To investigate the mechanism causing calcaneal fractures, we reproduced the fracture using an experimental model.
A specimen foot was obtained from a patient after a Syme amputation, and the soft tissue except for the intraosseous ligaments were removed. We hypothesized that the collision of the talus with the calcaneus when the ankle was inverted cause the calcaneal fracture. The tales was fixed to the calcaneus in extension-pronation-abduction position with Kirschner wires. The specimen was then put on a floor upside down. A ten kg-weight was dropped onto the heel from an 80cm height.
Roentgenographic and CT findings revealed the fracture line observed in the specimen to be joint depression type III according to the classification by Essex-Lopresti, and type IIA by Sanders.
In this experiment, we have succeeded in reproducing similar calcaneal fractures observed in clinical cases. We conclude that the injury of the subtalar joint contributes to cause a peculiar fracture line seen in this fracture, when the hindfoot is in inverted position.
