Spinal fusion for chronic low back pain: systematic review on the accuracy of tests for patient selection

BACKGROUND CONTEXT: Spinal fusion is a common but controversial treatment for chronic low back pain (LBP) with outcomes similar to those of programmed conservative care. To improve the results of fusion, tests for patient selection are used in clinical practice. PURPOSE: To determine the prognostic accuracy of tests for patient selection that are currently used in clinical practice to identify those patients with chronic LBP who will benefit from spinal fusion. STUDY DESIGN: Systematic review of the literature. SAMPLE: Studies that compared the results of magnetic resonance imaging (MRI), provocative discography, facet joint blocks, orthosis immobilization, and temporary external fixation with the clinical outcome of patients who underwent spinal fusion for chronic LBP. OUTCOME MEASURES: To determine the prognostic accuracy of tests to predict the clinical outcome of spinal fusion in terms of sensitivity, specificity, and likelihood ratios (LRs). METHODS: Data sources PubMed (1966 to November 2010), EMBASE (1974 to November 2010), and reference lists were searched without restriction by language or publication status. Two reviewers independently selected studies for inclusion, extracted data for analysis, and assessed the risk of bias with the Quality Assessment of Diagnostic Accuracy Studies checklist, modified for prognostic studies. Discrepancies were resolved by consensus. RESULTS: Ten studies met the eligibility criteria. Immobilization by an orthosis (median [range] positive LR, 1.10 [0.94-1.13] and negative LR, 0.92 [0.39-1.12]), provocative discography (median [range] positive LR, 1.18 [0.70-1.71] and negative LR, 0.74 [0.24-1.40]), and temporary external fixation (median [range] positive LR, 1.22 [1.02-1.74] and negative LR, 0.58 [0.15-0.94]) failed to show clinically useful prognostic accuracy. Statistical pooling was not feasible because of different test protocols, variability in outcome assessment, and heterogeneous patient populations. No studies reporting on facet joint blocks or MRI could satisfy the inclusion criteria. Obscure patient selection, high risk of verification bias, and outcome assessment with poorly validated instruments precluded strong conclusions for all tests. CONCLUSIONS: No subset of patients with chronic LBP could be identified for whom spinal fusion is a predictable and effective treatment. Best evidence does not support the use of current tests for patient selection in clinical practice