Analysis of surgical outcomes of asymmetrical pedicle subtraction osteotomy for thoracolumbar kyphoscoliosis caused by ankylosing spondylitis

English Keywords:Thoracolumbar kyphoscoliotic deformity  Ankylosing spondylitis  Pedicle subtraction osteotomy  Asymmetrical pedicle subtraction osteotomy  Comparative analysis

English Abstract:

  【Abstract】 Objectives: To analyze the clinical outcomes of asymmetrical pedicle subtraction osteotomy(APSO) in ankylosing spondylitis(AS) patients with thoracolumbar kyphoscoliotic deformity and to compare its effect of reconstructing sagittal balance with pedicle subtraction osteotomy(PSO). Methods: 55 patients with AS-related thoracolumbar deformity underwent spinal osteotomy in our hospital between January 2016 and June 2019 and were followed up for more than one year were analyzed retrospectively. PSO was performed in AS patients with sagittal deformity only, and APSO was performed in patients with biplanar deformity. Radiological parameters including Cobb angle in the coronal plane, coronal balance distance(CBD), global kyphosis(GK), sagittal vertical axis(SVA), pelvic tilt(PT), sacral slope(SS), lumbar lordosis(LL), osteotomized vertebral angle(OVA) and angle of fused segments(AFS) were measured on the standing full-spine anteroposterior X-rays preoperatively, postoperatively, and at the final follow-up. Oswestry disability index(ODI) and visual analogue scale(VAS) were filled in by the patients preoperatively and at the final follow-up. Results: Of the 55 patients, 20 received APSO and 35 received PSO. The average follow-up period was 27.3±8.1 months(range, 12-48 months). In APSO group, the Cobb angle was 18.9°±7.8°, 7.3°±3.6°, and 9.5°±4.4°, and CBD was 64.7±24.8mm, 26.7±13.4mm, and 27.4±15.3mm respectively at preoperation, postoperation, and the final follow-up, which were improved significantly at postoperation and final follow-up than those before operation(P<0.05), while no significant differences were observed between postoperation and final follow-up(P>0.05). The preoperative, right postoperative, and final follow-up SVA, GK, PT, LL, and SS were not significantly different between groups(P>0.05); the SVA, GK, and PT at postoperation and final follow-up of each group were reduced significantly than those before operation, respectively(P<0.05), and LL and SS were increased significantly(P<0.05); and the corrections of SVA, GK, PT, LL, and SS in the two groups were similar(P>0.05). In addition, the ODI and VAS score were also significantly improved at final follow-up than before operation(P<0.05); and there was no significant difference between groups at same follow-up time point(P>0.05). Concerning the OVA and AFS, no statistically significant differences were noted at the last follow-up respectively in APSO and PSO groups(P>0.05). But the OVA in APSO group was larger than that in PSO group significantly(P<0.05). The complications in the APSO group included 1 case of vertebral subluxation, 1 case of intraoperative dural tear, and 1 case of positional brachial palsy, while those in the PSO group included 2 cases of vertebral subluxation and 1 case of positional brachial palsy. There was no significant difference in the incidence of complications between the two groups(P=0.462). Conclusions: APSO and PSO have similar therapeutic effect on sagittal deformity correction; APSO can reconstruct biplanar balance in AS patients with thoracolumbar kyphosis and scoliosis.