Evolution of surgical strategy for superior kyphosis restoration in patients with Lenke 1 & 2 adolescent idiopathic scoliosis

Abstract Purpose To compare the outcomes of three sequential surgical techniques used over time for posterior spinal fusion (PSF) in adolescent idiopathic scoliosis (AIS) patients with Lenke 1 & 2 curves. Methods Three sequential cohorts of Lenke 1 & 2 AIS patients who underwent PSF between 2008 and 2021 were retrospectively identified. Surgical technique, including concave rod derotation (T1), concave en bloc reduction (T2), or convex-first differential rod contouring technique (T3), was recorded. Preoperative, intraoperative, and minimum 2-year postoperative variables were compared. Results Ninety-three Lenke 1 & 2 AIS patients were evaluated: 30 T1, 25 T2, and 38 T3. No significant differences were noted in demographics or preoperative radiographic measurements. The T3 group utilized higher implant density and more posterior column osteotomies (PCOs). Postoperatively, there was equivalent coronal correction index in all three cohorts. T3 resulted in significantly improved sagittal plane parameters, including final T5-T12 kyphosis (16.8° vs. 13.3° vs. 20.8° p = 0.011), final T2-T12 kyphosis (19.9° vs. 18.8°, 27.0° p = 0.033), delta T2-T12 kyphosis (-1.0° vs. -6.7° vs.1.5° p = 0.005), and delta 3D kyphosis (14.1° vs. 10.5° vs. 15.8° p = 0.034). Significant covariates of postoperative T5-T12 kyphosis included preoperative 3D kyphosis ( p = < 0.001) and number of PCOs ( p = 0.002). There were no differences in complications, readmissions, or unplanned reoperations. Conclusion Practice evolution using a recent technique, specifically the convex-first differential rod reduction technique (T3), results in superior restoration of thoracic kyphosis compared to older concave rod derotation (T1) or concave en bloc reduction (T2) techniques for Lenke 1 & 2 AIS patients.