The Benefits of Sparing Lumbar Motion Segments in Spinal Fusion for Adolescent Idiopathic Scoliosis Are Evident at 10 Years Postoperatively

Abstract

STUDY DESIGN: A prospective multicenter study. OBJECTIVE: To evaluate the effects of sparing lumbar motion segments on spinal mobility and Scoliosis Research Society-22 scores at 10 years after spinal fusion for major thoracic adolescent idiopathic scoliosis (AIS). SUMMARY OF BACKGROUND DATA: In surgical correction for major thoracic AIS, the long-term benefits of sparing lumbar motion segments remain unclear. METHODS: A prospective multicenter registry was reviewed and patients with major thoracic AIS (Lenke types 1-4) and availability of both preoperative and 10-year postoperative mobility data were included. Spinal fusions ending at L1 or above were defined as thoracic fusions (T), and at L2 or below as thoracic and lumber fusions (T + L). Spinal mobility was evaluated with a measuring tape. The excursions between the starting and ending positions were measured using the distance from the spinous processes of C7 to S1 for forward flexion (FF), and the distance from the tip of the middle finger to the floor for lateral flexion (LF). Substantial reduction of mobility was defined as a reduction rate (a ratio of postoperative change divided by preoperative mobility) of 40% or more. Motion data were correlated with lowest instrumented vertebra levels and group comparisons were performed. RESULTS: We identified 151 patients (average age, 25.1 years). The spinal mobility decreased with more distal lowest instrumented vertebrae (FF, rho = 0.208; right LF, 0.257; left LF, 0.371; P ≤ 0.01). Consequently, the incidence of substantial reduction of mobility was lower in the T group (n = 109) than in the T + L group (n = 42) (FF: 17.4% vs. 50%, LF: 14.8% vs. 51.2%; P < 0.001). Patients with substantial reduction in LF had lower Scoliosis Research Society-22 scores for pain, function, satisfaction, and total scores than those without substantial reduction at 10-year follow-up (P < 0.05). CONCLUSION: The sparing of lumbar motion segments demonstrated clinically significant benefits at 10-year postoperatively. LEVEL OF EVIDENCE: 2.