Timeline: Metal On Metal Hips

1975: Study describeslocal tissue reactions caused by cobalt and chromium ions from metal-on-metal hips
1988: Study shows human synoviocytes killed by cobalt in vitro (Rae T.Clin Orthop 1988;232:244–54)
1989: Metal-on-metal hip resurfacing designs start in Birmingham
1990: WHO International Agency for the Research on Cancer lists trivalent chromium as a potential carcinogen and cobalt ions as a probable carcinogen
1991: First metal-on-metal hip resurfacing device is implanted in Birmingham
1994: Study shows dissemination of cobalt and chromium ions into lymph, liver, and spleen5
1996: Patients with metal-on-metal hips found to be at increased risk of cancer compared with those with metal-on-plastic hips: relative risk of haematopoietic cancer 1.59 (95% confidence interval 0.8 to 2.8) and leukaemia 3.77 (0.9 to 17.6) (Visuri T, et al. Clin Orthop 1996;329 (suppl):S280–9)
1997: Birmingham Hip Resurfacing (BHR) implant comes onto the European market
1998: Particles of cobalt and chromium shown to be toxic to monocytes in culture (Haynes DR, et al. Clin Orthop 1998;352:223-30)
2000: NICE guidance on selection of prostheses for primary hip replacement and resurfacing sets a benchmark revision rate for conventional hip replacement of ≤10% at 10 years
2003: Derek McMinn and Ronan Treacy publish paper showing positive results with BHR. This kickstarts the trend for larger heads in total hip replacement
2004 McMinn, designer of the BHR, says, “Caution still needs to be exercised until longer term results are available”
2004 One of DePuy’s modified stems with a shortened trunnion is cleared by the FDA, which says the modified design “does not raise any new issues of safety or effectiveness”
2005: Internal DePuy memo reflects early concerns about health risks of wear debris from metal on metal hips. “In addition to inducing potential changes in immune function, there has been concern for some time that wear debris may be carcinogenic”
2006: MHRA Committee on Safety of Devices says there’s growing concern over the biological risks of metal wear debris
2006: The Department of Health’s Committee on Mutagenicity concludes that “some metal on metal (those using cobalt-chromium) hip replacements may be associated with increased DNA-changes, and increased genotoxicity in patients.” It says this “may present a potential risk of carcinogenicity in humans”
2007: Implantation of large diameter metal-on-metal hips starts to increase rapidly in the UK, and resurfacing peaks. Metal-on-metal hips account for 20% of market this year
2007: UK expert advisory group chooses not to contraindicate metal-on-metal hips in women of child bearing age—even though metal ions had been detected in the umbilical cord and placental blood
2007: The MHRA’s Committee on Safety of Devices recommends that all patients sign a consent form setting out the risks associated with metal wear debris. But this recommendation is not widely communicated
2008: Study shows 20% of patients with DePuy’s Pinnacle hip system have metal ion levels over the upper limit accepted by occupational health experts
2009: Japanese surgeons raise concerns with the design of DePuy’s large diameter metal-on-metal system. They report seeing “generated metal debris between stem taper and head, and final necrosed tissue” and blame it on the poor connection between the two
2009: All joint replacement implants are re-classified as class III devices after the implementation of Directive 2005/50/EC
2010: In an internal email obtained by the BMJ, a senior figure in DePuy writes: “I feel the problem [with large diameter metal on metal] is emerging as more serious than first thought.”
2010: DePuy recalls its ASR hip prostheses. Some studies show a failure of the total hip replacement secondary to adverse reactions to metal debris of 50% at 6 years
2010: DePuy promotes Pinnacle—including metal-on-metal—as “an alternative for the majority of patients”
2011: Tony Nargol and his team warn the MHRA of failures with the Pinnacle implants
2011: British Orthopaedic Association writes to surgeons to say that large diameter metal-on-metal total hip replacements should be “carefully considered and possibly avoided”
2011: A two year follow-up study in 144 patients shows an incremental increase in metal levels over the study period in a range of large head metal-on-metal implants made by companies including Zimmer, DePuy, and Smith and Nephew
2011: FDA writes to about 20 manufacturers to say that it is requiring post-marketing studies in cases where an implant’s failure could have serious consequences. Companies would be expected to take blood samples from patients to measure metal ions.
2011: National Joint Register describes large diameter metal-on-metal and resurfacing prostheses in some people as a “cause for concern”
2011 Trial comparing large diameter Birmingham hip replacement with conventional hip is terminated after 2 years. Metal ion levels were raised above the MHRA advised safety level (7 µg/L) in 20% of the metal-on-metal group and in one patient in metal-on-polyethylene group (who had a metal-on-metal implant on the contralateral side)27
2012: At the annual American Academy of Orthopedic Surgeons conference manufacturers promote metal-on-metal products to the 40 000 attendees






With much thanks to Connie. Read her blog, My DePuy Hip Recall