Comparison of three-point bending test and peripheral quantitative computed tomography analysis in the evaluation of the strength of mouse femur and tibia.

We compared the mechanical and densitometric testing methods in evaluating the mechanical strength of mouse cortical bones. The femora and tibiae of 10 male mice (weight 32.8 +/- 4.0 g) were utilized. Volumetric cortical bone mineral density (vCtBMD), cross-sectional cortical area at midshaft (CSA), cross-sectional moment of inertia (CSMI), and strength strain index (SSI) were measured by peripheral quantitative computed tomography (pQCT). The precision of pQCT expressed as a coefficient of variation (CV) was 1.1%, 2.7%, and 6.4% for vCtBMD, CSA, and CSMI, respectively. The mechanical properties were measured by a three-point bending test. The method error measured from paired bones was 7.3%-10.1% for breaking bending force, 15.0%-15.2% for stiffness, 2.0%-2.4% for vCtBMD, 5.2%-6.4% for CSA, 13.5%-17.6% for CSMI, and 8.9%-18.1% for SSI. CSMI and CSA were found to be the best explanatory variables for the breaking force of femur and tibia, respectively, while CSA and CSMI were the best predictors for the elastic modulus of femur and tibia, respectively. CSA had a higher correlation with mechanical parameters than vCtBMD. On the basis of this study, the mechanical tests and the pQCT measurements are relevant in biomechanical studies on mouse bones and justify the use of the murine model. High-resolution pQCT gives better precision than the three-point bending test in studies of mouse bones.