Improved resistance to wear and fatigue fracture in high pressure crystallized vitamin E-containing ultra-high molecular weight polyethylene.

Higher crystallinity and extended chain morphology are induced in ultra-high molecular weight polyethylene (UHMWPE) in the hexagonal phase at temperatures and pressures above the triple point, resulting in improved mechanical properties. In this study, we report the effects of the presence of a plasticizing agent, namely vitamin E (alpha-tocopherol), in UHMWPE during high pressure crystallization. We found that this new vitamin E-blended and high pressure crystallized UHMWPE (VEHPE) has improved fatigue strength and wear resistance compared to virgin high pressure crystallized (HP) UHMWPE.

Highly cross-linked ultrahigh molecular weight polyethylene with improved fatigue resistance for total joint arthroplasty: recipient of the 2006 Hap Paul Award.

Eliminating postirradiation melting and stabilizing the residual free radicals of radiation cross-linked ultrahigh molecular weight polyethylene (UHMWPE) with vitamin E resulted in improved fatigue crack propagation resistance without compromising wear resistance. We designed a cantilever postbending test to determine the bending fatigue resistance of alpha-tocopherol-doped, irradiated UHMWPE (alpha-TPE) in comparison to conventional UHMWPE. The bending fatigue behavior of alpha-TPE was comparable to conventional UHMWPE.

The effects of high dose irradiation on the cross-linking of vitamin E-blended ultrahigh molecular weight polyethylene.

Vitamin E-stabilized, highly cross-linked ultrahigh molecular weight polyethylene (UHMWPE) is a promising oxidation and wear resistant UHMWPE with improved mechanical strength in comparison with the first generation, irradiated and melted UHMWPE. One approach of incorporating vitamin E in UHMWPE is through blending of vitamin E in UHMWPE powder followed by consolidation and radiation cross-linking. However, radiation cross-linking efficiency of UHMWPE decreases in the presence of vitamin E.

Effects of solvent dehydration on creep resistance of poly(vinyl alcohol) hydrogel.

As a synthetic replacement material for osteochondral defect repair, poly(vinyl alcohol) (PVA) hydrogels offer a great potential due to their high water content and strong mechanical integrity. To survive the high stress environment in the joint space, high creep resistance becomes one of the key requirements for hydrogel implants. We hypothesized that reducing the equilibrium water content (EWC) of hydrogels would improve their creep resistance.

Wear resistance and mechanical properties of highly cross-linked, ultrahigh-molecular weight polyethylene doped with vitamin E.

Our hypothesis was that cross-linked, ultrahigh-molecular weight polyethylene (UHMWPE) stabilized with vitamin E (alpha-tocopherol) would be wear-resistant and fatigue-resistant. Acetabular liners were radiation cross-linked, doped with vitamin E, and gamma-sterilized. Hip simulator wear rate of vitamin E-stabilized UHMWPE was approximately 1 and 6 mg/million-cycles in clean serum and in serum with third-body particles, respectively, a 4-fold to 10-fold decrease from that of conventional UHMWPE.

Mechanisms of decrease in fatigue crack propagation resistance in irradiated and melted UHMWPE.

Adhesive/abrasive wear in ultra-high molecular weight polyethylene (UHMWPE) has been minimized by radiation cross-linking. Irradiation is typically followed by melting to eliminate residual free radicals that cause oxidative embrittlement. Irradiation and subsequent melting reduce the strength and fatigue resistance of the polymer.

Characterization of irradiated blends of alpha-tocopherol and UHMWPE.

Adhesive/abrasive wear in ultra-high molecular weight polyethylene (UHMWPE) has been minimized by radiation cross-linking. Irradiation is followed by melting to eliminate residual free radicals and avoid long-term oxidative embrittlement. However, post-irradiation melting reduces the crystallinity of the polymer and hence its strength and fatigue resistance.