title: Radiographical predictors for postoperative sagittal imbalance in patients with thoracolumbar kyphosis secondary to ankylosing spondylitis after lumbar pedicle subtraction osteotomy.
abstract: METHODS
  A retrospective radiographical study.
  
  
  OBJECTIVE
  To identify the radiographical predictors for sagittal imbalance in patients with thoracolumbar kyphosis secondary to ankylosing spondylitis (AS) after 1-level lumbar pedicle subtraction osteotomy (PSO).
  
  
  BACKGROUND
  Few studies had correlated the preoperative sagittal parameters with postoperative sagittal alignments to determine the radiographical predictors for postoperative sagittal imbalance in patients with AS after 1-level lumbar PSO.
  
  
  METHODS
  Thirty-six patients with thoracolumbar kyphosis secondary to AS who underwent 1-level lumbar PSO were recruited with a minimal follow-up of 24 months (mean = 27.4 mo; range, 24-53 mo). Correlation analysis and subsequent stepwise multiple regression analysis were used to evaluate the correlations between preoperative parameters, including global kyphosis, local kyphosis, thoracic kyphosis, thoracolumbar Cobb angle, lumbar lordosis, pelvic incidence (PI), pelvic tilt, sacral slope, and sagittal vertical axis (SVA), as well as SVA at the last follow-up. All these patients were further divided into 2 groups according to the PI value (group A: PI >50°; group B: PI ≤50°). The correction outcomes were compared between these 2 groups.
  
  
  RESULTS
  The preoperative SVA was not significantly different between group A and group B (157.6 mm vs. 124.5 mm; P> 0.05), and both groups had similar magnitudes of kyphosis corrections at the last follow-up (global kyphosis: 42.9° vs. 46.1°; local kyphosis: 42.7° vs. 40.5°; lumbar lordosis: 35.7° vs. 43.0°). However, group A patients had significantly larger SVA at the last follow-up (73.2 mm vs. 28.7 mm; P< 0.05) and a higher incidence of postoperative sagittal imbalance (77.8% vs. 25.9%; P< 0.05) than those in group B. The stepwise multiple regression analysis demonstrated that both preoperative SVA and PI were significant independent predictors of postoperative sagittal alignments, which explained 52.0% and 9.7% of the variability of SVA at the last follow-up, respectively.
  
  
  CONCLUSIONS
  Patients with AS with either larger preoperative SVA or larger PI are more likely to experience failed sagittal realignments after 1-level lumbar PSO. For these patients, additional osteotomies may be recommended for satisfactory correction outcomes.
  
  
  METHODS
  4.
authors: From the Department of Spine Surgery, the Affiliated Drum Tower Hospital of Nanjing University Medical School, Nanjing, China.
authors: Bang-ping
authors: BP
authors: Qian
authors: Jun
authors: J
authors: Jiang
authors: Yong
authors: Y
authors: Qiu
authors: Bin
authors: B
authors: Wang
authors: Yang
authors: Y
authors: Yu
authors: Ze-zhang
authors: ZZ
authors: Zhu
mesh_terms: D000328:Adult; D005500:Follow-Up Studies; D006801:Humans; D007738:Kyphosis / Q000209:etiology / Q000503:physiopathology / Q000601:surgery*; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging* / Q000503:physiopathology / Q000601:surgery; D008297:Male; D008875:Middle Aged; D010027:Osteotomy / Q000379:methods*; D011184:Postoperative Period; D057234:Preoperative Period; D011859:Radiography; D012189:Retrospective Studies; D013167:Spondylitis, Ankylosing / Q000150:complications / Q000601:surgery*; D013904:Thoracic Vertebrae / Q000000981:diagnostic imaging* / Q000503:physiopathology / Q000601:surgery; D016896:Treatment Outcome; D055815:Young Adult