title: Indication for spinal fusion and the risk of adjacent segment pathology:  does reason for fusion affect risk? A systematic review.
abstract: METHODS
  A systematic review.
  
  
  OBJECTIVE
  To determine whether different indications or reasons for spinal fusion are associated with different risks of subsequent adjacent segment pathology (ASP) in the lumbar and cervical spine.
  
  
  BACKGROUND
  Pre-existing degeneration at levels adjacent to an arthrodesis may play a role in the development of symptomatic adjacent segment pathology. Although most spinal arthrodeses occur in patients with degenerative spinal disease, spinal fusion occurs in the pediatric and trauma population, and also congenitally. Evaluating the risk of ASP in these populations may shed light on its etiology.
  
  
  METHODS
  A systematic search was conducted in PubMed and the Cochrane Library for articles published between January 1, 1990, and December 31, 2011. We included all articles that described the risk of radiographical adjacent segment pathology (RASP) following surgical fusion for degenerative disease, for trauma, or for conditions requiring fusion in pediatrics in the lumbar or cervical spine. In addition, we included studies recording ASP in patients with congenital fusion.
  
  
  RESULTS
  Nineteen studies met our inclusion criteria. In patients who underwent fusion in the lumbar spine for degenerative reasons, the RASP rate averaged 12.4% during an average of 5.6-year follow-up. For patients who underwent fusion in the cervical spine for degenerative reasons, the average RASP rate was 25.3% during a 2.3-year follow-up. For patients with Klippel-Feil syndrome and congenital fusion, the RASP rate averaged 49.7% during an average of 23.5-years of follow-up. In patients who were fused for scoliosis, the average RASP rate was 20.3% of 3.9-year follow-up. However there is significant variation between studies in patient population, follow-up, and definition of RASP.
  
  
  CONCLUSIONS
  In the cervical spine, the rate of RASP in patients with fusion for degenerative reasons indications is greater than the rate of RASP in patients with congenital fusion suggesting that the pre-existing health and status of the adjacent level at the time of fusion may play a contributory role in the development of ASP. There is insufficient evidence in the literature to determine whether the indication/reason for fusion affects the risk of RASP in the lumbar spine
  
  
  METHODS
  In the cervical spine, the rate of RASP in patients with fusion for degenerative reasons indications is greater than the rate of RASP in patients with congenital fusion suggesting that the pre-existing health and status of the adjacent level at the time of fusion may play a contributory role in the development of ASP. Strength of Statement: Weak.
authors.affiliation: Department of Orthopaedic Surgery, University of Washington Medical Center, Seattle, WA 98195, USA. mjl3000@u.washington.edu
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Lee
authors.forename: Joseph R
authors.initials: JR
authors.lastname: Dettori
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Standaert
authors.forename: Claire G
authors.initials: CG
authors.lastname: Ely
authors.forename: Jens R
authors.initials: JR
authors.lastname: Chapman
mesh_terms: D002574:Cervical Vertebrae / Q000473:pathology* / Q000601:surgery; D005500:Follow-Up Studies; D006801:Humans; D008159:Lumbar Vertebrae / Q000473:pathology* / Q000601:surgery; D012307:Risk Factors; D013122:Spinal Diseases / Q000209:etiology / Q000473:pathology* / Q000601:surgery; D013123:Spinal Fusion / Q000009:adverse effects / Q000379:methods; D016896:Treatment Outcome