Continuing Education Activity

Epidural steroid injections have been used for pain relief since 1952. When indicated, they are an invaluable nonsurgical treatment for low back pain radiating to the lower extremities and, less commonly, for neck pain radiating to the arms. Performing an effective epidural steroid injection requires the steroids to reach the epidural space. Successful epidural steroid injections provide pain relief, restoring function and return to a physical therapy regimen when indicated. The 3 primary routes for epidural steroid delivery include the transforaminal, interlaminar, and caudal approach. The standard of care involves using fluoroscopy or, less commonly, computed tomography guidance to ensure proper needle placement with the aid of contrast flow.

This activity reviews the indications and techniques for performing an effective epidural steroid injection, equipping clinicians with procedural knowledge. Epidural steroid injections are crucial for chronic pain management, requiring a multidisciplinary team for patient-centered care. Nurses handle pre- and post-procedural care, physical therapists support rehabilitation, and primary care clinicians educate on lifestyle changes, ensuring informed consent, ethical practices, and effective interprofessional communication.

Objectives:

• Identify appropriate indications for epidural steroid injections based on patient history and severity of symptoms.
• Evaluate the preparation required for epidural steroid injections involving necessary personnel.
• Interpret the potential complications of epidural steroid injections post-procedure.
• Implement interprofessional team strategies to advance the appropriate and safe use of epidural steroids for low back pain.

Introduction

Epidural steroid injections have been used to treat pain caused by lumbar disc injuries since the 1950s.[1][2][3] These injections are often used in treating radicular pain, a neuropathic pain syndrome that radiates down a dermatome of 1 or more spinal nerves. Typically, the pain is due to nerve root irritation from mechanical compression by an intervertebral herniated disc, leading to inflammation. Additional etiologies leading to mechanical spinal nerve compression include spondylosis, spondylolisthesis, and ligamentum flavum hypertrophy, resulting in neuroforaminal stenosis. In patients with lumbosacral radiculopathy, more than half of the patients report interference in their activities of daily living, and a quarter continue to have severe pain that does not respond well to oral pharmacological treatments.[4][5][6]

Approximately 14% of patients with lumbosacral radiculopathy eventually require surgery for severe pain that may or may not be associated with a neurological deficit.[7] However, in many cases, radicular pain secondary to intervertebral disc herniation improves with medical and rehabilitative treatment. Steroid injection into the epidural space is used to achieve inflammation reduction and pain relief and limit medications or surgery.

The 3 primary routes for epidural steroid delivery include the transforaminal, interlaminar, and caudal approach. The standard of care involves using fluoroscopy or, less commonly, computed tomography guidance to ensure proper needle placement with the aid of contrast flow.[8] The efficacy of epidural steroid injections in lumbosacral radiculopathy has been widely studied, and based on a recent systematic review including 8 randomized controlled trials, a strong recommendation on moderate-quality evidence demonstrates that transforaminal epidural steroid injections can be used to reduce pain at 3 months. However, a clear improvement in physical disability and reduction in surgery was not consistently observed in the literature.[9]

Cervical epidural steroid injections have similarly been shown to provide short-term relief for radicular cervical pain, but long-term outcomes have not been well studied. Limited high-quality evidence suggests that cervical epidural steroid injections can be beneficial for radiculitis secondary to disc herniation and discogenic pain.[10] Most studies focus on interlaminar cervical epidural steroid injections instead of transforaminal cervical epidural steroid injections.[11] Although rare, the morbidity associated with these injections can be catastrophic.

Anatomy and Physiology

The spinal cord and brain are covered by 3 protective layers known as meninges. The innermost layer is the pia mater, which articulates directly with the surface of the spinal cord. The middle layer is known as the arachnoid mater. The dura mater is the spinal cord's outermost and toughest protective layer. This layer is separated from the vertebrae by the epidural space. The epidural space contains the dural sac, blood vessels, fat, connective tissue, and spinal nerves. The contents of the dural sac include the spinal cord (ending at L1 or L2) and the cauda equina. The spinal dura mater is critical to the peripheral nervous system in creating pathways through dural sheaths by surrounding exiting nerve roots from the spinal cord.

The vertebral column protects the spinal cord and consists of 33 vertebrae—7 cervical, 12 thoracic, 5 lumbar, 5 fused sacral, and 4 fused coccygeal vertebrae. There are 23 intervertebral discs that separate the vertebral bodies, starting between C2 and C3 and ending between L5 and the sacrum. Spinal nerve roots exit the spinal column through 2 lateral openings called intervertebral foramina, formed between 2 contiguous vertebrae.[12]

The intervertebral foramen is bounded anteriorly by the intervertebral disc, the superior and inferior endplates of the vertebral bodies, and posteriorly by the superior and inferior articular processes, which articulate as the facet joint. The adjacent pedicles form the roof and floor at that level. The dorsal and ventral roots form a spinal nerve within the intervertebral foramen. Each spinal nerve divides into a ventral ramus and a smaller dorsal ramus upon exiting the foramen.

