[Models of the geometry of the XXXX ankle bone pulley: two series of geometric models for demonstrating the biomechanics of the ankle joint].

@entity1 @entity10460
2 series of models demonstrate the geometrical shape of the @entity1 @entity10460 tali. We have changed step by step the shape of the 2 flanking articular facets of the @entity10460 , the course of the edges of the @entity10460 , and the length of their radii, and so we have found a model responding to the biomechanic conditions of the @entity10460 tali. The convex surface of this model (corresponding to the superior articular surface, i.e. the facies superior trochleae tali) is a torse, the medial flanking facet (corresponding to the medial articular facet of the @entity10460 , i.e. the facies malleolaris medialis) is a flat cone, the lateral flanking facet (corresponding to the lateral articular facet of the @entity10460 , i.e. the facies malleolaris lateralis) is a screwed (helicoidal) face. The resulting model shows the 2 completely different phases of motion in the ankle joint: During dorsiflexion (motion setting out from the neutral position towards the final position of dorsiflexion), the internal malleolus leads the talus, whereas the external malleolus is pushed outwards by the screwed lateral articular facet of the trocheal. The @entity10460 is moved like a hinge. In the final position of dorsiflexion, the malleoli tightly embrace the 2 flanking facets of the @entity10460 , whilst an obvious cleft appears dorsally and medially between the superior articular surface of the @entity10460 and the tibial roof (i.e. the facies articularis inferior tibiae). During plantarflexion (motion setting out from the neutral position towards the final position of plantarflexion), the external malleolus leads the talus, whereas the medial articular facet of the @entity10460 withdraws from the internal malleolus. The @entity10460 is moved like a screw. In the final position of plantarflexion, the superior articular surface of the @entity10460 closely contacts the tibial roof, whilst an obvious cleft appears between the medial articular facet of the @entity10460 and the internal malleolus.
