The effects of wear particles on artificial hip joints are well documented. Aseptic loosening has been demonstrated to be dependent on both particle numbers and particle size. This study investigated the effects of stem material and surface finish on particles produced at the stem/cement interface in cemented artificial hips. Three commonly used implant materials of different hardness were investigated: cobalt chrome, the hardest of the three materials, stainless steel and titanium alloy which was the softest material tested.

The surfaces of three femoral stems with different surface finishes were measured and used as templates; the Exeter which is highly polished, the Charnley which is moderately rough and the Capital which is very rough. Test plates were manufactured in each material and with each surface finish making 9 sets of plates in all.

The plates were opposed to cement pins (CMW) in a sliding wear tester. The volume of debris produced was calculated from measurements of the pins pre- and post-test. The debris was collected, filtered and examined under the electron microscope, which allowed particle sizes of a representative sample of debris to be measured. From this mean particle size was calculated.

Volume of debris: for all three materials the roughest surface produced the greatest volume of debris and the smoothest surface the least. For any given surface finish the softest material produced the greatest volume of debris and the hardest material the least.

Size of particles: for all three materials the roughest surfaces produced the largest particles and the smoothest surface the smallest particles. For any given surface finish the hardest material produced the smallest particles and the softest material produced the largest particles.