Figure 4.

Schematic of the mechanical advantage provided by adaptive periosteal bone formation. (a) Mechanical loading of the lower limb stimulates adaptive bone formation. (b) Adaptive bone formation on the periosteal surface (denoted by dashed lines) adds mass furthest from the neutral axis in bending, and thus, increases the cross-sectional moment of inertia (CSMI, strength in bending). Note that CSMI is proportional to the fourth power of the outer radius (r₁), and therefore, bone formation on the periosteum is advantageous in increasing the strength of the bone in bending. (c) An increase in resistance to bending will result in a stiffer bone, or a shift to the left of the linear portion of the load–deformation curve (denoted by the dashed line). In the elastic region where strains are not pathophysiological, the bone will deform less for a given load. (d) An increase in stiffness due to periosteal bone deposition will theoretically result in lower strains for a given load, and therefore, attenuated microdamage generation and suppression of targeted bone remodeling. Suppression of targeted remodeling is expected to inhibit the pathological remodeling loop (depicted in Figure 2). (A color version of this figure is available in the online journal.)