On the modelling of the ankle motion under static loads by a sequential procedure: model definition and preliminary results

A previously proposed kinematic model of the tibiotalar (or ankle) joint passive motion is generalized by means of a sequential procedure. The previous model is a parallel spatial mechanism, that features two rigid bodies (representing the tibia and talus) interconnected by five rigid binary links that mimic three articular contacts and the two isometric fibres of the tibiocalcaneal and calcaneofibular ligaments respectively. The mechanism links are considered as deformable in the new model and other passive structures are added. The new model can replicate the behaviour of the joint when external static loads are applied; moreover, it can replicate the ankle passive motion with the same accuracy as the previous kinematic model. In order to verify the potentiality of the procedure, the model is defined from experimental and published data; loads are applied to the model in order to simulate two common clinical tests, and the predicted ankle motion is compared with published results. These preliminary results show a good agreement between simulated and experimental data, thus making the model a promising candidate for further additional validations.