Small animal bone biomechanics

Abstract

Animal models, in particular mice, offer the possibility of naturally achieving or genetically engineering a skeletal phenotype associated with disease and conducting destructive fracture tests on bone to determine the resulting change in bone's mechanical properties. Several recent developments, including nano- and micro-indentation testing, microtensile and microcompressive testing, and bending tests on notched whole bone specimens, offer the possibility to mechanically probe small animal bone and investigate the effects of aging, therapeutic treatments, disease, and genetic variation. In contrast to traditional strength tests on small animal bones, fracture mechanics tests display smaller variation and therefore offer the possibility of reducing sample sizes. This article provides an analysis of what such tests measure and proposes methods to reduce errors associated with testing smaller than ideal specimens.

Figure 1

(a) µCT images of different mouse long bones at the midshaft region where notching and failure occur. (B) Testing setup showing largest possible span length for different mouse bones. (Reprinted from the Journal of Biomechanics Vol. 38. Schriefer J, Robling A, Warden S, Fournier A, Mason J and Turner C. A comparison of mechanical properties derived from multiple skeletal sites in mice. p.469 ©2005, with permission from Elsevier.)

Figure 2

Cross-sectional images of mice bone showing cortical thickness, endosteal and periosteal diameters measured at three diphyseal location using microCT (Scanco Viva CT).