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Wednesday, November 21, 2012

Why Diagnosing Problems in Stryker Rejuvenate Hip Implants is So Difficult


When the Stryker Rejuvenate and ABGII were recalled in July of 2012, citing potential risk of fretting and corrosion at the neck juncture, many of the implants had already been removed during revision surgeries. Unfortunately, since most physicians were unaware of the problems with the implants, the operative reports were unlikely to list this corrosion. In other words, since the doctors hadn’t been told what issues to look for, there were few records stating that corrosion was a factor in the revision surgery. When Stryker originally told hospitals and surgeons (in an Urgent Field Safety Report in April of 2012) that there could be corrosion or fretting and release of metal ions, there was still no mention of that corrosion occurring anywhere except at the neck juncture.

Therefore, the neck juncture would likely have been the only place physicians would have examined when taking out the implant. In the same vein, when implant recipients came to their doctor complaining of pain or other symptoms, the doctor would have ordered x-rays, an MRI and a bone scan. Again, without clear information regarding what to look for, many physicians might have attributed their patient’s complaints to external issues such as the aging process.  The Rejuvenate, unlike former metal-on-metal hip implants, is a four-part device with a ceramic ball and a plastic liner in the cup. Because of these improvements, it was believed there would be no metal parts rubbing against one another causing metal ion shear.

Unfortunately, the company may have not considered the potential of the small metal “trundles,” located on either end of the neck piece, as a risk for metal ion release. These trundles allow the neck piece to slip inside of them then the trundles on the neck pop into the stem on one end and into the ball on the other. Body fluids can become trapped inside these trundles, causing corrosion and leading to metal ions being released into the surrounding tissues or into the bloodstream. While the level of metal in the body would not reach the same levels as with the all-metal implant, there is no good amount of metal to have in the body. Elevated levels of cobalt and chromium can lead to:

·         Chronic pain
·         Infection
·         Failure of the hip implant
·         Necrosis (tissue death)
·         Pseudo tumors
·         Metal toxicity

So long as physicians are not informed about the potential risks of hip implants, they will be unaware of what they need to look for and may even have dismissed patient complaints or misdiagnosed patient concerns. More information is crucial so that patients are informed of the risks of hip implants and surgeons are apprised of the potential risk of the implants. 



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