Wright Medical Warned FDA About Inadequate Data Concerning MoM Hips
Eric ChaffinAugust 28, 2012 2:00 PM
Should the opinions of one hip implant manufacturer concerning the products of another hip implant manufacturer have any bearing on FDA approval of those products? Most would say they should not, but in one case, the competitor may have been correct.
Around 2005, Smith & Nephew applied for approval of the Birmingham hip resurfacing system, a metal-on-metal (MoM) resurfacing artificial hip replacement system designed for younger, more active patients. Competitor Wright Medical, who designed the Conserve MoM implant, filed a citizen’s petition against the Birmingham hip. Wright Medical alleged that the study used to show the Birmingham was safe and effective was inadequate, because it was performed by the same doctor who designed the implant, which created a conflict of interest.
Wright Technology Officer Points Out Flaws in Study Data
According to the petition, written by Wright Medical Senior VP Chief Technology Officer Jeffrey G. Roberts, the study used to provide clinical data supporting the Birmingham violated the FDA’s rules for approval. Dr. Derek McMinn developed the Birmingham implant, and Smith & Nephew used only his cases as proof of the implant’s success and safety.
A former attempt in 2004 to gain the FDA’s approval based solely on McMinn’s evidence was denied. When McMinn returned with additional data in 2006, which, according to Roberts, consisted of anecdotal reports from other physicians, the implant was approved.
Smith & Nephew Recalls Some Birmingham Devices
Once the device was on the market, reports of problems started coming into the FDA. In 2008, Smith & Nephew recalled 185 of its Birmingham hip resurfacing implants because of reports of patients having to undergo revision surgery. The company explained that a mishap with the packaging of the product had resulted in a mixing together of different sizes of the acetabular cup, resulting in implantation mistakes. The majority of Birmingham devices, however, were left on the market.
Ironically, Wright Conserve hip implants were also later linked to serious complications like pain, instability, metal toxicity, and premature loosening and failure. In September 2011, the National Joint Registry for England and Wales issued a report indicating that revision rates for the Wright Conserve devices were significantly higher than other implants reviewed.
All MoM Devices Linked with Problems
Problems with the Birmingham and the Conserve were only the tip of the iceberg with metal-on-metal hip implants. In August 2010, DePuy Orthopaedics implemented a recall of its ASR all-metal implant because of unacceptably high failure rates of 12-13 percent. A March 2012 study published in Lancet determined that MoM implants should be banned. Thousands of lawsuits have been filed alleging that manufacturers like DePuy, Zimmer, Biomet, Wright Medical, and Smith & Nephew failed to warn of the risks with their products.
Metal-on-metal implants typically place a metal ball inside a metal cup. In some cases, these two components can wear against one another, releasing small shards of cobalt and chromium into the bloodstream. This metal contamination can cause tissue inflammation and damage, changing the inner workings of the joint and leading to premature loosening of the implant. Metallosis, caused by metal shards from the implant, can also cause bone loss and systemic side effects like dizziness and headaches.