Tribological performances of a novel biopolymeric material HD-HA for hip joint implants

Abstract

For most modern hip joint implants, metal-on-plastic pairs are preferred over metal-on-metal ones, where cobalt (Co)–chromium (Cr) alloy and ultrahigh-molecular-weight polyethylene (UHMWPE) are commonly used as the femoral head and socket, respectively. In such implants, the durability of the UHMWPE component is not up to the mark due to severe wear. This study presents better tribological performance of a novel biopolymeric material coded as HD-HA prepared from high-density polyethylene (HDPE) and hydroxyapatite. In the first part, wear tests showed specific wear rates of 4.85 × 10−6and 5.27 × 10−6(mm3/N)/m for HDPE and UHMWPE, respectively, whereas the specific wear rate was 3.19 × 10−6(mm3/N)/m for HD-HA. Comparison revealed that HD-HA had a 60–65% lower wear rate than the others. Similarly, in the second part, the friction coefficient is found to be 0.23 and 0.11 for UHMWPE and HDPE, respectively, and 0.06 for HD-HA, which shows a 20–50% decrease in frictional values. Atomic force microscopy images revealed that the rough peaks were 296, 486 and 1100 nm for HD-HA, HDPE and UHMWPE, respectively, whereas the scanning electron microscopy images showed fewer loose particles around the worn HD-HA surface. This shows that HD-HA has a smoother surface, and based on the overall tribological performance, it should be preferred for the acetabular component of hip joint implants.