Steady-state penetration rates of electron beam-irradiated, highly cross-linked polyethylene at an average 45-month follow-up.

Steady-state penetration rates were determined on 53 total hip arthroplasties with a minimum 3-year follow-up using electron beam highly cross-linked melted polyethylene by determining the femoral head penetration occurring after the first year in vivo. These data were compared with that of a matched control group. The average steady-state penetration rate of the control group was 144 +/- 191 mum/y, significantly higher than that of the highly cross-linked polyethylene group, 25 +/- 99 microm/y (P = .0001). Linear regression analysis indicated that the magnitude of femoral head penetration did not increase with time in the cross-linked groups. Also, no significant difference existed between the steady-state wear rates of the highly cross-linked groups with two head sizes (28 vs 32 mm, P = .39).