FDA Orders Investigation of Metal-on-Metal Hip Implants

On May 6, 2011 the FDA ordered twenty-one artificial hip manufacturers to conduct an extensive investigation into whether the devices cause heavy metal poisoning in patients who receive them.

Following up on medical reports of excessive levels of cobalt and chromium found in patients who received a particular type of hip prosthesis, the FDA cited medical literature linking excessive levels of heavy metal ions to cardiac and neurologic complications.

The devices in question are commonly known as metal-on-metal implants. In this type of implant, both the ball and socket are made of metal. It is believed that once implanted, excessive wear produces metal debris or shavings that in turn contaminate the implant site. The debris can result in a condition known as metallosis if the metals travel throughout the body.

The FDA said that the health consequences of elevated metal ions are unknown despite the reports cited above. As a result, they ordered manufacturers to design and submit detailed testing protocols to study the issue.

The FDA’s action follows the 2010 recall of DePuy’s ASR metal-on-metal hip implant. Currently, tens of thousands of patients who received DePuy’s device are either having the implant removed or are being closely monitored by physicians for signs of elevated heavy metal in their systems. DePuy is but one of 21 manufacturers of similar metal on metal hip implants.

DePuy Orthopaedics, a subsidiary of Johnson & Johnson, has voluntarily recalled two of its hip replacement systems after a staggering number of patients were forced to undergo revision surgeries as a result of failure and premature deterioration of the devices. This recall comes on the heels of several others recently issued by the healthcare products conglomerate: eleven total recalls since September 2009, leading to serious questions about their quality control.

A spokesperson for the company has advised that patients, who have an ASR XL Acetabular System or the ASR Hip Resurfacing System, should consult with their surgeon for immediate evaluation of the device’s performance and for enhanced monitoring. The recall may affect as many as 93,000 patients worldwide who have been implanted with one of the 29 models of these defective hip devices.

The ASR XL Acetabular System, released in 2004, was available worldwide, while the ASR Hip Resurfacing System, launched in 2003, had only been approved for use outside the United States. Approximately one in eight patients implanted with ASR products has required corrective surgery within the first five years after the initial implant. According to the National Joint Registry of England and Wales, the failure rates of 13% and 12% respectively are about twice the industry average for similar devices.

The hip systems consist of metal ball and socket components – the socket portion is at the outer edge of the pelvis and the ball portion atop the femur, which fits into the socket. These components wear over time as they move against each other, causing microscopic metallic particles to break away from the devices. In addition to metallosis, some patients have experienced inflammatory reactions to these metallic shavings. Those who reported adverse events and underwent surgical intervention reported symptoms such as pain, swelling, and difficulty walking.

While these symptoms are sometimes considered normal for patients who have recently received a hip replacement, they can also signal a problem when the symptoms persist or worsen over time. According to DePuy’s website, prolonged complaints of these symptoms may be a sign of loosening of the hardware (when the implant does not stay attached to the bone in the correct position), fracture (where the bone around the implant may have broken), or dislocation (where the two parts of the implant that move against each other are no longer aligned).