CHARACTERISTICS ON WEAR OF DIFFERENTS MET AL-POLYETHYLENE TOTAL KNEE BEARING SURFACES

Purpose of the study Wear of artificial components joint is the most i mportant factor in long term durability. Only few studies have analyse d in laboratory experimentation the quality of differents alloys on th e same type of prosthesis. Material During the development of a new kn ee prosthesis, we studied the friction mechanisms of the metal/polyeth ylene (UHMWPE) couple and particularly the value of titanium alloy (Ti -6Al-4V) treatment using an ionic nitrogen implantation process (IMPLA TEC). Two friction surfaces were studied in vitro:one in flexion-exten sion between femoral component and tibial plateau, the other in rotati on between tibial plateau and ''metal-back''. Methods The implanted Ti -6Al-4V was compared with 316L stainless steel, cobalt chromium molybd enium alloy and with Ti-6Al-4V using a prosthesis of each configuratio n. The samples were tested on a TRIBOCUP friction machine during 3 x 1 0(6) cycles in Ringer 's solution. The friction couples were controlle d every 200 000 cycles and the loss of polyethylene mass every 500 000 cycles. We have also evaluated the roughness and the rubbing surface macroscopically. Results The results analysis shows that friction coup les such as Cobalt Chromium and implanted Ti-6Al-4V are weakest but im planted Ti-6Al-4V over time, tends to match the strength of Ti-6Al-4V without treament, With implanted Ti-6Al-4V and with Cobalt Chromium al loy, the loss of polyethylene is slight comparatively to the stainless steel and non implanted Ti-6Al-4V. Surface analysis showed good prote ction of titanium alloy by ionic implantation especially in the femora l component where roughness is close (0.04 mu m) to that of Cobalt Chr omium alloy (0.07 mu m). Discussion Our study confirms the results wit h pin-on-disk and cup-on-ball with results for the Ti-6AL-4V implanted and Cobalt Chromium alloys with protection of the metal surface and d ecrease of polyethylene wear comparatively to stainless steel and non implanted Ti-6Al-4V. Conclusion Our conclusion is for this type of exp erimental device that the surface condition is satisfactory for such f riction couples as implanted Ti-6Al-4V/polyethylene and Cobalt-chromiu m/polyethylene, with very similar results. However, the long-term dura bility of the nitrogen implanted on Titanium Alloy remains unknown.