INTRAARTICULAR FRACTURES OF THE CALCANEUS - PATHOLOGICAL ANATOMY AND VALUE OF COMPUTED-TOMOGRAPHY

Computed tomography (CT) is of cardinal importance in the study of dis placed intra-articular fractures of the calcaneus, as with this imagin g technique the primary fracture line of Palmer can be followed and it s various locations visualised. If the three-stage classification syst em of these fractures as vertical, horizontal or mixed fractures, base d on their radiological appearance, is adopted, a correlation can be e stablished between the location of Palmer's line and these three anato mical types. The fundamental fracture line is medial in the vertical t ypes, lateral in the horizontal types and is located in the centre of the posterior facet in the mixed types. It can be seen that the fundam ental fracture line separates a laterally detached fragment which is a lways tilted, giving a vertical slope to the surface of the posterior facet which it supports and thus giving a vertical image. This fragmen t is itself separated from a medially detached fragment which is tilte d horizontally and produces a horizontal image on the lateral view. Th e CT sections must be examined for the presence of a secondary sagitta l line completely isolating the horizontally tilted fragment. The impo rtance of the location of the fundamental fracture line, which is on t he borderline between tilting and horizontalisation, suggests that pro nation-supination of the foot is a factor in the causal mechanism of t hese fractures. A clear understanding of the three-dimensional positio n of the fragments and of their displacement, essentially defined by t he location of the fracture line, is a perequisite before attempting s urgical reduction of calcaneal fractures.