The use of saline in preserving bone specimens may affect the mechanical properties of specimens. Yet, the reported effects varied and contradicted to each other, with a lack of investigating constitutive material parameters. Therefore, we quantified the effects of preservation time on the constitutive properties of cortical bone.Methods:
We collected 120 specimens from the mid-diaphysis of six male bovine femora, which were assigned to five groups, including fresh-frozen for 60days (−20°C), storage in saline for 3, 10, 36 and 60days (25°C). All specimens underwent quasi-static three-point bending tests with a loading rate of 0.02mm/s. Using the optimization method combined with specimen-specific finite element models, the Young's modulus, tangent modulus, yield stress, effective plastic strain, yield strain, ultimate stress, and toughness were calculated.Findings:
Saline preservation resulted in a significant decrease of Young's modulus, yield stress, ultimate stress and pre-yield toughness (P<0.001), and a significant increase of effective plastic strain (P=0.034). After 10days of preservation, yield stress and pre-yield toughness decreased −14.9% and −21.4%, respectively, and they continued to decrease with longer preservation time. After 36days of preservation, Young's modulus and ultimate stress decreased −19.2% and −17.3%, respectively, and continued to decrease with longer preservation time. Our data also showed changes of material properties collected after 3-day saline preservation, while the low statistical power must be considered for this group.Interpretation:
Saline preservation impacts on mechanical properties of cortical bone tissue and the effect is already observable after 3days.