Loading of the acetabulum by polyethylene and all-ceramic inserts in metal-backed acetabular cups.

Both static and dynamic loads were applied to metal-backed acetabular cups with ceramic or polyethylene inserts and the resulting load transmissions at a simulated bone interface were determined. Perfect fit and under-sized and over-sized cavities were prepared in simulated bone substrates, lined with Fuji pressure sensitive film, and acetabular cups inserted with physiological loads. The magnitude and location of contact forces between the cup and bone were measured. These cups were then subjected to a controlled impact load and the intensity and frequency of the loads transmitted to the substrate were determined. The results suggest that a polyethylene backing for ceramics is not necessary as there were no major differences in the static and dynamic stresses transmitted to the cup-bone interface with all polyethylene or ceramic inserts.