Peg Shearing as a Method of Failure in Highly Cross-Linked Polyethylene Patellar Components Used in Patellofemoral Arthroplasty.

Highly cross-linked polyethylene (HXLPE) is commonly used in knee arthroplasty due to its improved wear resistance. However, increased crosslinking reduces the tensile strength and fatigue resistance of polyethylene, which may be detrimental in high shear environments such as a cemented patellar button. In patellofemoral arthroplasty (PFA), patellar components are exposed to substantial shear stresses, which may predispose polyethylene components to fatigue-related failure and peg shear. We report a case series of patellar component failures in PFA, including several HXLPE patellar buttons demonstrating peg fracture and loosening, as well as 1 ultra-high molecular weight polyethylene patellar button with a similar failure pattern. To our knowledge, these represent the first reported cases of HXLPE patellar component peg shear in PFA, a complication previously described only in the setting of total knee arthroplasty.