May 21, 2014 - If you currently have a Stryker Rejuvenate hip implant in your body, then you are likely well aware of the Stryker recall which occurred in July, 2012. Although the reason for the recall was stated as a higher-than-normal risk of fretting and corrosion which could cause a release of cobalt and chromium ions into the body, it was later discovered that several other issues with the Rejuvenate existed as well. Following the Stryker hip recall, some of the issues found, included problems with the metal trunnions at either end of the Stryker Rejuvenate neck component, the special coating on the Stryker components, a higher cobalt concentration in Stryker recipients, dissimilar metals used in the construction of the Stryker Rejuvenate, excess amounts of frictional torque and a Morse taper which may not have worked as expected.
Higher Cobalt Levels?
Cobalt and chromium toxicity has led many recipients of a metal-on-metal implant to experience many adverse health issues. Unlike other metal-on-metal hip devices, patients with a Stryker Rejuvenate appear to show a wide variance between cobalt and chromium levels, with the cobalt levels being significantly more elevated. It is believed this disparity is caused by the wear on the Rejuvenate being concentrated in the neck and stem portion rather than the cup and ball.
What About the Morse Taper?
The Rejuvenate implements a Morse taper between stem and neck which is hammered until it locks into place. It is now widely believed that where the Morse taper meets the stem, cross-ionization occurs between the titanium stem and the cobalt in the Rejuvenate neck. Rather than providing additional “give,” and adapting to the different sizes of patients, the Morse taper has instead created additional stress. This stress leads to fraying and the release of metal ions into the surrounding hip tissues and into the bloodstream.
How the Metal Trunnions May Have Led to Problems with the Rejuvenate
Body fluids can accumulate under the metal trunnions, causing corrosion, and the release of cobalt and chromium. The Bone Joint Research Journal notes that most trunnions have been shortened, allowing the base of the trunnion to sit inside the taper, which increases the possibility of edge loading. Orthopedic trunnion tapers are no longer standardized, meaning they can vary in length, angle and dimension as well as design and surface characteristics. These variances can influence the probability of wear, corrosion and longevity of the implant.
Dissimilar Metals Leads to Stryker Rejuvenate Problems
The extremely high level of corrosion seen in the Stryker Rejuvenate could be attributed, at least in part, to the use of mismatched components. One study showed that 28% of hip implants using similar metals exhibited moderate to severe corrosion, while 42% showed the same amounts of corrosion when mixed metals were used. The Stryker Rejuvenate implements a titanium stem and a cobalt and chromium neck; over two decades before Stryker began marketing the Rejuvenate, studies reported the potential dangers of mixing metal alloys in hip implants.
Coating on the Stryker Rejuvenate
Two types of coating on the Stryker Rejuvenate may have led to problems; the first is a hydroxyapatite porous coating which is meant to encourage bone ingrowth. The Rejuvenate has a rough, deep coating which may release into the bone tissue, putting Rejuvenate patients at a higher risk of osteolysis, or weakening of the bone. The second coating is a proprietary blend of titanium, molybdenum, zirconium and iron which is sprayed on the implant in an attempt to avoid the issue of mismatched metals, however the TMFZ spray did not deliver as promised.
While the exact reasons behind the Stryker hip recall may not have come to light, what is known is that Stryker hip metallosis and Stryker chromium and cobalt poisoning are very real issues experienced by many with a Stryker Rejuvenate hip implant. If you believe you have suffered harm from a Stryker Rejuvenate, it could be beneficial to contact a Stryker hip recall lawyer and consider filing a Stryker hip lawsuit.