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DePuy knew about hip implant’s high failure rate three years before it was recalled

BMJ 2013; 346 doi: http://dx.doi.org/10.1136/bmj.f626 (Published 29 January 2013) Cite this as: BMJ 2013;346:f626
  1. Deborah Cohen
  1. 1BMJ

Post-marketing studies carried out by the US orthopaedic company DePuy showed a high revision rate for its ASR (articular surface replacement) hip implant three years before it was recalled from the global market, newly released internal documents show.

The controversial prosthesis was recalled in August 2010 after “new data” from the National Joint Registry of England and Wales showed that it was failing at a higher rate than competing implants, a “Dear doctor” letter sent out by the company to surgeons said. It stated revision rates of 8-9% at three years.

The ASR comes in two types, one used in a resurfacing technique and the other as part of a total hip replacement called the ASR XL.

However, an unpublished survival analysis conducted in June 2007 from the company’s own database showed that the ASR XL had a 10.1% failure rate at 2.5 years.

Then in 2011, when DePuy was publicly playing down data from the national registry showing that the implant would fail in about a third of people with it, the company conducted another survival analysis. This indicated that the ASR XL would have a projected failure rate of 37% (95% confidence interval 24.3% to 49.5%) at 4.5 years.

A spokesperson from DePuy told the BMJ that the internal analysis was “based on a small, limited set of data that could not be used to generalise the revision rate for ASR, unlike published data from national joint registries that include large numbers of patients and detailed revision information.”

The documents were released by the lawyers of the plaintiff Loren Kransky in the first trial against DePuy—a subsidiary of Johnson and Johnson—held in a Californian court. The company faces 10 000 lawsuits in the US and thousands of others worldwide. Around 93 000 patients have received an ASR.

The failing prosthesis has several pathological effects. Metal debris from wear of the implant can lead to reactions that destroy the soft tissues surrounding the joint, leaving some patients with long term disability. Ions of cobalt and chromium, the metals from which the implant was made, are also released into the blood and cerebral spinal fluid in some patients.1

An internal health hazard and risk evaluation conducted by the company just before the recall said that the ASR was a “defective product” that could cause “health problems.”

The documents also show that in April 2008 senior DePuy engineers recognised the extent of the problem and the fact that the ASR was “susceptible to extreme metal ion levels,” especially in women. They discussed redesigning the implant.

An internal email in 2008 from Graham Isaac, senior engineering fellow at DePuy, stated that “we need to start an ASR upgrade sooner than our previous plans had suggested.” A month later he said that the cup, the part of the implant that fits into the pelvis, was the main problem, as previously described in the BMJ.1 That redesign never occurred, and DePuy continued to market its implant.

Later that year DePuy took out advertisements in the US stating that the ASR XL had a 99.2% survival rate at three years. A reference in the advertisement said that this was based on unpublished data from the National Joint Registry.

Documents show that this statistic had been identified by Mick Borroff, a senior DePuy executive who is an industry representative on the registry, rather than the registry itself. Released emails suggest that the registry did not give permission for DePuy to use this statistic for marketing.

DePuy did not respond to the question about why it decided not to redesign.

A spokesperson said: “DePuy believes the evidence to be presented at trial will show the company acted appropriately and responsibly.”

Notes

Cite this as: BMJ 2013;346:f626

Footnotes

  • Competing interests: DC is in a relationship with an expert witness in the trial.

  • bmj.com Feature: How safe are metal-on-metal hip implants? (BMJ 2012;344:e1410, doi:10.1136/bmj.e1410); Feature: Out of joint: the story of the ASR (BMJ 2011;342:d2905, doi:10.1136/bmj.d2905).

References