Showcase of Undergraduate Research and Creative Endeavors (SOURCE)

The Effect of Physiological Loading on Cortical Bone Remodeling in White-Tailed Deer Proximal Humerus

Richardson Ballroom (DIGS)

Remodeling, the replacement of primary bone with secondary (osteonal) bone, was shown to be affected by the type of stress (compression versus tension) and its magnitude. This study investigated the effect of loading on the morphology and geometry of secondary osteons in the proximal humerus of white-tailed deer. Two cross-sections from the proximal diaphysis of four white-tailed deer humeri were prepared using a low-speed, water-cooled diamond saw. One cross-section of each humerus was embedded in an epoxy block and viewed using a scanning electron microscopy (SEM), and the other cross-section was decalcified and viewed with a polarized light microscope. Next, multiple images of each cross-section were captured and then stitched together (PTGUI©) to create a full view of each humerus’ proximal transverse plane, in order to determine the areas of bone remodeling. Finally, secondary osteons’ geometries and sizes were measured (ImageJ©) for each humerus in the medial, lateral, cranial and caudal regions. Our results showed that secondary osteons in the cranial region are significantly larger, more angled medially, and less porous (with a smaller ratio of central canal area to osteonal area) than those found in the other three regions. On average, the osteon area in the cranial region is 6369 pixels² compared to 4085, 3717, and 4163 pixels² in the medial, caudal, and lateral regions, respectively. Osteons in the cranial aspect of the humerus are angled on average 105.8° to the frontal plane, while osteons in the other three regions are almost perfectly normal to that plane (~90°). The central canal area to osteonal area ratio is 3.7% for the cranial region, 4.8% for both the medial and lateral regions, and 4.7% for the caudal region. These findings are consistent with previous reports in other bones and species.