The counterface, surface smoothness, tolerances, and coatings in total joint prostheses

Proper counterface material combinations, surface finish, and tolerances of contact surfaces are important issues in minimizing friction, wear, and co rrosion of total joint prostheses. In the current study, the potential of n ovel amorphous diamond coatings to solve some present problems in total joi nt prostheses was studied by using tribological tests with a hip joint simu lator and pin-on-disk testers. Based on the tests, the wear of amorphous di amond is negligible compared with conventional hip joint materials (10,000 to 1,000,000 times lower). The coefficient of friction of diamond-coated ar tificial hip joint was 0.03 to 0.06 when tested in saline solution with loa ds from 200 to 1000 kg for as many as two million cycles. The friction rema ined stable throughout the tests. Methylmethacrylate (bone cement) is a typ ical source of third body wear particles in cemented total hip replacements . The wear tests showed that bone cement (containing hard ceramic particles of barium sulfate or zirconia) severely scratched cobalt chromium molybden um alloy samples. These scratches enhance the wear of softer counterpart ma terials, such as polyethylene or bone cement, whereas diamond-coated surfac es remained undamaged, High quality amorphous diamond coatings offer superi or stability (minimal wear debris release in surrounding tissues) and good biomechanical performance.