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Implant design primary cause of tibial post wear damage
Dolan MM. Clin Orthop Relat Res. Published online: August 2010.
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In posterior-stabilized knees, implant design was the primary cause of post wear damage, according to New York researchers.
Mark M. Dolan, MD, and colleagues at the Hospital for Special Surgery, New York City, used a subjective scale to grade post damage in 113 retrieved Zimmer NexGen, 103 Exactech Optetrak and 58 Smith & Nephew Genesis II posterior-stabilized inserts.
All of the retrieved implants had wear damage. Total wear scores varied by design: Optetrak, 20±4; NexGen, 13±4; and Genesis II, 8±3. Scores for wear damage on the anterior post also differed according to design: Optetrak, 5±1; NexGen, 3±1; and Genesis II, 1±1.
On the Optetrak implant, wear damage was mostly anterior. The NexGen had more global wear damage and the Genesis II had mostly posterior wear damage. Implant design was the biggest reason for tibial post and anterior post wear damage; length of implantation and revision diagnosis caused wear damage to a lesser degree.
“The constraint provided by the posterior-stabilized post-cam contact in modern knee arthroplasties is reflected in the wear damage patterns that occur during in vivo use,” the authors wrote. “Unintended constraint such as anterior impingement should be addressed through design modifications for future posterior-stabilized knee arthroplasties.”