This paper describes torsional testing on the components of a unique total ankle design, to establish the range and conditions of torsional constraint. For this design, the torsional constraint was found to be dependent on the relative flexion and inversion angles between components. Dorsiflexion provides greater torsional stability than plantarflexion. The maximum torque values were recorded at 25 degrees of dorsiflexion with no relative inversion. Under these conditions, and with a weight bearing load of 1200 N, the ankle resisted 2200 N-mm at 5 degrees of rotation and 3300 N-mm at 15 degrees of rotation. Torsional stability decreased as the relative inversion or eversion of the components increased. When the components were inverted more than a few degrees, the initial rotational stiffness became negligible.

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