Trabecular bone mechanical properties

Mechanical and Degradation Properties. Studies characterizing the mechanical properties of these highly crosslinked materials indicate properties that are intermediate between those of cortical and trabecular bone. Table I summarizes these results along with the mechanical properties of bone. 

Keaveny, T. M., and Hayes, W. C., Mechanical properties of cortical and trabecular bone. Bone 1,285-344 (1993). 

Use of 3D foams is also a popular method for bone regeneration applications, although they are most often employed for trabecular bone regeneration [152,154]. There are a few methods utilized to create foams for this application, one of the most popular being a polymer foam replication technique, in which a polymer foam is either electrosprayed or immersed into a HAp/bioactive glass particle slurry in order to fully coat the foam and create a trabecular bone-like aichitecture. However, other methods are also utilized, including creating composite foam solutions that are injectable and form once inside the body [153]. Results of Fu et al. [152] have indicated mechanical properties similar to those of natural trabecular bone. 

As stated earlier, this chapter has concentrated on the elastic and viscoelastic properties of compact cortical bone and the elastic properties of trabecular bone. At present there is considerable research activity on the fracture properties of the bone. Professor William Bonheld and his associates at Queen Mary and Westfield College, University of London and Professor Dwight Davy and his colleagues at Case Western Reserve University are among those who publish regularly in this area. Review of the literature is necessary in order to become acquainted with the state of bone fracture mechanics. 

Inspired by the hierarchical structures that enable bone function, Deng et al. recently developed a mechanically competent 3D scaffold mimicking the bone marrow cavity and the lamellar structure of bone by orienting electrospun polyphosphazene-polyester blend nanofibers in a concentric manner with an open central cavity (Figure 11.9b and c) [66]. The 3D biomimetic scaffold exhibited mechanical characteristic similar to native bone. Compressive modulus of the scaffold was found to be within the range of human trabecular bone. When tuned to have desired properties, the concentric open macrostructures of nanofibers that structurally and mechanically mimic the native bone can be a potential scaffold design for accelerated bone healing. 

Ciarelli, M. J., Goldstein, S. A., Kuhn, J. L., Chdy, D. D., and Brown, M. B. (1991), Evaluation of orthogonal mechanical properties and density of human trabecular bone from the major metaphyseal regions with materials testing and computed tomogr diy, J. Orthop. Res. 9(5) 674—682. 

Linde, F., Norgaard, P., Hvid, I., Odgaard, A., and Soballe, K. (1991), Mechanical properties of trabecular bone Dependency on strain rate, J. Biomech. 24(9) 803-809. 

Kopperdahl, D. L., and Keaveny, T. M. (2002), Quantitative computed tomography estimates of the mechanical properties of human vertebral trabecular bone, J. Orthop. Res. (in press). 

Tissue Properties. The properties of human tissues when the body is considered a linear, passive mechanical system are summarized in Table 10.1 (von Gierke et al., 2002 Goldstein et al., 1993). The values shown for soft tissues are typical of muscle tissue, while those for bone depend on the structure of the specific bone. Cortical bone is the dominant constituent of the long bones (e.g., femiu, tibia), while trabecular bone, which is more elastic and energy absorbent, is the dominant constituent of the vertebrae. The shear viscosity and bulk elasticity of soft tissue are from a model for the response in vivo of a human thigh to the vibration of a small-diameter piston (von Gierke et al., 1952)... 

FIGURE 15.2 Scanning acoustic microscopy image of vertebral trabecular bone from a young individual. The vertical beams and the horizontal struts form a three-dimensional network to maximize the mechanical properties while minimizing weight. 

The relationships between the static mechanical properties of trabecular bone and apparent density vary for the different types of trabecular bone because of the anatomic site-, age-, and disease-related variations in trabecular architecture. Both linear and power-law relationships can be used to describe the dependence of modulus and compressive strength on apparent density (Tables A2.2, A2.3), with typical coefficients of determination (r values) in the range 0.5-0.9. Differences in the predictive... 

Contains a theoretical analysis of some possible underlying deformation and failure mechanisms of individual trabeculae, based upon analogies to cellular solids. Goldstein S.A. (1987) The mechanical properties of trabecular bone Dependence on anatomic location and function. /. Biomech., 20, 1055-1061. 

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