Anatomic changes in lateral spondylolisthesis associated with adult lumbar scoliosis

Study Design. Prospective consecutive series. Objective. To analyze the anatomic changes in lateral spondylolisthesis. Summary of Background Data. Previous studies have focused on the correlation between lateral spondylolisthesis, and curve progression and pain. To our knowledge, there has not been any detailed report concerning anatomic changes in lateral spondylolisthesis. Methods. We examined 24 consecutive patients (mean age 66 years), with lateral spondylolisthesis associated with lumbar scoliosis who had computerized tomography (CT) after myelography. Coronal reconstruction CT was used to measure the vertebral translation. Vertebral rotation was measured by the Aaro method using transaxial CT. Results. The Cobb angle averaged 26 (range 13 degrees-75 degrees). Lateral spondylolisthesis was found most commonly at the lower-end vertebra. The cephalad-slipped vertebra rotated toward the convex side of the main curve, whereas the caudal vertebra rotated toward the convex side of the lumbosacral hemi (or fractional) curve below. Mean lateral translation and vertebral rotation were 7 mm and 8 degrees, respectively. There was a significant correlation between lateral translation and vertebral rotation (r = 0.49; P = 0.018). The convex superior articular process of the caudal vertebra had compressed the nerve root laterally in 21 patients, of whom 10 had radicular pain. The concave, inferior articular process of the cephalad vertebra had compressed the dural sac posteriorly, and 2 patients had radicular pain. Conclusions. To our knowledge, this study has been the first attempt to analyze anatomic changes in lateral spondylolisthesis using CT. It may offer further insight into the pathogenesis of adult lumbar scoliosis.