Recent research, conducted at Penn Presbyterian Medical Center, Philadelphia, Pennsylvania, reveals that Pinnacle hip replacement devices, constructed with a polyethylene liner and an acetabular shell, may be prone to damage.
Liner and shell separation was seen in cases involving patients who underwent a primary total hip arthroplasty with a Pinnacle acetabular component, manufactured by DePuy Orthopaedics. In each case studied, patients had to undergo revision surgery to remove and replace defective components, said The Journal of Bone and Joint Surgery.
The surgery involved polyethylene liners, meant to increase femoral head coverage. Increased coverage is meant to allow for larger femoral heads with smaller cup diameters, which should provide improved stability with no impingement risks, explained The Journal of Bone and Joint Surgery. These components are constructed to increase hip motion and stability and should theoretically enable surgeons to make fine adjustments to the device during surgery.
The team presented four patient cases in which the liner dissociated—or split—from the acetabular shell, necessitating the need for revision hip surgery. The average time from original implantation to revision surgery was 13.1 months, with a range from three to 36 months, said The Journal of Bone and Joint Surgery
All four suffered from spontaneous splitting of their polyethylene acetabular liners; had to undergo revision hip arthroplasty surgery between January 2007 and June 2010; and were female. The average patient age was 53 (ages 33 to 71), and all the women underwent original implantation with a combination of a Pinnacle acetabular component with an offset, face-changing polyethylene liner. The team said that direct trauma was not involved in any of the cases and, in every case, patients reported squeaking sounds from the area of the implant. The Journal of Bone and Joint Surgery pointed out that when the removed liners were examined, plastic deformation of the polyethylene liner rim was seen. Two patients said they suffered from nonlocalized hip pain; surgery revealed signs of metal transfer to the ceramic head and signs of metallosis in the joint.
The defect was seen with Zimmer’s Harris-Galante Porous I and II acetabular components; the culprit was determined to be failure of the locking mechanism, meant to secure the polyethylene liner to the metal acetabular shell. The weak locking mechanism can lead to liner deformation, rim wear, and implant dissociation and failure. The researchers noted that liner dissociation has been seen in devices with alternative bearings, including Zimmer’s Metasul® Metal-on-Metal Liners and Stryker’s Trident Tripolar Constrained Liner.
Lawsuits involving defective hip implants have been growing, mostly over all-metal or metal-on-metal devices and have centered on the hallmark problem with metal-on-metal hip implants, a defect that puts recipients at serious risk of permanent injuries like tissue and organ damage. Pinnacle lawsuits have been building slower than others involving all-metal components; however, other varieties of the device exist that do not use metal-on-metal components.
Meanwhile, lawsuits involving metal-on-metal versions of DePuy Orthopaedics’ Pinnacle hip replacement device continue to move forward, with some 1,800 lawsuits pending and alleging that the all-metal model of the DePuy Pinnacle hip replacement device caused metallosis and other injuries similar to those seen with other metal-on-metal hip implants, including DePuy’s recalled ASR hip implants. The DePuy ASR hip replacements were named in worldwide recall in August 2010, and plaintiffs in the Pinnacle litigation assert the metal-on-metal Pinnacle implants should have been recalled, as well.
Like other metal-on-metal hip implants, the DePuy Pinnacle is prone to shed miniscule metal fragments through the implants’ normal wear-and-tear. The all-metal version of the DePuy Pinnacle litigation is only one of several metal-on-metal hip implants that have raised safety concerns in recent years. Several studies have found that such devices can disperse dangerous amounts of chromium and cobalt into patients’ bloodstreams, leading to a number of serious health problems, such as pain; swelling; dislocation; and metallosis, a reaction that leads to tissue and bone loss, the formation of pseudotumors, and long-term heart, kidney, nerve, and thyroid problems.