Abstract:
Bone loss is a serious health problem. In vivo
studies have found that mechanical stimulation may inhibit
bone loss as elevated strain in bone induces osteogenesis,
i.e. new bone formation. However, the exact relationship
between mechanical environment and osteogenesis is less
clear. Normal strain is considered as a prime stimulus of
osteogenic activity; however, there are some instances in the
literature where osteogenesis is observed in the vicinity of
minimal normal strain, specifically near the neutral axis of
bending in long bones. It suggests that osteogenesis may also
be induced by other or secondary components of mechanical
environment such as shear strain or canalicular fluid flow. As
it is evident from the literature, shear strain and fluid flow
can be potent stimuli of osteogenesis. This study presents a
computational model to investigate the roles of these stimuli
in bone adaptation. The model assumes that bone formation
rate is roughly proportional to the normal, shear and fluid
shear strain energy density above their osteogenic thresholds.
In vivo osteogenesis due to cyclic cantilever bending
of a murine tibia has been simulated. The model predicts
results close to experimental findings when normal strain,
and shear strain or fluid shear were combined. This study also
gives a new perspective on the relation between osteogenic
potential of micro-level fluid shear and that of macro-level
bending shear. Attempts to establish such relations among
the components of mechanical environment and corresponding
osteogenesis may ultimately aid in the development of
effective approaches to mitigating bone loss.
