The impact of osteotomy grade and location on regional and global alignment following cervical deformity surgery

Abstract

Introduction: Correction of cervical deformity (CD) often involves different types of osteotomies to address sagittal malalignment. This study assessed the relationship between osteotomy grade and vertebral level on alignment and clinical outcomes. Methods: Retrospective review of a multi-center prospectively collected CD database. CD was defined as at least one of the following: C2-C7 Cobb >10°, cervical lordosis (CL) >10°, C2-C7 sagittal vertical axis (cSVA) >4 cm, and chin-brow vertical angle > 25°. Patients were evaluated for level and type of cervical osteotomy. Results: 86 CD patients were included (61.4 ± 10.6 years, 66.3% female, body mass index 29.1 kg/m2). 141 osteotomies were in the cervical spine and 79 were in the thoracic spine. There were 19 major osteotomies performed, with 47% at T1. Patients with an osteotomy in the cervical spine improved in T1 slope minus CL (TS - CL), CL, and C2 slope (all P < 0.05). Patients with upper thoracic osteotomies improved in TS - CL, cSVA, C2-T3, C2-T3 sagittal vertical axis (SVA), and C2 slope (all P < 0.05). Minor osteotomies in the upper thoracic spine showed improvement in cSVA (63 mm to 49 mm, P = 0.022), C2-T3 ( P = 0.007), and SVA (-16 mm to 27 mm, P < 0.001). The greatest amount of C2-T3 angular change occurred for patients with a major osteotomy at T2 (39.1° change), then T3 (15.7°), C7 (16.9°°), and T1 (13.5°°). Patients with a major osteotomy in the upper thoracic spine showed similar radiographic changes from pre- to post-operative as patients with three or more minor osteotomies, although C2-T3 SVA trended toward greater improvement with a major osteotomy (-22.5 mm vs. +5.9 mm, P = 0.058) due to lever arm effect. Conclusions: CD patients undergoing osteotomies in the cervical and upper thoracic spine experienced improvement in TS - CL and C2 slope. In the upper thoracic spine, multiple minor osteotomies achieved similar alignment changes to major osteotomies at a single level, while a major osteotomy focused at T2 had the greatest overall impact in cervicothoracic and global alignment in CD patients.