[The fatigue fracture of the calcaneous. The experimental proof of its mechanical genesis (author's transl)].

: The calcaneus is generally stressed by bending. Spongious bone has a trajectorial structure, and is adapted to the stress to an optimal degree. In fatigue fractures, the dense zone runs perpendicularly to the compressive bundles of the spongious bone. Presuming a mechanical genesis, the sclerotic band is expected to run rectangularly to the tensile bundles. This mechanical condition can be performed in a photoelastic experiment. The proof of the presence of a similar mechanical situation during movement of the foot may be derived from electromyygraphic examinations (Mac Conaill 1969, Basmajian 1974). The appearance of these fractures shows that the time is too short to allow the bone to adapt functionally. It may be concluded from this, that the cause of the fracture is a sudden, sharp increase in exercise.