In vivo study of acute effects of hip and knee positions on blood flow in canine sciatic nerve.

We studied blood flow in the canine sciatic nerve using a laser Doppler flowmeter. Blood flow was measured in 20 hind limbs of ten adult dogs at varying angles of hip flexion, hip rotation and knee flexion. Blood flow decreased as flexion and internal rotation of the hip increased and also with only slight flexion of the knee. With 90 degrees knee flexion, the mean blood flow did not change significantly when the hip was internally rotated from 0 degrees to 30 degrees. When the knee was straight, the blood flow changed significantly during the same procedure. To prevent sciatic nerve palsy, attention should be paid to the positioning of the hip and knee during total hip arthroplasty.