[Intraarticular fractures of the calcaneus: pathological description. Contribution of x-ray computed tomography].

Computed tomography (CT) is of cardinal importance in the study of displaced intra-articular fractures of the calcaneus, as with this imaging technique the primary fracture line of Palmer can be followed and its various locations visualised. If the three-stage classification system of these fractures as vertical, horizontal or mixed fractures, based on their radiological appearance, is adopted, a correlation can be established between the location of Palmer's line and these three anatomical types. The fundamental fracture line is medial in the vertical types, 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 fundamental fracture line separates a laterally detached fragment which is always tilted, giving a vertical slope to the surface of the posterior facet which it supports and thus giving a vertical image. This fragment is itself separated from a medially detached fragment which is tilted horizontally and produces a horizontal image on the lateral view. The CT sections must be examined for the presence of a secondary sagittal line completely isolating the horizontally tilted fragment. The importance of the location of the fundamental fracture line, which is on the borderline between tilting and horizontalisation, suggests that pronation-supination of the foot is a factor in the causal mechanism of these fractures. A clear understanding of the three-dimensional position of the fragments and of their displacement, essentially defined by the location of the fracture line, is a prequisite before attempting surgical reduction of calcaneal fractures.