Tibiales Malalignment bei Mobile-Bearing-Prothesen

Total knee replacement requires exact implantation in order to avoid long term failure. Longitudinal in vivo studies of malaligned prostheses are problematic for ethical reasons. To assess the critical angle of tibial (varus / valgus) malalignment of knee prostheses in vitro, a simulator investigation was performed. Mobile-bearing- prostheses were implanted in a simulator with 1°-30 valgus- and varus malalignment as well as in neutral position. More extreme malalignment caused unexceptional forces in the simulator. After each 500,000 cycles (ca. 0,5 years of walking) the replicas of the polyethylene inlay were examined and the extent of the tribocontact-areas was measured until 1,500,000 total cycles. Finally the original polyethylene was examined with a scanning electron microscope. The polyethylene showed only abrasive wear without any fatigue effect. Tribocontact-areas of 900-1,500mm2 were observed under malalignment of mobile-bearing prostheses according to the producer’s reference. With 1-30 of malalignment tribocontact-areas were located at untypical polyethylene-zones, but still showing abrasive wear only. Increasing malalignment due to a lift off of the femoral part of the prostheses with a strong torsional strength of the polyethylene made an extremer simulation impossible. 3 degree of Malalignment could be suggested as maximum in-vivo tolerability, perfect alignment with ideal implantation should be aimed at. Soft tissue is less considered within this simulator-study.

Level thesis:degree_level

thesis.doctoral

Grantor dc:publisher

Ludwig-Maximilians-Universität

Year

2002

Author dc:creator

• Löer, Ingo

Repository record source_url

https://edoc.ub.uni-muenchen.de/639/

OAI identifier oai:identifier

oai:edoc.ub.uni-muenchen.de:639