Mariconda, Zanforlino, Celestino et al., 2000

The Beaujon score for neurological deficit goes from 0 (major or sphincter dysfunction) to 4 (none).

21

22

23

Some information on the efficacy of conservative vs. surgical treatment for patients with severe symptoms may be obtained from prospective surgical trials provided pretreatment patient characteristics are clearly stratified and reported, and patients have previously failed conservative treatment. As discussed later in Chapter 5, few surgical studies report the use of and failure of prior conservative therapy. Two single arm surgical trials (no nonsurgical patients were included in the studies) have reported patient characteristics and the failure of prior conservative treatment (Weiner, Walker, Brower et al., 1999; Kleeman, Hiscoe, and Berg, 2000). These studies provide some evidence that patients with severe symptoms will not benefit from conservative treatment but will benefit from surgical treatment. Independent evaluation of patient outcomes in both trials increases the validity of this.

Weiner et al. (1999) demonstrated that partial laminectomy improved walking ability in 30 patients with severe neurogenic claudication (average age of 68 years). Nine months after surgery, the average walking ability increased from approximately 100 m to between 300 m and 600 m. Other measures of patient outcomes also improved; 13 patients had almost complete pain relief and 13 patients had a good deal of pain relief. In a similar study with 54 patients with neurogenic claudication (average age 71 years), Kleeman et al. (2000) used partial laminectomy to relieve leg pain. Two and a half years after surgery, 65 percent of patients reported complete relief from their leg pain and 33 percent reported that their pain was better.

Single arm trials (noncontrolled) have a large potential for bias in favor of the therapy under investigation. Therefore, the studies by Weiner et al. (1999) and Kleeman et al. (2000) may be biased in favor of reporting successful results for surgical treatment. Uncontrolled, nonrandomized controlled trials, and historically controlled trials have been shown to favor new therapies over the control therapy compared to RCTs (Sacks, Chalmers, and Smith, 1982; Colditz, Miller, and Mosteller, 1989). Uncontrolled single treatment trials may therefore be expected to produce an over estimate of the benefits of the therapy.

Katz et al. (1999) prospectively evaluated the pain and walking ability of 263 preoperative patients and 199 patients at 2 years post surgery. Patients had a mean age of 69 years at enrollment (range of 50 to 92 years). The use of prior conservative therapy is not reported. Katz et al. (1999) reported that there were no significant differences between patients who dropped out (27 percent of patients by 2 years) and those who remained in the study. At enrollment, 81 percent of patients reported they were in severe pain. By 2 years after surgery, this was 31 percent. Also at 2 years, the percentage of patients who could walk two blocks had increased from 39 percent to 67 percent, and the percentage of patients who could walk 1 mile increased from 13 percent to 42 percent. Eighty percent or more of the patients in this study may be in the severe category of symptoms, but patient outcomes were not stratified according to preoperative conditions.

Other single arm prospective trials of surgical treatment also suggest that patients improve after surgery (Jonsson, Annertz, Sjoberg et al., 1997; Javid and Hadar, 1998). However, these trials have patients with a wide range of ages and symptoms that limit the use of their data for determining if mild-, moderate-, or severe-symptom patients benefit from surgery. Jonsson et al. (1997) examined 105 patients with an average age of 65 years, but a range of 37 to 83. All patients reported preoperative leg pain and dysfunction and were given partial laminectomies. Eighty-six patients were available through the 5 year followup period. At 2 years, leg pain was relieved in 67 percent of patients, and the percentage of patients with poor walking ability (<0.5 km) declined from 70 percent to 30 percent. By 5 years, only 52 percent of patients were free of leg pain and 35 percent of patients could not walk more than 0.5 km. These results for walking capacity should be contrasted with those of Weiner et al. (1999). In this study, patients improved from less than 100 meters to an average of 500 meters. Under the Jonsson et al. (1997) rating of walking ability, the Weiner et al. (1999) patients would still be considered to have poor walking ability. These differences in approach to rating walking ability and the wide ranges in walking ability complicate the comparison of study results and reduce the value of the data presented by Jonsson et al (1997). Average walking distances are not reported for each of the categories of walking ability in Jonsson et al. (1997). Therefore, we are not able to judge the degree of improvement associated with each initial category of walking ability, nor compare patients from Jonsson et al. (1997) with patients of the same condition in Weiner et al. (1999).

