Thanks to BMJ for raising the important issue of the need for postmarketing surveillance of medical implantable devices. The orthopaedic community has raised and discussed this issue over and over again without the benefit of the media hype that a BMJ press release can generate.
The fiasco with metal on metal hip replacements clearly shows that regulators need to more carefully consider the role of both premarketing evaluation as well as postmarketing survelliance. This is illustrated by the fact that regulators were slow to act when results from the Australian joint registry clearly indicated much higher revision rate with ASR ( DePuy marketed)metal on metal type arthroplasty.
The spotlight thrown by BMA gives us an opportunity to have an informed debate on regulation of medical implants. However, I am concerned that Deb Cohen ( or the companion article from Henegan et al) does not attempt to reassure patients that Metal on metal hip replacement arthroplasty remains an excellent option for a selected group of patients.
The debate on medical device regulation should not detract from the message that metal on metal hip replacement remains a useful surgical option. It would be useful to reassure that most patients who have had metal on metal hip replacements are NOT at increased risk. The best available evidence is from the national joint registry data from around the world. Although there is scope for argument that in many respects revision data is a surrogate outcome and may not truly reflect patient status this is the best outcome report we have to date and although revision rates are higher for metal on metal hip replacements more than 80-90% of patients typically do NOT undergo revision at 7-9 years after primary surgery. A review of joint registry data from around the world suggests that when the diameter of femoral head is <32 mm the risk of metal sensitivity is quite low. On the other hand, following resurfacing metal arthroplasty patients with >50 mm femoral head actually do better. Animal models have suggested an increased risk of carcinogenesis from high metal ion levels in blood.There is evidence of increased aneuploidy and chromosomal translocations in case of humans but a meta-analysis involving more than 1 million person-years has shown no overall increase in cancers after hip replacement.
Rapid Response:
Re: How safe are metal-on-metal hip implants?
Thanks to BMJ for raising the important issue of the need for postmarketing surveillance of medical implantable devices. The orthopaedic community has raised and discussed this issue over and over again without the benefit of the media hype that a BMJ press release can generate.
The fiasco with metal on metal hip replacements clearly shows that regulators need to more carefully consider the role of both premarketing evaluation as well as postmarketing survelliance. This is illustrated by the fact that regulators were slow to act when results from the Australian joint registry clearly indicated much higher revision rate with ASR ( DePuy marketed)metal on metal type arthroplasty.
The spotlight thrown by BMA gives us an opportunity to have an informed debate on regulation of medical implants. However, I am concerned that Deb Cohen ( or the companion article from Henegan et al) does not attempt to reassure patients that Metal on metal hip replacement arthroplasty remains an excellent option for a selected group of patients.
The debate on medical device regulation should not detract from the message that metal on metal hip replacement remains a useful surgical option. It would be useful to reassure that most patients who have had metal on metal hip replacements are NOT at increased risk. The best available evidence is from the national joint registry data from around the world. Although there is scope for argument that in many respects revision data is a surrogate outcome and may not truly reflect patient status this is the best outcome report we have to date and although revision rates are higher for metal on metal hip replacements more than 80-90% of patients typically do NOT undergo revision at 7-9 years after primary surgery. A review of joint registry data from around the world suggests that when the diameter of femoral head is <32 mm the risk of metal sensitivity is quite low. On the other hand, following resurfacing metal arthroplasty patients with >50 mm femoral head actually do better. Animal models have suggested an increased risk of carcinogenesis from high metal ion levels in blood.There is evidence of increased aneuploidy and chromosomal translocations in case of humans but a meta-analysis involving more than 1 million person-years has shown no overall increase in cancers after hip replacement.
Competing interests: No competing interests