Fig. 7. Interaction between osteonal orientation and shear flow, under torsional load. Schematic diagrams of tissues. (A) In laminar bone, shear flow is continuous in the circumferencial `sheets' of bone. (B) In radial bone, radial cavities interrupt the shear flow, because they go through circumferential planes. Bone tissue near cavities undergoes highly concentrated stresses and will yield prematurely. Longitudinal bone would have intermediate characteristics.