Javid and Hadar (1998) examined 86 patients with central stenosis (average 65 years, range of 27 to 89) and 23 patients with lateral recess stenosis (average 54 years, range of 25 to 79), all of whom received a standard wide laminectomy. Preoperative leg pain and walking difficulty was reported by 98 percent and 76 percent of patients with central stenosis, respectively, and 96 percent and 57 percent of patients with lateral recess stenosis, respectively. Data on walking ability are only reported at the last followup (range 1 to 11 years). At the last followup, patients with central stenosis judged their walking ability as much better or somewhat better (69 percent), no different (10 percent), and somewhat or much worse (21 percent). Patients with lateral recess stenosis judged their walking ability as much better or somewhat better (68 percent), no different (9 percent), and somewhat or much worse (23 percent). These walking data are of little value because 24 percent of the central stenosis patients and 43 percent of the lateral recess stenosis patients originally reported no difficulty in walking, yet their evaluation of walking ability is included in the last followup data. As in Jonsson et al. (1997), no average walking distances are reported for each of the categories of walking ability, and therefore, no comparisons to other studies are possible.

Summary

The lack of comparable patient groups and pretreatment data are a common problem in evaluating studies that examined both surgical and nonsurgical treatment groups. Typically, the two patient groups differ in the extent to which lumbar spinal stenosis affects their signs and symptoms and their pretreatment outcome measurements. This leads to treatment selection based on the extent of disease, and patients are not randomly assigned to treatment groups, except in the recent study published by Amundsen et al. (2000). Less severe cases may tend to receive conservative treatment, and more severe cases may tend to receive surgery. Data are lacking on the effect of conservative treatment on patients with severe stenosis because these patients seem to receive surgery shortly after diagnosis. In Swezey (1996), those patients who did not fare well with conservative treatment tended to have greater stenosis, but data on spinal canal diameter are not reported, and this trend cannot be verified. The trial published by Amundsen et al. (2000) offers the best available evidence that patients with severe symptoms benefit more from surgery than conservative treatment. In this trial, the apparent superiority of surgery in moderate-symptom patients may be an artifact caused by inclusion of severe-symptom patients in the moderate-symptom group. The failure of these patients to respond to conservative therapy supports the benefits of surgery for patients with severe symptoms. The studies by Herno et al. (1996) and Mariconda et al. (2000) suggest that patients with moderate stenosis may improve after receiving only conservative treatment. However, the data presented by Atlas et al. (1996, 2000) suggest that at one year after treatment, patients with moderate pain will benefit more from surgery than from conservative treatment. The statistical significance of the observed long-term effects in this study (4 years) is not robust to a worst-case sensitivity analysis of dropouts.

Degree of Stenosis

Table 37. Relationship between Degree of Stenosis and (more...)

Table 37. Relationship between Degree of Stenosis and Surgical Results

Authors and Year	Modality	Results (most severe stenosis first)
Hurri, Slatis, Soini et al., 1998	Myelogram	Mean Oswestry score Severe stenosis: 39.0 Moderate stenosis: 28.0
Airaksinen, Herno, Turunen et al., 1997	Myelogram (403), CT (35)	Mean Oswestry score Total block: 28 ± 17 (mean ± SD) Subtotal block: 30 ± 19 Less than 10 mm: 35 ± 19 10 to 12 mm: 36 ± 17 More than 12 mm: 37 ± 15
Nishizawa and Fujimura, 1997	Myelogram, CT	Recovery rate Grade 3 myelogram: 78% Grade 2 myelogram: 80% Grade 1 myelogram: 75% Grade 3 CT: 56% (p = NS) Grade 2 CT: 81% Grade 1 CT: 81%
Sato and Kikuchi, 1997	Myelogram	Mean JOA score Two-level stenosis: 21.6 One-level stenosis: 24 (p = NS)
Silvers, Lewis, and Asch, 1993	Myelogram	Satisfactory pain relief Complete block: 12/15 (80%) Incomplete or no block: 70/113 (62%) 1 Resume normal activity Complete block: 12/15 (80%) Incomplete or no block: 60/113 (53%) Overall satisfaction Complete block: 14/15 (93%) Incomplete or no block: 82/113 (73%)
Johnsson, Uden, and Rosen, 1991	Myelogram	Overall improvement (patient opinion) Complete block: 9 improved, 5 worse Moderate stenosis: 17 improved, 7 unchanged, 6 worse Pain level Complete block: 6 good, 6 fair, 2 poor Moderate stenosis: 13 good, 14 fair, 3 poor
Jalovaara, Lahde, Iikko et al., 1989	Myelogram	Overall result Marked stenosis: 6 good, 12 fair, 4 unchanged, 3 worse Moderate stenosis: 3 good, 2 fair, 1 unchanged, 0 worse
Surin, Hedelin, and Smith, 1982	Myelogram	Overall result Marked stenosis: 3 excellent, 9 good, 3 fair or poor Moderate stenosis: 5 excellent, 2 good, 0 fair or poor Back pain Marked stenosis: 3 none, 4 mild, 2 severe Moderate stenosis: 3 none, 4 mild, 0 severe
Johnsson, Willner, and Pettersson, 1981	Myelogram	Overall result Complete block: 3 excellent, 2 good, 1 unchanged, 1 worse Partial block: 7 excellent, 4 good, 3 unchanged, 1 worse No compression: 0 excellent, 0 good, 1 unchanged, 4 worse
Scafuri and Weinstein, 1981	CT (first generation)	Excluded due to use of obsolete technology
Verbiest, 1977	No imaging reported	Not relevant to this question
Paine, 1976	Myelogram	Overall result AP diameter 0-5 mm: 7 excellent, 5 good, 4 fair, 5 poor AP diameter 6-10 mm: 14 excellent, 13 good, 6 fair, 6 poor AP diameter 11-15 mm: 14 excellent, 8 good, 2 fair, 1 poor AP diameter > 15 mm: 2 excellent, 3 good, 1 fair, 0 poor

