Does Location of Rotation Center in Artificial Disc Affect Cervical Biomechanics?. Issue 8 (15th April 2015)

• Record Type: Journal Article
• Authors: Mo, Zhongjun; Zhao, Yanbin; Du, Chengfei; Sun, Yu; Zhang, Ming; Fan, Yubo
• Is Part Of: Spine. Volume 40:Issue 8(2015)
• Publication Date: 2015-04-15
• Subjects: cervical disc replacement -- rotation center -- cervical kinematics -- stiffness -- facet stress; Spine -- Abnormalities -- Periodicals; Spine -- Diseases -- Periodicals; Spine -- Surgery -- Periodicals; 616.73005
• DOI: 10.1097/BRS.0000000000000818
• Languages: English
• ISSNs: 0362-2436

Abstract

Abstract : Study Design: A 3-dimensional finite element investigation. Objective: To compare the biomechanical performances of different rotation centers (RCs) in the prevalent artificial cervical discs. Summary of Background Data: Various configurations are applied in artificial discs. Design parameters may influence the biomechanics of implanted spine. The RC is a primary variation in the popular artificial discs. Methods: Implantation of 5 prostheses was simulated at C5–C6 on the basis of a validated finite element cervical model (C3–C7). The prostheses included ball-in-socket design with a fixed RC located on the inferior endplate (BS-FI) and on the superior endplate (BS-FS), with a mobile RC at the inferior endplate (BS-MI), dual articulation with a mobile RC between the endplates (DA-M), and sliding articulation with various RCs (SA-V). The spinal motions in flexion and extension served as a displacement loading at the C3 vertebrae. Results: Total disc replacements reduced extension moment. The ball-in-socket designs required less flexion moment, whereas the flexion stiffness of the spines with DA-M and SA-V was similar to that of the healthy model. The contributions of the implanted level to the global motions increased in the total disc replacements, except in the SA-V and DA-M models (in flexion). Ball-in-socket designs produced severe stress distributions in facet cartilage, whereas DA-M and SA-V produced more severe stress distribution on the bone-implant interface. Conclusion: Cervical stability was extremely affected in extension and partially affected in flexion by total disc replacement. With the prostheses with mobile RC, cervical curvature was readjusted under a low follower load. The SA-V and BS-FS designs exhibited better performances in the entire segmental stiffness and in the stability of the operative level than the BS-MI and BS-FI designs in flexion. The 5 designs demonstrated varying advantages relative to the stress distribution in the facet cartilages and on the bone-implant interface. Level of Evidence: 5 Abstract : Implantations of 5 prostheses with different rotation centers were simulated. The results revealed that the location of the rotation center does effect cervical biomechanics. The ball-in-socket with fixed rotation center performed best in providing stability and stiffness, whereas sliding articulation exhibited better ability in relieving the facet cartilage stress.