Microvascularization of the hypermineralized calcified fibrocartilage and cortical bone in the sheep proximal femur.

It is well known that the incidence of hip fractures is increasing as the population ages, and that vascularity is one of the most important characteristics for any tissue (the proximal femur being no exception). Additionally, calcified fibrocartilage from tendon and ligament insertions comprises a significant portion of the fractional area of the proximal femur's cortical shell. The goal of the present investigation was to quantify and compare the microvascularity of the cortical bone and calcified, fibrocartilage of the proximal femur in a sheep model. There were no regional differences in the vascular density of the cortical bone. However, the calcified, fibrocartilage from tendon and capsular insertions were determined to be avascular, and regions of the proximal femur with insertions lacked a vascularized periosteum. If a vessel was present in the calcified fibrocartilage, it was located within an isolated region of bone tissue or osteoid. Since blood vessels appear to be a significant contributor to the health and remodeling of mineralized tissue, it is hypothesized that the large areas of avascular calcified fibrocartilage present on the elderly femoral neck may predispose these regions to damage accumulation. Therefore future research should examine the role of the -vascularity to the proximal femur in the mechanisms of numerous pathological conditions, such as avascular necrosis, osteopenia, and hip fractures.