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Database of Abstracts of Reviews of Effects (DARE): Quality-assessed Reviews [Internet]. York (UK): Centre for Reviews and Dissemination (UK); 1995-.

Database of Abstracts of Reviews of Effects (DARE): Quality-assessed Reviews [Internet].

Fusion for low-grade adult isthmic spondylolisthesis: a systematic review of the literature

WC Jacobs, A Vreeling, and M De Kleuver.

Review published: 2006.

Link to full article: [PMC free article: PMC3489314]

CRD summary

This review concluded that outcomes were generally good and better with fusion techniques than with non-operative treatments, but that it was unclear which fusion technique is the best. Given the variation between studies and the limited comparisons with other non-operative treatments, these conclusions should be regarded with caution.

Authors' objectives

To carry out a systematic review of fusion techniques for the treatment of low-grade lumbar isthmic spondylolisthesis in adults.


The Cochrane Controlled Trials Register (Issue 1, 2004), Current Contents (from 1996), MEDLINE (from 1966) and EMBASE were searched up to March 2004; details of the search strategy were reported. The reference lists of retrieved articles were also checked. No language restrictions were applied, but only articles published in peer-reviewed journals were eligible for inclusion.

Study selection

Study designs of evaluations included in the review

Studies that included at least 10 eligible participants qualified for inclusion in the review. Studies reported in the review included both retrospective and prospective observational studies and comparative studies. The duration of follow-up in the included studies ranged from 1 to 7 years.

Specific interventions included in the review

Studies assessing at least one surgical fusion technique with or without instrumentation were eligible for inclusion. The studies had to adequately describe the instrumentation used, the application of decompression and the intention to reduce the listhesis. Comparative studies included in the review evaluated the effect of different posterolateral fusion (PLF) techniques (e.g. with and without anterior interbody fusion with Brantigan cage, decompression, or bone graft substitute such as an allograft). PLF techniques were also compared with non-operative techniques such as exercise and techniques with and without instrumentation (e.g. Cottrell-Dubousset instrumentation or variable screw placement).

Participants included in the review

Studies that assessed adult participants with low-grade isthmic spondylolisthesis at one lumbar level were eligible for inclusion. Low-grade spondylolisthesis was defined as grade I or II or less than 50% slip, and the participants had to have failed to respond to conservative treatment in order to be eligible for inclusion. Where other participants without low-grade isthmic spondylolisthesis (more than 5% of the population) were included in the study, the results had to be presented separately for the eligible population.

Outcomes assessed in the review

Studies that assessed radiological outcome measures (e.g. fusion rates, lordotic angles and correction rates), clinical outcome measures (e.g. pain scores, complication rates, reoperation rates) or functional outcome measures (e.g. the Short-form Health Survey, Van Tulder score, Western Ontario and McMaster Universities Index of Osteoarthritis, and the Oswestry Disability Index) were eligible for inclusion. The review also assessed complications.

How were decisions on the relevance of primary studies made?

Two reviewers independently selected studies for inclusion in the review; if consensus could not be reached a third reviewer was consulted.

Assessment of study quality

Two reviewers independently assessed the validity of each study and reached a consensus decision; a third reviewer was consulted if necessary.

Randomised controlled trials (RCTs) were assessed using items from a published checklist by van Tulder. The criteria included: valid method of randomisation; allocation concealed; comparable participant characteristics; blinding of the patient, surgeon or outcome assessor; cointerventions described; acceptable compliance; drop-out less than 10%; comparable outcome assessments between study groups; and intention-to-treat analysis used. A maximum score of 11 points was possible; studies scoring 6 or more points were considered to be of a high quality. Uncontrolled studies were assessed using criteria published by Cowley; studies scoring 9 or more points out of a maximum of 17 were considered to be high quality. Both sets of criteria were scored as 'yes', 'no' or 'unsure'.

Data extraction

One reviewer extracted the data and a second reviewer checked the extraction. Standard deviations were reported where available, or were estimated from ranges if appropriate. Relative risks were calculated for dichotomous outcomes and weighted mean differences for continuous outcomes; 95% confidence intervals were reported.

Methods of synthesis

How were the studies combined?

The authors intended to perform a meta-analysis but this was not possible due to the heterogeneity between studies. The data were therefore grouped according to study design (with RCTs being used to provide evidence about the 'best surgical treatment' and observational studies providing evidence on outcomes after surgery), then summarised in a narrative text and tables.

How were differences between studies investigated?

Differences between the studies were evident from the data tables and some were discussed in the text of the review. The results from high-quality RCTs were used to provide the 'best evidence'.

Results of the review

Twenty-nine studies (n=1,181) were included in the review: 8 RCTs (n=385) and 21 observational studies (n=796).

