Fig. 1A–B.

(A) Load-displacement behavior for a whole bone structural test is shown. The structural stiffness is determined from the initial linear region, where F is load and d is displacement. The structural strength is the load required to fail the whole bone. These parameters depend on the loading mode; a compressive load (F) is shown, but loading can also be a bending (M) or torsional moment (T). (B) Stress-strain behavior for a materials test is shown. These measurements are independent of specimen size and shape but do depend on the loading mode (tension, compression, bending, or shear). The modulus of elasticity (E) is determined from the initial linear elastic region; yield stress (σ_y) is the transition from linear to nonlinear behavior and is based on 0.2% offset of the linear region (dashed line); and ultimate strength (σ_u) is the maximum stress (strength). For the tensile specimen shown, F is the tensile load, A_i is the initial area, and L_i is the initial specimen length.