Basic Sciences (Anatomy), New York Chiropractic College
Friday All day, Clinch Concourse
Haversian structure densities increase and bone mass decreases with age among humans. Both may be affected, by sex of the individual, by disease and nutritional status and thus reflect the life history of individuals. Densities of haversian structures (complete and fragmentary osteons) and bone resorption are examined in the midshafts of the human humerus, radius, ulna, clavicle, femur, tibia and fibula in a sample of 16 males (mean age 68) and 23 females (mean age 80). They range in age from 14 to 107 years. Resorption is assessed as percent of the microscopic field composed of solid bone. Osteon and fragment densities are quantified as structures per sq. mm. Rates of resorption vary with age by bone. Among males, there is little change with age among all bones examined. Females have significantly more bone resorption, and as bone mass decreases, haversian structures per sq. mm. increase, even as bone mass per sq. mm. decreases. Resorption does not differ among bones in males. Among females, it is significantly greater in some bones, particularly the femur and humerus. Osteon density differs signficantly among bones in males, being higher particularly in the tibia and humerus, but not so among females. Increased cortical thinning coupled with increasing density of haversian structures among females suggests an adaptation to applied loads on a decreased total cross sectional area of bone. Each bone responds independently to aging, rather than demonstrating a systemic response, each bone acting as an idependent organ.