The effect of freezing and intraosseous fluid on the stiffness behavior ofcanine 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 femo ra were tested after freezing at -20 degrees C. The intact femoral head spe cimens were subjected to a load of physiologic magnitude, and then the stif fness of the underlying trabecular bone was determined in intact femora, in drilled femora with a disrupted intraosseous fluid compartment, and subseq uently after refilling the compartment with fluid. Drilling of the femoral head and disrupting its bony fluid compartment resu lted in a 40% decrease in stiffness (P<.001). This effect was seen only wit h 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. Re moval of the intraosseous fluid decreases the mechanical stiffness of canin e trabecular bone, and freezing the specimens appears to alter the intraoss eous fluid compartment behavior. It is necessary to gain a better understan ding of the dynamic mechanical properties of intact bone to improve the exi sting analytical and experimental mechanical bone models. The effect of int raosseous fluid and freezing should be considered in these models.