title: Combined anterior-posterior surgery is the most important risk factor for developing proximal junctional kyphosis in idiopathic scoliosis.
abstract: BACKGROUND
  Several studies have identified risk factors for proximal junctional kyphosis (PJK) after instrumentation for scoliosis, but the relative risks are unclear.
  
  
  OBJECTIVE
  We identified risk factors for PJK in idiopathic scoliosis and determined their relative risks in a predictive model.
  
  
  METHODS
  We retrospectively reviewed the charts of all 249 patients with idiopathic scoliosis who underwent surgery from 1996 to 2008. We compared those who developed PJK to those who did not. We identified risk factors for PJK and performed univariate and multivariate analyses to determine independent risk factors. We then used a Cox proportional-hazards model to evaluate the time to the development of PJK. The minimum followup time was 1.5 years (mean, 4 years; range, 1.5-9 years).
  
  
  RESULTS
  The incidence of PJK in our series of patients with idiopathic scoliosis was 17%. There was no difference in Scoliosis Research Society-22 scores between patients without and with junctional kyphosis. Independent risk factors included proximal fusion to T1 through T3 and sagittal sacral vertical line, while in the Cox model a combined anterior-posterior approach surgery was the most important risk factor.
  
  
  CONCLUSIONS
  Patients with a T1 through T3 upper instrumented level, combined anterior-posterior surgery, and increased sagittal sacral vertical line difference had a higher likelihood of developing PJK. Of these risk factors, anterior-posterior surgery was the strongest risk factor.
  
  
  METHODS
  Level III, prognostic study. See Guidelines for Authors for a complete description of levels of evidence.
authors.affiliation: Department of Orthopaedic Surgery, Hospital for Special Surgery, 535 East 70th Street, New York, NY 10021, USA. hanjokimmd@gmail.com
authors.forename: Han Jo
authors.initials: HJ
authors.lastname: Kim
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Yagi
authors.forename: Joseph
authors.initials: J
authors.lastname: Nyugen
authors.forename: Matthew E
authors.initials: ME
authors.lastname: Cunningham
authors.forename: Oheneba
authors.initials: O
authors.lastname: Boachie-Adjei
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D006801:Humans; D007738:Kyphosis / Q000209:etiology*; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D012600:Scoliosis / Q000601:surgery*; D013123:Spinal Fusion / Q000009:adverse effects* / Q000379:methods; D013904:Thoracic Vertebrae / Q000601:surgery*; D055815:Young Adult
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