A new evaluation method for lumbar spinal instability: passive lumbar extension test.
BACKGROUND AND PURPOSE: Although many studies have described clinical examination measures for the diagnosis of lumbar spinal instability, few of them have investigated the sensitivity and specificity of the measures that were used. The authors devised a passive lumbar extension (PLE) test for assessing lumbar spinal instability. The purpose of this study was to investigate the sensitivity, specificity, and positive likelihood ratio of this test. SUBJECTS AND METHODS: The PLE test as well as the instability catch sign, painful catch sign, and apprehension sign tests were done for 122 subjects with lumbar degenerative diseases. The subjects were divided into 2 groups-instability positive and instability negative-on the basis of findings on flexion-extension films of the lumbar spine. The sensitivity, specificity, predictive values, and positive likelihood ratio of each test were investigated. RESULTS: The sensitivity and specificity of the PLE test were 84.2% and 90.4%, respectively. These values were higher than those of other signs. The positive likelihood ratio of the PLE test was 8.84 (95% confidence interval=4.51-17.33). DISCUSSION AND CONCLUSION: The PLE test is an effective method for examining patients for lumbar spinal instability and can be performed easily in an outpatient clinic.