Part 2: Metal Hips: What Did They Know and When Did They Know It?

This study comes from the Karolinska Institute in Sweden and was reported in the Journal of Bone and Joint Surgery in July 1991. Researchers studied nine uncemented hip prostheses that had been revised (removed).

In four of the nine hips, researchers found tissue discoloration and corrosion at the head-neck junction.  Most of the cases showed tissue necrosis (death) as a result of the metal debris from hip wear. Wear was observed in the hip head and the crevice between the head and the neck appeared to be a potential site for corrosion in modular designed hip replacements.

What’s more, this discussion says that the toxic effects of cobalt and chromium had been seen as early as 1968!

These findings are certainly relevant to the recalled DePuy ASR metal-on-metal (MoM) hip. But even when device maker Stryker attempted to improve the Mom hip with the Stryker Rejuvenate hip replacement with its ceramic components for the ball and socket, (metal was used in the neck and stem) the improvements failed.

The Stryker Rejuvenate Modular and ABG II modular-neck hip stem components were recalled earlier this month because of the wear, fretting, and corrosion at or about the modular-neck junction “which may result in adverse local tissue reactions manifesting with pain and/or swelling,” said the company’s website.

Even back in this 1991 report, the possible carcinogenic effects of metal implants is recognized as “of growing concern” with reports of local tumors as well as lymphatic and blood malignancies associated with hip implants.

Clearly there were early indications that the metal components of a hip replacement could tremendous complications. Why would the device makers then go ahead and manufacture these controversial devices?

Part of the problem lies with the FDA. The agency’s own approval process for medical devices does not require scientific studies and clinical trials for safety and efficacy.  That sounds absurd that a permanently implanted medical device does not have to go through a safety review, but that is exactly the present state of affairs as long as a device maker can claim their new device is “substantially equivalent” in design to another device approved and on the market.

Even the Institute of Medicine last year said the 510(k) approval process, the fast-track approval process, is a patient safety loophole that has left thousands of patients with corroding metal implants, is “fatally flawed” and should be abolished.

This is the head-in-the-sand approach to regulating that relies on the integrity of device makers to put a safe product on the market. It’s clear that confidence is misplaced.

Since more than 17,000 adverse event reports have been filed with the FDA by patients who have suffered premature hip failure, pain, metallosis, pseudotumors, infection and other debilitating injuries, and the FDA just convened its first Advisory Panel to look at the problems, it’s clear we are a long way away from taking these dangerous and defective medical devices off the market.

The best we can hope for is that surgeons review the literature and listen to the few injured Americans who were able to make it to the FDA hearing to show regulators and the industry face-to-face what a defective metal device injury does to a productive citizen. Increasingly we are hearing that these surgeons are stopping the use of metal-on-metal hip replacements. Let’s hope others follow suit and soon.