The intervertebral foramen also contains arteries, veins, and epidural fat. The spinal nerves are supplied segmentally by radicular arteries, which travel with each nerve root. In the thoracic and lumbar spine, radicular arteries arise from branches of the aorta and intercostal arteries. The intercostal and lumbar arteries divide into 3 segments—a dorsal segment supplying the paraspinal muscles, a somatic branch that travels ventral to the spinal cord and supplies the dura, and a radicular artery that supplies the spinal nerve and nerve roots within the intervertebral foramen. The ascending cervical, deep cervical, and vertebral arteries give rise to the radicular and spinal medullary arteries that pass through the cervical intervertebral foramina.

A major concern during transforaminal epidural steroid injections is the careful avoidance of the radicular arteries. Specific needle approaches and protocols are designed to minimize and detect an intravascular injection. The largest radicular artery is the artery of Adamkiewicz, which anastomoses with the anterior spinal artery and supplies the thoracolumbar spinal cord in adults. The origin of this artery generally takes off at T9 but is variable and can arise as low as L5. The artery of Adamkiewicz is left-sided in 68% to 85% of cases and is located in the superior or mid-portion of the intervertebral foramen.[13][14][15] The vertebral arteries course between the transverse foramina of the C2 to C6 vertebrae, typically anterior to the cervical facet joints and the ventral ramus of the cervical nerve root, though variations exist.[16]

Indications

Epidural steroid injections treat pain caused by irritation and inflammation of spinal nerve roots. A specific type of pain, radicular pain, radiates along the dermatome of the affected spinal nerve. Many conditions may irritate the spinal nerve roots, often causing low back (lumbar) pain that radiates down the buttocks or legs, commonly referred to as sciatica. Patients with neck (cervical) pain that radiates to the arms are also common.[17][18][19]

The most common cause of spinal nerve root irritation is pathology of the intervertebral discs. In the case of a herniated disc, the center portion of the disc, known as the nucleus pulposus, breaches the outer layer, the annulus fibrosus, exerting pressure on and pinching the adjacent spinal nerve root. This pressure leads to symptoms such as pain, weakness, and numbness along the path of the affected nerve. Similarly, degenerative disc disease involves the gradual breakdown of intervertebral discs, causing the intervertebral space to collapse and compress spinal nerve roots.

Another common indication for epidural steroid injection is nerve root irritation secondary to spinal stenosis. Spinal stenosis is a condition causing the narrowing of the spinal canal or the foramina of exiting nerve roots. This narrowing is most commonly caused by arthritis of the vertebral joints (facets) or intervertebral disc pathology, as discussed above.

 Other conditions where epidural steroid injections may be indicated include:

• Nonspecific radiculitis  
• Vertebral bone spurs impinging spinal nerve roots 
• Thickening of ligamentum flavum 
• Postlaminectomy syndrome 
• Facet or nerve root cyst with radicular pain 
• Postherpetic or posttraumatic (including intercostal) neuralgia 
• Compression fracture with radicular pain 
• Spondylolysis 
• Spondylolisthesis 
• Scoliosis causing nerve root irritation    

A systematic review evaluated 70 studies on lumbar epidural steroid injections; evidence for efficacy was good for lumbar disc herniations, fair for spinal stenosis, and poor for failed back surgery syndrome.[20] Another meta-analysis demonstrated good efficacy for the use of epidural steroid injections for spinal stenosis and lumbar radiculopathy.[21] Kennedy et al published the results of a prospective study showing the effectiveness of epidural steroid injections in treating lumbar radicular pain. Although patients had pain relief, the relief was short-lived.[22] Another study conducted by Singh et al showed that 2-level transforaminal epidural steroid injections provide better pain relief compared to 1-level transforaminal epidural steroid injections.[23] Although the evidence of efficacy for epidural steroid injections is strong, the longevity of pain relief is limited, and patients require additional therapy for sustained pain relief.[24][25][26]

Contraindications

Absolute contraindications to epidural steroid injections include:

• Systemic infection or local infection at the site of injection
• Bleeding diathesis or full anticoagulation
• Significant allergic reaction or hypersensitivity to contrast, anesthetic, or corticosteroid
• Local malignancy
• Patient refusal

Relative contraindications to epidural steroid injections:

• Uncontrolled diabetes mellitus
• Congestive heart failure
• Pregnancy due to fluoroscopy

Equipment

Epidural steroid injections require the following equipment and materials:

