title: Location change of center of rotation after single-level cervical total disc replacement with ProDisc-C.
abstract: OBJECTIVE
  Previous studies reported that the location of the center of rotation (COR) at instrumented level after cervical total disc replacement (TDR) deviated from its preoperative location. However, currently, it is unknown whether the deviated COR is linked to the range of motion (ROM) at instrumented level. The purpose of this study was to evaluate the clinical outcomes after cervical TDR with ProDisc-C (Synthes, West Chester, PA, USA), as well as investigate the location change of COR at instrumented level and its clinical significance.
  
  
  METHODS
  A total of 23 patients who underwent single-level cervical TDR with ProDisc-C were included. Japanese Orthopaedic Association (JOA) score and Neck Disability Index (NDI) were used to assess clinical outcomes. Radiographic parameters such as cervical ROM, instrumented segmental ROM, adjacent segmental ROM, and intervertebral height were analyzed. Additionally, the location change of COR at instrumented level and its clinical significance were further analyzed by the alteration of its coordinates (COR-X, COR-Y).
  
  
  RESULTS
  JOA scores increased significantly, while NDI scores decreased at final follow-up. No differences were found in cervical global ROM, instrumented segmental ROM, adjacent segmental ROM, and COR-Y at instrumented level between preoperative and final follow-up measurements (p>0.05); however, intervertebral height and COR-X increased significantly (p<0.05).
  
  
  CONCLUSIONS
  Cervical global ROM, instrumented segmental ROM, and adjacent segmental ROM could be effectively maintained, and intervertebral height was increased after TDR with ProDisc-C. The location of COR at instrumented level shifted forward after cervical TDR.
authors.affiliation: Spine Center of Orthopaedic Department, West China Hospital, Sichuan University, Chengdu, China.
authors.forename: Jigang
authors.initials: J
authors.lastname: Lou
authors.affiliation: Spine Center of Orthopaedic Department, West China Hospital, Sichuan University, Chengdu, China.
authors.forename: Huibo
authors.initials: H
authors.lastname: Li
authors.affiliation: Spine Center of Orthopaedic Department, West China Hospital, Sichuan University, Chengdu, China.
authors.forename: Xin
authors.initials: X
authors.lastname: Rong
authors.affiliation: Spine Center of Orthopaedic Department, West China Hospital, Sichuan University, Chengdu, China.
authors.forename: Wenjie
authors.initials: W
authors.lastname: Wu
authors.affiliation: Spine Center of Orthopaedic Department, West China Hospital, Sichuan University, Chengdu, China.
authors.forename: Hao
authors.initials: H
authors.lastname: Liu
mesh_terms: D000328:Adult; D000368:Aged; D001696:Biomechanical Phenomena; D002574:Cervical Vertebrae / Q000000981:diagnostic imaging* / Q000601:surgery*; D002681:China; D017586:Diskectomy / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011859:Radiography; D016059:Range of Motion, Articular; D012189:Retrospective Studies; D012399:Rotation; D059145:Total Disc Replacement / Q000379:methods*; D016896:Treatment Outcome