title: Does postsurgical cervical deformity affect the risk of cervical adjacent segment pathology? A systematic review.
abstract: METHODS
  Systematic review.
  
  
  OBJECTIVE
  To assess whether the presence or magnitude of postsurgical malalignment in the coronal (scoliosis) or sagittal plane (kyphosis/spondylolisthesis) affects the risk of cervical adjacent segment pathology (ASP).
  
  
  BACKGROUND
  ASP occurs in selected patients who have undergone surgical treatment for cervical spondylosis. The reasons are multifactorial; however, postsurgical alignment may play a key role. To elucidate this issue, a systematic review of the literature was undertaken.
  
  
  METHODS
  A systematic search in PubMed was conducted for literature published in English language through February 15, 2012. Studies in adults, designed to evaluate postsurgical sagittal or coronal malalignment as risk factors for radiographical or clinical ASP, were sought. Studies of pediatric or oncological patients were excluded. Case reports, case series, and patient populations of less than 10 patients were also excluded. Unadjusted risk ratios (RRs) and 95% confidence intervals were calculated to evaluate the association between alignment and the risk for developing ASP.
  
  
  RESULTS
  The search yielded 338 citations. Of that, 311 were excluded at the title and abstract level. Of the 27 selected for full-text review, 5 poor-quality retrospective studies met the inclusion criteria and described sagittal imbalance measures as risk factors for radiological ASP after anterior surgery. No studies examined ASP after posterior cervical surgery. Three studies provided data from which unadjusted RRs and 95% confidence intervals could be calculated. These studies showed an increased risk of ASP associated with malalignment (RR, 2.24 [95% confidence interval, 1.40-3.56]; RR, 2.40 [1.33, 4.33]; RR, 1.32 [0.96, 1.81]). No study evaluating coronal imbalance as a risk factor for cervical ASP was found and none reported on clinical ASP.
  
  
  CONCLUSIONS
  There is low-grade evidence from 3 published studies that postsurgical sagittal imbalance may increase the risk for cervical radiological ASP.
  
  
  METHODS
  An attempt should be made to maintain or restore cervical lordosis in surgical intervention for cervical disorders. Strength of Statement: Weak.
authors.affiliation: Krembil Neuroscience Center, Spinal Program, University Health Network, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Mitchell A
authors.initials: MA
authors.lastname: Hansen
authors.forename: Han Jo
authors.initials: HJ
authors.lastname: Kim
authors.forename: Ellen M
authors.initials: EM
authors.lastname: Van Alstyne
authors.forename: Andrea C
authors.initials: AC
authors.lastname: Skelly
authors.forename: Michael G
authors.initials: MG
authors.lastname: Fehlings
mesh_terms: D002574:Cervical Vertebrae / Q000473:pathology* / Q000601:surgery; D006801:Humans; D007738:Kyphosis / Q000473:pathology* / Q000601:surgery; D012307:Risk Factors; D012600:Scoliosis / Q000473:pathology* / Q000601:surgery; D013123:Spinal Fusion / Q000009:adverse effects*; D013131:Spine / Q000473:pathology / Q000601:surgery; D016896:Treatment Outcome