Differences between contralateral bones of the human lower limbs: A multiscale investigation

This study addressed side asymmetry between human lower limb long bones. A multiscale approach was taken to investigate differences between contralateral femurs, tibias and fibulas, at body-level (total-body CT-scans, anatomical dissection), organ-level (volume and moments of areas; structural stiffness and strain distribution in bending and torsions) and tissue-level (mineral density, elastic modulus, hardness). Because of the large amount of measurements taken, the study was limited to two donors. However, high statistical power within the same donor was achieved thanks to a large number of highly-repeatable measurements. Muscle cross-sections suggested that both donors were right-legged. The right bones had higher structural stiffness (up to þ115%, statistically sig- nificant, except for the tibia). The right bones also experienced generally lower strain than the contralateral ones (up to ␣25%, statistically significant). The right bones had larger volume (up to þ16%) and moments of area (up to þ116%, statistically significant in most cases) than the left ones. Difference in tissue density between contralateral bones (< 7%) was not stat- istically significant in most cases. Also the differences found in elastic modulus of the femur cortical tissue (2–5%) were not statistically significant. Similarly, tissue hardness in the right bones was only marginally higher than in the contralateral ones (þ1% to þ4%, not statistically significant). Therefore, it seems that structural differences between contralateral bones associated with laterality are mainly explained by differences in bone quantity (volume) and organization (area moments). Bone tissue quality (density, hardness) seems to give a marginal contribution to structural side asymmetry.