title: Adjacent segment motion after anterior cervical discectomy and fusion versus Prodisc-c cervical total disk arthroplasty: analysis from a randomized, controlled trial.
abstract: METHODS
  Post hoc analysis of data acquired in a prospective, randomized, controlled trial.
  
  
  OBJECTIVE
  To compare adjacent segment motion after anterior cervical discectomy and fusion (ACDF) versus cervical total disc arthroplasty (TDA).
  
  
  BACKGROUND
  TDA has been designed to be a motion-preserving device, thus theoretically normalizing adjacent segment kinematics. Clinical studies with short-term follow-up have yet to demonstrate a consistent significant difference in the incidence of adjacent segment disease.
  
  
  METHODS
  Two hundred nine patients at 13 sites were treated in a prospective, randomized, controlled trial of ACDF versus TDA for single-level symptomatic cervical degenerative disc disease (SCDD). Flexion and extension radiographs were obtained at all follow-up visits. Changes in ROM were compared using the Wilcoxon signed-rank test and the Mann-Whitney U test. Predictors of postoperative ROM were determined by multivariate analysis using mixed effects linear regression.
  
  
  RESULTS
  Data for 199 patients were available with 24-month follow-up. The groups were similar with respect to baseline demographics. A significant increase in motion at the cranial and caudal adjacent segments after surgery was observed in the ACDF group only (cranial: ACDF: +1.4° (0.4, 2.4), P = 0.01; TDA: +0.8°, (-0.1, +1.7), P = 0.166; caudal: ACDF: +2.6° (1.3, 3.9), P < 0.0001; TDA: +1.3, (-0.2, +2.8), P = 0.359). No significant difference in adjacent segment ROM was observed between ACDF and TDA. Only time was a significant predictor of postoperative ROM at both the cranial and caudal adjacent segments.
  
  
  CONCLUSIONS
  Adjacent segment kinematics may be altered after ACDF and TDA. Multivariate analysis showed time to be a significant predictor of changes in adjacent segment ROM. No association between the treatment chosen (ACDF vs. TDA) and ROM was observed. Furthermore clinical follow-up is needed to determine whether possible differences in adjacent segment motion affect the prevalence of adjacent segment disease in the two groups.
authors.affiliation: Department of Orthopedic Surgery, Washington University, St. Louis, MO, USA. kellymi@wudosis.wustl.edu
authors.forename: Michael P
authors.initials: MP
authors.lastname: Kelly
authors.forename: James M
authors.initials: JM
authors.lastname: Mok
authors.forename: Richard F
authors.initials: RF
authors.lastname: Frisch
authors.forename: Bobby K
authors.initials: BK
authors.lastname: Tay
mesh_terms: D000328:Adult; D001178:Arthroplasty / Q000379:methods*; D002574:Cervical Vertebrae / Q000503:physiopathology / Q000601:surgery; D017586:Diskectomy / Q000379:methods*; D005260:Female; D006801:Humans; D007403:Intervertebral Disc / Q000503:physiopathology / Q000601:surgery; D055959:Intervertebral Disc Degeneration / Q000503:physiopathology / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D011446:Prospective Studies; D016059:Range of Motion, Articular; D013122:Spinal Diseases / Q000503:physiopathology / Q000601:surgery*; D013123:Spinal Fusion / Q000379:methods*; D016896:Treatment Outcome