A neutron diffraction study of the bones of the foot.

The preferential orientation of the apatite crystals in the lower tibia, talus and calcaneus, as determined by neutron diffraction, serves as an indicator of the lines of stress in the foot. The main stress flows down from the tibia to the heel and the ball of the foot and there is noteworthy orientation along the line of the plantar aponeurosis which acts as a tie. Orientation is particularly marked above the point of attachment of the Achilles tendon, where the edge of the calcaneus functions as a beam. The centre of the talus serves as a junctional region for forces and is relatively unoriented.