SUBTALAR JOINT STABILITY - TALOCALCANEAL INTEROSSEOUS LIGAMENT FUNCTION STUDIED IN CADAVER SPECIMENS

We used 6 fresh-frozen foot specimens to evaluate the contribution of the talocalcaneal interosseous ligament (IOL) in stabilizing the subta lar (talocalcaneal) joint. The tibia and ankle joint were secured, and the calcaneus was subjected to a bending and axial force applied circ umferentially. The position of the calcaneus relative to the talus was monitored with a magnetic tracking system. Motion was recorded at eve ry half degree in the 0 degrees to 360 degrees are before and after se ctioning of the IOL. The results in the intact feet indicated that, wi th circumferential loading of the subtalar joint, there were two stabl e zones (supination stable zone, pronation stable zone) during which l ittle displacement occurred and two transition zones during which the supination and pronation movement occurred. There was a greater degree of supination displacement after IOL sectioning (p = 0.008), but no p ronation displacement. The lot. contributed substantially to subtalar joint stability, particularly in supination.