Stryker Rejuvenate Coating Defects and How They Contributed to the Recall

After gaining FDA approval in 2008, the Stryker Rejuvenate began receiving negative feedback soon after its release. Over 9,000 Rejuvenate devices were implanted into consumers who believed the implants were safe. Following an April, 2012 Urgent Field Safety Notification regarding the Rejuvenate, the device was recalled in July, 2012. At the time of the recall, Stryker cited fretting and corrosion, leading to excess metal ion debris generation as well as a higher-than-normal failure rate. Many patients implanted with the Rejuvenate began experiencing symptoms of metallosis and metal toxicity, and these injured patients were looking for answers. While Stryker has largely remained silent regarding the specific design defects of the Rejuvenate (likely due to the number of lawsuits filed against Stryker since the recall), research offers several theories.

Mismatched Components and Frictional Torque

One theory centers around mismatched components, or the pairing of a titanium stem with the much harder cobalt and chromium neck piece. Studies done over a decade ago showed that mixing alloys could result in excess corrosion, yet Stryker chose to disregard this research when designing the Rejuvenate. Frictional torque is also an issue with the Rejuvenate; while most hip implant devices show the most frictional torque at the head-neck junction, the Rejuvenate shows the most frictional torque and wear at the neck-stem taper junction. When a patient is active, that activity causes frictional torque at the cobalt-chromium/titanium taper junction, leading to the shearing away of metal ion debris.

Stryker Rejuvenate Coating Defects

Stryker claimed that the proprietary blend of alloys which coated the Rejuvenate would prevent the problem of mismatched components. This mixture of titanium, molybdenum, zirconium and iron (TMZF) was mixed with a plasma spray and the Rejuvenate stem and neck were coated. Post-market data shows the coating failed to live up to expectations. While the coating may not have increased the amount of metal shear, it certainly failed to prevent it. Further, while most metal implants release chromium and cobalt in fairly equal proportions, the Rejuvenate appears to release higher levels of cobalt.

Whether this is related to the TMZF coating is unclear, however what is becoming increasingly clear is that Stryker may have had knowledge of at least some of the risks associated with the Rejuvenate at the time of its release. Another coating used on the stem of the Rejuvenate is known as HA or hydroxyapatite porous coating and is meant to encourage bone ingrowth. On the Rejuvenate, this HA coating is very deep and rough, making it extremely difficult to remove a Rejuvenate device in the event of revision surgery. Unfortunately, while the HA coating allows the Rejuvenate to bond to bone tissue, the coating may release into the bones, putting Rejuvenate patients at risk for osteolysis, or weakening of the bone. Should the bone surrounding the implant weaken enough, total failure of the implant is likely.

 

So What Is Wrong With the Stryker Rejuvenate?

Some implant recipients and surgeons feel the FDA approval process—known as the 510(k)—under which the Rejuvenate gained approval is inherently risky. The 510(k) process allows medical devices to be marketed once the manufacturer proves the device is substantially equivalent a device already on the market. The Rejuvenate gained approval based on the Wright Profemur hip implant device even though the only similarity between the two is the titanium stem. The Profemur has had problems of its own, and it gained approval based on yet another potentially flawed device. The 510(k) process allows manufacturers to skip clinical trials and conduct few safety tests prior to selling the device to consumers. This means that unsuspecting consumers and surgeons choose a product based on the company’s claims, believing it to be safe.

Results of Stryker Rejuvenate Corrosion

Many adverse reactions can occur once corrosion of the Rejuvenate hip implant occur. Metallosis and metal toxicity are caused by tiny metal ions which shear away following corrosion of the implant. These metal ions may enter the surrounding hip tissues, leading to inflammation, infection, chronic pain, bone loss and the destruction of hip tissue. As the inflammation increases, and the metal ions continue to enter the hip tissue, it is likely that hip revision surgery will become necessary as the implant fails. While Stryker has declined to put a number on the exact failure rate of the Rejuvenate, some research indicates it could be as high as 40%. In fact, prior to the recall, Stryker claimed that adverse reactions to the Rejuvenate were “rare,” occurring in no more than 1% of Rejuvenate patients. It is clear that this is hardly the case by the number of patients who have experienced metallosis and metal poisoning after being implanted with a recalled Rejuvenate.

