DETERMINATION OF LOADING PARAMETERS IN THE CANINE HIP INVIVO

The loading parameters in the canine hip were determined from multiple studies, involving the collection of kinematic and force plate data i n vivo joint reaction force from an instrumented hip replacement prost hesis, and in vivo femoral cortical bone strain gauge data in differen t dogs. In the middle of the stance phase of gait the canine femur was flexed 110-degrees with respect to the pelvis and formed a 20-degrees angle relative to the floor. At this point in the gait cycle, a line passing from the superior to the inferior aspect of the pubic symphysi s was parallel to the floor. The joint reaction force measurements sho wed that the net force vector during midstance was directed inferiorly , posteriorly, and laterally, with a peak magnitude of up to 1.65 time s the body weight. A torsional moment of 1.6 N m is exerted about the femoral shaft. In vivo strain data showed that during gait peak compre ssive strains of -300 to -502 microstrain were produced on the medial aspect of the femoral cortex and peak tensile strains of +250 to +458 midstrain were produced on the femoral cortex. At the midstance phase of gait, principal cortical bone strains were rotated up to 29-degrees relative to the long axis of the femur, suggesting torsional loads on the femur. These data in combination provide valuable insights on the loading parameters of the canine hip which can be used in future appl ications of the canine as a model for evaluating mechanically based ph enomena such as bone ingrowth and remodeling or hip prostheses.