Hip replacement implants made with metal-on-metal components have been causing problems for patients worldwide, particularly active individuals, forcing many to undergo further surgery.
There are two types of hip replacement surgery. In hip resurfacing, a metal cap is fitted on the femoral head, and the acetabulum (socket of the ball-and-socket hip joint) typically is reamed and relined with an artificial cup. In total hip arthroplasty, the top of the femur is sawed off below the femoral head, the femur's stem is hollowed, and a metal stem is fitted into it. An artificial femoral head is then placed on the new stem. Metal-on-metal ("MoM") hips have metal femoral heads and metal acetabular cups. The MoM hip has become more popular for total hip arthroplasty in recent years. The medical community believed that the wear of these modern metal articular surfaces would be negligible and medically inconsequential.
Identified Problems with Metal-on-Metal Hips
MoM hips appear to be failing and requiring early revision (further surgery to replace one or more components) more often than other types. The most common reasons for revision surgery–which has a lower probability of a successful outcome than the original hip replacement–are pain and recurrent dislocations. Some revision surgeries require well-fixed components to be removed, which can cause bone loss and tissue damage. A New York Times series describes how the failure occurs (New York Times, The High Cost of Failing Artificial Hips, December 28, 2011; New York Times, Sources of Debris in Artificial Hips, December 27, 2011).
Serious complications leading to MoM hip failure include aseptic loosening, osteolysis, metallosis, and neurological problems. Aseptic loosening occurs when a component, usually the acetabular cup, becomes loose for reasons other than infection or another organic disease process. Osteolysis (bone loss) is suspected to be caused by the wear of MoM articular surfaces and the resulting release of metal ions into the body. Metallosis is the body's reaction to the accumulation of metal ions or metal debris; an accumulation of a thick, gray fluid at the hip joint may signal this condition. Further reactions and complications from metallosis include the development of pseudotumors, tissue death, and bone degradation. Recpients of MoM implants may be exposed to cobalt and chromium ions, which may be associated with headaches, persistent metallic taste in the mouth, memory issues, and cardiac abnormalities.
Some MoM hips appear to be wearing out faster–and producing more metal ions and debris–than manufacturers anticipated. With at least some MoM hips' designs, the acceptable range for the angle of inclination for implanting the cup–the margin of error–is much narrower than it is with other artificial hips. A cup that is implanted outside this narrow range is more susceptible to excessive wear and what is called "edge loading"–a disproportionate amount of weight borne at the rim of the cup–as the ball articulates in the socket. For years, surgeons were not told of this narrower margin for implantation.
Recipients of MoM hips may not experience pain as an early symptom of device failure, so they are being advised to be monitored by their orthopedic surgeons. Periodic testing of cobalt and chromium levels in the blood is now recommended. In May 2011, the FDA ordered 21 manufacturers to conduct post-market surveillance studies, requiring them to submit a research protocol that addresses specific safety issues related to these devices.
Types of Defective Metal-on-Metal Hips
Zimmer Durom Cup - The Zimmer Durom Acetabular Component was the first MoM hip to be identified with potential problems after surgeons began to report a higher than normal rate of early revisions due to cup loosening and cup migration. Issues with the coating that is designed to promote bony ingrowth are suspected as a possible cause. In 2008, Zimmer recalled the Durom cup, but about 12,000 were implanted in the United States and many of them remain implanted and continue to fail.
DuPuy ASR - Due to design defects, many patients receiving either the DePuy ASR™ XL Acetabular System or ASR™ Hip Resurfacing Platform found themselves back under the knife within five years of the initial surgery. In the United States, only the ASR XL Acetabular System was approved for use in hip replacement surgeries. The DePuy device came on the market in 2005 after being cleared by the FDA by a process known as 510(k) approval. This process allowed Johnson & Johnson to obtain market approval of this MoM hip replacement device with very little clinical testing–and with no human testing–based upon its claim that the ASR device was "substantially similar" to another product already on the market.
