Intra-articular calcaneal fractures: Effect of open reduction and internalfixation on the contact characteristics of the subtalar joint

Intra-articular calcaneal fractures are associated with significant long-te rm morbidity, and considerable controversy exists regarding the optimum met hod of treating them. The contact characteristics in the intact subtalar jo int were determined at known loads and for different positions of the ankle and subtalar joint, using pressure-sensitive film (Super Low; Fuji, Itochu Canada Ltd, Montreal, Quebec). We measured the contact area to joint area ratio (pressure > 5 kg force/cm(2) [kgf/cm(2)]) which normalizes for differ ences in joint size and the ratio of high pressure zone (>20 kgf/cm(2)) as a reflection of overall increase in joint pressure. Three simulated fractur e patterns were then created and stabilized with either 1 or 2 mm of articu lar incongruity. Eight specimens were prepared with a primary fracture line through the posterior facet, eight with a joint depression-type fracture, and six with a central joint depression fracture. A measure of 1 to 2 mm of incongruity in the posterior facet for all three fracture patterns produce d significant unloading of the depressed fragment, with a redistribution of the overall pattern of pressure distribution to parts of the facet that we re previously unloaded.