When an item is galvanized the word refers to a process in which the item is covered with metal using a galvanic current or coating—usually of iron or steel with added zinc to protect it from rusting. The process generally consists of hot dipping the metal into the coating in order to prevent corrosion and rusting. The Stryker Rejuvenate and ABGII are comprised of several different components which are selected according to the patient’s body type and level of activity. The Rejuvenate has a titanium stem and a cobalt and chromium neck. The stem is coated or galvanized with a proprietary blend of titanium, molybdenum, zirconium and iron, then coated with a hydroxyapatite porous coating which encourages bone growth into the device.
It was believed the TMZF coating would prevent the problems which can occur when dissimilar metals come in contact with one another. Instead, it appears the coating adds yet another issue to the problems with the ABGII and the Rejuvenate. When the metal components of the Rejuvenate experience friction from activity of the implant recipient, the coating may flake away, and corrosion will occur. This corrosion leads to a variety of adverse health issues and even total failure of the hip implant. In short, despite the lack of a metal-on-metal bearing surface, the Rejuvenate and ABGII do suffer metal articulation at the point where the neck inserts into the stem and the two dissimilar metals come into contact.
Widespread reports of excessive wear and premature device failure due to metal toxicity plagued such metal hip implants as the DePuy ASR. Stryker aggressively marketed the Rejuvenate and ABGII as a much better alternative as it implemented a ceramic ball, therefore there would be no risk of metallosis-related failure. Potential implant recipients felt their health would be much more protected as there would be little chance of metal toxicity from the Rejuvenate due to this ceramic ball component. The dual modularity system of the Rejuvenate was also believed to be far superior to the older single modularity design.
By 2012—just a few short years after the Rejuvenate and ABGII gained FDA approval—rising concerns related to metal toxicity and metallosis were coming to light. The FDA began receiving adverse event reports throughout 2011 and early 2012 from individual patients and clusters of patients who had developed premature device failure, elevated cobalt and chromium levels and other signs of metal toxicity within months of implantation. Stryker issued a notice to doctors and hospitals stating the increased risk of corrosion and fretting which could lead to metal ion debris and hip implant failure.
A large number of adverse health issues have been linked to cobalt and chromium toxicity including organ failure, the premature onset of Alzheimer’s disease, loss of hearing and vision, numbness and tingling in the extremities, cardiac arrhythmias, cognitive dysfunction, extreme fatigue, the development of pseudo-tumors, some forms of cancer, thyroid and renal disease, bone and tissue deterioration and disruption of DNA. Recipients of the recalled Stryker Rejuvenate must speak with their doctor regarding any unusual symptoms and have regular blood tests, MRIs, CT scans, x-rays and bone scans in order to catch any increase in cobalt and chromium levels or evidence of hip implant failure.