The geometry of the adult canine proximal femur.

The canine is often used as a model to study functional bone adaptation after total hip replacement. To improve our understanding of the model, we defined the central tendencies and statistical variations in the cross-sectional geometry, angle of anteversion, and cervicodiaphyseal angle of the proximal femur in 15 adult male mongrel dogs and compared the results with published reports of the human femur. Numerous similarities in the cross-sectional geometry of the canine and the human femur were noted, supporting the use of the canine as a model. The two species differed in that the orientation of the principal axes in the proximal cross sections was not related to the angle of anteversion in the canine femur, whereas these angles are related in humans. In addition, the canine medullary canal is larger than the human medullary canal relative to the external dimensions of the femur, and hence the canine has relatively thinner cortical bone. This difference in femoral cross-sectional geometry may explain, in part, why the canine provides an accentuated model of bone loss in hip arthroplasty experiments.