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Retrieval analysis of an explanted Mobi-C cervical disc replacement: A case study

Lookup NU author(s): Goksu KandemirORCiD, Justin Nissen, Andrew Bowey, Professor Tom Joyce



This is the authors' accepted manuscript of an article that has been published in its final definitive form by Elsevier Ltd, 2021.

For re-use rights please refer to the publisher's terms and conditions.


© 2021. IPEMEx vivo analysis of artificial discs is essential to better understand their ability to replace degenerated intervertebral discs. The Mobi-C differs from some other contemporary disc designs in that it has a mobile polyethylene insert that is sandwiched between superior and inferior cobalt chromium endplates. While some studies claim the Mobi-C to have restored normal cervical spinal biomechanics, others have noted high levels of migration. Our objective was to contribute to this debate by, for the first time, analysing an explanted Mobi-C cervical disc which was removed due to worsening myelopathy at the nano and macro scales. Intraoperatively, the insert was found to have excessively migrated and it compressed the spinal cord. Roughness was measured as 0.016 ± 0.006 μm (Sa) and 0.055 ± 0.020 μm (Sa) for the superior and inferior plates, and 1.210 ± 0.154 μm (Sa) and 0.446 ± 0.083 μm (Sa) for the superior and inferior surfaces of the insert. Compared to unworn surfaces, the roughness increased for the superior and inferior plates and decreased for both surfaces of the insert. However, the only statistically significant change occurred on the articulating surface of the inferior plate (p = 0.04). At the nanoscale, valleys dominated the articulating surfaces. The superior plate had a burnished appearance whereas the inferior plate appeared matt. Impingement was observed on the endplates. The insert was severely damaged, burnished and had scratches. Additionally, subsurface whitening and internal cracking were observed on the insert.

Publication metadata

Author(s): Kandemir G, Pitsika M, Nissen JJ, Bowey A, Joyce TJ

Publication type: Article

Publication status: Published

Journal: Medical Engineering and Physics

Year: 2021

Volume: 90

Pages: 54-65

Print publication date: 01/04/2021

Online publication date: 25/02/2021

Acceptance date: 17/02/2021

Date deposited: 06/05/2021

ISSN (print): 1350-4533

ISSN (electronic): 1873-4030

Publisher: Elsevier Ltd


DOI: 10.1016/j.medengphy.2021.02.007


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