Theories of Why the Stryker Rejuvenate is Failing—Part Two

June 11, 2015 - Following the Stryker Rejuvenate recall in 2012, many more theories developed as to why the Rejuvenate failed. Part two will explore additional theories as to what caused the failure of the Stryker Rejuvenate hip implant device. While Stryker noted, at the time of the recall, that the Rejuvenate had a higher-than-normal failure rate and was prone to the excess release of metal ions, later many more potential problems were identified such as:

·         Taper to Taper Variability in Manufacturing—Aside from the problems associated with Stryker’s use of a modified Morse taper, there was also a variability among those modified tapers. In fact, later research showed a wide variability in flexural rigidity between the various tapers, with a trend toward the trunnions becoming shorter and less rigid with time. This could explain why taper corrosion is seen with increasing frequency in the Stryker Rejuvenate hip implant devices.

·         TMZF Coating on the Stryker Rejuvenate Components—Two types of coatings are used on the Stryker Rejuvenate. The first, a hydroxyapatite porous coating, encourages the bone to attach firmly to the implant device. The second coating is known as TMZF, and is a proprietary blend of titanium, molybdenum, zirconium and iron. The TMZF coating is sprayed over all the implant components, ostensibly to avoid the problems associated with dissimilar metals. Because studies done more than a decade ago advised caution when pairing dissimilar metals (such as the titanium stem and cobalt and chromium neck of the Stryker Rejuvenate), Stryker made the TMZF coating a selling point for the Rejuvenate, claiming it would prevent corrosion. The coating did not deliver on those claims, and failed dismally to prevent the problems associated with dissimilar metals. While the TMZF spray may not have contributed to the failure of the Stryker Rejuvenate, neither did the coating help prevent that failure.

·         Titanium Dioxide—In many cases, when a Stryker Rejuvenate is removed from the body, the stem is covered with a black substance. Scientists identify this as titanium dioxide resulting when titanium is exposed to the fluids and oxygen in the body. This layer of dioxide essentially forms a boundary between the biological medium (the hip tissue) and the metal Rejuvenate implant. Titanium is a highly reactive metal, potentially contributing to the formation of titanium dioxide as well as the corrosion seen in removed Rejuvenate hip implants.

Many patients whose Rejuvenate hip implant did not actually fail still developed symptoms of Stryker Rejuvenate hip metallosis such as inflammation, chronic and severe pain in the hip, thigh and groin areas, deterioration and necrosis of hip bone and the surrounding tissues and the necessity for Stryker hip revision surgery. The current Stryker hip settlement offers Stryker hip monetary compensation only to those patients who were required to undergo Stryker hip revision surgery.