[Experimental in vitro investigations of hardness changes in hip prosthesis polyethylene cups caused by x-rays and...

The aim of this paper was to determine the influence of X-rays and ageing on the mechanical properties of polyethylene cups of Weller type hip prostheses. Polyethylene cups produced in the period between 1987 and 1992 were investigated. Some of the cups were exposed to a radiation dose exceeding greatly the average dose used in a routine X-ray examination. Polyethylene cups produced in different years and those subjected to "artificial ageing" (long-term exposure to high temperature) were examined. Brinell's method was used to assess the hardness of polyethylene. The results of this study indicate that both exposure to X-rays and ageing lead to hardening of the cups. This may in turn cause cup fractures--a potential source of complications following hip replacement procedures.