Extract
Hip simulator and early clinical studies of highly cross-linked ultra-high
molecular weight polyethylene have demonstrated less wear and less femoral
head penetration when compared with conventional ultra-high molecular weight
polyethylene1-6.
However, cross-linking also alters some of the mechanical properties of
ultra-high molecular weight polyethylene, including its ultimate tensile
strength, strain to failure, fracture toughness, and fatigue crack propagation
resistance7-9.
Analyses of early retrieved highly cross-linked components have shown
initiation of surface cracking, which is possibly related to the decrease in
ductility caused by
cross-linking10. A
reduction in ductility, fracture, and fatigue properties is the hallmark of
material embrittlement. Accordingly, newer so-called second-generation highly
cross-linked polyethylenes have been developed in an effort to better retain
the desirable mechanical properties of conventional ultra-high molecular
weight polyethylene as well as the benefits of
cross-linking11.