While the DePuy ASR metal-on-metal hip recall has been playing out amid lawsuits and federal probes, another battle has been playing out on another, quieter front – the pages of the British Medical Journal.
The Johnson & Johnson (NYSE:JNJ) orthopedics subsidiary fired back against a study published in February alleging that metal-on-metal implants may have exposed patients to toxic substances, calling the study "unnecessarily alarmist and in a number of instances factually incorrect."
The February study, which concluded that "hundreds of thousands of patients around the world may have been exposed to toxic substances after being implanted with poorly regulated and potentially dangerous hip devices," has spurred a spirited back-and-forth, in print, between a pair of DePuy spokesmen and the study’s main author.
DePuy has been the subject of class action and multi-district lawsuits, public outcry and FDA scrutiny since the company launched a recall of a pair of MoM hip implants in August 2010.
The BMJ study, led by Deborah Cohen, accused MoM hip makers, including Zimmer (NYSE:ZMH) and Smith & Nephew (FTSE:SN, NYSE:SNN), of knowingly manufacturing implants prone to erosion that could release particles of their chromium-cobalt alloy as the metal parts wear against each other, causing tissue and bone death and possibly exposing patients to the risk of developing cancer or even altering their DNA.
"Despite the fact that these risks have been known and well-documented for decades, patients have been kept in the dark about their participation in what has effectively been a large, uncontrolled experiment," according to Cohen.
DePuy spokesmen Graham Isaac and Simon Sinclair rebuffed the notion that DePuy had concealed MoM erosion risks – an allegation Cohen denied making – writing in a response posted mid-April that "contrary to the suggestion in the article, the potential for reactions to wear debris from metal-on-metal hip implants has been known and studied for over 2 decades, and the reported incidence of such adverse reactions is very low."
"It has long been known that patients with metal-on-metal hip implants – and also occasionally hip implants with other bearing surfaces – have ‘raised levels of ions,’" they added. "Data for prior generations of metal implants did not indicate clinical problems from these releases in well-functioning implants, some of which had been in place more than 15 years."
The DePuy PR reps further noted that the FDA has yet to establish what levels of ions would pose a danger to patients, citing insufficient evidence to make a determination.
Device makers, they said, began pursuing MoM devices after the previous generation, made of polyethylene, was found to release damaging debris in patients’ bloodstreams. The polyethylene themselves were a response to the problems that arose from early failures in the 1st generations of MoM implants, "largely attributed to limitations in the manufacturing process."
Cohen shot back early this month, stating that DePuy’s report "sidesteps the substantive concerns described in the BMJ feature."
"We do think it is necessarily alarming rather than ‘unnecessarily alarmist’ that design changes to implants that were already known to release potentially toxic metal ions passed through the regulators without any need for clinical studies," she added.
Cohen’s main beef appears to be with regulatory systems that allowed the devices, which featured certain design and material changes from prior models, to hit the market without new clinical studies despite the knowledge that they may release toxic compounds into patients’ bodies.
"Given this, one would have thought DePuy would carefully follow up a cohort of patients once the implant was on the market measuring ion data and monitoring both local and systemic effects," she wrote.
She went on to question DePuy’s relationships with its researchers, writing that "internal DePuy documents obtained by the BMJ suggest investigators were discouraged from publishing ion data," and that 2 of the 3 authors involved in a company study cited in DePuy arguments were paid large sums of money for their work.
"Is it any wonder the regulators have little evidence to draw upon to make their decisions about the effects of metal ions?" she asked. "Despite the metal-on-metal Pinnacle having been implanted into between 300,000-500,000 people worldwide, there are only data for metal ions in under 150 patients with this prosthesis in the literature to date."
"All in all, we feel that this article was not ‘unnecessarily alarmist,’ but it provided a necessarily alarming portrait of the state of medical device regulation today," Cohen concluded.
DePuy filed a formal response today further highlighting the "factual errors and omissions in Deborah Cohen’s article" and reiterating some of the company’s arguments.
DePuy did not reply to requests for comment.