The Effects of Spinal Fusion on Lumbar Disc Degeneration in Patients with Adolescent Idiopathic Scoliosis: A Minimum 10-Year Follow-Up.

ABSTRACT

STUDY DESIGN: Retrospective study. OBJECTIVES: This study focused on patients with adolescent idiopathic scoliosis (AIS) who were followed up for more than 10 years, and assessed the influence of spinal balance on lumbar degenerative changes at distal unfused segments (DUS). SUMMARY OF BACKGROUND DATA Previous studies suggested that longer fusion segments may result in higher rates of occurrence of disc degeneration (DD) at unfused segments adjacent to the distal fused area. However, there are no existing studies that correlate the degree of DD to the location of lower instrumented vertebra (LIV) and the amount of the residual lumbar curve during the follow-up period. METHODS: Radiologic measurements were recorded at the time of surgery, immediately after surgery, and 10 years after surgery. The Pfirrmann grading scale was used to rate the MR images of these patients. The presence of vertebral DD was also used to classify patients into DD+ and DD- groups. RESULTS: 93 patients with AIS participated in this study. The average age at the time of surgery was 15.2 years; the average follow-up time was 154 months. DD was found in 45 patients (48%) and L5/S1 was the most common (40%) location in those patients. The L1 group experienced DD at a frequency of 34%, whereas the frequency increased with lower LIV placement. There was a significant difference between DD+ and DD- in age at the time of operation, the L4 tilt (pre Op. and post. 10 years), and the number of mobile segments. CONCLUSIONS: Disc degeneration occurred in 48% of the patients at the time of postop. 10 years. Disc degeneration had a tendency to occur in patients with greater preoperative and postoperative 10 years L4 tilt angle and fewer mobile segments in the lower lumbar spine. LEVEL OF EVIDENCE Level III.