Change of esophageal length measured on computed tomography after corrective osteotomy for cervicothoracic kyphosis in patients with ankylosing spondylitis and its clinical significance

Abstract

Objective: To investigate the change of esophageal length measured on computed tomography after C(7) pedicle subtraction osteotomy (PSO) for cervicothoracic kyphosis in ankylosing spondylitis (AS) patients and its clinical significance. Methods: Eight male AS patients with cervicothoracic kyphosis, who underwent PSO at C(7) level from December 2014 to November 2018 at Nanjing Drum Tower Hospital, were retrospectively reviewed. The mean age was (35±7) years (range, 26-49 years). The cervicothoracic kyphosis, C(2)-T(1) sagittal vertical axis (SVA) and angle of fusion levels (AFL) were measured on lateral cervical radiographs and chin-brow vertical angle (CBVA) was measured on clinical photographs preoperatively and postoperatively. Anterior height of the osteotomized vertebra (AHOV) and esophageal length from the lower endplate of C(6) to the inferior endplate of the lower instrumented vertebrae were measured on sagittal plane of reconstructed computed tomography preoperatively and postoperatively. Oswestry Disability Index (ODI), Neck Disability Index (NDI) and Numerical Rating Scale (NRS) were collected to evaluate the clinical outcomes. Results: The average follow-up duration was (15±9) months (range, 3-51 months). The average correction of cervicothoracic kyphosis, C(2)-T(1)SVA, AFL and CBVA was 35.9°±7.3°, (44.7±11.6) mm, 32.0°±4.8° and 38.1°±11.5°, respectively. The average reduction of AHOV was (5.6±1.6) mm. ODI was improved from 17±14 preoperatively to 13±10 at the final follow-up. The NDI before operation and at the final follow-up was 18±15 and 10±6, respectively. The preoperative NRS was 4.8±2.4, and it decreased to 1.0±1.2 at the final follow-up. The change of esophageal length showed significant correlation with the improvement of cervicothoracic kyphosis, C(2)-T(1)SVA, AFL and CBVA(r=0.84, 0.83, 0.83, 0.73, all P<0.05). Conclusions: The operation of C(7)PSO increases esophageal length after cervicothoracic kyphosis in AS patients. The esophageal elongation is closely related with changes of parameters measured on radiographs and clinical photographs. Spine surgeons should be aware of the potential risk of esophagus-related complications caused by esophagus lengthening after C(7)PSO.