When the metal ions enter the bloodstream, any number of negative health issues can occur, many of them extremely serious. Once the implant is removed, some of these issues will decrease, although in some cases the damage is irreversible. Such symptoms as loss of vision and hearing, neurological and cardiovascular problems, renal and thyroid disorders, vertigo, skin disorders, gastrointestinal problems, DNA disruption, the development of pseudo-tumors, anxiety, irritability, depression and reproductive disorders can occur in those with a Rejuvenate hip implant device. While some people appear to be more sensitive to metals in the body and may develop serious symptoms even though their tested metal levels are relatively low, there are really no safe levels of cobalt and chromium in the body. Others who are less sensitive to metals may test high for cobalt and chromium but have not yet developed serious health issues. Even so, considering the high rate of failure of the Rejuvenate, many of those with no current overt symptoms may become sick in the future.

Are You a Victim of Stryker Rejuvenate Defects?

Whatever the reasons behind the failure of the Rejuvenate and its subsequent recall—many of which may never be known—consumers deserved a safe implant, and it appears Stryker failed to deliver. Following the recall, lawsuits began being filed, and will likely continue until the statute of limitations has expired. In most states that statute is two years from the time of the recall in July, 2012. Recently a Florida Circuit Court granted consolidation for thirteen cases regarding the Rejuvenate, coordinating the individual lawsuits for discovery purposes only.

Estimates for Stryker Hip Recall May Soon Rival Those of DePuy Hip Recall

When consumer health issues such as metal poisoning and metallosis are potential consequences of a recalled metal hip implant, the costs to the manufacturer can be substantial. Stryker Corp, the manufacturer of the recalled Stryker ABGII and Rejuvenate hip implant devices, has increased the original estimates of $190-$390 million to over $1.1 billion for expenses related to the July, 2012 recall. Of course the ultimate cost will depend on a variety of factors, including the number of Stryker lawsuits, the amount of the settlements and the costs of revision surgery and other treatment for victims of the recalled hip implants.

Over 400 lawsuits are pending in a Minnesota Court under U.S. District Judge Donavan Frank, with over 600 more pending in state court in New Jersey. Consolidation of product liability cases is common in order to avoid conflicting pretrial rulings from many different judges as well as to allow sharing of discovery. Johnson & Johnson is estimating over $3 billion in settlement costs for the DePuy ASR metal hip device for the over 10,000 lawsuits filed in response to the recall. With time left for most states under the statute of limitations, it is likely many more Stryker lawsuits will be filed.

Metal poisoning symptoms occur when the hip device suffers corrosion, leading to the generation of microscopic metal ions which enter the bloodstream. Such serious health issues as loss of hearing and vision, memory loss, vertigo, neurological disorders, changes to DNA, the development of pseudo-tumors, cardiovascular problems, renal and thyroid issues, reproductive disorders, gastrointestinal issues and chronic headaches can result. Should the cobalt and chromium ions enter the hip tissue, inflammation, chronic pain and the deterioration of bone and tissue can occur, leading to hip failure and the necessity of revision surgery. At the time of the ABGII and Rejuvenate recall, Stryker stated the risk of fretting, corrosion and the release of metal ion debris at the neck-stem taper junction.

Unlike the traditional one-piece neck and stem, Stryker offered surgeons a variety of neck and stem components of varying angles and lengths which allowed the surgeon to custom-fit the device to the individual patient. Unfortunately, the innovative design which was meant to offer longer implant life and greater freedom of motion failed to live up to expectations. The neck-stem taper junction created friction during periods of activity, and that friction led to dangerous and premature levels of corrosion, despite the use of a ceramic ball rather than a metal ball. 

While there is no United States database which comprehensively tracks hip implants, it is estimated that over 20,000 of the devices were implanted into consumers between FDA approval in 2009 and the time of the recall. Revision surgery, should it become necessary, is considered riskier and more expensive than the original implant surgery, with a considerably longer recovery time. Patients harmed by the recalled Stryker Rejuvenate or ABGII should undergo the necessary testing to determine whether they have dangerous levels of cobalt and chromium in their bloodstream. Legal representation may also be beneficial for those seeking to recover expenses associated with the recalled implants.

