Although the Stryker Rejuvenate and ABGII were designed with enhanced stability in mind, the very things that made these designs unique may also have contributed to the eventual recall of both models in July, 2012. Stryker’s new designs offered a variety of stems and necks which allowed surgeons to fit the implant specifically to the patient’s body size and level of activity. The neck portion of both the Rejuvenate and ABGII is constructed of cobalt and chromium while the stem piece is made of titanium in the belief the titanium was a little more flexible or malleable. The harder cobalt and chromium was used at the taper junction due to the amount of wear in that area.
This combination was used in spite of the fact that it has been well-known for years that titanium and cobalt/chromium don’t mix and can cause excessive corrosion where the two metals meet. Stryker did coat the pieces with a proprietary formula of titanium, iron, polybenium and zirconium mixed with plasma spray to “cure” the issues found to exist between the different metals. In fact, in Stryker’s promotion materials and on their website the company claimed “Laboratory testing demonstrates the compatibility of those materials without concern for threading corrosion.” Of course it has since been found that the spray did not prevent the known issues of mixing alloys and, in fact, excessive corrosion has been found repeatedly at the neck/stem junction where the metals meet.
FDA 510(K) Approval vs. Premarket Approval
Although the Rejuvenate was approved in 2008, it was done through an FDA process known as the 510(k) which is more a clearance than an actual approval. This type of clearance is granted based on the fact that the device is substantially equivalent to a device already on the market. The more stringent type of FDA approval is the Premarket Approval (PMA) which requires an application submitted to the FDA to request approval along with “sufficient valid scientific evidence that provides reasonable assurance that the device is safe and effective for its intended use or uses.”
PMA approval requires clinical trials and extensive safety testing while the 510(k) process requires neither. At the time the Rejuvenate was submitted for 510(k) approval, the neck was not constructed of cobalt and chromium—this was changed in 2009. As a condition of the Rejuvenate’s 510(k) approval, the company promised a study called the Rejuvenate Modular Outcome Study with two benchmarks at five and ten years of revision-free wear. There is little information regarding the progress of that study, however it may become a factor during the lawsuits against Stryker.
The Urgent Field Safety Notice Issued By Stryker Prior to the Recall
Stryker issued a field safety notice to doctors and hospitals three months prior to the July 2012 recall which acknowledged certain flaws in the design such as a failure at the tapered neck junction between the neck and stem due to corrosion and fretting. The notice also stated a higher than normal risk of tissue necrosis, adverse soft tissue reactions and the formation of pseudo-tumors. While admitting the Rejuvenate and ABGII had flaws, the company attempted to offset those statements by shifting the focus to femoral offset. In other words, they stated that a patient’s excess weight could contribute to the failure of the device as well as the patient’s specific body chemistry.
The end effect was that physicians ended up documenting these risk factors, thus showing up on revision records. Stryker also suggested inadequate locking, cleaning or assembly of the tapers. Although Stryker stated during the recall issue that they would be reimbursing patients for testing, treatment, revision surgery if necessary and other costs related to the recall, there were no specifics noted which would allow patients to receive this reimbursement.
Symptoms of Cobalt Poisoning from Hips
When the neck juncture becomes corroded, metal ions are released into the body, finding their way into the surrounding tissues and entering into the bloodstream. Destruction and death of muscle, tissue and bone can result from this corrosion as well as a variety of metal toxicity symptoms such as: Neurological, cardiovascular, renal, gastrointestinal and thyroid disorders, loss of vision and hearing, DNA disruption, vertigo, memory loss, depression, anxiety, irritability and the formation of pseudo-tumors. As time passes, it is likely the number of Stryker Rejuvenate hip recall lawsuits will continue to increase and questions will likely be asked as to just how much Stryker knew about the potential risk factors of the Rejuvenate and ABGII prior to the recall.