Architecture of the cancellous bone of the human talus.

The trabeculae of the cancellous bone are formed along the direction of the lines of stresses to which a bone is subjected. The talus sustains the weight of the body and transmits the weight in different directions (i.e., the calcaneus and navicular). The aim of the present study was to investigate the architecture of the cancellous bone of the talus to understand the mechanism of transmission of force within the bone. Twenty-five dry, macerated tali of adult male humans were used to study the trabecular architecture. In a few bones, serial longitudinal (parasagittal), transverse (coronal), and horizontal sections were cut; in other bones, the trabecular bone was exposed by removal of cortical bone. Trabecular architecture was studied by dissection microscope and by taking radiographs of the slices. The body of the talus consisted of vertical, parallel plates arranged posteroanteriorly. This kind of orientation of the plates facilitates the transmission of weight, when the tibia rolls posteroanteriorly on the trochlear surface during walking. The trabecular architecture in the head of talus consisted of semiarched plates running parallel to each other. The vertical limb of these semiarched plates were situated above the middle and anterior calcaneal facets on the plantar surface of the head, whereas the horizontal limbs of the arches were deep to the navicular articular surface of the head. The vertical plates of the body and semiarched plates of the head were interconnected by a meshwork of irregularly arranged trabecular bone of the neck. The architecture of this meshwork was such that it could facilitate the change in the direction and nature of force. In conclusion, the part of compressive force, acting vertically downward on the body of the talus during standing, was converted to tensile force in the neck, and its direction was made perpendicular to enable this force to go toward the head of the talus. In a similar manner, the semiarched pattern of plates in the head facilitated the change in the direction of the force, at the end of the stance phase, from the downward (toward calcaneus) to the forward (toward navicular) direction.