Subchondral architecture in bones of the canine shoulder.

The distal scapula and proximal humerus from each shoulder of nine adult dogs were slab-sectioned, cleaned of soft tissues, embedded in white plastic and stained black with a silver stain. These preparations were then photographed for automated, digital, morphometric analysis of subchondral bone structure. Comparison of transverse and coronal sections through the left and right shoulders demonstrated essential isometry of trabecular patterns within each bone. Comparison of the scapula and humerus revealed significant differences in bony architecture. The subchondral plate was an average of 5.6 times thicker under the glenoid fossa than in the opposing humeral head. Deeper trabecular structure also differed with the trabecular bone volume (density) in the humerus being greater than that in the scapula. This difference reflects a greater trabecular density in the humerus with comparable trabecular thickness in both bones. These structural differences are consistent with previous functional studies of the same two bones that revealed greater mechanical stiffness beneath the glenoid fossa and greater hydraulic resistance within the humeral head.