Effect of L2 and L3 pedicle subtraction osteotomy on radiological and clini̇cal outcomes in ankylosing spondylitis-associated thoracolumbar kyphosis wi̇th similar sagittal alignment

Study design A retrospective study. Objectives This study aimed to evaluate the clinical and radiological outcomes of pedicle subtraction osteotomy (PSO) at L2 and L3 levels in ankylosing spondylitis (AS) patients with similar kyphotic deformities. The primary focus was to compare these levels in terms of spinal alignment, sagittal balance, and functional improvements. Methods A retrospective analysis was conducted on 28 AS patients who underwent L2 or L3 level PSO between 2010 and 2021. Patients were divided into two groups based on osteotomy levels (14 in each group) and matched for similar kyphosis angles and deformity patterns. Radiological parameters, including pelvic tilt (PT), pelvic incidence (PI), sacral slope (SS), lumbar lordosis (LL), thoracic kyphosis (TK), global kyphosis (GK), spinosacral angle (SSA), sagittal vertical axis (SVA), osteotomized vertebral angle (OVA) were measured preoperatively, immediately postoperatively, and at final follow-up using SURGIMAP. Functional outcomes were assessed using VAS, ODI, and BASFI scores. Results Both groups showed significant improvements in sagittal alignment parameters such as PT, LL, and SVA postoperatively ( p < 0.01). The L3 group demonstrated better sagittal balance, achieving the recommended SVA value (<47 mm) at follow-up, while the L2 group did not. There was no significant difference in radiological parameters between the groups ( p > 0.05). Functional outcomes, including VAS, ODI, and BASFI scores, improved significantly in both groups ( p < 0.001), with no significant differences between them. Conclusions L2 and L3 PSO levels yielded comparable radiological and functional outcomes in AS patients with similar curve patterns. Both levels can be effectively utilized for correcting rigid kyphotic deformities, with L3 providing slightly better sagittal balance.