The effect of freezing and intraosseous fluid on the stiffness behavior of canine trabecular bone

The effect of disrupting the intraosseous fluid compartment and freezing on the mechanical stiffness of trabecular bone in intact canine femoral head specimens was investigated. Twenty-four skeletally mature dogs were divided into two groups. Twelve paired fresh femora were tested and 12 paired femora were tested after freezing at -20 degrees C. The intact femoral head specimens were subjected to a load of physiologic magnitude, and then the stiffness of the underlying trabecular bone was determined in intact femora, in drilled femora with a disrupted intraosseous fluid compartment, and subsequently after refilling the compartment with fluid. Drilling of the femoral head and disrupting its bony fluid compartment resulted in a 40% decrease in stiffness (P<.001). This effect was seen only with fresh specimens and not frozen specimens. Refilling the bony compartment with fluid restored the stiffness of the fresh femoral head. These results demonstrate the mechanical properties of trabecular bone in canine femoral head specimens in vitro are affected by intraosseous fluid and freezing. Removal of the intraosseous fluid decreases the mechanical stiffness of canine trabecular bone, and freezing the specimens appears to alter the intraosseous fluid compartment behavior. It is necessary to gain a better understanding of the dynamic mechanical properties of intact bone to improve the existing analytical and experimental mechanical bone models. The effect of intraosseous fluid and freezing should be considered in these models.