Worldwide Recall of Faulty Hips Prompts Widespread Litigation

In August 2010, DePuy Orthopaedics (a division of Johnson & Johnson) recalled two hip-replacement units: the ASR XL Acetabular System and the ASR Hip Resurfacing System. According to DePuy, more than 90,000 patients worldwide had one of these two products implanted.

Just what went wrong

To understand just what went wrong, it is necessary to know the basics of how a hip works. The hip has two major components that fit together like a ball in a socket. The socket part of the hip is called the acetabulum. The rounded head of the femur (leg) bone is the ball that fits into the curved acetabulum. When the hip joint is damaged or deteriorates, this can eventually cause severe pain that makes it difficult to walk or even stand. Many patients who reach this stage opt for partial or total hip replacement surgery.

Around 250,000 people in the United States receive hip replacements each year, with about 1/3 receiving metal-on-metal implants (such as the ASR devices). According to some orthopedic doctors, the DePuy ASR replacements contained a design flaw that made them difficult to implant. Specifically, the ASR cup (the device that replaces the acetabulum) is shallower than comparable devices, making it difficult to place the device where it needs to be in a recipient’s body.

Dangerous side effects

This design flaw has led to a number of dangerous side effects. One is that metal particles can be released into a patient’s bloodstream, causing reactions such as pseudotumors. In addition, the metal cap (ball) attached to the femur can come lose, resulting in a bone fracture or dislocation of the ball from the socket. Swelling, pain, and difficulty walking can result.  For approximately 1 in 8 patients, the severe side effects result in the need for a second surgery to remove and replace the faulty ASR device.

Quick approval by the FDA

One might reasonably ask how such a design flaw was overlooked. Normally, before a medical device can be sold to the public, the U.S. Food and Drug Administration (FDA) must approve it for safety and efficacy based on the results of clinical trials.  The ASR, however, was cleared through a regulatory pathway known as 501(k), which does not require clinical trials. 501(k) clearance is permitted for devices that are “substantially similar” to those already on the market. DePuy claimed that the ASR was not significantly different from another of its products, the “Pinnacle.” But while the Pinnacle was designed to fasten to a patient’s bone with screws, the ASR relied on natural bone growth as a means of fixation. (And, in fact, the Pinnacle might be recalled next!)

Some experts have speculated that the metal fragments deposited by an ASR inhibit bone growth. This results in the ASR never properly adhering to a patient’s body, which in turn results in loosening and failure of the device. Had DePuy acknowledged the significant difference between the ASR and the Pinnacle, it stands to reason that clinical trials could have uncovered the potential dangers of the ASR devices.