| Basic experiments. The knowledge of the regulation of bone marrow blood flow is of high clinical importance. However, relatively little is known about the regulation of the microcirculation in the bone marrow and developing callus. In our present study we have measured the changes of bone marrow microcirculation at two different ipsilateral sites (femur and tibia) of the rabbit with laser-Doppler flowmetry. Intra-arterial bolus injections of neuropeptides and vasoactive substances were given to elicit reactions of the microcirculation. Changes in flow, vascular resistance, and duration of action of the substances were measured and calculated. However, the basal blood flow velocities of the both bones were considerably different, but no statistically significant difference could be revealed between the local microvascular reactions of the femur and the ipsilateral tibia, thus the femur can be used as a reference site in our future investigations of the microcirculation of the developing callus in the gap osteotomy of the tibia.;Gap osteotomy model. Bone healing is regulated by a number of humoral factors, inflammatory mediators, growth factors and by other biologically active substances, such as hormones and neuropeptides. This process is accompanied by angiogenesis and neural ingrowth requiring satisfactory substrate- and oxygen-supply. The regulation of tissue blood flow during the course of callus development is extremely limited. We investigated the effects of intraarterially applied neuropeptides and vasoactive substances on the microcirculation of the developing callus in rabbit tibiae 10 and 15 days after osteoetomy. The changes of blood flow reactions of the developing callus and the ipsilateral femoral bone marrow were detected by laser-Doppler flowmetry. Active substances can elicit vasoactive reactions early following bone injury, possibly because reactive neural structures grow into the developing callus parallel with blood vessels and at a very early stage of callus formation. Differences in the neutralizing or re-uptake mechanisms could be responsible for the observed variations in the recovery times. |
