Radiologic and clinical outcomes of combining pedicle subtraction osteotomy and Smith–Peterson osteotomy in correcting severe ankylosing spondylitis kyphosis

The aim of this study was to explore the validity and safety of the combination of one-level pedicle subtraction osteotomy (PSO) and one-level Smith-Petersen osteotomy (SPO) in correcting severe ankylosing spondylitis kyphosis. Twenty-five AS patients undergoing one-level PSO and one-level SPO with a minimum of 2-year follow-up were included. Radiographical analyses included T5-T12 kyphosis (TK), L1-S1 lordosis (LL), global kyphosis (GK), osteotomized vertebral angle (OVA), sagittal vertical axis (SVA) and pelvic parameters. The computed tomographic (CT) scans of the spine were used to measure the aortic diameter and length. Clinical outcomes were evaluated by Oswestry Disability Index (ODI) questionnaire. The mean correction of OVA at PSO level and SPO level was 33.6° ± 9.2° and 26.0° ± 13.2° respectively. An average correction of 69.3° ± 23.2° in GK was achieved. The mean operation time was 372.6 ± 60.1 min and the estimated blood loss averaged 1790.4 ± 953.3 ml. The mean increase of aortic length after surgery was 3.6 cm. An average decrease of 0.25 cm in aortic diameter at the PSO level was observed after surgery. There was no significant difference in aortic diameter at the SPO level between pre- and post-operation. ODI was improved from 30.2 ± 19.3 before surgery to 15.5 ± 13.9 at the last visit. The combination of one-level SPO and one-level PSO could achieve satisfactory correction outcomes in AS patients with severe kyphosis (GK ≥ 80°) needing a correction of > 60°.