Twelve pairs of the tibia and the fibula were taken from amputated limbs. The specimens were embedded in polyester resin and serial sections were made in frontal, sagittal and horizontal planes. Microradiographic survey of each section was carried out in order to observe the outer contour of the bones and the density as well as the arrangement of the bone trabeculae.
The results were summarized as followings:
1, Trabeculae of the distal part of the tibia and the fibula were divided into five groups; central group, both malleolar groups, shoulder of the medial malleolus group and base of the lateral malleolus group.
2, The central group was seen in the facies articularis inferior of the tibia. The trabeculae originated from the metaphyseal cortex and reached to the epiphyseal plate. From the epiphyseal plate, dense trabeculae ran vertically to the articular surface.
3, In the both malleoli, trabeculae arranged along the outer contour of the tibia as well as the fibula. Moreover the trabeculae radiated from insertions of ligaments and joint capsule.
4, In the shoulder of the medial malleolus, several thicker trabeculae were oriented transversely.
5, At the base of the lateral malleolus where tibiofibular ligament attached, thick trabeculae were originated from the medial surface of the fibular cortex transversely. Moreover the epiphyseal plate of the fibula and the thick lateral cortex situated also in this part.
6, These findings of trabecular architecture indicated that each group had its own function:
a) The central group supported the vertical compression force of body weight.
b) The trabeculae of both malleoli corresponded with tension which was acted by inversion as well as eversion of the talus.
c) Trabeculae of the shoulder of the medial malleolus and base of the lateral malleolus corresponded with bending force.