When the Zimmer Durom Cup Replacement first entered the US market in 2006 it was hailed as a medical device innovation for hip replacement surgeons and patients suffering from arthritic hips. Two years later, Zimmer Inc. faces lawsuits from patients as well as a class action lawsuit from Zimmer Inc. shareholders who argue that the company should have told them that the hip replacement medical device was defective.
When the medical device was first available in the US, doctors were impressed with the favorable results in Europe. However, soon after complaints began surfacing about hip and back pain. The first one to notice there might be a problem with the device itself was Dr. Lawrence Dorr, a California surgeon who’s been performing hip replacements for 30 years. When Dorr contacted Zimmer about his concerns, company officials told him that there was no issue with the Zimmer Durom Cup. The problem stemmed from doctors who weren’t following correct procedures in implanting the hip replacement device. After other doctors complained, Zimmer launched an aggressive public relations campaign including an instructional program designed to teach doctors the proper way to implant the one piece medical device. In spite of Zimmer’s efforts, doctors continue to voice concerns over the design of the hip replacement cup. These same doctors estimate that many hip replacement patients who’ve had the Zimmer Durom Cup implanted will face the pain and expense of revision surgery.
Zimmer Inc., recognizing the potential legal risk regarding the controversial hip, has set aside more than $40 million to cover the exposure resulting in the defective medical device.
The Durom Acetabular Component is a monoblock of cobal chromium alloy. It is designed for use in combination with Zimmer’s Metasul Metal-on-Metal Tribological Solution Large Diameter Heads (LDH). However, the implant has been found to loosen, requiring hip revision surgery.
A September 2010 study from the University of Wisconsin Clinical Science Center finds a significantly higher failure rate for the Zimmer Durom Cup Hip Implant when compared to the Zimmer Trilogy Hip Implant. The well designed study compared 63 Zimmer Durom Cup implant patients with 100 Zimmer Trilogy hip implant patients and followed them for one year. The two groups were matched for age and sex and no factors were found that would explain the high failure rate in the Durom Cup other than a defect in the design of the Durum cup. There were no failures in the Trilogy implant patients. All of the Durum cup implant patients who had failures had to have a revision surgery to have the cup implant replaced with another model. The cups fail because bony ingrowth to the back of the cup from the hip bone has not been occurring. That bony ingrowth is necessary to secure the cup in position in addition to the press fit when the cup is implanted.
There has been considerable discussion in the medical community about reports from some doctors that the Zimmer Durom Cup has unacceptably high failure rates. Zimmer suspended sales for the Durom Cup for several weeks in 2008 and provided surgeons with special training programs for implantation. After sales of the Zimmer cup were resumed in 2008 failures continued and the Durom Cup was discontinued in 2010.
There have been numbers of individual lawsuits and a few class action lawsuits filed. However, it still has not been publicly known why bony ingrowth is not occurring with the Durum cups causing failure. The cup is designed with a 165 degree hemisphere whereas most other hip implant cups use a 180 degree hemisphere. The Durom Cup also has a large femoral head metal on metal design. The purpose of the 165 degree design and the large femoral head is to try to give the patient a greater range of motion. However, this possible benefit is not justified by an 11.1 % risk of failure of the surgery and the hardship and risk of undergoing a second surgery to redo the hip implant.
The 11.1% failure rate found by the researchers at the University of Wisconsin in their study should be predictive of the failure rate across all patients in the United States. This unacceptably high failure rate documented in this study is scientific proof that there is a defect in the durom cup that could be the cause of a patient’s hip surgery failure. There are certainly other possible causes of a failure with the Durum cup such as infection in an individual patient. Therefore, Durom Cup patients who have continuing pain or who have had a revision surgery should get medical and legal advice to determine whether the most likely cause of their hip failure was the design of the Durom Cup.
The University of Wisconsin study is entitled: Large-Head Metal-on-Metal Total Hip Arthroplasty Using the Durom Acetabular Component at Minimum 1-Year Interval; The Journal of Arthroplasty, Vol 25, No.6 Supp Sept, 2010
On July 22, 2008 Zimmer suspended US sales of the Zimmer Durom Cup citing incorrect implant procedure. According to Dr. Dorr, a well-paid consultant of Zimmer, wrote that:
This failure rate has occurred within the first two years. In the first year the x-rays looked perfect. We have revised four that did not have any radiolucent lines or migration (and John Moreland revised one). These early cups fooled us, but the symptoms were so classic for a loose implant that we operated the patients. When we hit on the edge of the cup it would just pop free. As time goes by the cups begin developing radiolucent lines. We now have one cup at two years that has actually migrated a short distance. It has tilted into varus. We do not believe the fixation surface is good on these cups. Also there is a circular cutting surface on the periphery of the cup that we believe prevents the cup from fully seating. We stopped using the cup after the first revisions.”
If you’ve had hip replacement surgery and are experiencing pain three months after surgery, you should consult your physician to determine if you have a Zimmer Durom Cup implant.
The implantable hip device is manufactured by Zimmer Holdings. The Zimmer hip, has received complaints from surgeons and patients who state that the design is flawed causing many patients to undergo revision hip surgery. Zimmer officials claim that the design is not defective but admits that some surgeons have found the device difficult to implant. Zimmer’s comments come on the heels of its own investigation into the implant after some surgeons had complained to them about the medical device. Since it was first sold in the United States in 2006, the Durom cup has been implanted in more than 12,000 patients. According to a report in the NY Times, “The issue with the device surfaced in April when a surgeon in Los Angeles, Dr. Lawrence Dorr, publicly warned other orthopedists about cup failures his patients were experiencing. In response, Zimmer said it would start an investigation but said it saw no reason to take added action like halting sales.” Dorr has said that he won’t start using the hip device again, “It is a bad design.”
At the 2006 Annual Meeting of the American Academy of Orthopaedic Surgeons, Zimmer announced the June launch of a new metal-on-metal hip replacement system: the Durom® Acetabular Shell with Metasul® LDH™ Large Diameter Femoral Heads. The “next generation” system had gained FDA clearance on March 16, 2006.
The Durom/Metasul Large Diameter Head system was “designed to restore patient function by providing natural joint restoration, maximizing range of motion and reducing the potential for post-operative dislocation.”
Zimmer explained that Metasul-bearing technology was first introduced in 1988 and, unlike competitor systems, it is made of a forged, high carbon cobalt-chromium alloy product – anticipated to set the industry standard for strength and low metal-on-metal wear.
Zimmer’s 2006 Annual Report described the Durom system as the “only metal-on-metal offering that is forged, not cast, with a high carbon content producing a smoother, harder surface that could lead to less wear and greater implant longevity.”
Zimmer’s 2007 Annual Report described the Durom system similarly, but dropped the phrase, “greater implant longevity,” foreshadowing the recall to be announced July 22, 2008.
In April 22, 2008, Lawrence Dorr, M.D., founder and medical director of The Arthritis Institute, wrote to his colleagues in the American Association of Hip and Knee Surgeons to report an unacceptably high failure rate. Dr. Dorr stated that within the first two years of implantation, he had identified an unacceptably high failure rate of 14 among 165 patients. Dr. Dorr believed the fixation surface of the shells was poor and that a circular cutting surface on the periphery of the cup prevented it from fully seating.