Foot Rig

Device for passively loading a cadaver ankle

The device allows constant loading of the tibia to simulate body weight, while continuous natural six-DOF motions of the ankle complex are induced. The foot is placed on an anti-skid surface with no additional fixation (from pins, etc.). A plate is mounted on top of the proximal tibia, and a flexible cable is fastened to each of the four corners of this plate. The cables run parallel to one another and pass through guide holes near the ankle, and weight cages are attached to the ends of the cables underneath the foot. Motions of dorsiflexion/ plantarflexion, inversion/eversion, internal/external rotation, and combinations thereof are induced by moving the shank while the foot remains approximately stationary on the non-skid surface (like a joy stick). When the tibia is moved away from a vertical orientation, the load along the long axis of the tibia remains nearly constant since the cables remain parallel to the tibia; the guide holes allow the cables to slide slightly up and down appropriately.

The device was designed for the purpose of simulating body weight on the ankle while tests of foot and ankle kinematics are conducted (e.g. using video-based motion analysis). The loading corresponds to the primary component of load experienced in vivo, and the experimenter may easily apply any type of movement to the ankle complex. Additionally, the device may be upgraded to include application of constant tendon forces, and tendon excursion measurement for determination of mechanical advantage of the various muscles acting at the ankle complex.

Dorsiflexion is being applied, with constant axial load applied to tibia by weight cages hanging underneath foot.Plantarflexion, inversion/eversion, internal/external rotation, and combinations thereof can also be applied. Here, reflective markers are attached to the specimen for video-based motion analysis.