Diagnostic efficacy of clinical tests for lumbar spinal instability

BACKGROUND: Although various clinical tests are utilized to assess lumbar spine instability (LSI), few have documented diagnostic efficacy. We assessed the diagnostic efficacy of four clinical and one radiographic test for LSI in patients with degenerative lumbar disease. METHODS: A cohort of 52 patients with pain attributed to lumbar spine stenosis and degenerative spondylolisthesis were prospectively evaluated utilizing dynamic X-rays, the passive lumbar extension (PLE) test, instability catch sign, painful catch sign, and the apprehension sign. The results of these preoperative tests were compared with spinal surgeons’ intraoperative documentation of spinal instability considered in this study as the “gold” standard. RESULTS: Intraoperatively, 33 patients demonstrated instability (63.5%) whereas 28 had motion documented on preoperative dynamic radiography. The sensitivity, specificity, positive, and negative predictive value and accuracy of dynamic radiography were 84.8%, 100%, 100%, 79.1%, and 90.4%, respectively. The diagnostic efficiency of PLE was higher than other additional studies – sensitivity 78.8%, specificity 94.7%, positive predictive value 96.3%, negative predictive value 72%, and accuracy rate 84.6%. CONCLUSION: Dynamic radiography was more reliable than any of the clinical tests in diagnosing LSI. Among the latter, PLE had the highest diagnostic value for establishing LSI.