Effect of head surface roughness and sterilization on wear of UHMWPE acetabular cups

The impact of femoral head surface roughness on wear of γ‐irradiation sterilized (3 MRad in nitrogen, crosslinked) and nonsterilized (not crosslinked) UHMWPE acetabular cups has been evaluated. Gravimetric wear testing was performed in a hip joint simulator for 2 × 106 cycles. CoCrMo heads were used with different surface roughness (Ra = 15 nm and Ra = 400 nm). The surface roughness after wear test was unchanged for the roughened heads, whereas the initially smooth heads showed a few scratches. The roughened heads increased the wear of the acetabular cups 2‐fold. The γ‐irradiated cups tested against rough heads underwent the highest wear. The absorption of water was highest for the γ‐irradiated cups (0.0204% compared to 0.0031% after 85 days). Raman spectroscopy showed small but significant crystallinity changes in the wear zone, where the γ‐irradiated cups with the most extensive abrasion increased in crystallinity, whereas the nonsterilized cups underwent a crystallinity decrease. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2009