Wl. Sauer et al., FATIGUE PERFORMANCE OF ULTRA-HIGH-MOLECULAR-WEIGHT POLYETHYLENE - EFFECT OF GAMMA-RADIATION STERILIZATION, Biomaterials, 17(20), 1996, pp. 1929-1935
Ultra-high-molecular-weight polyethylene (UHMWPE) failure presents a s
ignificant materials concern in the orthopaedic community. Clinical fa
ilure following joint arthroplasty can result from the biological resp
onse to wear debris as well as structural failure owing to UHMWPE fati
gue. In this study, cantilever rotating beam fatigue testing was condu
cted on GUR 415 UHMWPE in both the unsterilized and gamma radiation st
erilized conditions. Calculations of flexural fatigue stresses were ba
sed on extreme fibre stresses and assumed negligible plastic deformati
on. Both material conditions exhibited similar fatigue strengths at 25
0,000 cycles (approximately 41 MPa) and at one million cycles (approxi
mately 36 MPa), but a large difference developed after two million cyc
les. At ten million cycles, the unsterilized condition exhibited a fat
igue strength of approximately 31 MPa, while the gamma-sterilized cond
ition exhibited a reduced fatigue strength of approximately 18 MPa, an
approximate decrease of 42%. High-cycle fatigue testing was necessary
to fully characterize this behaviour owing to the pronounced differen
ce in fatigue behaviour beyond two million cycles. These results sugge
st that gamma radiation sterilization of UHMWPE medical implants reduc
es their resistance to cyclic loading and, subsequently, may contribut
e to the associated fatigue-related failures which have been reported
clinically. (C) 1966 Elsevier Science Limited.