• Fluoroscopic c-arm x-ray device 
• Epidural spinal needles
• Local anesthetics, such as lidocaine or bupivacaine
• Steroids, such as methylprednisolone acetate, triamcinolone acetate, betamethasone acetate, betamethasone phosphate, or dexamethasone phosphate)
• Loss of resistance syringe
• Contrast solution
• Sterile gloves and drapes
• Betadine

Epidural steroid injection may be completed with only topical local anesthesia or under intravenous sedation. In either case, blood pressure cuffs, cardiac monitors, and pulse oximeters monitor vital signs. Previously particulate steroids, such as triamcinolone, methylprednisolone, and betamethasone acetate, have been favored by some clinicians due to their theorized depot effect, or increasing the duration the medication is deposited at the site of pathology. The same particulate effect theoretically providing an analgesic benefit poses a safety concern as the particulates can aggregate to form particles larger compared to a red blood cell. In contrast, nonparticulate steroids, such as dexamethasone betamethasone phosphate, are 10-fold smaller compared to a red blood cell and do not aggregate under light microscopy.[27]

Animal studies show that intravascular injection into the vertebral artery of particulate steroids causes neurological injury, whereas nonparticulate steroids do not.[28][29][28] The theoretical analgesic advantage of particulate steroids has not been established regarding pain reduction or functional outcomes.[30][31][32][33][34] Perhaps, for this reason, nonparticulate steroids are increasingly favored for transforaminal epidural steroid injections.[35][36][37][38][39]

Personnel

The staff includes a physician trained in epidural steroid injections, a nurse or assistant, a fluoroscopic c-arm operator, and an anesthesia clinician who monitors the patient during the procedure. All staff should be trained to manage potential complications of the procedure.

Preparation

The risks and benefits of the procedure should be discussed with the patient, and if they agree, the patient must sign a written consent form. Before the injection, a time-out is necessary to verify the patient's identity and site. The patient is to lie in a prone position on the fluoroscopy table, and once the injection site is identified, the area should be marked, cleaned with betadine, and covered with sterile draping.

Technique or Treatment

Epidural steroid injections may be classified by location (cervical, thoracic, or lumbar) and the needle's path (interlaminar, transforaminal, or caudal). The techniques include interlaminar (between the lamina), transforaminal (across the foramen), and caudal (through the sacrum) epidural steroid injections.

Interlaminar Epidural Steroid Injection

With the patient lying prepped and prone, the interlaminar space between 2 contiguous vertebrae is identified through an anteroposterior view on a fluoroscopic x-ray. Next, the skin and underlying tissue are injected with local anesthetics, such as lidocaine or bupivacaine. Using a midline or paramedian approach between the spinous processes, an epidural spinal needle is inserted into the intended injection site. From superficial to deep, the needle penetrates the skin, subcutaneous tissue, supraspinous ligament (median approach) or paraspinal muscles (paramedian approach), and the ligamentum flavum. A lateral view with the fluoroscopic x-ray is then obtained to confirm the position of the needle. The needle is then advanced using a loss-of-resistance syringe filled with 1 mL of air or normal saline. As the needle passes the ligamentum flavum and enters the posterior epidural space, a sudden loss of resistance occurs, allowing the syringe to inject minimal air or normal saline into the epidural space due to the change in pressure. The loss-of-resistance syringe is then replaced with a syringe filled with the contrast solution, which is then injected to confirm the placement of the needle in the epidural space. After the spread of contrast is confirmed in anteroposterior and lateral views, a steroid, such as methylprednisolone, triamcinolone, betamethasone, or dexamethasone, with or without a local anesthetic is injected into epidural space. Finally, the needle is withdrawn, and pressure is maintained at the injection site to prevent bleeding.

Transforaminal Epidural Steroid Injection

With the patient lying prepped and prone, the lateral foraminal space between 2 contiguous vertebrae is identified through an oblique view on a fluoroscopic x-ray. This view displays the classic Scottie dog, an anatomical landmark for needle guidance. Once the proper injection site is identified, the skin and underlying tissue are injected with a local anesthetic, such as lidocaine or bupivacaine. An epidural spinal needle is then inserted and directed under the pedicle of the superior vertebrae. A lateral view on an x-ray is obtained to determine needle depth and prevent nerve root damage. The needle is then advanced until reaching the outer intervertebral foramen. Contrast injection confirms needle position in both lateral and anteroposterior views displaying epidural spread. A steroid, such as dexamethasone, with or without a local anesthetic is then injected into the epidural space. Finally, the needle is withdrawn, and pressure is maintained at the injection site to prevent bleeding.