What is wrong with the Stryker ABGII—Are Problems Due to Mismatched Components?

When the Stryker ABGII recall occurred in July, 2012, there were many recipients of the hip implant as well as surgeons who implanted the ABGII who were left wondering how an unsafe device had been implanted in over 9,000 people. Soon after the ABGII received FDA approval in 2009, adverse events were reported to the agency. In April, prior to the recall in July, Stryker issued an Urgent Field Safety Notification, warning surgeons and hospitals of the increased risks of corrosion and fretting of the ABGII. This corrosion can lead to the excess generation of cobalt and chromium ions, causing those metal shards to enter the body. Stryker also noted a higher-than normal rate of failure for the ABGII. The manufacturer did imply, however, that the problems associated with the ABGII could be attributed to surgeon error or patient issues such as extreme sensitivity to metals, being overweight, or having a previous health condition which caused the corrosion. Stryker did not mention the fact that when the ABGII is implanted, the Morse taper is hammered into the stem, potentially releasing cobalt and chromium ions into the body.

Stryker ABGII Mismatched Components and the Resulting Problems

Therefore, even though the design of the ABGII was originally believed to be much safer than that of other all-metal hip implants, those beliefs were not upheld once the ABGII was implanted. Unlike other all-metal hip implants the ABGII used a ceramic ball rather than a cobalt and chromium ball. Further, while using a cobalt and chromium neck and a titanium stem, Stryker sprayed those components with a proprietary TMZF coating, claiming this would alleviate the problems associated with mismatched components. Again, this claim turned out to be less than true. It is hard to understand why Stryker designed the ABGII using mismatched components since research from over a decade ago warned of the increased levels of corrosion when dissimilar metals come into contact. Scientists believe that because the cobalt and chromium neck component is much harder than the titanium stem, excess corrosion can result.

One study done over a decade ago noted that moderate to severe corrosion was seen in up to 28% of similar alloy hip implants while 42% of implants using mixed alloys showed signs of corrosion. In another study, implants removed from patients showed significant levels of corrosion among those of mixed metals while those which implemented similar metals showed little or no corrosion. In scientific terms, the active metal (titanium) or anode is attacked by the cathode—the more resistant metal, and, in this case, the cobalt and chromium neck. This is known as galvanic corrosion, and while some metals form a sort of film once they are implanted in the body—which would theoretically protect the implant recipient from the effects of mismatched components—this film only remains present and protective when there is no motion or wear. This means that the film would only be protective if the implant recipient never engaged in any sort of activity. Cobalt and chromium has a hardness factor of 4.5 GPa (gigapascal) as opposed to titanium, which has a hardness factor of 3.0 GPa. (One gigapascal is equal to 140,000 psi).

Stryker ABGII Design Problems

Despite what appeared to be an innovative design on the part of Stryker at the time the ABGII was released, the implant did not live up to the expectations. Stryker claimed the implant would last as long as twenty years, yet scores of patients were forced to have their ABGII implant

How Many Victims of Stryker ABGII Design Problems Are There?

Following the recall of the Stryker ABGII in July, 2012, many wondered just how many victims of the defective hip implant there really were.  The Stryker Corporation is a Fortune 500 Company, with an estimated worth of over $20 billion dollars. It is estimated that over 9,000 people were implanted with an ABGII device between the time it gained FDA approval in 2009 and the time of the recall.

Stryker ABGII Defects

While the ABGII device is not a true all-metal implant, it has nonetheless experienced the same types of problems as other metal-on-metal devices. The ABGII uses a ceramic ball, rather than a metal ball, which led patients and surgeons to believe it was a much safer alternative to the all-metal implants. The ABGII is composed of a variety of stem and neck components rather than the traditional one-piece design. This design allows surgeons to more precisely fit the hip implant to the individual patient, according to body size and type as well as level of activity.

