A UNIFORM STRAIN CRITERION FOR TRABECULAR BONE ADAPTATION - DO CONTINUUM-LEVEL STRAIN GRADIENTS DRIVE ADAPTATION

In this paper, it is postulated that the apparent density of trabecula r bone adapts so that continuum-level strains within the bone are unif orm and, as a consequence, spatial strain gradients within the bone/ma rrow continuum are minimized. The feasibility of a uniform strain crit erion was tested using computational finite-element analysis of the pr oximal femur. We demonstrated that (1) this criterion produced a reali stic apparent density distribution in the proximal femur, (?) the solu tions for apparent density were convergent and unique, (3) predicted a pparent densities compared well to experimental measurements, and (4) strain gradients within the bone/marrow continuum were reduced substan tially. Thus, a possible goal of trabecular bone adaptation may be the reduction of strain gradients within the bone/marrow continuum. Osteo cytes within the bone tissue and bone cells on the surface of a trabec ulum are mechanosensitive and play a role in bone adaptation. In addit ion, the bone marrow is rich in osteoprogenitor cells near the bone su rface that are mechanosensitive. Strain gradients within bone/marrow c ontinuum cause pressure gradients in the marrow, causing extracellular fluid flow which could stimulate osteoprogenitor cells and contribute to bone adaptation. (C) 1997 Elsevier Science Ltd.