Investigation on Viscoelastic Properties of Cortical Surfaces Using Dynamic Mechanical Analysis

In silico models of bone adaptation attempted to simulate loading-induced osteogenesis (i.e. new bone formation) at cortical bone surfaces (periosteal and endocortical). These models, however, fall short in fitting the site-specific new bone formation at cortical envelops especially at endocortical surface. An anticipated reason may be that same mechanical properties were considered for both periosteal and endocortical surfaces, whereas, properties may be different and location-specific at the two surfaces. Site-specific mechanical properties at cortical bone envelops are not investigated well in the literature. This study mainly aims to characterize mechanical properties (especially viscoelastic properties) at periosteal and endocortical surfaces of Wistar rats femora using Dynamic Mechanical Analysis (DMA). Viscoelastic properties such as storage and loss moduli are estimated. Properties are also compared along anterior, posterior, medial, and lateral sites of cortex at both surfaces. Experimental outcomes indicate that periosteal surface has higher stiffness than endocortical surface across all the anatomical locations, in which, medial region had highest stiffness at the two surfaces. These findings may be useful in developing advanced computer models to precisely predict osteogenesis which may help clinicians in providing informed recommendation on biomechanical strategies such as physical exercise to treat site-specific bone loss.