Prosthesis design influences segmental contribution to total cervical motion after cervical disc arthroplasty
We investigated a new metric for assessing the quality of motion of the cervical segments over the arc of extension-to-flexion motion after cervical disc arthroplasty (CDA). We quantified: (1) the amount of motion contributed by individual spinal segments to the total cervical spine motion, termed segmental motion fraction, and its variation throughout the arc of extension-to-flexion motion and (2) how cervical disc arthroplasty using two distinct prosthesis designs may influence the segmental motion contributions.
Materials and methods
We tested 16 human C3–T1 spine specimens under physiologic loads; first intact, after CDA at C5–C6, and then at C5–C6 and C6–C7. The M6-C (Orthofix, USA) and Mobi-C (Zimmer, USA) disc prostheses were used in eight specimens each.
Results and conclusions
The designs of the cervical disc prostheses tested significantly influenced the variation in segmental motion fraction as the spine underwent motion between the endpoints of extension and flexion. While the mean segmental motion contribution to the total cervical motion was not influenced by prosthesis design, the way the motion took place between the extension and flexion endpoints was significantly influenced. The M6-C artificial disc restored physiologic motion quality such that implanted segments continued to function in harmony with other segments of the cervical spine as measured before arthroplasty. Conversely, the Mobi-C prosthesis, while maintaining average motion contributions similar to the pre-implantation values, demonstrated large deviations in motion contribution over the extension-to-flexion arc motion in ten of 16 implanted segments. Such non-physiologic implant kinematics could cause excessive prosthesis wear and motion and stress shielding at adjacent segments.
KeywordsCervical Total disc replacement Cervical disc arthroplasty Quality of motion Segmental motion fraction
This work was supported in part by research funding from the Department of Veterans Affairs and Chicago Association for Research and Education in Science, Hines, Illinois.
Compliance with ethical standards
Conflict of interest
AG. Patwardhan is a consultant to Orthofix Inc., Lewisville TX, USA. RM. Havey has no conflict of interest.
- 2.Coric D, Nunley PD, Guyer RD, Musante D, Carmody CN, Gordon CR et al (2011) Prospective, randomized, multicenter study of cervical arthroplasty: 269 patients from the Kineflex C artificial disc investigational device exemption study with a minimum 2-year follow-up. J Neurosurg Spine 15(4):348–358CrossRefGoogle Scholar
- 3.Zigler JE, Delamarter R, Murrey D, Spivak J, Janssen M (2013) ProDisc-C and anterior cervical discectomy and fusion as surgical treatment for single-level cervical symptomatic degenerative disc disease: five-year results of a Food and Drug Administration study. Spine 38(3):203–209CrossRefGoogle Scholar
- 4.Davis RJ, Kim KD, Hisey MS, Hoffman GA, Bae HW, Gaede SE et al (2013) Cervical total disc replacement with the Mobi-C cervical artificial disc compared with anterior discectomy and fusion for treatment of 2-level symptomatic degenerative disc disease: a prospective, randomized, controlled multicenter clinical trial. J Neurosurg Spine 19(5):532–545CrossRefGoogle Scholar
- 7.Hipp JA, Wharton ND (2008) Quantitative motion analysis (QMA) of motion-preserving and fusion technologies for the spine. In: Motion preservation surgery of the spine. Philadeplhia, Saunders, pp 85–96Google Scholar
- 9.Patwardhan AG, Voronov L, Havey RM, Tzermiadianos M, Carandang G, McIntosh B et al (2009) P152. Limited restoration of primary and coupled motions in lateral bending and axial rotation after total disc replacement: a common finding in cervical disc prostheses. Spine J 9(10):192S–193S (Abstract)Google Scholar
- 17.Beaurain J, Bernard P, Dufour T, Fuentes JM, Hovorka I, Huppert J et al (2008) Mobi-C. Motion preservation surgery of the spine: advanced techniques and controversies (Part III), pp 231–237Google Scholar