Abstract
Since wear of the polyethylene (Ultra High Molecular Weight Polyethylene or UHMWPE) ace- tabular liner is considered to be the main cause of loosening of the artificial hip joint, the cross-linked and vitamin E-doped UHMWPE, designated Vita-E UHMWPE, with high durability to wear has been developed. This paper deals with the mechanical properties of Vita-E UHMWPE as well as the impact load transmission through the complex of an artificial hip joint consisting of a Vita-E UHMWPE acetabular liner, a metallic femoral head and stem. Ultrasonic, stress relaxation and impact compressive tests on conventional and Vita-E UHMWPE were first performed to detennine their elastic properties. A series of impact compressive tests on the complex was also performed to investigate the effects of material (conventional or Vita-E UHMWPE) and setting angle of the liner on force transmission using the split-Hopkinson pressure bar (SHPB) apparatus. Vita-E UHMWPE showed lower elastic moduli in all experiments than conventional UHMWPE. Attenuation of impact force during its transmission through the liner was assessed in terms of the impact load transmission ratio (ILTR), and the ILTR showed lower values in Vita-E UHMWPE than in conventional UHMWPE independently of the setting angle.
