Theories of Why the Stryker Rejuvenate is Failing—Part One

June 05, 2015 - Perhaps you are one of the thousands of consumers implanted with a Stryker Rejuvenate hip implant device. The Rejuvenate and the ABGII gained FDA approval in 2008 and 2009, but were not marketed in earnest until early 2010. Yet, little more than two and a half years later, both models were being recalled by Stryker due to a higher-than-normal failure rate as well as corrosion and fretting which could lead to Stryker Hip Metallosis (excess amounts of metal debris being sheared away from the device and deposited in the hip tissues and the bloodstream). Following the recall of the Rejuvenate, the device was studied much more closely, and additional theories of why the Rejuvenate may have failed were established. Some of those theories include the following:

·         Galvanic Corrosion—Galvanic corrosion refers to corrosion damage which occurs when two dissimilar metals are paired and a corrosive electrolyte is present. The extremely high levels of corrosion seen in the Stryker Rejuvenate could be attributed to mismatched components. Specifically, the stem of the Rejuvenate is titanium while the neck portion is constructed of cobalt and chromium. One study showed 28% of hip implant devices which implemented similar metals showed moderate to severe levels of corrosion, while more than 42% showed moderate to severe levels of corrosion when mixed metals were used. In theory, the softer titanium paired with the extremely hard cobalt and chromium causes excess levels of corrosion. Further, heavy metal toxicity may be closely related to electromagnetic toxicity; the more your system is contaminated with heavy metals, the more it begins to concentrate radiation, leading to corrosion. The body’s biorhythms could be causing an electric current “grounding mechanism,” in response to the Rejuvenate implant. Putting a large titanium, cobalt and chromium hip implant into the body not only causes corrosion, it also vastly increases the body’s susceptibility to disease. In light of the research and studies which warned against the use of dissimilar metals in hip implants, it is unclear why Stryker paired the titanium stem with the cobalt and chromium neck.

·         Bad Taper Design—Some physicians have reported 100% evidence of taper wear when removing a Stryker Rejuvenate. The modular components of the Stryker Rejuvenate are attached with a modified Morse taper, which is a slightly angular junction on either end of the hip implant components. The modified Morse taper is tapped into the component end until it locks into place. Apparently Stryker did not want to pay Wright Medical for the widely-used Morse taper, so designed a modified version which has much more surface contact area between the taper and the stem. Research shows the area between the taper and the stem is insufficient to prevent erosion at a junction responsible for supporting as much as seven times the patient’s body weight. As a result, the area where the modified Morse taper meets the stem is an area where excess cobalt and chromium ions are released. The use of the modified Morse taper has been linked to complications such as inflammation, aseptic loosening, osteolysis and necrosis due to the added stress at this particular location. In fact, the modified Morse taper can lead to weakening of the entire implant as the axial load is crucial and it appears the coaxial load of the Stryker Rejuvenate modified Morse taper is at an angle, resulting in excess taper wear.