Abstract
Burn injury results in the acute loss of bone as well as the development of progressive vitamin D deficiency. Bone loss occurs acutely due to resorption, which is then followed by apoptosis of osteoblasts preventing repair of the bone loss. The acute resorption is due to a combination of the inflammatory response and the stress response to the burn injury. The resultant production of inflammatory cytokines and endogenous glucocorticoids initially stimulate the osteoblasts to produce RANK ligand, which stimulates marrow stem cell differentiation into osteoclasts. As the stress response persists for approximately one year post-burn the glucocorticoids produced by the body will cause osteoblast apoptosis and adynamic bone, impairing the ability of bone to recover its resorptive losses. The vitamin D deficiency is due to the failure to supplement the diet of burn patients with vitamin D on discharge from hospital and to failure of the skin to make normal quantities of vitamin D on sunlight exposure. Because the bone resorption can be prevented by the acute administration of bisphosphonates it is unlikely that vitamin D deficiency is responsible for the early-onset bone loss following burns. However, because a deficit in trabecular bone remains for at least two years post-burn, it is possible that vitamin D deficiency prevents the recovery of trabecular bone density over the long term.