Artificial joints are becoming increasingly common for relieving pain and restoring mobility in patients suffering from joint degeneration. Wear particles released from ultrahigh molecular weight polyethylene (UHMWPE) bearing components in artificial joints contribute significantly to osteolysis and late aseptic loosening. The ability to measure wear rates accurately is essential in order to compare the osteolytic potential associated with different implants.

Current wear measurement techniques (linear penetration, gravimetric, and volumetric) are not accurate enough to quantify effectively the low wear rates associated with highly crosslinked and thermally stabilised UHMWPE. The persistence of machining marks following wear has led to controversial claims of very little wear in acetabular liners. While highly crosslinked UHMWPE has reduced wear rates, the particles are smaller and more biologically active leading to a greater need for accurate quantification of low wear rates.

The purpose of this work was to develop a quantitative model relating the change in height of machining marks to the amount of material lost from the UHMWPE surface through wear. The result is a model that may be expressed mathematically as:​

where h₀ and Δh are the initial sample thickness and the change in thickness, So and 6 are the initial and residual machining mark heights, and KIP is the experimentally determined ratio of the effective elastic modulus of the UHMWPE to the applied contact pressure.

Experimental work indicates that the model is quantitatively correct, and that machining marks may remain in the presence of significant amounts of wear.