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 spondyloli sthesis, whether flexion/extension radiographs should be obtained with the patient in the lateral decubitus or standing position has been an ecdotal. Methods. Fifty consecutive adult patients with spondylolisthe sis underwent flexion/extension lumbar spine radiographs in both posit ions. Abnormal motion was considered above 12-degrees dynamic angulati on or 8% translation. Results. Thirty-one of 50 patients displayed abn ormal translation. Of these, 18 had abnormal motion only when they wer e examined in the lateral decubitus position and not when standing. Ni ne displayed excessive motion in both positions. Only four displayed m ore translation while standing. There was no statistical difference in the evaluation of dynamic angulation based on patient position. Neith er 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 s hould be obtained in the lateral decubitus position.