Safe Upper Limits of Serum Cobalt and Chromium Levels for a Metal-on-Metal Total Hip Bearing: A 10-Year Follow-Up Study

Maarten C. Koper*, Brechtje Hesseling, Wim E. Tuinebreijer, Hans van der Linden, Nina M.C. Mathijssen

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

2 Citations (Scopus)


Background: Long-term survival of metal-on-metal (MoM) prostheses and the development of adverse reaction to metal debris (ARMD) around these bearings are still unclear. Serum levels of cobalt (Co) and chromium (Cr) are used as a screening tool to anticipate failure in MoM bearings and detect ARMD.

Methods: One hundred sixty primary large head MoM prostheses were followed up for 10 years. To estimate the revision risk, the cumulative incidence function (CIF) was used. Subdistribution hazard modeling was used to investigate the associations between cumulative incidence of revision for ARMD and Co levels, Cr levels, gender, age, head size, and cup inclination. Furthermore, the safe upper limits (SULs) for Co and Cr were determined.

Results: Univariate analyses showed an increased risk in revision for ARMD in females (subdistribution hazard ratio [sdHR] 3.43, 95% confidence interval [CI] 1.01-11.7, P =.049) and cup inclination angles over 45° (sdHR 4.70, 95% CI 1.63-13.58, P =.004). In addition, a higher last measured Co level (sdHR 1.05, 95% CI 1.03-1.07, P <.001) and last measured Cr level (sdHR 1.21, 95% CI 1.14-1.29, P <.001) were associated with a higher probability of revision for ARMD. We determined our bearing-specific SULs at 4.1 parts per billion (ppb) and 4.2 ppb for Co and Cr, respectively.

Conclusion: Guidelines regarding follow-up and surveillance should include a complete clinical assessment with bearing-specific SULs of serum metal ion levels. For the M2a-Magnum MoM bearing we advise an SUL for Co and Cr levels of 4.1 and 4.2 ppb, respectively.

Original languageEnglish
Pages (from-to)2080-2086
Number of pages7
JournalJournal of Arthroplasty
Issue number6
Publication statusPublished - 1 Jun 2021

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© 2021 Elsevier Inc.


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