1

Our own calculation.

Hurri et al. (1998) used a two-point quantitative scale to measure stenosis: whether the sagittal (anterior-posterior) diameter of the dural sac (measured by myelography) was more or less than 7 mm. Their 1998 articlereports disability rates among their patients at long-term (12 years) followup. They used the Oswestry index to measure back pain disability (100 is completely disabled). Patients with severe stenosis at the time of treatment had greater disability (mean Oswestry index: 39.0) than patients with moderate stenosis (mean Oswestry index: 28.0). The difference was statistically significant both for the unadjusted score and when adjusted for age, sex, and other factors. Hurri et al. (1998) did not distinguish between patients given surgical and nonsurgical treatment. We cannot determine from this article whether surgical treatment was more effective in one group or the other (Hurri, Slatis, Soini et al., 1998).

A Finnish study reported stenosis grade in a five-point scale: total block, subtotal block, anterior-posterior diameter less than 10 mm, 10 to 12 mm, and more than 12 mm (Airaksinen, Herno, Turunen et al., 1997). All 438 patients in this series were treated surgically, so we cannot use these results to see whether image data can be used for patient selection. As with Hurri et al.'s (1998) trial, the Finnish group found a statistically significant association between stenosis degree and Oswestry score at followup (mean 4.3 years). However, this group found the opposite relationship; more severe stenosis was associated with better, not worse, outcomes. If more data from this study had been reported, it may have been possible to resolve this apparent contradiction. Preoperative Oswestry score data could have allowed one to determine if patients with the most severe pretreatment stenosis in the Finnish trial, like those in the Hurri trial, had more severe symptoms than patients with a lesser degree of stenosis.

Nishizawa and Fujimura (1997) used a three-point scale and reported myelography and enhanced CT results separately. Surgical outcomes were reported using the Japan Orthopaedic Association score. The "recovery rate" reported as the outcome measure controlled for preoperative condition because it measured the percentage degree to which patients' scores returned to normal. The percentage of patients with successful surgical outcomes was not significantly affected by stenosis degree. However, the statistical test used by the authors was not reported, and we cannot independently verify the findings. As with the Finnish group, no nonsurgical control group existed to compare results (Nishizawa and Fujimura, 1997).

The study by Johnsson et al. (1991) compared patients with complete block on myelography to patients with moderate stenosis. Patients with spinal canal diameter of 12 mm or more were excluded. Patients who were not operated on were used as a control group, but patients were not randomized to that group. Comparisons of the operated and nonoperated groups are analyzed as part of Question 6. The mean spinal canal measurement was slightly larger in the nonoperated group than in the moderate stenosis group, and it was not reported whether any of the nonoperated patients had complete block. Several outcome measures were reported, including patients' and clinicians' estimations of results (worse, unchanged, improved), degree of pain, and estimation of walking distance. None of the results appeared to be associated with degree of stenosis (χ² for overall results = 4.31, df = 2, p = 0.12; χ² for pain = 0.19, df = 2, p = 0.91) (Johnsson, Uden, and Rosen, 1991).

