Spinal energy balance can predict post-operative spine alignment in Lenke 1 Adolescent Idiopathic Scoliosis

Objectives The preoperative planning of adolescent idiopathic scoliosis (AIS) remains largely debated. We hypothesized that adopting a biomechanical energetic framework could provide valuable insights for exploring the impact of spinal arthrodesis. Using this approach, we conducted a comparative analysis to quantify discrepancies between in silico simulations derived from preoperative radiographs and the actual three-dimensional spinal alignment obtained from postoperative imaging. Methods Fifty-two consecutive patients with Lenke Type 1 AIS (mean age: 16 years; mean thoracic Cobb angle: 52°) who underwent posterior spinal fusion were included in the analysis. All patients had complete biplanar radiographs at three time points: preoperatively, postoperatively and at two-years follow-up. Discrepancies between in silico simulated surgery, calculated using preoperative radiographs and a biomechanical model, and actual clinical outcomes was quantified using two metrics: maximum coronal/sagittal deviations (MaxC/MaxS) from T1-L5, and a comprehensive predictability factor (a _c and a _s ) measuring cumulative 3D position discrepancies across 17 vertebral levels, normalized by total spinal length. Results Mean MaxC was 4.7 mm (SD=4.9) and MaxS was 5.7 mm (SD=3.8). Mean values of a _c was 3.4% (SD=3.8) and a _s was 4.1% (SD=2.6). Of the cohort, 44 patients (90%) showed very good or good agreement in the coronal in silico simulation and 43 patients (88%) in the sagittal in silico simulation. When the coronal and sagittal results were combined, 38 patients (78%) showed very good or good agreement. Conclusion Distribution of biomechanical energy obtained from pre-operative radiographs is reliable to simulate spine alignment after arthrodesis in a Lenke 1 AIS cohort.