Four of the 8 RCTs were described as high quality. With the exception of 1 RCT that scored only 1 point; the remaining trials scored 4 or 5 points out of a possible 11. Of the 5 uncontrolled cohort studies included in the analysis only, two were considered to be of a high quality; the remaining studies scored either 5 or 7 points out of a possible 17. Ten of the 21 observational studies failed to clearly identify consecutive patient selection.

Best surgical treatment (8 RCTs, n=385).

Four RCTs (n=169) compared PLF with or without instrumentation, but found no additional benefits of using instrumentation. A 'best evidence analysis' compared fusion rates in the 2 high-quality RCTs (n=115) and found non significant differences in both studies which favoured the non-instrumented group (78% non-instrumented versus 65% instrumented; and 84% non-instrumented versus 73% instrumented). A further 3 RCTs (n=105) found no significant differences when PLF was compared with modifications of PLF including the addition of anterior interbody fusion (1 RCT), decompression (1 RCT) and bone graft substitute (1 RCT). One low-quality RCT (n=111; quality score 1) reported that PLF was superior to exercise.

Outcome after surgical techniques (21 observational studies, n=796).

Twenty-four patient groups were included in the analysis: 15 PLF groups, 5 anterior interbody fusion groups, 2 posterior interbody fusion groups, 1 posterolateral endoscopic foraminal decompression group and 1 unspecified treatment group.

Clinical outcomes.

The proportion of participants achieving good or excellent clinical outcomes in the PLF groups ranged from 60 to 98%, and fusion rates varied from 81 to 100%. For the anterior interbody fusion groups, good or excellent clinical outcomes ranged from 85 to 94% and fusion rates from 47 to 90%. For posterior interbody fusion groups, good or excellent clinical outcomes were reported to be 45% and fusion rates 80% and 95%. For posterolateral endoscopic foraminal decompression, 79% of the participants achieved a good or excellent clinical outcome; the fusion rate was not reported.

Radiological outcomes.

Three PLF studies reported an average reduction of the listhesis of 12.3% and an average loss of reduction at follow-up of 5.9%. One PLF study reported that reduction was maintained at follow-up. Data for pre-operative lordotic angles varied considerably.


Eighteen studies (including RCTs) reported complications. Complications rates varied between studies but, overall, the rates were lower for PLF than for anterior interbody fusion and posterior interbody fusion (12%, 16% and 24%, respectively). Complications varied and included neurological complications, instrument failure and infections. Eight types of instrument failures (in 388 patients) were reported for PLF. Adjacent segment failures were not reported in any of the studies.

Authors' conclusions

The evidence suggested that outcomes for surgical fusion techniques are generally good and better than for non-operative treatments. However the current evidence could not distinguish which fusion technique is the most effective.

CRD commentary

This review was based on a clearly described research question with adequate, but sometimes necessarily wide, inclusion criteria. A reasonable search was made to locate relevant information in all languages but, as the authors reported, the search may be subject to publication bias as only articles published in peer-reviewed journals were eligible for inclusion. However, the risk of bias and error in the other review processes was minimised through verification of the study selection, quality assessment and data extraction.

Although a large number of studies were identified, the authors' analyses were limited by the presence of study heterogeneity and poor reporting. The authors excluded studies that did not report adequate details of the participants and this might have introduced selection bias. Comparisons with other non-operative techniques were also limited. Given these difficulties, the use of a narrative synthesis appeared justified. The authors' conclusions about the superiority of fusion techniques should be regarded with caution.

Implications of the review for practice and research

Practice: The authors stated that there was no evidence to support the use of posterior instrumentation, as clinical and radiological outcomes were not better and complication rates were higher. There was also no evidence that decompression is required, although it may be used within clinical settings for nerve root pain.

Research: The authors stated that an RCT is required to compare reduction with modern instrumented PLF with and without anterior column support, with uninstrumented PLF without reduction (control). This study should ensure that participant characteristics, details of the intervention and descriptions of the outcome parameters are adequately reported.

Bibliographic details

Jacobs W C, Vreeling A, De Kleuver M. Fusion for low-grade adult isthmic spondylolisthesis: a systematic review of the literature. European Spine Journal 2006; 15(4): 391-402. [PMC free article: PMC3489314] [PubMed: 16217665]

Indexing Status

Subject indexing assigned by NLM


Adult; Humans; Lordosis /pathology; Research Design; Spinal Fusion /adverse effects /methods; Spondylolisthesis /pathology /surgery; Treatment Outcome



Database entry date


Record Status

This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn.

CRD has determined that this article meets the DARE scientific quality criteria for a systematic review.

Copyright © 2014 University of York.

PMID: 16217665


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