RADIOGRAPHIC EVALUATION OF INSTABILITY IN SPONDYLOLISTHESIS

Study Design. The amount of intervertebral motion seen during dynamic radiography when imaged with the patient in the standing position was compared with that obtained with the patient in the lateral decubitus position. Summary of Background Data. Regarding analysis of spondylolisthesis, whether flexion/extension radiographs should be obtained with the patient in the lateral decubitus or standing position has been anecdotal. Methods. Fifty consecutive adult patients with spondylolisthesis underwent flexion/extension lumbar spine radiographs in both positions. Abnormal motion was considered above 12-degrees dynamic angulation or 8% translation. Results. Thirty-one of 50 patients displayed abnormal translation. Of these, 18 had abnormal motion only when they were examined in the lateral decubitus position and not when standing. Nine displayed excessive motion in both positions. Only four displayed more translation while standing. There was no statistical difference in the evaluation of dynamic angulation based on patient position. Neither age, degree of slip, listhetic level, nor type of spondylolisthesis correlated with abnormal motion. Conclusions. When spondylolisthesis is being analyzed, to maximize motion, flexion/extension radiographs should be obtained in the lateral decubitus position.