Regulators in the U.K. are once again issuing advice to doctors and other healthcare professionals involved in the follow-up of patients with metal-on-metal hip replacement devices. In an alert issued by the Medicines and Healthcare products Regulatory Agency (MHRA), guidance is provided for four groups of metal-on-metal hip implant recipients including:
- Metal-on-metal hip resurfacing implants
- Metal-on-metal total hip replacements with a head diameter <36mm
- Metal-on-metal total hip replacements with a head diameter ≥36mm
- DePuy ASR hip replacements comprising ASR acetabular cups for hip resurfacing arthroplasty or total hip replacement; ASR surface replacement heads for hip resurfacing arthroplasty; and ASR XL femoral heads for total hip replacement.
Notably, the MHRA guidance recommends that both symptomatic and asymptomatic patients implanted with either metal-on-metal total hip replacements with a head diameter ≥36mm or any DePuy ASR model be followed annually for the life of their implant. Imaging tests, including MARs, MRIs or ultrasound, are recommended for any symptomatic patient who has received an implant with a head diameter ≥36mm, as well as all DePuy ASR recipients regardless of symptoms. All patients with the larger implants or any type of DePuy ASR hip replacement device should undergo an initial blood ion test regardless of symptom presentation. Patients should be retested in three months if they are found to have a blood ion level greater than 7ppb. According to the MHRA, revision surgery should be considered for patients in these groups when their imaging appears abnormal, or blood tests indicate their ion levels are rising.
For patients who have undergone resurfacing with all-metal hip implants, or received devices with femoral head diameter <36mm, those experiencing symptoms should be followed up for the life of their implant. Imaging tests and an initial blood test should be administered to all of these patients. A repeat blood test should be administered in three months for patients who have metal ion levels greater than 7ppb.
Metal-on-Metal Hip Implant Background
Concerns about all-metal hip implants started to mount in 2010, when DePuy Orthopaedics issued a worldwide recall of its ASR hip replacement devices, after it was found that they were failing in about 12 percent of patients within just five years of implantation. In the U.S., the Food & Drug Administration (FDA) began studying all-metal hip implants shortly after the DePuy ASR hip implant recall to determine if the devices are shedding dangerous levels of metal ions into patients’ surrounding tissue and blood streams. An FDA advisory panel is scheduled to take up metal-on-metal hip implants during a two-day meeting later this week.
Last week, the FDA revealed that it had received more than 16,000 adverse event reports related to metal-on-metal hip implants from 2000-2011. Reports spiked in 2008, and then again after DePuy Orthopaedics recalled its ASR hip replacement devices in August 2010. Adverse event reports in 2011 totaled 12,137 for the metal-on-metal devices, compared with 6,332 associated with other types of hip implants, according to a report from Bloomberg News. Revision surgery was the most reported side effect (over 14,000 reports) followed by reports of pain (more than 8,000).
As we’ve reported previously, metal-on-metal total hip replacements were introduced for their purported advantages over conventional devices, such as low rates of wear and increased stability. According to Bloomberg, in 2006 and 2007 the devices made up about 30% of the market, but that has since fallen to about 10%.
Metal-on-Metal Hip Implant Lawsuits
The controversy surrounding metal-on-metal hip implants has sparked thousands of lawsuits against DePuy Orthopaedics and other manufacturers. DePuy ASR hip implant lawsuits have been consolidated in federal court in Ohio. In February, a multidistrict litigation was established in the U.S. District Court for the Northern District of Georgia for lawsuits involving the all-metal Wright Conserve Hip Replacement System. Claims involving a metal-on-metal version of DePuy’s Pinnacle hip implant have been consolidated in a multidistrict litigation in Texas. Several lawsuits are also pending in the U.S. over Biomet metal-on-metal hip implants.
Bellwether trials in the DePuy ASR multidistrict litigation are expected to start early next year.