title: How to Calculate the Exact Angle for Two-level Osteotomy in Ankylosing Spondylitis?
abstract: METHODS
  A prospective case series study.
  
  
  OBJECTIVE
  To describe and assess a two-level osteotomy method for the management of severe thoracolumbar kyphosis (TLK) in patients with ankylosing spondylitis (AS).
  
  
  BACKGROUND
  To achieve better postoperative outcomes in these patients, a sophisticated preoperative surgical plan is required. Most deformities are managed using a one-level osteotomy and a two-level osteotomy is seldomly reported. Till date, no study has described a two-level osteotomy for these cases.
  
  
  METHODS
  From January 2011 to December 2012, 10 consecutive patients with ankylosing spondylitis who underwent two-level spinal osteotomy were studied. Pre- and postoperative full-length free-standing radiographs, including the whole spine and pelvis, were available for all patients. Pre- and postoperative radiological parameters, including T5-S1 Cobb angles, TLK, lumbar lordosis, pelvic incidence, pelvic tilt, sacral slope, and sagittal vertical axis were measured. Health related quality of life , including Oswestry Disability Index and Scoliosis Research Society-22 surveys were administered before surgery and at 1-year follow up.
  
  
  RESULTS
  The preoperative and postoperative T5-S1 Cobb angles was 51.3° and -7.1°, respectively (P < 0.001). All patients demonstrated changes in postoperative radiographic parameters including decreased pelvic tilt (from 37.1° to 14.3°, P < 0.001), TLK (from 36.9° to 12.6°, P < 0.001), and sagittal vertical axis (from 21.4 cm to 7.1 cm, P < 0.001), increased lumbar lordosis (from -5.1° to -47.1°, P < 0.001), sacral slope (from 13.4° to 37.7°, P < 0.001), but no significant change in pelvic incidence. Health related quality of life scores at 1-year follow up were significantly improved compared to those before surgery.
  
  
  CONCLUSIONS
  This calculation of two-level osteotomy provides an accurate and reproducible method for ankylosing spondylitis correction. By which, we can obtain satisfactory radiological parameters and clinical outcomes.
  
  
  METHODS
  4.
authors: Department of Orthopedics, General Hospital of Chinese People's Liberation Army, Beijing, PR China.
authors: Guoquan
authors: G
authors: Zheng
authors: Kai
authors: K
authors: Song
authors: Ziming
authors: Z
authors: Yao
authors: Yonggang
authors: Y
authors: Zhang
authors: Xiangyu
authors: X
authors: Tang
authors: Zheng
authors: Z
authors: Wang
authors: Xuesong
authors: X
authors: Zhang
authors: Keya
authors: K
authors: Mao
authors: Geng
authors: G
authors: Cui
authors: Yan
authors: Y
authors: Wang
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D007738:Kyphosis / Q000601:surgery; D008141:Lordosis / Q000601:surgery; D008297:Male; D008875:Middle Aged; D010027:Osteotomy / Q000379:methods; D011184:Postoperative Period; D011446:Prospective Studies; D011788:Quality of Life; D013167:Spondylitis, Ankylosing / Q000601:surgery*; D016896:Treatment Outcome