title: Proximal junctional kyphosis as a distinct form of adjacent segment pathology after spinal deformity surgery: a systematic review.
abstract: METHODS
  Systematic review.
  
  
  OBJECTIVE
  To review the literature on proximal junctional kyphosis (PJK) as a specific form for proximal adjacent segment pathology and report on the incidence, timing, risk factors, and effect on health-related quality of life (HRQOL) outcomes reported for PJK.
  
  
  BACKGROUND
  PJK is a complication of spinal deformity surgery that can compromise outcomes and necessitate revision surgery. Multiple risk factors have been associated with PJK, making the etiology multifactorial. Knowledge of the risk factors is important for minimizing the occurrence of PJK and to allow surgeons to take measures for its prevention when possible.
  
  
  METHODS
  A systematic search of PubMed, CINAHL, EMBASE, the Cochrane Library, and Google Scholar through February 15, 2012, was performed. The focus was on studies designed to evaluate PJK in patients who had surgery for scoliosis and/or kyphosis. Adjusted effect sizes and significance based on adjusting for confounders were reported if available, otherwise, crude risk ratios and 95% confidence intervals were calculated.
  
  
  RESULTS
  The search yielded 85 citations and 8 met the criteria for inclusion. The incidence of PJK ranged from 17% to 39% and the majority seemed to occur within 2 years of surgery. The most common patient demographic associated with a higher PJK risk was increased age. Surgery-related risk factors were fusions to the sacrum, combined anterior/posterior surgery, thoracoplasty, and upper instrumented vertebra at T1-T3. Postoperative hypokyphosis or hyperkyphosis was associated with an increased risk of PJK. Despite the presence of PJK, health-related quality of life outcomes were not affected.
  
  
  CONCLUSIONS
  Patients at higher risk for PJK are those who are of older age, who had fusions to the sacrum, combined anterior/posterior surgery, thoracoplasty, and an upper instrumented vertebra at T1-T3. Despite the presence of PJK, no differences were noted in health-related quality of life outcomes.
  
  
  METHODS
  1. The risk of developing PJK above a spinal deformity fusion is 17% to 39%, with most noted by 2 years postoperative.
  
  
  METHODS
  Moderate. Strength of Statement: Strong. 2. The risk factors of PJK development include increased age, fusion to sacrum, combined ASF/PSF, thoracoplasty, UIV at T1–T3, and nonanatomic restoration of thoracic kyphosis.
  
  
  METHODS
  Low. Strength of Statement: Weak. 3. The development of PJK does not seem to have a detrimental effect on HRQOL outcomes, at least in milder/nonrevision forms.
  
  
  METHODS
  Moderate. Strength of Statement: Weak.
authors.affiliation: Hospital for Special Surgery, New York, NY, USA.
authors.forename: Han Jo
authors.initials: HJ
authors.lastname: Kim
authors.forename: Lawrence G
authors.initials: LG
authors.lastname: Lenke
authors.forename: Christopher I
authors.initials: CI
authors.lastname: Shaffrey
authors.forename: Ellen M
authors.initials: EM
authors.lastname: Van Alstyne
authors.forename: Andrea C
authors.initials: AC
authors.lastname: Skelly
mesh_terms: D006801:Humans; D015994:Incidence; D007738:Kyphosis / Q000473:pathology* / Q000601:surgery; D012307:Risk Factors; D012600:Scoliosis / Q000473:pathology* / Q000601:surgery; D013123:Spinal Fusion / Q000009:adverse effects; D013904:Thoracic Vertebrae / Q000473:pathology* / Q000601:surgery; D013905:Thoracoplasty / Q000009:adverse effects; D016896:Treatment Outcome