The threshold defining "marked" and "moderate" stenosis in the article by Jalovaara et al. (1989) was 10 mm. Patient outcomes were measured after a mean of 3.8 years of followup and were based mostly on degree of pain and return to normal activities. "Good" outcomes were attained when patients had no more than slight pain and resumed normal activity with few limitations. "Fair" outcomes were attained if patients had some relief of pain and could resume limited activities. The other two outcomes, "unchanged" and "worse," are self-explanatory. The results appear to be better for patients with moderate stenosis than for those with severe stenosis. However, as with the other trials, we do not know the patients' preoperative condition, so we cannot tell whether the improvement was the result of the surgery (Jalovaara, Lahde, Iikko et al., 1989).

Surin et al. (1982) reported on a trial with similar groups of patients. This trial was specifically intended to measure the effect of spinal canal measurement on surgical results, but the patients' preoperative condition was reported in little detail, making it difficult to distinguish treatment effects from pre-treatment differences between groups. This renders interpretation of the results difficult (Surin, Hedelin, and Smith, 1982).

Johnsson et al.'s (1981) case series included some patients with no compression of the spinal cord evident on the myelogram (spinal canal AP diameter 11 cm or more) as well as patients with complete or partial block observed. There was no improvement after surgery in any of the patients whose myelograms were negative for stenosis. Otherwise, outcomes reported in the article were not significantly different among patients with moderate stenosis than among patients with a complete block. The investigators did not explain the unusual results for patients with negative myelograms and provide little information on these cases. The types of symptoms of the patients without myelographic evidence of stenosis were not different from those of the other groups. However, the severity of symptoms and the presence or absence of other conditions that could cause these symptoms are not reported. One can question whether these patients did in fact have spinal stenosis. While stenosis is usually defined by its radiographic appearance, Johnsson et al. (1981) included patients in this report based on surgical findings, but those surgical findings do not appear to involve any evaluation of the spinal canal itself. Their definition of spinal stenosis was hypertrophy of the neural arches and especially the facet joints, as well as a lack of dura pulsation and epidural fat. Considering that all the other trials reported using the imaging findings to define spinal stenosis, interpretation of the results of Johnsson et al. (1981) is difficult (Johnsson, Willner, and Pettersson, 1981).

Measurements at surgery were also reported by Verbiest (1977), whose case series spanned the period of 1948 to 1975. No imaging findings were reported in this article, so we cannot determine whether he concurs with Johnsson et al. (1981) about the surgical results of patients with negative myelograms.

Paine reported surgical results from a large series of patients (n = 457) with disk herniation (Paine, 1976). Degenerative spinal stenosis was diagnosed in addition to disk herniation in 95 patients, and myelography results were reported for 91 of them. Details of the methods are lacking, but Paine's article includes a table correlating overall results (combining return-to-work information and patients' pain complaints) with degree of stenosis. Our chi-squared test on these data found no significant difference in results between stenosis groups (χ² = 8.51, df = 9, p = 0.48).

Number of Stenotic Levels

Sato and Kikuchi (1997) measured the number of stenotic levels rather than the degree of stenosis. They did not find statistically significant differences in JOA scores between patients with stenosis at both L4 and L5 and patients with stenosis only at L5. Data reported in the article are insufficient to permit us to verify this finding or to determine whether the findings resulted from a lack of statistical power in the study design (Sato and Kikuchi, 1997).

Paine (1976) also found that surgical results were better among patients with stenosis of only one vertebral level, compared to patients with two or more levels of stenosis, but our reanalysis of the data found no statistically significant difference (χ² = 8.355, df = 6, p = 0.21). Preoperative condition of the patients was not reported, so we cannot determine whether surgery was more effective for the patients with mild stenosis (Paine, 1976).

Spondylolisthesis and Scoliosis Measurement

McCullen et al. (1994) reported a regression analysis for the effect of various patient characteristics and imaging findings on surgical outcomes. Stenosis grade or spinal measurements were not included in the analysis, but scoliosis and spondylolisthesis measurements before and after surgery were included. They obtained the data from measurements of plain film x-rays. From those data, we calculated correlation coefficients and their significance (McCullen, Bernini, Bernstein et al., 1994).