The ASR Hip Resurfacing Platform was not approved for use or sold in the US. Citing data they received from the National Joint Registry of England and Wales, DePuy voluntarily recalled both the ASR XL Acetabular and ASR Hip Resurfacing Systems on August 26, 2010. The data showed that the need for a second replacement operation, a revision surgery, within five years of the original surgery was higher than expected. The 2010 National Joint Registry data showed that of the patients with DePuy ASR hip devices, 13% with complete hip replacements and 12% with resurfacing devices needed corrective surgeries within an average of 5 years.
The ASR devices were formally recalled on August 24, 2010. It is estimated that 93,000 patients worldwide have received one or the other of the defective hip devices. In 2009, DePuy discontinued manufacture of both hip implants, allegedly due to declining demand and a desire to develop the next generation of hip replacement and resurfacing devices. A suit against the company filed by a California construction worker claims that DePuy knew for years that the ASR hip implants were defective. By the end of 2008, there were approximately 300 reports of hip implant failures in surgeries using the ASR hip devices.
The reported failure rate of DePuy ASR hips is rising. A statement published in 2011 by the president of the British Orthopaedic Society, summarizing presentations on large-diameter metal hips at the organizations annual conference, revealed that early revision rates for the ASR CL were 21 percent at 4 years and 49 percent at 6 years.
If you have received either of the ASR implants, DePuy is recommending that you visit your surgeon and undergo yearly monitoring to make sure that it is functioning properly. Any unexplained hip pain or if it feels like the hip implant is loosening may indicate that the hip replacement is failing and should be reported to your surgeon immediately.
DePuy Pinnacle - DePuy also manufactures the Pinnacle system, which has a modular acetabular cup with a cup liner made of either polyethylene or metal. Metal on metal combinations are used frequently. As with the DePuy ASR, the primary issues in failure appear to be cup loosening and metallosis.
FDA Warnings on Two Other DePuy Products - A warning letter was dated August 19, 2010—seven days before the company issued its recall of both ASR hip implants, the FDA issued a warning claiming that DePuy violated the Federal Food, Drug, and Cosmetic Act by marketing its TruMatch™ Personalized Solutions System and Corail®Hip System without first receiving the required marketing clearance and/or approval.
Wright Conserve - The Wright Medical Conserve® Cup features a similar design to the DePuy ASR™ Cup. The Wright Conserve® Hip Implant System is a metal-on-metal design, which consists of cast cobalt chromium molybdenum that provides the receptacle for the cobalt chromium molybdenum femoral head. The metal femoral head rotates within the metal monoblock Conserve® Cup, without a liner, resulting in the release of metal particles that can cause metal toxicity in the blood, soft tissue and bone. This can result in metallosis, tissue necrosis, pseudotumors and other serious health problems.
Since the FDA approved the Wright metal-on-metal hip replacement system under the same 510(k) premarket approval system, hundreds of adverse event reports have been submitted to the FDA by patients and physicians. As with other MoM implants, this device's design inherently causes friction between the femoral head and the acetabular cup, creating even more initial friction during leg movement than other similar implants. The elevated friction is transferred to the acetabulum from the junction between the acetabulum and the acetabular cup.
In May 2011, the FDA asked Wright Medical and other metal-on-metal hip makers such as DePuy, Stryker and Zimmer, to obtain more information about the level at which the metal particles released by hip replacements becomes dangerous, how much metal they actually release and to quantify the potential side effects of metallosis.
Failure shortly after implantation may be unrelated to MoM replacement implants; however, the DePuy implants should be monitored medically.Your Legal Options
Our defective medical device attorneys are currently evaluating cases concerning the defective hip implants, including the ASR XL Acetabular System used in hip surgeries performed in the United States. If you or a loved one has received a DePuy ASR implant, one of the implants listed above, or a failed MoM implant leading to pain or revision surgery, please contact us through this simple form or our toll-free number, 800-598-0314.