Chapter 12: Biomechanics of Fracture Healing Elise F. Morgan and Thomas A. Einhorn

From the Primer on the Metabolic Bone Diseases and Disorders of Mineral Metabolism, 7th Edition. www.asbmrprimer.org Figure 1 Figure 1 Representative torque-twist curve for a mouse tibia 21 days after fracture. The curve is annotated to show definitions of basic biomechanical parameters. Torsional rigidity is computed by multiplying the torsional stiffness by the gage length. Analogous definitions hold for bending tests. Figure 1 Representative torque-twist curve for a mouse tibia 21 days after fracture. The curve is annotated to show definitions of basic biomechanical parameters. Torsional rigidity is computed by multiplying the torsional stiffness by the gage length. Analogous definitions hold for bending tests. © 2008 American Society for Bone and Mineral Research

From the Primer on the Metabolic Bone Diseases and Disorders of Mineral Metabolism, 7th Edition. www.asbmrprimer.org Figure 2 Figure 2 Torque-twist curves for healing rabbit tibias at various time points (in days) after fracture (after White et al.(6)). Comparison of these curves to that in Fig. 1 shows species differences in the rate of healing. Healing progresses more rapidly in smaller animals (e.g., mouse vs. rabbit), and 21 days postfracture in the mouse corresponds to stage 2. The larger size of the bone and callus in larger animals also leads to greater values of maximum torque, stiffness, and toughness. Figure 2 Torque-twist curves for healing rabbit tibias at various time points (in days) after fracture (after White et al.(6)). Comparison of these curves to that in Fig. 1 shows species differences in the rate of healing. Healing progresses more rapidly in smaller animals (e.g., mouse vs. rabbit), and 21 days postfracture in the mouse corresponds to stage 2. The larger size of the bone and callus in larger animals also leads to greater values of maximum torque, stiffness, and toughness. © 2008 American Society for Bone and Mineral Research

From the Primer on the Metabolic Bone Diseases and Disorders of Mineral Metabolism, 7th Edition. www.asbmrprimer.org Figure 3 Figure 3 (A) Longitudinal cut-away views of 3D μCT reconstructions of representative saline- (control) and PTH-treated murine fracture calluses at 14 days after fracture (data from Ref. 9). (B) Longitudinal cross-sections of the fracture callus and cortex at 6 wk after fracture in rats treated with saline (control) and zolendronic acid (ZA) beginning 2 wk after fracture (from Ref. 10; images not to scale). Figure 3 (A) Longitudinal cut-away views of 3D μCT reconstructions of representative saline- (control) and PTH-treated murine fracture calluses at 14 days after fracture (data from Ref. 9). (B) Longitudinal cross-sections of the fracture callus and cortex at 6 wk after fracture in rats treated with saline (control) and zolendronic acid (ZA) beginning 2 wk after fracture (from Ref. 10; images not to scale). © 2008 American Society for Bone and Mineral Research

From the Primer on the Metabolic Bone Diseases and Disorders of Mineral Metabolism, 7th Edition. www.asbmrprimer.org Figure 4 Figure 4 Theories of the mechanobiology of skeletal tissue differentiation by (A) Carter et al.,(44) (B) Claes and Heigle,(45) and (C) Prendergast et al.(47) Figure 4 Theories of the mechanobiology of skeletal tissue differentiation by (A) Carter et al.,(44) (B) Claes and Heigle,(45) and (C) Prendergast et al.(47) © 2008 American Society for Bone and Mineral Research