title: Cervical disc prosthesis versus arthrodesis using one-level, hybrid and two-level constructs: an in vitro investigation.
abstract: BACKGROUND
  The purpose of this experimental study was to analyse cervical spine kinematics after 1-level and 2-level total disc replacement (TDR) and compare them with those after anterior cervical arthrodesis (ACA) and hybrid construct. Kinematics and intradiscal pressures were also investigated at adjacent levels.
  
  
  METHODS
  Twelve human cadaveric spines were evaluated in different testing conditions: intact, 1 and 2-level TDR (Discocerv™, Scient'x/Alphatec), 1 and 2-level ACA, and hybrid construct. All tests were performed under load control protocol by applying pure moments loading of 2 N m in flexion/extension (FE), axial rotation (AR) and lateral bending (LB).
  
  
  RESULTS
  Reduction of ROM after 1-level TDR was only significant in LB. Implantation of additional TDR resulted in significant decrease of ROM in AR at index level. A second TDR did not affect kinematics of the previously implanted TDR in FE, AR and LB. One and 2-level arthrodesis caused significant decrease of ROM in FE, AR and LB at the index levels. No significant changes in ROM were observed at adjacent levels except for 1-level arthrodesis in FE and hybrid construct in AR. When analysis was done under the displacement-control concept, we found that 1 and 2-constructs increased adjacent levels contribution to global ROMC3-C7 during FE and that IDP at superior adjacent level increased by a factor of 6.7 and 2.3 for 2-level arthrodesis and hybrid constructs, respectively.
  
  
  CONCLUSIONS
  Although 1- and 2-level TDR restored only partially native kinematics of the cervical spine, these constructs generated better biomechanical conditions than arthrodesis at adjacent levels limiting contribution of these segments to global ROM and reducing the amount of their internal stresses.
authors.affiliation: Department of Spine Surgery, University Claude Bernard Lyon 1, Hôpital P Wertheimer, 59 boulevard Pinel, 69394, Lyon, France. c.barrey@wanadoo.fr
authors.forename: Cédric
authors.initials: C
authors.lastname: Barrey
authors.forename: Sophie
authors.initials: S
authors.lastname: Campana
authors.forename: Sylvain
authors.initials: S
authors.lastname: Persohn
authors.forename: Gilles
authors.initials: G
authors.lastname: Perrin
authors.forename: Wafa
authors.initials: W
authors.lastname: Skalli
mesh_terms: D000368:Aged; D002102:Cadaver; D017586:Diskectomy / Q000009:adverse effects / Q000295:instrumentation / Q000379:methods*; D005260:Female; D006801:Humans; D007405:Intervertebral Disc Displacement / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications / Q000175:diagnosis* / Q000503:physiopathology / Q000517:prevention & control; D019919:Prosthesis Implantation / Q000009:adverse effects / Q000295:instrumentation / Q000379:methods*; D011859:Radiography; D013123:Spinal Fusion / Q000009:adverse effects / Q000295:instrumentation / Q000379:methods*; D055009:Spondylosis / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*