Effect of the discrepancy between sacral and pelvic obliquity on postoperative disk wedging below the lower instrumented vertebra in patients with Lenke type 5 adolescent idiopathic scoliosis: a retrospective study in Japan.

Abstract

Study design: Retrospective cohort study.

Purpose: To evaluate the effect of discrepancies between sacral and pelvic obliquity on postoperative disk wedging below the lower instrumented vertebra in Lenke type 5 adolescent idiopathic scoliosis (AIS).

Overview of literature: Previous studies have not fully explored the effect of discrepancies between sacral and pelvic obliquity on postoperative outcomes in patients with Lenke type 5 AIS.

Methods: Data from 35 patients with Lenke type 5 AIS (mean age, 14.7±1.8 years) followed for a minimum of 5 years were retrospectively analyzed. We investigated the effect of sacral coronal obliquity (S angle) and pelvic coronal obliquity (P angle) on postoperative coronal radiographic parameters. The angle between the S and P angles was defined as the sacral and pelvic (SP) angle. The patients were grouped by preoperative SP angle (<5°, n=23; ≥5°, n=12). Pre- and post-operative radiographic parameters were compared to determine whether the preoperative SP angle affected postoperative spinal alignment.

Results: The discrepancy between SP obliquity was reduced by correction surgery 5 years postoperatively. The mean lumbar Cobb angle correction rate in the ≥5° group was significantly lower than that in the <5° group (52.1%±17.8% vs. 65.5%±12.7%), and the mean wedge angle below the lower instrumented vertebra (LIV) in the ≥5° group was significantly larger than that in the <5° group (9.0°±2.6° vs. 4.7°±3.4°) 5 years postoperatively. No significant between-group differences were observed in age, Risser grade, thoracic Cobb angle correction rate, LIV-central sacral vertical line (CSVL), and C7-CSVL. The Scoliosis Research Society-22 outcomes were comparable between the two groups.

Conclusions: The ≥5° group exhibited a larger wedge angle below the LIV and lower lumbar Cobb angle correction rate than the <5° group 5 years postoperatively. Preoperative discrepancies between SP obliquity should be considered when planning corrective surgery for patients with Lenke type 5 AIS.