IN-VIVO OBSERVATIONS OF HYDRAULIC STIFFENING IN THE CANINE FEMORAL-HEAD

The role that intertrabecular contents and their boundary conditions h ave on the dynamic mechanical response of canine femoral heads was inv estigated in vivo. Femoral heads from paired intact hind limbs of cani ne specimens were subjected to a sinusoidal strain excitation, at phys iologic frequencies, in the cranio-caudal direction, The fluid boundar y conditions for the contralateral limbs were changed by predrilling t hrough the lateral fermoral cortex and into the femoral neck. The dril ling Associate Professor, procedure did not invade the head itself Thi s femoral head fluid boundary alteration reduced the stiffness by 19 p ercent for testing at I Hz, The results of this study demonstrate that fluid stiffening occurs in vivo as previously observed ex vivo.