title: Biomechanical effects of cervical arthroplasty with U-shaped disc implant on segmental range of motion and loading of surrounding soft tissue.
abstract: OBJECTIVE
  Various design concepts have been adopted in cervical disc prostheses, including sliding articulation and standalone configuration. This study aimed to evaluate the biomechanical effects of the standalone U-shaped configuration on the cervical spine.
  
  
  METHODS
  Based on an intact finite element model of C3-C7, a standalone U-shaped implant (DCI) was installed at C5-C6 and compared with a sliding articulation design (Prodisc-C) and an anterior fusion system. The range of motion (ROM), adjacent intradiscal pressure (IDP) and capsular ligament strain were calculated under different spinal motions.
  
  
  RESULTS
  Compared to the intact configuration, the ROM at C5-C6 was reduced by 90% after fusion, but increased by 70% in the Prodisc-C model, while the maximum percentage change in the DCI model was 30% decrease. At the adjacent segments, up to 32% increase in ROM happened after fusion, while up to 34% decrease occurred in Prodisc-C model and 17% decrease in DCI model. The IDP increased by 11.6% after fusion, but decreased by 5.6 and 6.3% in the DCI and Prodisc-C model, respectively. The capsular ligament strain increased by 147% in Prodisc-C and by 13% in the DCI model. The DCI implant exhibited a high stress distribution.
  
  
  CONCLUSIONS
  Spinal fusion resulted in compensatory increase of ROM at the adjacent sites, thereby elevating the IDP. Prodisc-C resulted in hyper-mobility at the operative site that led to an increase of ligament force and strain. The U-shaped implant could maintain the spinal kinematics and impose minimum influence on the adjacent soft tissues, despite the standalone configuration encountering the disadvantages of high stress distribution.
authors.affiliation: Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, Beijing Key Laboratory for Optimal Design and Evaluation Technology of Implantable & Interventional Medical Devices, International Joint Research Center of Aerospace Biotechnology and Medical Engineering of Ministry of Science and Technology, School of Biological Science and Medical Engineering, Beihang University, XueYuan Road No.37, HaiDian District, Beijing, 100191, People's Republic of China.
authors.forename: Zhong Jun
authors.initials: ZJ
authors.lastname: Mo
authors.forename: Yan Bin
authors.initials: YB
authors.lastname: Zhao
authors.forename: Li Zhen
authors.initials: LZ
authors.lastname: Wang
authors.forename: Yu
authors.initials: Y
authors.lastname: Sun
authors.forename: Ming
authors.initials: M
authors.lastname: Zhang
authors.forename: Yu Bo
authors.initials: YB
authors.lastname: Fan
mesh_terms: D000328:Adult; D001178:Arthroplasty / Q000379:methods*; D001696:Biomechanical Phenomena; D002574:Cervical Vertebrae / Q000601:surgery*; D006801:Humans; D007403:Intervertebral Disc / Q000601:surgery*; D008297:Male; D009333:Neck / Q000601:surgery; D011312:Pressure; D019736:Prostheses and Implants; D019919:Prosthesis Implantation / Q000379:methods; D016059:Range of Motion, Articular; D013123:Spinal Fusion / Q000379:methods*