Pressure-volume ratio in human cadaver hip joints.

In postmortem examinations 26 hip joints of 23 adult individuals were filled with Ringer's solution in order to furnish data on the relationship between intra-articular pressure, capsular content, and joint position. A tube system was connected to an 18-gauge needle and to a pressure transducer. After instillation of 2.5, 5.0, 7.5, and 10.0 ml of Ringer's solution, intra-articular pressure was recorded in six different joint positions (extension, 45 degrees and 90 degrees flexion, 40 degrees internal and 40 degrees external rotation, and 45 degrees abduction in extension). Intra-articular pressure depends mainly on the position of the joint, with highest values in external and internal rotation and lowest values in 45 degrees flexion. In this last position, the pressure was zero in two of four cases after injection of 10 ml, whereas with external rotation and instillation of 2.5 ml almost 60 kPa was recorded. In extension and after filling with 10 ml the pressure exceeded the level of normal systolic blood pressure in all cases. Under pathologic conditions intra-articular pressure of the hip joint can rise well above arterial pressure and thus eventually compromise vascular supply to the femoral head, even in the presence of only minimal intra-articular effusion.