Asymmetric Pedicle Subtraction Osteotomy for Adult Fixed Coronal Deformity: Surgical Strategy and Outcomes Based on Malalignment Subtype

Objective: This study aimed to evaluate the radiological and clinical outcomes of asymmetric pedicle subtraction osteotomy (APSO) in the treatment of rigid coronal malalignment (CM), and to investigate the impact of deformity subtype-based on the Obeid classification-on surgical strategy and outcomes.Materials and Methods: A total of 24 patients with rigid CM underwent APSO between 2015-2020.Patients were classified as type 1 or type 2 CM according to the T1 plumbline deviation.Radiological parameters, including Cobb angle, coronal vertical axis (CVA), sagittal vertical axis, pelvic incidence-lumbar lordosis (PI-LL) mismatch, and thoracic kyphosis, were compared pre-and postoperatively.Clinical outcomes were assessed using the visual analogue scale (VAS) and Oswestry disability index (ODI) scores at baseline, postoperative day 10, and one-year.Surgical maneuvers were stratified based on CM subtype.Statistical analysis included paired and independent t-tests and chi-square tests, with p<0.05 considered significant.Results: Radiographic correction was significant across the cohort, with mean Cobb angle improving from 34.8° to 8.1° (p<0.001),CVA from 9.1 cm to 2.2 cm (p<0.001), and PI-LL mismatch from 21.1° to 7.8° (p<0.001).Clinical scores improved significantly at both postoperative time points (VAS: 8.7 to 3.1; ODI: 84.5% to 27.4%, p<0.001).Type 2 CM patients required more extensive correction techniques, including interbody cages (88.9% vs. 40.0%,p=0.002), iliac screws (77.8% vs. 13.3%, p<0.001), and kickstand rods (66.7% vs. 6.7%, p<0.001), compared to type 1 CM patients.The overall complication rate was 16.7%, including dural tear (n=1), proximal junctional kyphosis (n=2), and implant loosening (n=1); no neurological deficits were observed.Conclusion: APSO provides effective three-dimensional correction in patients with rigid coronal deformity, yielding favorable clinical and radiological outcomes at one-year follow-up.CM subtype plays a critical role in surgical planning, in the need for distal extension and lumbosacral interventions.When tailored to deformity morphology, APSO is a safe and reliable alternative to more aggressive osteotomy techniques.