Many recipients of the Stryker Rejuvenate may well wonder what events led up to the recall of the hip implant device in July, 2012. Was the company aware of the Stryker Rejuvenate design problems prior to releasing the device? Was the propensity for Stryker Rejuvenate fretting known? Was sufficient safety testing done prior to release of the Rejuvenate or was consumer safety sacrificed in favor of a larger profit margin? While the entire truth may never be known, many attorneys and consumers feel that, at the very least, Stryker downplayed the risks of the implant device, even at the time of the recall.
What is Wrong with the Stryker Rejuvenate?
When the Rejuvenate was recalled, Stryker stated the device had a higher-than normal rate of failure, a greater likelihood of fretting and corrosion at the neck/stem taper, and that this corrosion could lead to excess metal ion debris being released into the body. These microscopic metal ions have been found to be responsible for metallosis and metal toxicity, depending on where they travel in the body. The tiny metal shards which burrow into surrounding hip tissue, result in moderate to severe pain for the implant recipient once inflammation and potential infection occur. The inflammation leads to deterioration of bone and tissue, and, eventually, the death of tissue and loss of bone.
The metal ions which reach the bloodstream are responsible for a wide array of serious health issues. Many patients who have suffered metal poisoning experience one or more of the following: Gastrointestinal, renal, thyroid, cardiovascular and neurological disorders, hearing and vision loss, balance problems, skin rashes, chronic headaches, irritability, depression, anxiety, altered DNA, the development of pseudo-tumors, reproductive disorders and the potential for certain cancers.
The Many Stryker Rejuvenate Design Problems
The design of the Rejuvenate—once considered highly innovative—allows surgeons to choose from a variety of stem and neck components. This means the implant can be more precisely fitted to the individual’s body type and level of activity. When the components are implanted, the Morse taper is hammered into the stem, possibly releasing excess cobalt and chromium ions into the body. The Rejuvenate also contains four small metal trunnions located on either end of the neck piece; when body fluids collect underneath the trunnions, corrosion can occur, causing more metal ions to shear away. The fact that the stem of the Rejuvenate is titanium and the neck portion is much harder cobalt and chromium, may be responsible for excess corrosion as well, as many studies have shown that mismatched metals create a higher level of corrosion.
Surgeons Note Stryker Rejuvenate Fretting and Corrosion
Prior to the recall, one surgeon notified Stryker that his patients were experiencing tissue degradation following implantation of a Stryker Rejuvenate. Another surgeon notified Stryker that after removing a Rejuvenate, he noted obvious “black rust” on the removed device. At this point, Stryker was still maintaining that the Rejuvenate was safe and that adverse reactions to the hip implant were “rare,” with only a 1% reported rate of fretting and corrosion. Even worse, Stryker attempted to lay the blame at the feet of the patients themselves as well as their surgeons. Stryker maintained that those who were showing adverse reactions to the Rejuvenate were either overly sensitive to metals, had an infection prior to the implant surgery or had a previous health issue such as diabetes which caused the implant to fail. Stryker further stated that many surgeons were simply not well-trained enough to properly place the Stryker hip implants and, when placed at the wrong angle, the device was more likely to experience undue friction, leading to corrosion.
Stryker Rejuvenate Component Friction
Aside from the problem of mismatched metals, it is believed that frictional torque was also responsible for many of the problems suffered by the Rejuvenate recipients. Researchers were surprised to find that in the Rejuvenate, corrosion occurred at the neck-stem taper, rather than the head-neck taper. (The taper is the portion of the component which allows the components to lock together). Frictional torque at the head-neck junction is considered common in hip implant devices, however less so at the neck-stem junction. Some believe the increased movement at the neck-stem junction could be due to the lever arm effect of the taper.
The neck-stem connection is also eccentrically loaded, leading to higher levels of stress. In other words, while there is little or no movement in one tight-cast piece of a hip implant, the Stryker Rejuvenate has a modular neck which fits into the stem piece, resulting in additional movement and frictional torque where the two pieces come together. As the bearing diameter increases, the frictional torque also increases, leading to excess wear on the hip joint, particularly during periods of activity. The excess wear results in higher cobalt and chromium levels due to the increased mechanical stress. This excessive wear at the neck-stem junction may also be responsible for the formation of pseudo-tumors, which are benign tumors which must be removed to prevent further damage.
Patients Harmed by Stryker Rejuvenate Defects
At the time of the recall, Stryker did not mention that mismatched components could be an issue, nor that frictional torque could be a problem with the Stryker design. The Rejuvenate gained FDA approval through a controversial process known as the 510(k), which allows manufacturers to gain approval for a device based on its “substantial similarity” to a device already on the market. Unfortunately, the device the new implant’s approval is based on, may well have problems of its own, and could, in fact, have gained FDA approval based on being similar to yet another device.
The Rejuvenate gained approval due to its similarity to the Wright Profemur, however the two models really only have a titanium stem in common. Prior to the recall of the Stryker Rejuvenate, a number of adverse reports had been sent to the FDA regarding metallosis and metal toxicity related to the device. Following the recall, many more implant recipients realized that at least some of their health issues could well be related to the Rejuvenate. Over 9,000 Rejuvenate implants were placed into consumers who believed the device was safe. Many of these have suffered serious health issues due to the Rejuvenate and have filed suit against Stryker in order to recoup at least some of the financial losses, although their health may never be the same.