Abstract
Risks presented by adverse local tissue reactions from
metal orthopedic implants have demonstrated a need for more
sophisticated pre-clinical studies with intrinsic sensitivity to the
complexity of both the surrounding biological environment and the composition
of degradation products. In this study, a novel cell culture
system with integrated tribometer and corrosion test rig was designed
and validated. Static normal contact load was applied between a mirror
polished CoCrMo disc and a 28mm diameter ceramic head during reciprocating
sliding motion. A solution of RPMI-1640 with 10 vol% fetal bovine serum
was selected as the test fluid, due to proven cell viability. All tests were
conducted inside an incubator at 37ᵒC and 5% CO2.
Two study parameters, applied
load and applied potential, were varied. The frequency of
1Hz and duration of the test of 24h were held constant for all tests while
varying values of static normal force (16N, 25.5N, and 35N) and
applied potential (OCP, .2V vs OCP, .4V vs OCP) yielded 5 test
condition combinations in a central composite design of experiment. Each test
was repeated in duplicate for a total of 10 tests. Total material loss of
CoCrMo was quantified by weight loss measurements with a high precision balance
and confirmed with volume loss measurements using white light interferometry. Material loss increased with load (p=0.001),
and this effect was more pronounced at 0.4V vs OCP. At 35N, wear at OCP and 0.4V vs OCP were not
statistically significantly different, implying wear rate was mechanically
dominated.