[Contact surfaces and anatomical joint surfaces of the upper ankle joint--methods for the determination of facet size and case representation].

The cartilage surfaces of six ankle joints were stained according to a triple dyeing technique. Using a load appliance and a pressure of 1600 N the largest possible weight-bearing areas were stained without damaging the ligaments. The joints were either plantar-flexed, in a 0 degree position or in dorsal extension. The contact areas of the joint, including both the cartilage surfaces and the ligaments, showed characteristic forms according to the joint's position. By projecting the respective contact areas of the tibial plateau onto the upper side of the trochlea tali we were able to estimate the cartilage weight-bearing area in the proper sense. According to this method, the upper side of the trochlea tali, without the facet of Fawcett, proved to have the largest weight-bearing area when in the 0 degree position, namely 56.4 +/- 4.9% of the anatomical joint surface. The next largest area, 51.9 +/- 4.8%, was found when the joint was in dorsal extension and the smallest, 47.1 +/- 3.6%, when plantar-flexed. The size of the anatomical joint surfaces and some morphometric values of the upper side of the trochlea tali were measured using 21 specimens.