To analyze the effects of implant design on the primary stability and the contact between bone and prosthesis of three different porous coated acetabular implants.

The distal part of sixty bovine femurs were employed. 52 mm acetabular cups were inserted tightly after 2mm under-reaming. Trilogy acetabular cups were inserted in Group I, Mallory head finned RingLoc cups in Group II, Duraloc spiked cups in Group III. The gaps between the acetabular cups and the bones were measured on the radiography. The axial compression test and rotation test were performed using Instron.

The gaps between the acetabular cup and bone of Gorup I and II was significantly smaller than Group III at its central adjacent and peripheral area (p<0.05) . The gap at the mid-portion decreased in order of Group I, II and III (p<0.05) . At the rim of the acetabular cup there was no measurable gap in all three groups. In the axial load of 300Kp, the mean micromotions were no statistical significances among three groups (p>0.05) . The mean torque of 1 degree rotation test was higher in the Group III than in the group I and II without statistical significance (p>0.05) . The mean torque of 2, 3 and 5 degree rotation test was highest in Group II among three, but there were no statistical differences among three groups (p>0.05).

Triology and Mallory-Head cup can be assumed to have better primary stability than Duraloc cup. And additional fin or spikes attached on the acetabular implant couldn't enhance the primary bone-prosthesis interface stability.