[Pathophysiology of fracture healing].

This article briefly summarizes our present knowledge on regulation of proliferation, differentiation and function of bone cells (osteoblasts, osteoclasts) by hormones (1,25-dihydroxyvitamin D3, parathyroid hormone, thyroid hormone, sex steroids, glucocorticoids and calcitonin), cytokines (IL-1, IL-4, IL-6, IL-11 und IFN-gamma) and growth factors (IGF-I, TGF-beta). Interaction of these factors in "basic multicellular units" acting locally on bone surfaces is thought to result in tight coupling of bone formation and resorption in bone-remodelling processes. The significance of the latter in different phases of fracture healing, which proceeds from mesenchymal cell proliferation through callus formation to calcification and bone modelling, is emphasized.