In the continuing trial over the DePuy ASR metal-on-metal hip implant device, testimony keeps pointing to issues with the controversial device’s design. DePuy Orthopaedics is a unit of Johnson & Johnson. The trial under way, filed by Loren Kransky, is the first of some 10,000 similar cases.
Kransky’s attorney recently called McGill University professor, Dennis Bobyn, as an expert witness on the plaintiff’s behalf, said Bloomberg News. Bobyn, a biomedical engineering expert said the ASR was constructed with a number of design defects that led to implant failure at much greater rates than other devices. Bobyn testified in state court in Los Angeles.
“Because it has the geometry that it does, it is susceptible to changing shape as it is forced into a patient’s pelvis…. If I have a larger object that has to go into a smaller hole, something has to move,” Bobyn testified. According to Bloomberg News, at the time the DePuy ASR was recalled in 2010, Johnson & Johnson said that 12 percent of the implants failed within five years. Some 93,000 ASRs were involved in the global recall. This type of failure results in the need for so-called “revision” surgery, a painful, complex process in which the faulty device is surgically removed and a different device is implanted in its place.
The device is constructed with a metal ball that rests atop the femur and rotates in a cup. That cup is placed in the hip, explained Bloomberg News. Because of the device’s allegedly defective design, these metal components rub against one another during normal wear; that rubbing causes dangerous cobalt and chromium to shed into patients’ bodies, which can lead to serious health reactions. According to Bobyn’s testimony, said Bloomberg News, a number of issues with the cup contributed to the device’s defective design and ultimate failure; namely, the metal cup’s shape, which is smaller than a half-circle; the cup’s thin wall; and that the cup is constructed in one, not two, pieces.
“Is it your opinion that the ASR hip implant has multiple design defects that alone or together cause it to fail at a much greater rate than other hip implants?” Kransky’s attorney asked Bobyn. Bobyn said it was, according to Bloomberg News. When asked if “any claimed benefits of the ASR were greatly outweighed by the risks of the implant” and if Kransky’s ASR implant was defective, “causing it to fail, generating excessive amount of cobalt and chromium wear debris.” Bobyn said, yes, those were his opinions, wrote Bloomberg News.
Bobyn also testified that the ASR was inferior to other hip devices, pointing out failure rates seen in other devices, such as a failure rate of 3.8 percent after 32 years in one device and a 2 percent failure rate in another device after five years, Bloomberg News said. Kransky’s attorney noted that an Australian national joint registry found that ASR’s failure rate exceeded 40 percent in the last year alone.
Prior to Bobyn’s testimony, jurors were shown a videotaped testimony from Paul Voorhost, a DePuy statistician. Voorhost said DePuy reviewed data that found that, at a Finland hospital, 28 percent of ASR hips failed. Also, data from a United Kingdom national joint registry in 2011 found that more than 27 percent of ASR hips failed just after seven years, Voorhost testified, wrote Bloomberg News.
Kransky’s lawsuit alleges that the DePuy ASR generated a toxic amount of chromium and cobalt ions into his body. This metal buildup allegedly led to complications that included blackened tissue and the need for him to undergo early revision surgery. Kransky, 65, from Montana, is a retired prison guard.
In an unprecedented move, the U.S. Food and Drug Administration (FDA) just announced that metal ion testing be conducted for all-metal hip replacement patients experiencing symptoms such as pain, swelling, or difficulty walking. In issuing these new guidelines, the agency also recommended diagnostic imaging and regular physical examinations be conducted, as well.
