title: Two-level pedicle subtraction osteotomy for severe thoracolumbar kyphotic deformity in ankylosing spondylitis.
abstract: METHODS
  A retrospective clinical study.
  
  
  OBJECTIVE
  To evaluate the outcomes of two-level (T12 and L3) pedicle subtraction osteotomy (PSO) for severe thoracolumbar kyphosis in ankylosing spondylitis (AS), and to discuss the surgical strategies of this surgery.
  
  
  BACKGROUND
  Cases were limited on the results of two-level PSO for correction of severe kyphosis caused by AS, nor on surgical strategies of this type of surgery.
  
  
  METHODS
  From March 2006 to December 2010, nine consecutive AS patients with severe kyphotic deformity, underwent T12 and L3 PSOs. Chin-brow vertical angle (CBVA) and radiographic assessments which contain thoracic kyphosis (TK), lumbar lordosis (LL), global kyphosis (GK), and sagittal vertical axis were carefully recorded pre and postoperatively to evaluate the sagittal balance. Intra and postoperative complications were also registered. All patients were asked to fill out Oswestry Disability Index before surgery and at the last follow-up visit.
  
  
  RESULTS
  All nine patients (8M/1F), averaged 41.4 years old (range 35-51 years), were received two-level (T12 and L3) PSO, and were followed up after surgery for a mean of 39.9 months (range 24-68 months). Good cosmetic results were achieved in all patients. Mean correction at two-level PSO was 67.9 ± 5.5°. All CBVA, TK, LL, and GK were changed significantly after surgery (P < 0.05), the mean amount of correction of which were 59.5 ± 13.8, 34.7 ± 3.8, 33.2 ± 2.4, and 54.0 ± 14.8 degrees, respectively, and with a small loss of correction at the last follow-up visit. Sagittal imbalance was significantly improved from 27.3 ± 4.4 to 3.4 ± 0.7 cm postoperatively. Neither mortalities nor any major neurological complications were found. The mean ODI score was significantly improved from 53.4 ± 15.5 before surgery to 8.2 ± 4.7 at the last visit.
  
  
  CONCLUSIONS
  The outcomes of follow-up showed that two-level (T12 and L3) PSO can effectively and safely correct severe thoracolumbar kyphosis in AS.
authors.affiliation: Department of Spine Surgery, Xiangya Hospital of Central South University, Xiangya Road 87, Changsha, China, zhq9996@163.com.
authors.forename: Hong Qi
authors.initials: HQ
authors.lastname: Zhang
authors.forename: Jia
authors.initials: J
authors.lastname: Huang
authors.forename: Chao Feng
authors.initials: CF
authors.lastname: Guo
authors.forename: Shao Hua
authors.initials: SH
authors.lastname: Liu
authors.forename: Ming Xing
authors.initials: MX
authors.lastname: Tang
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D007738:Kyphosis / Q000000981:diagnostic imaging / Q000209:etiology* / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D010027:Osteotomy / Q000379:methods*; D065289:Pedicle Screws; D011183:Postoperative Complications / Q000175:diagnosis; D011859:Radiography; D012189:Retrospective Studies; D013167:Spondylitis, Ankylosing / Q000150:complications* / Q000000981:diagnostic imaging; D013904:Thoracic Vertebrae / Q000601:surgery*; D016896:Treatment Outcome