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

## TL;DR

This study examines how preoperative lumbosacral takeoff flexibility affects postoperative correction in spinal fusion for adolescent scoliosis.

## Contribution

The study introduces preoperative LSTOA flexibility as a new consideration for selective thoracic fusion decisions.

## Key findings

- Larger preoperative LSTOA and bending correction predict greater postoperative LSTOA correction.
- 15% of patients experienced postoperative worsening of their LSTOA despite surgical intervention.
- Selective fusion outcomes depend on preoperative LSTOA, bending correction, and lumbar Cobb angle factors.

## Abstract

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.

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.

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).

Preoperative static and bending LSTOA measurements may help surgeons decide between selective and non-selective fusion in patients with AIS.

Level of evidence: 3