Bone marrow perfusion in healthy subjects assessed by scintigraphy after application of a tourniquet

By means of a gamma camera technique involving a bolus injection of autologous 99mTc-labeled erythrocytes, we found that despite a tourniquet on the limb, the erythrocytes entered the bone marrow, and caused oozing in both lower (10 subjects) and upper limbs (14 subjects). The 24 healthy volunteers, 18 men, had a mean age of 50 (range 20-86) years. The activity reached the distal femur in a median of 365 (quartile 278-560) seconds and the distal humerus in a median of 280 (quartile 208-370) seconds. The median velocity for movement of erythrocytes in the femur was 3.7 (quartile 2.74.4) cm/min and in the humerus, it was 4.0 (quartile 3.1-5.3) cm/min. In 21 subjects, this activity reached the periarticular soft tissue. After 15 min with the tourniquet inflated, the activity in the distal femur of the tourniquet limb was 9 (quartile 5-18)% of that in the limb without a tourniquet. This study shows that although a tourniquet effectively occludes the extra-osseous blood supply, some intra-osseous blood supply is retained, which makes it difficult to obtain a bloodless field in some patients, despite the use of a tourniquet.