Caudal Epidural Steroid Injection

With the patient lying prepped and in a prone position, the sacral hiatus is identified through an anteroposterior view on a fluoroscopic X-ray. Once the proper injection site is identified, the skin and underlying tissue are injected with a local anesthetic, such as lidocaine or bupivacaine. An epidural spinal needle is then inserted and directed through the sacral hiatus. A lateral view on an x-ray is obtained to determine needle depth. Needle placement below the S2 to S3 intervertebral disc space decreases the risk of dural puncture. Contrast injection confirms needle position in both lateral and anteroposterior views displaying epidural spread. The steroid is then injected into the epidural space. Finally, the needle is withdrawn, and pressure is maintained at the injection site to prevent bleeding.[40][41][42]

Complications

Although rare, possible complications include:

• Bleeding 
• Infection      
• Allergic reaction 
• Nerve injury 
• Transient lower or upper extremity numbness and tingling 
• Dural puncture causing positional headache 
• Epidural abscess 
• Epidural hematoma 
• Transient back or lower extremity pain
• Side effects of steroids, such as transient flushing or hot flashes, fluid retention, weight gain, elevated blood sugars, and mood swings
• Adrenal suppression
• Spinal cord infarction (cervical transforaminal epidural steroid injections with particulate steroids)
• Cerebral infarction (cervical transforaminal epidural steroid injections with particulate steroids) [43][44][45]

Clinical Significance

Epidural steroid injections effectively treat cervical or lumbosacral radicular pain and, in certain cases, bypass the need for operative intervention. Previous investigations into the efficacy of epidural steroid injections, including case series, retrospective studies, prospective clinical trials, and systematic reviews, have limitations, including heterogeneous methods and broad inclusion criteria. Published reviews often encompass various delivery routes, such as transforaminal, interlaminar, and caudal, and also include a wide variety of indications in addition to radicular pain, such as axial back pain, failed back syndrome, and spinal stenosis.

Recent studies, including several reviews and meta-analyses, have shown that transforaminal and interlaminar epidural steroid injections can provide reliable pain relief for patients with low back pain associated with radicular symptoms but not axial back pain.[46][47] In some cases, epidural steroid injections can provide long-term benefits lasting up to 12 months and prolong the need for surgery.[48][49][50] For radicular pain secondary to disc herniation, the evidence is good with steroids combined with local anesthetics and fair with local anesthetics alone.[51] Theoretically, the transforaminal route is superior to interlaminar and caudal approaches in delivering medication near the exiting spinal nerve, anterior epidural space, and dorsal root ganglion.[21][52] However, comparing the transforaminal approach with the interlaminar approach shows similar efficacy at 6 months but an early benefit at 2 weeks for transforaminal.[53][54] Other studies have shown that interlaminar epidural steroid injections for primarily axial pain, regardless of etiology, lack effect, except for short-term pain relief.[55] Literature reviews investigating the dose of steroids in epidural steroid injections indicate no dose-dependence in analgesic effect for chronic low back pain or lumbosacral radicular pain.[56][57]

Studies on cervical epidural steroid injections show similarly heterogeneous methods and outcome measures. There is more evidence supporting the use of interlaminar cervical epidural steroid injections compared to transforaminal injections. The evidence demonstrates durable pain relief and improved disability measures at 12 to 24 months. Several studies required multiple injections, and similar efficacy exists between epidural steroid injections with local anesthetics versus local anesthetics alone. The indications included radicular pain, disk herniation, cervical spinal stenosis, and cervical post-surgery syndrome.[11]

Enhancing Healthcare Team Outcomes

Epidural steroid injections are crucial for managing chronic pain, necessitating care coordination from a multidisciplinary team to ensure patient-centered care, optimal outcomes, and safety. Successful administration of epidural steroid injections hinges on the specialized skills and strategic planning of clinicians trained in pain management techniques, underscored by ongoing education in evidence-based practices. Nurses are integral to the process and responsible for pre- and post-procedural care, including monitoring for complications and ensuring patient comfort. Including physical therapists in the care plan underscores the holistic approach to chronic pain management and rehabilitation. Primary care clinicians should educate patients on lifestyle changes such as regular exercise, discontinuing smoking, maintaining a healthy weight, and avoiding a sedentary lifestyle. 

Adherence to ethical principles, including informed consent and confidentiality, alongside a commitment to managing patient expectations through clear communication about the benefits and risks of epidural steroid injections, is essential. Interprofessional communication involves informed decision-making and care coordination, ensuring comprehensive discussions about patient selection, risks, and expected outcomes are shared across disciplines.

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Disclosure: Ketan Patel declares no relevant financial relationships with ineligible companies.

Disclosure: Pooja Chopra declares no relevant financial relationships with ineligible companies.

Disclosure: Seth Martinez declares no relevant financial relationships with ineligible companies.

Disclosure: Sekhar Upadhyayula declares no relevant financial relationships with ineligible companies.