RADIOGRAPHIC GEOMETRIC VARIATION OF EQUINE LONG BONES

As more sophisticated research is performed to refine fracture fixatio n techniques for horses, it is important that normal values for the ge ometric properties of the bones of the appendicular skeleton be determ ined and that suitable controls be available. We evaluated the geometr ic properties of total bone width, cortical bone width, and medullary canal/trabecular bone width measured from 2 radiographic projections o f equine long bones (humerus, radius, third metacarpal bone, femur, ti bia, and third metatarsal bone) obtained from a general population of horses. Measurements were performed on slices separated by intervals e qual to 5% of the bone's length. Slices were then grouped into 5 regio ns: proximal epiphysis, proximal part of the metaphysis, diaphysis, di stal part of the metaphysis, and distal epiphysis. Results validated u se of the contralateral bone as a control for assessing experimental m odels or clinical cases. Of 858 homotypic slice comparisons between le ft and right bones, significant (P less than or equal to 0.05) differe nces were detected in 31 (3.6%) of the comparisons. Of 168 homotypic r egion comparisons, significant differences were observed in 3 (1.8%) o f the comparisons. The greatest variation between left and right bones was observed in metaphyseal regions, areas with bony protuberances, a nd regions with prominent bone superimposition. At a power of 0.8 for the statistical tests performed in this study, the mean homotypic vari ation of bones in each region is < 5.8% for the proximal epiphysis, 11 .3% for the proximal part of the metaphysis, 6.8% for the diaphysis, 1 2.2% for the distal part of the metaphysis, and 5.2% for the distal ep iphysis.