September 16, 2014 - Problems Associated With the DePuy ASR
Like other metal-on-metal hip implants, the friction between the metal components is responsible for metal shear and the release of metal ions. When the cobalt and chromium ions land nearby (in the hip tissues) symptoms of metallosis will occur such as: severe inflammation, chronic and potentially severe pain, the destruction and death of tissue and bone, failure of the hip implant and the necessity of revision surgery. When the implant cup is set at a less-than-optimal angle, a phenomenon known as edge loading can occur. Edge loading causes the ball to press the inside of the cup in an uneven manner, leading to increased pressure on the edges of the cup. This increased pressure leads to a higher incidence of undue wear, causing even more cobalt and chromium ions to enter the hip tissues and the bloodstream.
The ASR has a smaller diameter head, placing the recipient at potentially higher risks of metallosis. DePuy did conduct clinical trials on the ASR Hip Resurfacing System; during these clinical trials more femur fractures occurred than expected, causing DePuy to withdraw their application for FDA approval in the U.S. Despite these results, DePuy continued to sell the ASR Hip Resurfacing System in other countries, and U.S. surgeons could choose to implant the device for “off label” use, which is, unfortunately, largely undocumented.
When the metal ions of the DePuy ASR reach the bloodstream, cobalt and chromium toxicity can occur, leading to neurological disturbances such as memory loss and vertigo, emotional disturbances including depression, anxiety and irritability, vision and hearing loss, cardiovascular problems, renal and thyroid issues, chronic pain, reproductive disorders, skin problems, DNA disruption and pseudo-tumor formation. It is highly likely that any recipient of an ASR metal-on-metal hip implant will experience some level of metallosis or metal toxicity at some point as the metal ions shear away and build up in the body.
DePuy Failure Rates
The National Joint Registry of England reported (prior to the August 2010 recall) that DePuy ASR patients could expect a failure rate of about 13% within five years of implantation. In 2011, however, this same organization updated those findings, increasing that number to 33%. DePuy had apparently been conducting internal research of its own during this time, and, according to the New York Times, that research placed the failure rate at 40% within five years.12 Despite these results, DePuy neglected to make this research public and continued to downplay the risks of failure associated with the ASR.
The FDA raised concerns regarding the safety of the DePuy ASR hip implants in 2009, however Johnson & Johnson continued in the sales of implants from their inventory prior to the recall. A New York Times article reported that the FDA asked DePuy to provide more safety data for the ASR implant and told DePuy it was rejecting efforts to sell the resurfacing version of the ASR in the U.S. due to concerns regarding the “high concentration of metal ions,” in the blood of patients who received it.13 DePuy failed to disclose this ruling to regulators in other countries where the resurfacing version of the implant was still being marketed. The New York Times further noted that Andrew Ekdahl, head of the DePuy Orthopedic Unit, was given warning by a company consultant in 2008 that the implant appeared to have a design flaw.
The extremely high failure rates of the ASR almost guarantee that potentially half of all ASR recipients will experience some level of failure of their metal-on-metal hip implant. Due to the statute of limitations, many of these victims may find themselves left with serious injury and no recourse against a company that many believe was aware of the dangers associated with the ASR long before the recall was issued. Patients have developed metallosis as well as cobalt and chromium toxicity, many to the point that their lives will never be the same, even following revision surgery.