BILATERAL SYMMETRY OF BIOMECHANICAL PROPERTIES IN RAT FEMORA

In many studies, bone healing and remodeling have been examined in var ious animal models using one femur as a control for the contralateral femur based on the assumption that they are bilaterally symmetrical. S ymmetry studies have been limited mainly to geometrical properties. Th e purpose of this study was to determine whether or not there is symme try in the mechanical properties of rat femora. Two strain gauges were attached to the anterior surface parallel to the long axis of explant ed femora of retired female breeder and 120-day-old male Sprague Dawle y rats. Femora were mechanically tested in cantilever bending and the strain values were recorded. Moments of inertia, cortical areas, and m oduli of elasticity were determined from strains and cross-sectional p roperties. Female femora showed a bilateral strain difference of less than 2.2% and an elastic modulus difference of less than 8.7%. Males h ad less than 2.0% and 7.9% differences for strain and elastic moduli, respectively. Statistical analysis showed no significant difference be tween left and right femoral strain values for the females, but modulu s differences were significantly different at the p = 0.05 level. Ther e was no significant difference in strain and modulus values for the m ales, indicating mechanical and geometrical symmetry of their femora. (C) 1996 John Wiley & Sons, Inc.