Will Metal-on-Metal Hip Implants Become Extinct?

Posted: December 14, 2010
Find more content on: Manufacturing, Orthopaedic Implants, Orthopaedic Technology, Regulatory

In many cases, technology that has been around for years keeps getting better and better. Sometimes it doesn’t. In the instance of metal-on-metal (MoM) hip implants, the jury is still out. The recall of DePuy’s ASR hip system in August drew attention to the device’s incidence of revision rates and a deeper problem with MoM hip implants. A hip and knee surgeon from the Rothman Institute tells me that this problem has not only severely hurt the use of these products, but begs the question of whether the use of MoM hip implants will ever gain traction again. According to Javad Parvizi, MD, nearly 35% of hip replacements that were performed in the United States in 2009 used a MoM-bearing surface. The device increased in popularity until literature from Europe reported local reactions to the implants.

"People started getting concerned about possible release of the metal parts,” says Parvizi, who has been performing hip implant procedures for 12 years. “There was also the issue of metal particulates being released into the bloodstream and affecting kidney function perhaps across the placenta in pregnant females; the possibility of the metal particles, mainly cobalt chromium, resulting in future cancer; and the lists began to grow.” It was then that Parvizi saw a sudden and extremely sharp decline in the usage of MoM, particularly in resurfacing. Use of MoM hip implants is currently below 5% in the United States, says Parvizi.

In addition to this massive decline in usage, Parvizi thinks it’s unlikely that product adoption will increase, if at all. It certainly will never go back to 35% adoption. “We’re all very eager to see what happens—there have been reports of stroke blindness, renal failure, and numerous other toxicities that are attributed from the release of particulates from the MoM surface at this point,” says Parvizi. “Whether they’re exactly correct or not, these issues are concerning enough for surgeons not to be using MoM at this point."

Do you think the era of MoM hip implants has ended, or is there hope for the future of this technology?

-Maria Fontanazza

Published in Orthotec, January/February 2011, Volume 2, No. 1


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MOM Implants

Submitted by bchabansky on December 15, 2010 - 4:36pm.

After several years of evaluation for a good solution, in Jan 2008 I went through a resurfacing procedure using the ASR hip implant. I wish I knew then about possible cobalt chrom particulates going into the blood stream and the large number of revisions.

Interestingly, the physician that performed the procedure on me, was a member of the DePuy implant design team. He thinks that most of the problems were due to the the fact that the implant was made with very thin wall (maybe too thin?), and that often it was not sized properly when installed.

-Bruce

MoM Hip Implants

Submitted by MfgE on December 15, 2010 - 2:28pm.

Unless the FDA bans the use of this type of implant, they will likely keep selling, although in small numbers. The other likelihood is that ortho companies will pull the MoM product and try to fill the gap with more traditional products.

I feel this is another example where poor execution is the culprit, not the technology. Actually a properly executed bearing couple will have a short break-in period where wear debris is relatively high compared to a poly/metal interface. But after this brief break-in period,this wear rate falls dramatically well below the wear rate of tradition bearings. The key here is "properly" executed. The surfaces and features of an MoM bearing couple must be held in the micron tolerance range. Any implants that fall out of this "sweet spot" are bound to wear abnormally. This has been proven over and over and over again in the laboratory. The trouble is that properly done, MoM is expensive to produce. A few bean counters have again helped ruin the market for an excellent technology that has helped thousands of people when properly executed. Darn Shame.