Defective Hip Implants
The hip joint, scientifically referred to as the acetabulofemoral joint, is the joint between the femur (the thigh bone) and the acetabulum (the hip socket) of the pelvis, and its primary function is to support the weight of the body in both static (i.e., standing) and dynamic (i.e., walking or running) postures.
An artificial hip implant is designed to replicate the human anatomy – that is, the relatively simple ball and socket structure of the human hip joint. Hip replacement surgery can be performed as a total replacement or a hemi (half) replacement. Hip replacement is currently the most common orthopedic operation in the United States with more than 420,000 patients undergoing a hip replacement procedure each year.
Total hip replacement is most commonly used to treat joint failure caused by osteoarthritis. Other indications include rheumatoid arthritis, avascular necrosis, arthritis associated with Paget’s disease of the bone, ankylosing spondylitis and juvenile rheumatoid arthritis. The aims of the procedure are to provide pain relief and improvement in hip function. Hip replacement surgery is usually considered only once other therapies, such as pain medications and physical therapy, have failed.
Total Hip Arthroplasty
Total hip replacement (also known as total hip arthroplasty) surgery involves implanting an artificial ball and socket into the patient’s damaged hip joint. During a hip implantation procedure, the surgeon first removes the patient’s femoral head. The surgeon then hollows out a portion of the top of the femur bone and inserts a metal femoral stem into the remaining femur. The femoral stem may be either cemented or “press fit” into the bone. The decision to press fit or to cement the components is based on a number of factors, including the quality and strength of the patient’s bone.
A ball-shaped, metal or ceramic femoral head is placed on the tapered top end of the femoral stem known as the trunnion. The ball replaces the damaged femoral head that was removed.
Next, the surgeon reams out the patient’s natural acetabulum and inserts a ceramic, metal or plastic acetabular cup in the resulting space. The surgeon often uses a hammer to tap the acetabular cup into place. Screws or cement are sometimes used to hold the cup in place.
In most hip implant systems, a metal, plastic or ceramic liner is then fitted inside the acetabular cup and between the new ball and socket. Finally, the surgeon fits the ball of the femoral stem into the liner of the acetabular cup where it should move easily, without friction or pain to the patient.
Metal-on-Metal Hip Implants & Device Failure
Many different types of designs and materials are used in artificial hip joints. Most hip implant components are comprised of cobalt and chromium alloys, or titanium. However, ceramic and plastic components are also common.
Metal-on-metal hip implants consist of a shell, ball, stem, and at times liner, all made of metal materials. Metal-on-metal hip implants were thought to be more durable than previous devices and were designed to decrease the chance of device fracture and dislocation. Metal-on-metal hip implants have been used in about one-third of all hip replacement surgeries in the United States each year, totaling a quarter million annually.
Unfortunately, research demonstrates that metal-on-metal devices are failing far sooner than expected and at an alarming rate. Despite an expected life span of fifteen years or more, some individuals have required replacement surgery within a year or two following implantation of a metal-on-metal device.
Studies have found that when metal-on-metal implants break down prematurely, tiny particles of cobalt and chromium wear off the implant causing metallosis. Over time, the metal particles can cause damage to the bone surrounding the implant and joint, inflammatory reactions, and death of the surrounding tissue. This may cause the implant to become loose or result in significant pain necessitating a replacement surgery. Cobalt and chromium may also get into the bloodstream. Replacement surgeries for metal-on-metal devices can be complex and the absorption of metal debris into tissue or bloodstream can leave patients with lasting complications.
Symptoms of metallosis generally include pain around the site of the implant, pseudotumors (a mass of inflamed cells), and/or a noticeable rash that indicates tissue necrosis. Metallosis can cause dislocation of implants as the healthy tissue that would normally hold the implant in place is weakened or destroyed. Metallosis has also been demonstrated to cause osteolysis (the degeneration of bone tissue).
Numerous metal-on-metal hip implants have been associated with early failure and found to contribute to metallosis, including the following devices:
• Biomet M2a
• Biomet Magnum
• DePuy ASR
• DePuy Pinnacle
• Smith & Nephew Birmingham
• Wright Conserve
• Wright ProFemur
• Zimmer MIS Mini-Incision
• Zimmer Durom Cup
Modular Hip Implants & the Problem with “Trunnionosis”
Historically, early hip replacement devices consisted of a non-modular femoral head with a single neck option known as the “monobloc.” This meant that restoring leg length and offset was challenging, and could result in instability and abductor dysfunction in some patients. The concept of modularity was introduced into the design of hip prostheses and has become increasingly common in the last two decades. Modularity aimed to provide surgeons with additional versatility when attempting to restore normal biomechanical function in patients.
Modularity can be exhibited at the junction between the femoral head and the neck of the femoral stem. The junction between the femoral head and femoral stem typically consists of a trunnion located at the neck or top of the stem which has a machined taper allowing for an interference fit with the femoral head. The taper interface is where the femoral head (female taper surface) attaches to the trunnion (male taper) of the femoral stem.
The taper interface is designed to prevent motion when assembled; however, studies have demonstrated that forces across the interface are sufficient to induce micromotion at the interface which can result in the generation of metal particles and/or ions from the malfunctioning taper. Similarly, studies have also shown that corrosion at the taper interface can result in a similar release of metal particles and/or ions, particularly cobalt and/or chromium.
