Metal-on-Metal Design Behind DePuy ASR Hip Replacement Failures

In August, Johnson & Johnson unit DePuy Orthopaedics issued a worldwide recall for its ASR Hip Replacement System. The DePuy recall came several years after J&J unit began receiving complaints against DePuy that the ASR Hip Implant was prone to early failure. Recipients of a DePuy ASR Hip Replacement were advised that additional testing and treatment may be necessary to ensure the hip is functioning well. In some cases, patients may need additional surgery.

A hip implant should last for 15 years or so. However, recent data from the National Joint Registry of England and Wales showed that 1 out of every 8 patients (12%-13%) who had received the recalled devices had to undergo revision surgery within five years of receiving it. That report prompted DePuy to issue the worldwide recall of the <"">ASR XL Acetabular System, a hip socket used in traditional hip replacement, and the ASR Hip Resurfacing System, a partial hip replacement that involves placing a metal cap on the ball of the femur. Only the ASR XL Acetabular System was approved for use in the US.

Why is the DePuy ASR Hip Replacement prone to early failure? The DePuy ASR system is a metal-on-metal hip implant. It consists of a large, metal-on-metal, ball-and-socket joint, with the socket made out of cobalt chrome. According to a report published earlier this year in The New York Times, metal-on-metal hip implants have been used in about one-third of the approximately 250,000 hip replacements performed annually in the US. However, many of the nation’s leading orthopedic surgeons have reduced or stopped use of these devices because of concerns that they can cause severe tissue and bone damage.

The cause of the problem isn’t entirely clear, but studies in recent years indicate that in some cases all-metal devices can quickly begin to wear. This creates a large amount of metallic debris that is absorbed into a patient’s body. The metallic debris can cause inflammatory reactions that lead to pain in the groin, death of tissue in the hip joint and loss of surrounding bone. These metal particles can infiltrate organs and tissues, and may even create large, painful cysts. The limited studies conducted so far on metal-on-metal hip implants estimate that 1 to 3 percent of implant recipients could be affected by the problem.

Metal-on-metal hip implants have also caused problems outside of the US. In April, for example, European regulators announced they would be conducting a review of 40,000 metal-on-metal hip replacements over fears that the devices could cause non-cancerous tumors and tissue damage. At the time, officials with the United Kingdom’s Medicines and Healthcare Products Regulatory Agency (MHRA) said anyone considered at risk would be given tests to establish whether there are high levels of metal compounds in the blood.

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