Meeting Abstract

P2.52  Friday, Jan. 4  Internal structure of distal humeral articulation in carnivorans EGI, N.; Japan Monkey Centre egi@pri.kyoto-u.ac.jp

External shape and internal trabecular structure of articular bones have been suggested to correlate with animal�s locomotion and mechanical requirements although observations on internal structure have been rare. This study examined variation of trabecular bone and cortical bone thickness in the distal humeral articulation of small to medium carnivorans. The sample included adult individuals of canids, mustelids, procyonids, felids, viverrids, and herpestids. Distal humeri were scanned using a pQCT scanner with a 0.05 mm voxel size. The following measurements were taken from the capitulum, the trochlear groove, and the anterior trochlea: orientations and degree of anisotropy of trabeculae, cancellous bone volume fraction, and cortical thickness. In the distal humeri of the sample species, trabeculae develop better in the parasagittal plane than other orientations, reflecting the hinge movement of the elbow joint. Orientation of the trabeculae in the anterior trochlea shifts slightly more laterally than those in the other parts, presumably due to the anterolaterally faced anterior surface of the trochlea. Isotropy and elongation indices are lower in the anterior trochlea than in the capitulum in most of the sample species, indicating that the disk-like trabecular network develops better in the anterior trochlea. However, trabeculae in the trochlea of cursorial canids are more isotropic than those in the capitulum and those in the trochea of other species. Arboreal species such as Nandinia and Potos show more isotropic trabeculae in the capitulum. The cortical thickness varies among species but it does not correlate with body size. Overall, the internal structure of the articulation, particularly in the trochlea, showed influences from the hinge movement of the joint. Interspecific variation due to behavioral differences seemed to be less prominent.