DePuy Orthopaedics’ ASR hip implant has been in the news quite a bit recently, following a recall of the devices last summer, and the legal fallout that came in its wake. But the defective ASR implants are not the only hip

replacements causing legal woes for DePuy. It turns out that the company’s Pinnacle device is also the subject of DePuy lawsuits.

Like the ASR implants, the Pinnacle hip replacement is a metal-on-metal device. In metal-on-metal hip replacement, the articulating surfaces are made from cobalt-chrome, which purportedly offers high wear resistance and has much smaller debris particles than those with metal-on-plastic devices.

According to a New York Times report published in March 2010, metal-on-metal hip implants have been used in about one-third of the approximately 250,000 hip replacements performed annually in this country. 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. According to the Times, studies in recent years indicate that in some cases the devices can quickly begin to wear, generating high volumes of metallic debris that is absorbed into a patient’s body, leading to cobalt poisoning. 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 such problems.

In October, the American edition of the Journal of Bone and Joint Surgery (JBJS) published a case study regarding two patients who received metal-on-metal total hip replacements and experienced adverse events. After the revision surgeries, the symptoms improved. Both patients were fit, healthy 49-year old males. Their experience reports that cobalt toxicity – arthroprosthetic cobaltism – developed within their bodies after the all-metal devices were implanted. The case report states that a larger group study will be required to define the prevalence and spectrum of cobalt poisoning due to hip arthroplasty.

In August, the DePuy recall of the ASR XL Acetabular System was issued worlwide. The recall involved 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. The recall was issued after 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 experienced painful DePuy hip replacement complications and had to undergo revision surgery within five years of receiving it. DePuy now recommends that implant patients have a blood test to check for high levels of chromium and cobalt.

Recent lawsuits involving the Pinnacle hip implant allege design defects similar to those connected with DePuy’s ASR devices that may make them susceptible to premature failure. According to one suit, filed in early December in U.S. District Court for the Western District of Washington, the plaintiff has undergone six surgeries due to metal poisoning he sustained as a result of a Pinnacle hip implant he received in 2007.

A second suit filed in November U.S. District Court for the Central District of California alleges that another Pinnacle recipient has suffered abnormal gait, nerve pain and other problems since receiving the device in 2004. That plaintiff is scheduled to undergo revision surgery this month.