Biomechanical changes in long limb bones of HAN-Wistar rats during postnatal development.

From a total of 648 male and 638 female HAN-Wistar rats the bones of 12 males and 12 females were examined at seven week intervals from the 35th to the 1129th day after birth. Biomechanical properties of the femora, tibiae and humeri were defined in a bending test using a tension testing machine. Load deflection diagrams in bending were produced, and the values of maximum bending load, bending breaking load, maximum deflection and ultimate deflection were correlated to age, body weight and bone length. The mean values of weight, bone length and biomechanical data are significantly higher in male rats. In both sexes biomechanical properties show a clear dependence on age. Up to the age of 330 days the tibia is more flexible than the femur or humerus. Values of partial correlation coefficients demonstrate that weight exerts more influence on the biomechanical properties of bones than age or bone length. With increasing weight, the loading capacity of bones rises in both sexes.