Research

Bone material is a stiff, lightweight and relatively elastic composite material comprised of inorganic substance (hydroxyapatite), organic substances (mostly collagen type-I) and water. In its highest structural level, the bone material can construct two distinct “architectures” - dense cortical bone tissue which forms the outer cortex and porous trabecular bone tissue which is an internal bony structure, residing within the cortical bone shell. Trabecular bone is similar to cortical bone tissue material-wise, but it differs in its structural properties, mainly much higher porosity (ranging 50-90% of tissue volume). Consequently, the mechanical behavior of bones (the organ) depends on bone material properties (e.g. the amount of hydroxyapatite), but it also depends substantially upon the three-dimensional macro-architecture; this is especially true for trabecular bone tissue.

While bone tissue seems to be stagnant, it is actually active and responsive throughout life. Ample evidence demonstrates that bone tissue will adjust and modify its structure in response to decrease in use (bone resorption; e.g. microgravity in space, bed rest), increase in use (bone deposition; e.g. running, playing tennis), change in loading direction (e.g. altering joint angle), and disease (e.g. osteoporosis). This phenomenon, previously termed “Wolff’s law”, is nowadays known as “bone functional adaptation”.

In my lab, we are studying the relation between cortical and trabecular bone structures and their mechanical properties, as well as the relationship between bone structure and function. To this end we use three approaches: (I) mechanically testing the orthotropic properties of cortical bone tissue in various bones and different locations along the bone, (II) 3D printing trabecular bone structures (both original/intact and after the structure was altered, e.g. simulating disease or bone modeling) and mechanically testing them in compression from different orientations, and (III) using Finite Element Analysis (FEA) to map stresses and strain distribution and to predict areas of weakness which are prone to fail first.