Prevention of fatigue cracks in ultrahigh molecular weight polyethylene joint components by the addition of vitamin E

Abstract

Flaking-type wear, so-called delamination, is often observed in polyethylene joint components. This is thought to occur partly due to crack formation and propagation at grain boundaries. This study examined the effect of vitamin E on the crack formation and/or propagation in UHMWPE by using 2-dimensional sliding fatigue testing and micro indenter testing. An in vitro sliding fatigue test was performed under two simplified articulating movements, and the cracks produced were observed by scanning acoustic tomography (SAT). Gamma-irradiated ultrahigh molecular weight polyethylene (UHMWPE) specimens demonstrated a smaller area of accumulated cracks as compared to virgin specimens, when the loading movement was reciprocated on a single linear locus. However, four out of five gamma-irradiated UHMWPE specimens exhibited severe flaking-like destruction under the complicated sliding condition, suggesting that gamma irradiation accelerated crack propagation under multidirectional loading. All the gamma-irradiated vitamin-E-containing specimens demonstrated no subsurface crack formation and no flaking-like destruction. Results using micro indenter testing showed that the dynamic hardness at grain boundary was higher than that in grain, and was increased by gamma irradiation. This hardening at grain boundary was reduced by adding vitamin E. It is possible that the presence of vitamin E prevents crack propagation partly due to reduced hardness at grain boundaries. The gamma-irradiated vitamin-E-containing UHMWPE is a promising material to prevent flaking-like destruction of polyethylene joint components.

Antioxidant effectiveness of vitamin E in HDPE and tetradecane at 32°C

“…Also it has shown potential for the reduction of off-flavours related to polymer oxidation during processing [22]. Recently vitamin E has also been found to prevent fatigue cracks in UHMWPE for medical implants [23]. Vitamin E activity at >120 Ci n oxidising polypropylene was found to be very effective, but less so than some other industrial phenols [4,5].…”

Wear Performance of UHMWPE and Reinforced UHMWPE Composites in Arthroplasty Applications: A Review

“…To sum up, the previous studies [51,52,58] showed that vitamin E alone with up to 0.4 wt% concentration have a marginal effect on the mechanical properties of UHMWPE. However, some studies [44,57,59] suggested that vitamin E-stabilised UHMWPE has a significantly higher tensile strength, yield strength, elongation at break and fatigue resistance, especially at concentrations exceeding 0.1 wt% [59]. More detailed information on the mechanical properties of vitamin E-stabilised UHMWPE is shown in Table 2.…”

Vitamin E-stabilized UHMWPE for Total Joint Implants: A Review

“…A study comparing the wear of vitamin E-blended (0.3 wt%), unirradiated UHMWPE versus conventional UHMWPE in a knee simulator showed lower wear volume and different debris for the former [75], suggesting vitamin E alone may improve the wear/delamination resistance [77].…”