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

Retrospective cohort study. 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). 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. 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. 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. 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.