Influence of the hip joint position on the intraosseous pressures in the juxta-articular bones. An experimental investigation in dogs.

In 6 mongrel dogs (eleven hips) the intraosseous pressure was measured in the femoral head as well as acetabulum in various hip joint positions. The control position for the measurements was 90 degrees flexion in which the pressures were found low and stable. The intraosseous pressure in both locations were subjected to consistent pronounced variations when the joint position was altered. In the femoral head, significant pressure increases (p less than or equal to 0.01) were found in maximal extension, maximal flexion, maximal adduction, 90 degrees external rotation, 45 degrees internal rotation, and maximal internal rotation. The pressure in acetabulum rose significantly in maximum flexion, 45 degrees internal rotation, and maximum internal rotation, whereas the pressure increase in maximal extension and maximum adduction was consistent but not significant. The pressure increase is most probably caused by inhibition of the venous drainage changing the bone hemodynamics in the juxta-articular bones. A complete obstruction of venous drainage was not observed since the intraosseous pressure in none of the measurements reached the level of the arterial pressure.