May 21, 2013

Cobalt Hip Poisoning From Stryker Rejuvenate & ABGII Hip Implants: 510(k) Approval for the Rejuvenate and ABGII Rather than Full PMA Approval



Cobalt poisoning from hips is becoming more and more common among those recipients of a metal-on-metal hip implant device. Stryker Rejuvenate and ABGII were placed on the market in 2009, yet shortly after adverse reports began coming in regarding side effects of these two Stryker models. The Rejuvenate and ABGII both gained FDA clearance through a process known as the 510(k). To gain this type of clearance a medical device must only show it is substantially equivalent to a similar device. The problem with this type of clearance is that many times the device the new application is claiming to be similar to may have had its own share of safety issues.

There is a much more stringent type of FDA approval known as Premarket Approval or PMA. This approval requires the company to conduct clinical trials and safety testing—essentially to prove the device is safe and effective prior to marketing it to consumers. The 510(k) process requires little in the way of scientific research to prove safety. Further, at the time the Rejuvenate gained its 510(k) approval the neck was not constructed of cobalt and chromium, rather was changed later in 2009 without benefit of further FDA approval. The FDA did ask that Stryker conduct a study known as the Rejuvenate Modular Outcome Study which would follow patients for five and ten years to determine whether they had revision-free wear with no serious issues. At present this study shows it is ongoing, but not recruiting new participants.

Did the Design of the Rejuvenate and ABGII Contribute to Cobalt Hip Poisoning?
At the time the two Stryker designs were released, they were considered cutting edge as far as the innovation of the design. Offering a variety of necks and stems allowed surgeons to more closely match the implant to the patient’s individual size as well as their activity level. The titanium stem was believed to be more flexible than the much harder cobalt and chromium, adding a little “give” at the joint, while the cobalt and chromium neck were believed to be more durable. The Rejuvenate and ABGII were believed to be more stable and were advertised as being extremely long-lasting—maybe even up to twenty years. Because the two models were covered with a proprietary blend of titanium, molybdenum, zirconium and iron mixed with plasma spray, Stryker claimed there would be no corrosion from the dissimilar metals of the titanium stem and cobalt/chromium neck to worry about.

This coating failed to offer the resistance to corrosion Stryker expected, and, in fact, corrosion and fretting were occurring at significantly higher rates at the neck and stem junction. This corrosion caused microscopic metal ions to shear away from the hip implant, entering the bloodstream or the hip tissues. When the cobalt ions entered the hip region, pain as well as destruction and death of the tissue, muscle and bone could occur. Cobalt ions which entered the bloodstream caused metal toxicity among many Stryker patients. Symptoms of cobalt poisoning included: Gastrointestinal, renal, thyroid, cardiovascular and neurological damage, loss of vision and hearing, vertigo, DNA disruption, the formation of pseudo-tumors and issues such as irritability, depression and anxiety.

What did Stryker Know Prior to the Recall of the Rejuvenate and ABGII?
An “Urgent Field Safety Notice” was issued by Stryker in April prior to the recall in July of 2012. This safety notice went to doctors and hospitals—but not to recipients of the implants or consumers considering a Stryker hip implant. The notice admitted to certain flaws, claiming there was a higher-than-normal risk of fretting, corrosion and metal debris. Stryker went on to say that such things as the patient’s weight, whether the patient suffered from diabetes or had an infection, and the patient’s sensitivity to metals could all be responsible for a failed hip implant. They further stated that in some cases the neck pieces had not been adequately cleaned and that there were deficiencies in the locking and assembly of the tapers. It is unclear at this point exactly how much Stryker knew regarding the dangers of the Rejuvenate and ABGII prior to the recall. It is expected that this will be an issue in the pending Stryker Rejuvenate hip recall lawsuits as well as future lawsuits which are filed against Stryker.