Preoperative spondylolisthesis, measured as the percentage of slippage (displacement) between the vertebrae, had a significant negative association with surgical results (correlation coefficient −0.172, p = 0.03). This relationship lost statistical significance when regression results were adjusted for the patients' sex (correlation coefficient −0.148, p = 0.07). Scoliosis was not significantly associated with outcomes (sex-adjusted correlation coefficient −0.107, p = 0.24). As expected, decreases in spondylolisthesis after surgery had a highly significant association with positive surgical outcomes (sex-adjusted correlation coefficient −0.271, p = 0.004). Spondylolisthesis is a predictor of worse outcomes after surgery, but these data do not tell us whether measuring spondylolisthesis predicts whether surgery will help a particular patient.

Summary

No published trials provided the data necessary to determine whether a group of lumbar spinal stenosis patients with particular results on some diagnostic imaging test will have better results after surgery than another group. The one controlled surgical trial that reported imaging results (Hurri, Slatis, Soini et al., 1998) did not differentiate between surgical and nonsurgical patients in its published imaging results.

The results found in this set of clinical trials could have several different causes. Sufficient information is not available in any of the articles to permit us to prove an association between imaging findings and surgical results. At this time, we cannot use imaging results to identify patient groups that would be more or less likely to benefit from surgery. One trial (Johnsson, Willner, and Pettersson, 1981) found that patients with normal myelograms did not benefit from surgery, but there is a question as to whether those patients even had spinal stenosis.

Comparisons of Laminectomy Procedures in Patients With Central Lumbar Stenosis

Only three trials, Hanakita et al. (1999), Thomas et al. (1997), and Ray (1982), provided a possible comparison of results between surgical methods: laminectomy versus partial laminectomy or laminotomy. However, differences between outcomes measured and the mean ages of the patient groups being compared prevented any meaningful combination of data. Hanakita et al. (1999) compared patients all younger than 65 years, while the mean age for Thomas et al. (1997) was 64, and the mean ages for the laminectomy patients and the partial laminectomy patients in Ray were 54 and 46 years, respectively. Thomas et al. (1997) and Ray could have been combined, but each study used different outcome measures (Thomas et al. used walking, and Ray used a global assessment) as well as different followup periods (Thomas et al. used 24 to 62 months, and Ray used 10 and 13 months).

Hanakita et al. (1999) reported a retrospective study of patient evaluation of surgical outcome. Patients received laminectomy, laminectomy plus fusion, or partial laminectomy. No pretreatment data are available to determine patient status before surgery; therefore, there is no means of evaluating the success of each surgical procedure. Comparisons across surgical methods are also complicated by the fact that patients with more than a 10 mm slip distance or a slip of more than 15° received fusion, so the patient groups are not the same. Therefore, this study cannot be used to evaluate the relationship between surgical methods and successful outcomes (Hanakita, Suwa, and Mizuno, 1999).

Ray (1982) reported on patients who received laminectomy with partial laminectomy. The only patient information provided was average age and duration of pain before surgery. As in the previous study, the lack of data on pretreatment conditions prevents the use of this study to evaluate the relationship between surgical methods and successful outcomes (Ray, 1982).

Table 38. Analysis of Walking Capacity Data from Thomas, (more...)

Table 38. Analysis of Walking Capacity Data from Thomas, Rea, Pikul et al., 1997

Patient Group	Posttreatment Walking Distance without Pain (City Blocks)			Effect Size (Hedges' d) and Confidence Limits
	>3	1 to 3	<1
Laminectomy n = 12	5	2	5	−0.015 −0.787 to 0.756 p = 0.969
Laminotomy n =14	4	7	3

The Effect of Fusion and Instrumentation in Patients With Central Lumbar Stenosis

Table 39. Comparison of Effect Sizes for Data on Pain (more...)

Table 39. Comparison of Effect Sizes for Data on Pain Relief from Grob, Humke, and Dvorak, 1995

Surgical Method	Pain Relief Score	P Value of t-Test	Hedges' d	Confidence Limits
No fusion n = 15	6.0
Single-level fusion n = 15	5.8	0.25	0.429 p = 0.245	−0.294 to 1.153
Multiple-level fusion n = 15	5.8	0.92	0.037 p = 0.919	−0.679 to 0.753

The Effect of Fusion and Instrumentation in Patients With Lateral lumbar stenosis

Table 40. Comparison of Effect Sizes for Data on Global Assessment (more...)

