Impact of preoperative lumbosacral takeoff flexibility on postoperative correction following spinal fusion for adolescent idiopathic scoliosis: a new consideration for selective thoracic fusion

Purpose: Nonselective fusion for adolescent idiopathic scoliosis results in greater correction of the Lumbosacral Takeoff Angle (LSTOA); however, there are patients selectively fused that still have considerable change in their LSTOA. We sought to identify the relationship between preoperative LSTOA flexibility and postoperative correction of the LSTOA. Methods: This was a retrospective analysis of Lenke 1–6, lumbar B and C modifier patients in the Harms Study Group with 2-year follow-up. Only patients with a lumbar Cobb angle ≥ 38 and ≤ 56 were included. The cases were divided into selective (SF: 177) and nonselective fusions (NSF: 324). Multivariate regression analysis was used to identify independent preoperative factors associated with postoperative LSTOA, and postoperative LSTOA correction in the NSF and SF groups. Results: The mean postoperative LSTOA correction was 6.1 ± 3.8, with 75 (15%) patients experiencing postoperative worsening of their LSTOA. Among other variables, larger LSTOA (p < 0.001) and smaller bending LSTOA correction (p < 0.001) were predictors of larger postoperative LSTOAs in both groups. Among other variables, larger LSTOA (p < 0.001), and larger bending LSTOA correction (p < 0.01) were predictors of greater LSOTA correction in both groups. Satisfactory LSTOA correction in the selective fusion group was associated with larger preoperative LSTOA (p < 0.001), larger bending LSTOA correction (p < 0.001), larger lumbar Cobb angle bending correction (p: 0.034), and smaller lumbar apex to LIV distance (p: 0.003). Conclusions: Preoperative static and bending LSTOA measurements may help surgeons decide between selective and non-selective fusion in patients with AIS.