Metal-on-metal hip implants do not raise the risk of developing cancer.
Metal-on-Metal Hips Do Not Raise Cancer Risk in Finland
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At least if you live in Finland, according to a recent study published in the February 2014 edition of the medical journal, Acta Orthopaedica.
A cohort of 10, 728 metal-on-metal hip replacement patients and a reference cohort of 18, 235 conventional total hip replacement patients were extracted from the Finnish Arthroplasty Register for the years 2001–2010. Data on incident cancer cases and causes of death until 2011 were obtained from the Finnish Cancer Registry and Statistics Finland. The relative risk of cancer and death were expressed as standardized incidence ratio (SIR) and standardized mortality ratio (SMR). SIR/SIR ratios and SMR/SMR ratios, and Poisson regression were used to compare the cancer risk and the risk of death between cohorts.
The results showed that the overall risk of cancer in the metal-on-metal cohort was not higher than that in the non-metal-on-metal cohort (RR = 0.91, 95% CI: 0.82–1.02). The risk of soft-tissue sarcoma and basalioma in the metal-on-metal cohort was higher than in the non-metal-on-metal cohort (SIR/SIR ratio = 2.6, CI: 1.02–6.4 for soft-tissue sarcoma; SIR/SIR ratio = 1.3, CI: 1.1–1.5 for basalioma). The overall risk of death in the metal-on-metal cohort was less than that in the non-metal-on-metal cohort (RR = 0.78, CI: 0.69–0.88).
In other words, the overall risk of cancer or risk of death because of cancer is not increased after metal-on-metal hip replacement. The well-patient effect and selection bias contribute substantially to the findings concerning mortality. Arthrocobaltism does not increase mortality in patients with metal-on-metal hip implants in the short term. However, metal-on-metal hip implants should not be considered safe until data with longer follow-up time are available.
The authors of the study are Keijo T. Mäkelä, Tuomo Visuri, Pekka Pulkkinen, Antti Eskelinen, Ville Remes, Petri Virolainen, Mika Junnila and Eero Pukkala. They are from the Department of Orthopaedics and Traumatology, Surgical Hospital, Turku University Hospital, Turku; Hjelt Institute, Helsinki University, Helsinki; Coxa Hospital for Joint Replacement, Tampere Department of Orthopaedics and Traumatology, Peijas Hospital, Helsinki University Central Hospital, Helsinki; and the School of Health Sciences, University of Tampere, Tampere and the Finnish Cancer Registry, Institute for Statistical and Epidemiological Cancer Research, Helsinki, Finland.
To read more about the study, click here: http://informahealthcare.com/doi/full/10.3109/17453674.2013.878830
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This is a fascinating development. In my practice we've seen similar outcomes with the revised protocol. The key differentiator seems to be patient selection criteria. Has anyone else noticed the correlation with BMI thresholds?
Great point. I'd push back slightly on the conclusion, the sample size in the cited study is too small to draw population-level inferences. That said, the directional signal is compelling and worth a larger RCT.
We implemented a similar approach last year. Early results are promising but we're still gathering 12-month follow-up data. Happy to share our protocol if anyone is interested.
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