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Researchers find polyethylene wear after TKA is constant in most cases
In an analysis of 2,131 AP radiographs for 251 total knee arthroplasties, researchers showed a constant rate of polyethylene insert thickness loss in 92% of cases during a mean follow-up of 10 years. They also found lower survivorship among knees with accelerated wear.
"We conclude that wear is linear with rare exceptions and that higher wear is correlated with failure," Charles A. Engh Jr. MD, and colleagues wrote in the study.
For the study, a total of six postoperative anterior/posterior radiographs were taken of each knee, with the last taken at least 6.5 years postoperatively. The thickness of the knee implant was plotted versus time.
According to the study abstract, 92% of the knees had a mean wear of 0.09 ± 0.12 mm/yr and fit a linear model which indicated constant wear. The investigators found 10 knees that showed accelerated wear. Overall, 38 knees were revised.
"Higher linear penetration rates and an increasing penetration rate over time were associated with lower survivorship," the researchers wrote, who noted that knees with 0.15 mm/yr or greater wear had lower Kaplan-Meier survivorship rates.
They noted that their study of only one knee design could be a study limitation.
Disclosure: Engh Jr. received royalties, has stock in, received research support from and is a consultant for DePuy; has also received institutional support from Anderson Orthopaedic Research Institute and is a board member of American Association of Hip and Knee Surgeons. Collier received fixed payments from Renovis Surgical Technologies and institutional support has been received from Amp Orthopedics, Biomet, DePuy, a Johnson & Johnson company, Smith & Nephew and Zimmer within the past year. Hopper received research support from DePuy and institutional support from Amp Orthopedics, Biomet, DePuy, a Johnson & Johnson company, Smith & Nephew and Zimmer within the past year. Hatten received institutional support from Amp Orthopedics, Biomet, DePuy, a Johnson & Johnson company, Smith & Nephew and Zimmer within the past year. Engh received royalties from, made presentations for, and was a consultant for DePuy; was also an unpaid consultant and had stock in TGS Knee Innovations; and received institutional support from Amp Orthopedics, Biomet, DePuy, a Johnson & Johnson company, Smith & Nephew and Zimmer within the past year.