ABSTRACT
Human right calcaneus bone, consisting of hydroxyapatite and collagen fibers, was cut in the sagittal plane which was parallel to the long axes of the calcaneus bone and the human lower limb, into samples approximately 1.5 mm thick. The angular dependence of transmitted microwave intensity at 12 GHz was measured for each sample, using Osaki's microwave method. The direction and the degree of collagen-fiber orientation for the cut specimens changed with changing position from the heel end to the anterior, along to the long axis of the calcaneus bone. The direction of orientation deviated by about -60 degrees from the direction of the long axis of the human lower limb, in the region between the heel end and the middle, and by about 60 degrees near the anterior. The position at which the orientation angle changed drastically from negative to positive corresponded to the neck defined as the position where a posterior face of the talus contacts the calcaneus. The results suggest that the mechanical stress applied to the neck of the calcaneus bone from the lower limb may effectively disperse, on average, in two different directions where the collagen fibers are oriented at the neck.
