The possible role of mechanical stress in determining the patterns of
endochondral ossification in skeletal anlages was explored using
stress-analysis computer models of developing human sterna. It has been
hypothesized previously that the normal sequence of proliferation,
maturation, degeneration, and ossification of cartilage is accelerated in
regions of high cyclic octahedral shear stress and inhibited in regions of
intermittent compressive-hydrostatic (dilatational) stress. This hypothesis
was investigated using two-dimensional, all-cartilage, plane-stress
finite-element models of the three basic shapes of human sterna that were
identified by Ashley. A mathematical criterion, which combined the opposing
influences of the shear and dilatational stresses into a single net
stimulus for ossification, was used successfully to simulate the three
basic patterns of sternal endochondral ossification that were previously
documented. Our findings support the view that mechanical forces may
strongly influence skeletal morphogenesis, growth, and development,
beginning at a very early stage.