title: The predisposing factors for the heterotopic ossification after cervical artificial disc replacement.
abstract: BACKGROUND
  Heterotopic ossification (HO) is defined as a formation of bone outside the skeletal system. The reported HO occurrence rate in cervical artificial disc replacement (ADR) is unexpectedly high and is known to vary. However, the predisposing factors for HO in cervical ADR have not yet been elucidated.
  
  
  OBJECTIVE
  Investigation of the predisposing factors of HO in cervical arthroplasty and the relationship between degeneration of the cervical spine and HO occurrence.
  
  
  METHODS
  Retrospective study to discover predisposing factors of HO in cervical arthroplasty.
  
  
  METHODS
  A total of 170 patients who underwent cervical ADR were enrolled including full follow-up clinical and radiologic data.
  
  
  METHODS
  Radiologic outcomes were assessed by identification of HOs according to McAfee's classifications.
  
  
  METHODS
  This study enrolled a total of 170 patients who underwent cervical ADR. Pre-existing degenerative change included anterior or posterior osteophytes, ossification of the anterior longitudinal ligament, posterior longitudinal ligament, or ligamentum nuchae. The relationships between basic patient data, pre-existing degenerative change, and HO were investigated using linear logistic regression analysis.
  
  
  RESULTS
  Among all 170 patients, HO was found in 69 patients (40.6%). Among the postulated predisposing factors, only male gender and artificial disc device type were shown to be statistically significant. Unexpectedly, preoperative degenerative changes in the cervical spine exerted no significant influence on the occurrence of HOs. The odds ratio of male gender compared with female gender was 2.117. With regard to device type, the odds ratios of Mobi-C (LDR medical, Troyes, France) and ProDisc-C (Synthes, Inc., West Chester, PA, USA) were 5.262 and 7.449, respectively, compared with the Bryan disc.
  
  
  CONCLUSIONS
  Definite differences in occurrence rate according to the gender of patients and the prosthesis type were identified in this study. Moreover, factors indefinably expected to influence HO in the past were not shown to be risk factors thereof, the results of which may be meaningful to future studies.
authors.affiliation: Department of Neurosurgery, Spine and Spinal Cord Institute, Yonsei University College of Medicine, 50 Yonsei-ro, Sedaemun-gu, Seoul 120-752, South Korea.
authors.forename: Seong
authors.initials: S
authors.lastname: Yi
authors.forename: Dong Ah
authors.initials: DA
authors.lastname: Shin
authors.forename: Keung Nyun
authors.initials: KN
authors.lastname: Kim
authors.forename: Gwihyun
authors.initials: G
authors.lastname: Choi
authors.forename: Hyun Chul
authors.initials: HC
authors.lastname: Shin
authors.forename: Keun Su
authors.initials: KS
authors.lastname: Kim
authors.forename: Do Heum
authors.initials: DH
authors.lastname: Yoon
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002574:Cervical Vertebrae; D005260:Female; D006801:Humans; D055959:Intervertebral Disc Degeneration / Q000601:surgery; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D009999:Ossification, Heterotopic / Q000453:epidemiology* / Q000209:etiology*; D012189:Retrospective Studies; D012307:Risk Factors; D012727:Sex Characteristics; D059145:Total Disc Replacement / Q000009:adverse effects* / Q000295:instrumentation; D055815:Young Adult
keywords: Cervical artificial disc replacement; Heterotopic ossification; Pre-existing degeneration; Predisposing factor