Hylamer and conventional polyethylene acetabular liners of the same de
sign, revised for a variety of reasons, were examined and compared to
assess the performance of Hylamer as a bearing material. Clinical dama
ge modes, linear wear rates, oxidation levels, and mechanical properti
es were measured. In both series, many liners were retrieved for dislo
cation. Wear/osteolysis was the most common reason for retrieval in th
e Hylamer series, while none of the conventional polyethylene liners w
ere retrieved for this reason. Nearly all liners exhibited abrasion, b
urnishing, scratching, and creep. The Hylamer liners had more cracking
, delamination, and pitting. The Hylamer liners had an average linear
wear rate of 0.32 mm/year, while the conventional polyethylene liners
had an average wear rate of 0.20 mm/year. Due to sample size, no stati
stical difference in wear rate was noted between the two groups. In ge
neral, both the Hylamer and conventional polyethylene showed oxidation
peaks subsurface, resulting from their exposure to gamma radiation in
air. Liners with elevated oxidation had decreased ultimate tensile st
rength, elongation, and toughness. For given oxidation levels, the cor
responding mechanical properties of Hylamer appeared lower than those
of conventional polyethylene. The ultimate tensile strength values ran
ged from 14 to 33 MPa for Hylamer and 19 to 32 NPa for conventional po
lyethylene. Elongation ranges were 19% to 350% (Hylamer) and 80% to 37
5% (conventional). The Hylamer retrievals in this study gave initial i
ndications of performance; Hylamer appeared to behave similarly, but n
ot superiorly, to conventional polyethylene, in the early functional p
eriod with respect to clinical wear and clinical performance. Both Hyl
amer and conventional polyethylene liners were degraded by gamma steri
lization in air, with Hylamer liners demonstrating greater property ch
anges.