Orientational Distribution of Collagen Fibers in the Horizontal Plane of Human Adult Calcaneus

Abstract

Human right calcaneus bone consisting of hydroxyapatite and collagen fibers was cut in the horizontal plane, which was parallel to the long axis of the calcaneus bone and perpendicular to the human lower limb, into slice samples approximately 1.5 mm thick. The angular dependence of transmitted microwave intensity at 12 GHz was measured for each slice sample using Osaki's microwave method. It was found that the collagen fibers were mainly aligned in the direction of the long axis of the calcaneus in the region between the heel end and the middle and only in the upper and plantar layers near the anterior, but randomly aligned in the central part of the calcaneus near the anterior. The orientation of collagen fibers changed drastically near the neck, defined as the position where the posterior face of the talus contacts the calcaneus. It is concluded that the orientational distribution of collagen fibers in the horizontal plane of the calcaneus provides the strong resistance against the large stress when the mechanical stress is applied to the neck of the calcaneus from the lower limb.