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

Abstract 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. Level of evidence: 3