KRIZ, M.A.*; RENO, P.L.; MCCOLLUM, M.A.; HORTON, W.E.; LOVEJOY, C.O.: Comparative analysis of mammalian proximal femoral development

The mammalian proximal femur is highly complex in both anatomy and development. The greater trochanter and femoral head are each sites of secondary ossification even though both lie within a common epiphyseal cartilage. In some mammals (including humans), these two ossification centers are separate throughout the entire growth period but remain connected by a continuation of growth cartilage along the posterosuperior femoral neck (Ogden JA, 1981, Hip, 139-87). This intraepiphyseal region is histologically complex in these species. In other mammals, these distinct ossification centers coalesce such that a single bony epiphysis covers the entire end of the bone. Therefore, the bone of the superior femoral neck can be deposited under three histomorphological regimens: subchondral, subperiosteal, and epiphyseal. Here we present an analysis of morphometric variation associated with these two distinct ossification patterns, as well as a scanning electron microscopic (SEM) examination of their various depositional surfaces. Variations in the cellular organization of the growth plate appear to be reflected in the microscopic anatomy of the ossified metaphyseal surface. These observations would seem to require reevaluation of previous biomechanical assessments of proximal femur mechanics.