Changes in the unfused lumbar spine in patients with idiopathic scoliosis - A 5- to 9-year assessment after Cotrel-Dubousset instrumentation

Study Design. Postoperative changes in the lumbar spine were studied retrospectively in patients with adolescent idiopathic scoliosis who had been treated with Cotrel-Dubousset instrumentation. Objective. To examine middle-term changes in the unfused lumbar segments below an instrumented scoliosis fusion. Summary of Background Data. Scoliosis fusion by the Harrington method is known to be associated with a flat back in the fused area and subsequent degenerative changes in the segments below the fusion. No data have yet been published concerning a segmental instrumentation system. Patients and Methods. Thirty patients with idiopathic scoliosis, between the ages of 14 and 22 years at the time of surgery, were observed for 5-9 years after surgery. Activity, pain, complications, and 21 radiographic parameters were assessed. Results. The prevalence of low back pain increased from 3% before surgery to 20% al the final follow-up visit, although in none of the patients was the pain so severe that specific treatment was required. Radiographically, uninstrumented lumbar segments generally were realigned successfully in the frontal plane. Analyses in the sagittal plane revealed tendencies to a gradual increase in lumbar lordosis, anterior-upward tilting of the lowest instrumented vertebra, and posterior shift of the sagittal spinal balance. During the follow-up period, seven patients (23%) developed degenerative changes, including mild junctional kyphosis, retrolisthesis, narrowing of disc spaces, or osteophytes. Conclusion. Whereas the overall clinical and radiographic results of surgery were satisfactory, the unfused lumbar segments required careful surveillance, especially in the sagittal plane.