Table 40. Comparison of Effect Sizes for Data on Global Assessment from Lee and deBari, 1986

Patient Group	Preoperative Score	Postoperative Score	Improvement
With rods n = 12	18.9 ±8.72	50.50±12.37	31.58±17.59
Without rods n = 12	21.41±9.23	53.58±19.06	32.16±15.75
EffectsSize (Hedges' d)	−0.269	−0.185	−0.033
Confidence limits	−1.073 to 0.535	−0.989 to 0.617	−0.834 to 0.767
p value	0.512	0.651	0.935

Scores are presented as mean and standard deviation and are based on a 100-point rating system in which patients with scores less than 30 are considered in severe pain and have severe limitations on activities and patients with scores greater than 75 are considered to have limited or no pain and normal activities.

The Effect of Fusion and Instrumentation in Patients With Degenerative Spondylolisthesis

The randomized controlled trial of Thomsen et al. (1997) separately reported outcomes for patients with primary degenerative spondylolisthesis and patients with isthmic or secondary degenerative spondylolisthesis. Twenty-one patients with primary degenerative spondylolisthesis receiving partial laminectomy and fusion were compared to 20 patients with primary degenerative spondylolisthesis receiving partial laminectomy, fusion, and instrumentation. Functional outcome was assessed 2 years after surgery using the Dallas Pain Questionnaire. This questionnaire examines daily, work, and leisure activities; anxiety-depression; and social concerns, specifically among patients with low back pain. Mean differences of 73 and 37 between pretreatment and posttreatment scores were reported for the instrumented group and the noninstrumented group, respectively. An increase in scores indicates improvement. The authors reported that these differences in scores were not significant when using the Mann-Whitney test. The authors reported that 44 patients were needed in each treatment group to detect a clinically relevant difference in functional outcome of 15 in the Dallas Pain Questionnaire score. Sufficient patients were included in the total study, but within the primary degenerative spondylolisthesis subgroup, only 20 and 21 patients were available. Therefore, this study may have had too few primary degenerative spondylolisthesis patients to detect differences in outcomes due to treatment. Therefore, this study does not provide reliable evidence for the use of instrumentation with fusion (Thomsen, Christensen, Eiskjaer et al., 1997).

Table 41. Effect Size for Data on Global Assessment (more...)

Table 41. Effect Size for Data on Global Assessment from Fischgrund, Mackay, Herkowitz et al., 1997

Patient Group	Global Assessment				Effect Size (Hedges' d)	Confidence Limits
	Excellent	Good	Fair	Poor
Instrumentation n = 35	20	7	4	4	0.327 p = 0.181	−0.152 0.805
No instrumentation n = 33	16	12	1	4

Table 42. Effect Size for Data on Global Assessment (more...)

Table 42. Effect Size for Data on Global Assessment from Herkowitz and Kurz, 1991

Patient Group	Global Assessment				Effect Size (Hedges' d)	Confidence Limits
	Excellent	Good	Fair	Poor
Fusion n = 25	11	13	1	0	1.437 p = 0.000006	0.815 2.059
No fusion n = 25	2	9	12	2

Table 43. Effect Size for Data on Back and Leg Pain (more...)

Table 43. Effect Size for Data on Back and Leg Pain from Herkowitz and Kurz, 1991

Patient Group	Back Pain Score		Leg Pain Score
	Pre-	Post-	Pre-	Post-
Fusion n = 25	3.3	1.3	4.3	1.0
No fusion n = 25	2.9	2.5	4.0	1.7
Effect Size (Hedges' d)		0.571 p = 0.048		0.571 p = 0.048
Confidence Limits		0.006 1.137		0.006 1.137

The trial reported that patients with fusion had significantly less back pain and leg pain (p <0.05, Student t test). Since a standard deviation was not reported in this study, the Hedges' d effect size was calculated from a p value of 0.049. No analysis was reported for the comparison of pretreatment scores or the comparisons of posttreatment to pretreatment scores.

The randomized controlled trial of Bridwell et al. (1993) purposely violated the randomization procedure so that patients with pathological motion (>10° or >3 mm of slippage) always received partial laminectomy, fusion, and instrumentation (24 patients). Other patients received either partial laminectomy only (9 patients) or partial laminectomy and fusion (10 patients). Thus, patients with the most severe condition were segregated to one treatment, and any comparison to the other treatments containing patients with less severe conditions is biased. Therefore, we cannot use these data in a comparison of surgical methods (Bridwell, Sedgewick, O'Brien et al., 1993).

