İdris AVCI
Journal of Experimental and Clinical Medicine - 2026;43(2):145-152
To evaluate the effect of pedicle subtraction osteotomy (PSO) level-L3 versus L4-on pain and functional outcomes in patients with ankylosing spondylitis (AS) undergoing corrective surgery for rigid thoracolumbar kyphosis, using validated clinical measures including the Oswestry Disability Index (ODI) and Visual Analog Scale (VAS). This retrospective comparative study included 34 patients with ankylosing spondylitis who underwent single-level PSO at either L3 (n = 17) or L4 (n = 17) between January 2017 and December 2024. Osteotomy level was selected according to the apex of the kyphotic deformity, segmental sagittal morphology, and the intended correction point. Clinical outcomes were assessed using the Oswestry Disability Index and Visual Analog Scale. Radiological assessment included preoperative and postoperative sagittal vertical axis, pelvic tilt, sacral slope, and pelvic incidence-lumbar lordosis mismatch. Operative time, estimated blood loss, complications, and follow-up duration were also recorded. Both groups demonstrated significant postoperative improvement in Oswestry Disability Index and Visual Analog Scale scores. The mean ODI percentage improved from 53.6% preoperatively to 42.2% postoperatively, and VAS scores decreased from 5.6 to 3.3 overall. The L4 group showed greater mean improvement in ODI percentage than the L3 group, although the difference approached but did not reach statistical significance. Intergroup comparisons showed p-values of 0.162 for ODI score improvement, 0.067 for ODI percentage improvement, and 0.235 for Visual Analog Scale improvement. Radiological assessment showed improvement in sagittal vertical axis, pelvic tilt, sacral slope, and pelvic incidence-lumbar lordosis mismatch in both groups, with greater pelvic tilt correction in the L4 group. Mean follow-up duration was 18.7 +/- 5.4 months in the L3 group and 19.3 +/- 6.1 months in the L4 group. No major neurological complications were observed. Single-level PSO at either L3 or L4 is effective in improving pain and disability in patients with ankylosing spondylitis and fixed kyphotic deformity. While both levels yielded clinically meaningful outcomes, L4 osteotomy may offer additional functional and symptomatic benefit due to its influence on pelvic alignment. Further prospective studies are needed to confirm the optimal level of osteotomy in this patient population.
