Effect of bradykinin on pressure changes in the femur head epiphysis--an experimental and magnetic resonance tomography study

Abstract

The aim of this study was to evaluate the response of the femoral head to intraosseous pressure increases and to document blood flow of periarticular soft tissue after infusion of vasoactive substances. Beside that the value and imagery of native MRI after induced intraosseous pressure increase should be estimated for early detection of femoral head necrosis. The alteration of intraosseous pressure and peripheral blood flow of the femoral head of beagle dogs was examined after administration of bradykinin as a vasoactive substance followed by subsequent magnetic resonance imaging (MRI). Bradykinin was injected into the arteriae circumflexae femoris lateralis and medialis of six beagle dogs. The administrations were made using a standard protocol with simultaneous measurement of venous blood flow and intraosseous pressure distribution in the epiphysis of the femoral head. Bradykinin was applied in regular time intervals followed by MRI. At a mean epiphyseal pressure 14.66 mmHg (sigma: 2.42) in the femoral head, a mean flow of 91.6 ml/min (sigma: 16.08) was measured in the vena femoralis. After an administration of a defined concentration of bradykinin an increased epiphyseal pressure was recorded in the measured area. An average increase blood flow of the vena femoralis was observed at the beginning of the bradykinin-injection, followed by a circulatory volume reduction. The post-experimental MRIs showed massive oedema in the femoral musculature after bradykinin-application, however without osseous signal alterations in T1- or STIR-weighted images. Our results indicate that acute intraosseous pressure increases are not accompanied by signal alterations in MRI. Obviously more extensive pressure induced lesions are necessary for detectable signal alterations, as these have already been demonstrated in patients with diagnosed femoral head necrosis.