Hip Replacement Surgery:
All patients want their hip replacement to relieve their symptoms. However, they also want their implant to last a long time--hopefully the rest of their life. Over the past several decades, new hip replacement implants have come and gone, in hopes of finding improvements in implant design. While implants have improved, they still wear out, making doctors and patients interested in new designs that may lead to a better, longer lasting hip replacement implant.
Hip Replacement Implants:
Most patients have a tendency to want the newest type of implant, thinking that newer is likely better. However, one advantage of using an implant that has been around is that more is known about long-term results with the implant.
Metal-on-Metal Hip Replacements:
The second issue is concern about wear rates. All materials used for joint replacements wear out over time, some faster than others. One concern about standard metal-and-plastic hip implants is wearing out of the plastic over time. New materials have been investigated to find materials that don't wear out as easily. New plastics, ceramics, and metal are all materials used to address this concern.
Patients with these metal-on-metal implants have also been found to have high levels of metal ions in their blood stream, evidence of the microscopic wear particles escaping into the body. The effect of these metal ions in the bloodstream is not fully understood, although there is no evidence of problems in other parts of the body, just the effects on the hip itself.
What You Should Do Now:
Patients with other types of metal-on-metal hip replacement implants should also been seen regularly by their surgeon for continued evaluation. Only a limited number of metal-on-metal implants have been recalled, and even those recalled implants may not need to be removed. However, because of these concerns, these implants should be closely monitored to watch for potential problems.
Why Did This Happen?:
Surgeons need to be mindful of companies touting a new system that may lack clinical data. Patients need to be educated about potential risks of different types of implants. It is important to understand that all implant types have specific concerns, and determining which is best can be a challenge for doctors and patients.
Smith AJ, et al. "Failure rates of stemmed metal-on-metal hip replacements The Lancet, V. 379, Is. 9822, Pg. 1199 - 1204, 31 March 2012.
Depuy Orthopaedics: ASR Hip Replacement Recall Guide Updated: April 2012.
Meier B "Hip Device Phaseout Followed F.D.A. Data Request" New York Times, March 22, 2012.