title: ProDisc-C: an in vivo kinematic study.
abstract: METHODS
  A prospective study of 22 patients with single-level cervical spondylosis.
  
  
  OBJECTIVE
  To quantify the changes in the biomechanics of the cervical spine after the insertion of a ProDisc-C (Synthes Spine, Paoli, PA) artificial disc.
  
  
  BACKGROUND
  Cervical arthroplasty is designed to maintain cervical motion of the functional spinal unit (FSU) after cervical discectomy. The impact of the ProDisc-C on in vivo kinematics and sagittal alignment requires further assessment.
  
  
  METHODS
  Flexion/extension lateral radiographs of the cervical spine were prospectively collected and reviewed in 22 patients preoperatively and after the placement of ProDisc-C. Disc height (DH), FSU angle, range of motion (ROM), and center of rotation (COR) were calculated at each time point using validated, computer-assisted methods. Preoperative values were compared with the postoperative values using paired student t tests.
  
  
  RESULTS
  Mean follow-up time was 11.0 months (SD, 2.4 mo). At the surgical level, the ProDisc-C produced increased segmental ROM (P = 0.03), an anterior shift of 1.1 mm in COR X (P = 0.004), and increased DH both anteriorly (P < 0.0001) and posteriorly (P < 0.0001). At the inferior adjacent level, anterior DH decreased (P < 0.05) and posterior DH increased (P = 0.02) after surgery. The FSU angle at the surgical level increased (P < 0.0001), but the inferior adjacent-level FSU angle decreased (P = 0.002). No significant changes were observed at the superior adjacent level.
  
  
  CONCLUSIONS
  The ProDisc-C increased segmental ROM and shifted the COR anteriorly at the surgical level. DH increased at the surgical level. The surgical level became more lordotic, whereas the inferior adjacent level became more kyphotic after ProDisc-C implantation.
authors.affiliation: Division of Neurosurgery, London Health Sciences Center, London, Ontario, Canada. neil.duggal@lhsc.on.ca
authors.forename: Neil
authors.initials: N
authors.lastname: Duggal
authors.forename: Rudolf
authors.initials: R
authors.lastname: Bertagnoli
authors.forename: Doron
authors.initials: D
authors.lastname: Rabin
authors.forename: Nicholas
authors.initials: N
authors.lastname: Wharton
authors.forename: Izabela
authors.initials: I
authors.lastname: Kowalczyk
mesh_terms: D000328:Adult; D000368:Aged; D001178:Arthroplasty / Q000295:instrumentation* / Q000379:methods; D019643:Arthroplasty, Replacement / Q000379:methods*; D001696:Biomechanical Phenomena; D017586:Diskectomy / Q000295:instrumentation* / Q000379:methods; D005260:Female; D006801:Humans; D055959:Intervertebral Disc Degeneration / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D007595:Joint Prosthesis / Q000592:standards*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011859:Radiography; D055009:Spondylosis / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*