Despite the ceramic ball and the innovative design of the ABGII, very little time passed after marketing of the device began and the time implant recipients began experiencing problems related to their implant. In 2010 alone, the FDA received at least 60 adverse events involving an ABGII hip implant or a Stryker Rejuvenate which was also recalled at the same time as the ABGII. By the end of 2011, the number of adverse reports to the FDA regarding the ABGII hip implant had risen to 130, and by the beginning of 2012, to over 300.

Was Stryker Aware of the Problems with the ABGII?

Failures of ABGII hip implants in other countries were climbing as well; The Australian Registry calculated a failure rate of up to 8.1% in the first year following implantation. Despite these alarming numbers, Stryker continued to market the ABGII hip stems until April of 2012 when the obvious problems associated with the ABGII could no longer be covered up. At that time, Stryker sent an Urgent Field Safety Notification to hospitals and surgeons, warning them of the risks of fretting and corrosion associated with the ABGII. The fretting and corrosion could lead to the shearing away of metal ions into the body, causing serious medical problems and hip failure. Only a short time before this Urgent Field Safety Notification was sent out, Stryker had claimed that problems with the ABGII hip device were “rare,” affecting less than 1% of implant recipients, yet three months after the notification a recall was issued.

What is Wrong with the Stryker ABGII?

The ABGII was approved under an FDA process known as the 510(k), which allows manufacturers of medical devices to skip clinical trials which would evaluate effectiveness and safety by showing the device is substantially similar to a device already on the market. The only caveat of the process is that the medical devices will gain approval on the condition that post-market surveys will be done. By this time, however, the damage may already be done. There are several serious medical risks associated with the Stryker ABGII hip device, including pain and inflammation so severe as to require revision surgery, bone dissolution, premature tissue death, the formation of pseudo-tumors and symptoms of metal toxicity such as: Gastrointestinal, renal, thyroid, neurological and cardiovascular problems, loss of vision and hearing, reproductive disorders, disruption of DNA, anxiety, vertigo, depression, irritability, chronic headaches and skin rashes.

What Causes Stryker ABGII Component Friction?

There are a variety of theories as to why the Stryker ABGII failed; some believe mismatched components or frictional torque were the issue, others that the powder coating may have caused additional problems. Frictional torque could certainly have been a contributor, as the design of the ABGII allows the modular neck to fit into the stem via a taper junction. While in other hip implant devices, the primary area of wear is seen as the head-neck taper junction, in the ABGII, the extra movement the components allow leads to more frictional torque and more wear on the joint.

In fact, a wear analysis concluded that the majority of the wear and load-bearing in the ABGII occurred at the neck-stem taper junction, and that as bearing diameter increases, the mechanical stress will increase as well. As the neck-stem taper junction experiences excessive wear, corrosion and metal ion shear can occur as well as the formation of pseudo-tumors. Among retrieved neck-stem tapers, at least 35% of them showed signs of excessive wear and corrosion due to the frictional torque at this junction. Despite the oxide film covering the components, the stresses on the neck-stem taper unction can abrade the oxide film, increasing the rate of corrosion.

What Will Happen to Patients Harmed by Stryker ABGII Design Problems?

When mismatched metals are used—such as the titanium stem and cobalt and chromium neck piece of the ABGII—additional frictional torque and corrosion is likely. The higher the rate of corrosion, the more likely metal ions will enter the hip tissue and bloodstream. Whether ABGII implant recipients will ever fully understand how they came to be implanted with a device they were told was totally safe is unclear. It is hoped, however, that the lawsuits pending against Stryker will allow those harmed by the ABGII to at least recover some of the financial expenses associated with their implant and potential revision surgery.

The Many Stryker ABGII Defects—Including Coating—and How They Affect Implant Recipients

Stryker ABGII Coating Defects

While many theories of specific design defects abound regarding the Stryker ABGII hip implant device which was recalled in July, 2012, several have come to the forefront. When Stryker recalled the implant, the manufacturer cited the risk of fretting and corrosion, leading to an excess amount of ion debris generation and failure of the hip implant. Stryker offered few clues as to how the design of the ABGII contributed to the excess levels of corrosion and the higher-than-normal failure rate of the device. One theory revolves around the fact that Stryker used a titanium stem paired with a cobalt and chromium neck component piece. The two join together with a taper junction. Much research was available which clearly showed that using mismatched components results in a higher rate of corrosion, although scientists are not clear exactly why this is true.