Plotz and Benini (1998) retrospectively reviewed 106 patients who received decompressive surgery and separated patient data into three groups according to additional surgical methods: fusion, fusion plus translaminar screw fixation, or fusion plus AO internal fixator. At the time of followup, 9 to 120 months after surgery, the fusion only group had less than 10 patients, and there were 14 and 64 patients in the other groups, respectively. Since the control group had less than 10 patients, we did not perform any further analysis (Plotz and Benini, 1998).

Table 44. Effect Size for Data on Functional Status, (more...)

Table 44. Effect Size for Data on Functional Status, Back Pain, and Leg Pain from Yuan, Garfin, Dickman et al., 1994

Patient Group	Functional Status			Back Pain			Leg Pain
	Improved	No Change	Worse	Improved	No Change	Worse	Improved	No Change	Worse
Noninstrumented	1,927	192	13	1,941	165	15	1,945	176	4
Pedicle screw fixation	391	58	2	377	69	3	398	51	2
Hedges' d Effect Size	0.042 p = 0.035			0.086 p = 0.00007			0.037 p = 0.047
Confidence Limits	0.003 0.080			0.044 0.129			0.0004 0.073

Effect sizes were calculated using the odds ratio and the natural log transformation. The no-change and worse groups were pooled to calculate the odds ratio.

Satomi et al. (1992) reported on a retrospective study that divided patients into groups receiving fusion and instrumentation (no decompression) and those receiving various types of decompressive surgery. These groups also differed in mean age (51 vs. 69 years) and mean time from onset of disease (3.8 vs. 8.7 years). These differences in patient characteristics between treatment groups bias any comparison of treatment outcomes. Therefore, these data were not used in our analysis (Satomi, Hirabayashi, Toyama et al., 1992).

Table 45. Effect Size for Data on Global Assessment (more...)

Table 45. Effect Size for Data on Global Assessment from Lombardi, Wiltse, Reynolds et al., 1985

Patient Group	Global Assessment					Effect Size (Hedges' d)	Confidence Limits
	Excellent	Good	Fair	Poor	Failure
Laminectomy n = 20	6	10	1	3	0	−0.586 p = 0.066	−1.211 0.040
Laminectomy plus fusion n = 21	11	8	0	1	1

The number of patients in the fair, poor, and failure groups were combined into a single group in order to perform this analysis.

Fitzgerald and Newman (1976) conducted a retrospective examination of patients given a rigid brace as conservative treatment (29 patients) and a variety of decompressive surgical methods. Patients with less severe symptoms (no indication of nerve root compression) were placed in the conservative treatment group. The differences in methods within the surgery group and the differences in patient characteristics between groups prevent any meaningful comparison of treatment outcomes. Therefore, this study cannot be used in our analysis of surgical procedures (Fitzgerald and Newman, 1976).

Rosenberg (1976) retrospectively reported on patients receiving partial laminectomy (11 patients) and standard wide laminectomy (15 patients). The lack of a specifically defined global outcome scale and the lack of specific pretreatment patient characteristics to judge the effect of treatment prevent any meaningful comparison of treatment outcomes. Therefore, this study cannot be used in our analysis of surgical procedures (Rosenberg, 1976).

Summary

Taken as reported, the results of the randomized controlled trials of Thomsen et al. (Thomsen, Christensen, Eiskjaer et al., 1997) and Fischgrund et al. (Fischgrund, Mackay, Herkowitz et al., 1997) would seem to suggest that instrumentation in addition to fusion does not improve surgical outcomes among patients with spondylolisthesis. However, both trials likely had too few patients (and, therefore, insufficient statistical power) to render any definitive conclusion.

Herkowitz and Kurz (1991) provide evidence that fusion is beneficial compared to decompressive surgery alone in these patients. The other RCTs had flaws in design or reporting that made their results of questionable value.

Drawing conclusions from just one or two trials is, however, problematic. This is because such conclusions have a rather high potential to be influenced by publication bias (the potential that trials with negative findings are not published) or the "file drawer" problem (the tendency of investigators to not report findings that are not statistically significant). Until data from larger and well-designed randomized controlled trials are available, reliable conclusions are not possible.