Abstract

NASA: The authors examine the role of mechanical usage in skeletal development. Principle mechanisms of bone physiology include longitudinal bone growth; modeling drifts; micromodeling; remodeling by the basic multicellular unit and its effects on bone mass, bone turnover, and bone gain or loss; setpoint effects; microdamage and its repair; and the effects of mechanical usage. Biomechanical explanations for the architecture of growing long bones are examined. Clinical problems that involve principal biological mechanisms include osteopenia; influence of hormones, cytokines, drugs, other agents, and setpoints; osteoporosis and bone fragility; stress fractures; homeostasis and calcium; and fracture healing.