Sagittal alignment of the spine and pelvis in the presence of L5-S1 isthmic lysis and low-grade spondylolisthesis

Study Design. A radiographic study of 82 patients with L5-S1 spondylolysis or spondylolisthesis of less than 50% displacement of L5 on S1. Objective. To measure and describe the sagittal alignment of the spine and pelvis in patients with spondylolysis before the development of a large secondary deformity associated with progression of the spondylolisthesis. Summary of Background Data. Several publications have addressed the alignment of the spine and pelvis as an important factor in the occurrence, symptomatology, progression, and treatment of spondylolysis and spondylolisthesis. To our knowledge, this is the first report to systematically document the native sagittal alignment of affected patients and compare them to a large control population. Materials and Methods. The sagittal alignment in this cohort of 82 patients was compared with a control population of 160 patients without symptoms of back pain or radiographic abnormalities of the spine and pelvis that was the subject of a previous study. Results. Patients with spondylolysis and low-grade spondylolisthesis demonstrate increased pelvic incidence, increased lumbar lordosis, but less segmental extension between L5 and S1 than in a normal population. Conclusions. These data suggest that differences in the sagittal alignment of the spine and pelvis may influence the biomechanical environment that results in the development of spondylolysis and progressive spondylolisthesis.