Functional, Radiographic, and Patient-Reported Outcomes of Hybrid Fixation Versus Posterior Long Fusion for Double-Major Adolescent Idiopathic Scoliosis

Background: Posterior spinal fusion (PSF) provides reliable deformity correction for adolescent idiopathic scoliosis (AIS); however, it reduces lumbar mobility because of the fusion of motion segments. Hybrid fixation, which combines thoracic PSF with thoracolumbar/lumbar vertebral body tethering (VBT), aims to preserve lumbar function while maintaining satisfactory deformity correction. Methods: This retrospective, non-randomized comparative cohort study included 66 adolescents with double-major AIS treated with hybrid fixation (n = 30) or posterior long fusion (n = 36) at a single tertiary referral spine deformity center. Radiographic outcomes, lumbar flexibility, sagittal range of motion (ROM), lumbar core muscle strength (LCMS), SRS-22r Function scores, complications, and revision surgery were assessed after a minimum follow-up of 24 months. Multivariable regression analyses were used to identify independent predictors of postoperative functional outcomes. Results: Both procedures achieved excellent correction of the main thoracic curve and satisfactory global spinal alignment. Posterior long fusion provided greater thoracolumbar/lumbar curve correction (p < 0.001), whereas hybrid fixation resulted in significantly better lumbar flexibility, sagittal ROM, and LCMS (all p ≤ 0.006). Radiographic tether breakage occurred in eight hybrid patients (26.7%), though most were asymptomatic; revision surgery was required in two patients (6.7% vs. 0%, p = 0.20). Conclusions: Hybrid fixation was associated with better objective lumbar function than posterior long fusion, with satisfactory deformity correction, in adolescents with double-major AIS. This benefit should be weighed against a higher complication rate driven mainly by tether breakage, supporting individualized, shared decision-making for motion-preserving strategies.