Whether caused by wear or corrosion, the release of metal particles and/or ions can result in adverse local tissue reactions and, in some cases, systemic effects of the metal ion toxicity, including neurological (fatigue, weakness, poor coordination, cognitive dysfunction depression, vertigo, visual and hearing impairment, and peripheral neuropathy), hematological (polycythaemia), endocrine (hypothyroidism), and cardiac (arrhythmias and cardiomyopathy) complications.
The concept that corrosion could occur at the head-neck taper of the femoral component of a hip prosthesis was first identified by researchers in the early 1980s. Since that time, there have been numerous studies and reports demonstrating that the taper interface between a metal femoral head and metal femoral stem may be susceptible to corrosion and fretting resulting in metallosis and adverse local tissue reactions in patients. This phenomenon has been referred to as “trunnionosis.”
It had been previously thought that metal debris was generated solely from the weight bearing articulation in hip systems; however, with the evolution of modularity to aid surgical options, wear at the trunnion is becoming more apparent.
Trunnionosis can occur with metal-on-metal as well as metal-on-polyethylene hip implant systems.
Regulatory Action & Hip Implant Recalls
In July 2008, Zimmer Orthopaedics, the nation’s largest producer of orthopedic devices, announced the suspension of sales of its Durom Cup artificial hip implant due to a high failure rate. The Durom Cup was first sold in the U.S. in 2006, and was implanted in more than 12,000 patients over a two-year period. Soon after, other metal-on-metal Zimmer hip implants began to be recalled from the market.
The DePuy ASR XL Acetabular System is manufactured by DePuy Orthopaedics (a subsidiary of Johnson & Johnson) and first became available in the U.S. in 2005. Johnson & Johnson was given special clearance from the FDA in 2005 to market the ASR devices without first performing clinical trials.
In August 2010, DePuy Orthopaedics recalled more than 93,000 ASR devices worldwide. The recall came after data from a study indicated that the five-year failure rate of this product is approximately 13%, or 1 in 8 patients.
In February 2011, the United States Food and Drug Administration (FDA) advised the public that there are “unique risks” for “metal-on-metal” artificial hips because tiny metal ions can wear off and damage nearby tissue. The FDA further explained “[b]ecause the metal ball and the metal cup slide against each other during walking or running, some tiny metal particles may wear off of the device and enter into the space around the implant. Some of the metal ions from the metal implant or from the metal particles may even get into the bloodstream.”
In May 2011, the FDA ordered over twenty-one different metal-on-metal hip implant manufacturers to conduct a more in-depth study of these devices to determine, among other things, whether the implants are shedding high levels of metallic debris and to provide post hip-replacement data on patients who have been implanted with their products.
Rather than conduct the required safety studies, many manufacturers have discontinued selling metal-on-metal hip devices.
In May 2013, DePuy Orthopaedics announced that it would no longer sell its DePuy Pinnacle device when mated with a metal liner. When used with a metal liner, the Pinnacle device is a metal-on-metal hip implant. Over 7,000 DePuy Pinnacle cases are already on file against DePuy Orthopaedics in courts around the country and it is anticipated there will be a large number of DePuy hip lawsuit settlements.
Hip Implant Settlements
In 2008, Zimmer Orthopaedics announced that it had established a settlement fund of $47.5 million dollars to compensate claimants injured by its Durom Cup device. The settlement fund has reportedly increased to over $100 million. Despite the settlement fund, Zimmer is also continuing to litigate Durom Cup cases.
In November 2013, DePuy Orthopaedics announced a $2.75 billion settlement to compensate individuals injured by its ASR device. To be eligible to participate in the settlement, claimants must have undergone a qualifying revision surgery of their ASR device before August 31, 2013. Under the ASR Settlement Program, qualifying claimants are eligible for a $250,000 base award which is subject to deductions. Additionally, DePuy Orthopaedics has agreed to satisfy healthcare liens on behalf of claimants participating in the ASR Settlement Program. Since the settlement was announced, the ASR Settlement Program has been opened up to claimants who underwent a qualifying revision surgery between September 1, 2013 and January 31, 2015.
Compensation for Stryker Orthopaedics hip lawsuits is also substantial. In November 2014, Stryker Orthopaedics announced its agreement to pay no less than $1.4 billion to resolve qualifying claims of individuals injured by the company’s Rejuvenate & ABG II hip implants. Similar to the DePuy ASR Settlement Program, Rejuvenate and ABGII claimants are eligible for a base award totaling $300,000, which is subject to deductions. To be eligible to participate in the current Rejuvenate & ABGII Settlement Program, claimants must have undergone revision of their Rejuvenate or ABGII device on or before November 3, 2014. Claimants who have suffered significant additional injuries beyond revision are also able to file for an Extraordinary Injury Fund payment.
Whether you have undergone a revision surgery or not, if you or a loved one has been injured by a hip implant, you may be entitled to pursue a claim against the manufacturers for damages. For a free and confidential case evaluation, please call our office toll-free at (888) 747-5342 or complete our online contact form and we will promptly respond to your inquiry.