OBJECTIVETo establish the three-dimensional finite element model of calcaneus, and to discuss mechanism of calcaneal fracture.

METHODSThe calcaneus of normal person was scanned with spinal CT, and the finite element model was established with the Sap 93 software. The node and element number of this model was 1 959 and 1 496 respectively. After establishing the finite element model of the calcaneus, the axial load of 500 N was applied on the model in neutral position and back stretches 20 degree position. The stress distribution and the displacement of the models were observed.

RESULTSThe fracture line passed through the lateral articular facet of talocalcaneal joint when the ankle joint was in neutral position, and the stress distribution was maximal at calcaneus from posteromedial to anterolateral aspect. In addition, the stress distribution was maximal from calcaneus to position between posterior talar articular surface and calcaneal tendon when the ankle joint was in back stretch position of 20 degree.

CONCLUSIONWhen falling down, the fracture line will pass through the facet of talocalcaneal joint from lateral to posteromedial side if the ankle joint was in neutral position; and the line will through pass the calcaneus body to post spinula joint, as well as avulsion fracture of calcaneal tendon occurred if the ankle joint was in back stretch position of 20 degree.