The excess corrosion could be due to the much harder cobalt and chromium metals as compared to the softer titanium metal. To help alleviate this problem, Stryker sprayed the implant with a proprietary mix of alloys known as TMZF, however the spray did not offer the protection expected. A second theory is that the neck-stem taper junction is a source of considerable frictional torque. Other hip implants have a one-piece, tight-cast neck-stem component, but in the interest of allowing greater range of motion for recipients, Stryker used a new design which offered a variety of stems and necks in different lengths and angles. While surgeons were now able to fit the hip implant precisely to the patient, this taper junction had turned into a source of frictional torque, resulting in further corrosion, fretting and metal ion release.

Finally, the stem of the ABGII was coated with a hydroxyapatite porous coating in the interests of encouraging the growth of bone around implant. While the HA coating of the ABGII is shallower and smoother than that used on the also-recalled Stryker Rejuvenate, the coating may have still caused additional problems for recipients. The HA coating mimics the chemical makeup of calcium and other minerals found naturally in the human body, however the coating may seep into the bone tissue. This can put recipients of the ABGII hip implant at risk of osteolysis, or weakening of the bone. When the hip bone weakens, the implant may loosen, causing chronic pain and a loss of range-of-motion. The loosening hip stem can also create popping, cracking or squeaking noises, which can signal bone loss. Further, should revision surgery become necessary, the HA coating can make the ABGII much more difficult to remove.

What Stryker ABGII Design Problems Led to the Recall?

Whether the design problems listed above were responsible for the Stryker ABGII recall or there were other issues unknown at this time, many wonder whether Stryker was aware of the design problems at the time marketing of the device began. Because the ABGII gained FDA approval through the 510(k) process, there was no requirement of clinical trials, and little safety testing was done. The process only requires that the device be substantially similar to a device already on the market and that the manufacturer follow up with post-market data. Unfortunately, by the time post-market data is gathered, many consumers may have already suffered irreversible harm.

Patients Want to Know What is Wrong With the Stryker ABGII

When metal ions enter the body after corrosion and fretting take place, they may either enter the bloodstream or lodge in the hip tissues. When the metal shards enter the tissue, there may be degradation of bone and tissue, inflammation, infection and chronic pain for the patient. As the inflammation increases, the bone and tissue may undergo total death or destruction, causing the implant to fail completely. Should this occur, revision surgery will be required. Unfortunately, ABGII revision surgery can be much riskier and more expensive than the original surgery, requiring a recovery period of up to six weeks. When the metal ions enter the bloodstream, there are a variety of adverse health issues which can result including:

·         Gastrointestinal disorders

·         Reproductive disorders

·         The development of pseudo-tumors

·         Disruption of DNA

·         Cardiovascular problems

·         Neurological issues

·         The loss or diminishment of vision and hearing

·         Vertigo

·         Anxiety, depression, irritability

·         Chronic headaches

·         Skin rashes

·         Renal and thyroid problems

Stryker has declined to comment on the actual failure rate of the ABGII, however independent studies have placed that number as high as 40%. This means that even for the patients who have not yet experienced health problems due to their ABGII implant, the likelihood that they will, is high. As the lawsuits continue to mount, it is possible that more information may come to light as far as what design defects were present in the ABGII, and how much Stryker knew as they continued to sell the implants to an unsuspecting public.

While the ABGII is not considered a “true” metal-on-metal implant due to the use of a ceramic ball, the issues patients are experiencing are nearly identical to those experienced by recipients of all-metal implants. The levels of ABGII corrosion are extremely high, both at the neck-stem taper junction and under the small metal trunnions located on either end of the neck piece. All of these design defects will become legal issues, however for patients who are suffering severe, adverse health issues due to their ABGII hip implant, there may be little consolation in finally learning why the ABGII failed.