The role of mechanical load-induced fluid flow in osteocyte nutrition and its clinical implications

It has been shown that diffusion alone cannot account for sufficient molecular transport in the porous yet relatively impermeable tissue of bone. An alternate mechanism for such transport is intrinsic to the functional role of bone in transferring loads within the musculoskeletal system. Namely, mechanical loading causes minute deformations within the poroelastic tissue of bone, resulting in extravascular fluid displacements, i.e. load-induced fluid now. In order to study the effect of mechanical load-induced fluid flow on osteocyte nutrition, tracer transport studies were carried out to elucidate the pathways and to compare the extent of molecular transport through rat bone in vivo for unloaded and loaded bones. It was shown that mechanical loading enhances the transport of larger molecules, such as proteins, to osteocytes, insuring an adequate supply for maintenance of metabolic activity as well as for activation or suppression of re/modeling processes. This has implications for the clinic with regard to disuse osteoporosis, osteoarthritis, chronic infections and osseointegration