title: Risk factors for subsidence in anterior cervical fusion with stand-alone polyetheretherketone (PEEK) cages: a review of 82 cases and 182 levels.
abstract: BACKGROUND
  To determine risk factors for subsidence in patients treated with anterior cervical discectomy and fusion (ACDF) and stand-alone polyetheretherketone (PEEK) cages.
  
  
  METHODS
  Records of patients with degenerative spondylosis or traumatic disc herniation resulting in radiculopathy or myelopathy between C2 and C7 who underwent ACDF with stand-alone PEEK cages were retrospectively reviewed. Cages were filled with autogenous cancellous bone harvested from iliac crest or hydroxyapatite. Subsidence was defined as a decrease of 3 mm or more of anterior or posterior disc height from that measured on the postoperative radiograph. Eighty-two patients (32 males, 50 females; 182 treatment levels) were included in the analysis.
  
  
  RESULTS
  Most patients had 1-2 treatment levels (62.2 %), and 37.8 % had 3-4 treatment levels. Treatment levels were from C2-7. Of the 82 patients, cage subsidence occurred in 31 patients, and at 39 treatment levels. Multivariable analysis showed that subsidence was more likely to occur in patients with more than two treatment levels, and more likely to occur at treatment levels C5-7 than at levels C2-5. Subsidence was not associated with postoperative alignment change but associated with more disc height change (relatively oversized cage).
  
  
  CONCLUSIONS
  Subsidence is associated with a greater number of treatment levels, treatment at C5-7 and relatively oversized cage use.
authors.affiliation: Functional Neurosurgery Division, Neurological Institute, Taichung Veterans General Hospital, Taichung, Taiwan, ROC.
authors.forename: Ting-Hsien
authors.initials: TH
authors.lastname: Kao
authors.forename: Chen-Hao
authors.initials: CH
authors.lastname: Wu
authors.forename: Yu-Ching
authors.initials: YC
authors.lastname: Chou
authors.forename: Hsien-Te
authors.initials: HT
authors.lastname: Chen
authors.forename: Wen-Hsien
authors.initials: WH
authors.lastname: Chen
authors.forename: Hsi-Kai
authors.initials: HK
authors.lastname: Tsou
mesh_terms: D000328:Adult; D000368:Aged; D001577:Benzophenones; D001672:Biocompatible Materials; D002574:Cervical Vertebrae / Q000601:surgery*; D017586:Diskectomy / Q000379:methods; D005260:Female; D006801:Humans; D007405:Intervertebral Disc Displacement / Q000601:surgery*; D007659:Ketones; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D011092:Polyethylene Glycols; D011108:Polymers; D011475:Prosthesis Failure / Q000209:etiology*; D012189:Retrospective Studies; D012307:Risk Factors; D013123:Spinal Fusion / Q000295:instrumentation* / Q000379:methods; D055009:Spondylosis / Q000601:surgery*; D016896:Treatment Outcome
chemical_list: D001577:Benzophenones; D001672:Biocompatible Materials; D007659:Ketones; D011108:Polymers; C063834:polyetheretherketone; D011092:Polyethylene Glycols
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