The aim of this study was to investigate changes in the blood microcirculation of skin, subcutaneous tissue, and striated muscle, and the venous and lymphatic outflow from hind limb, after a standardized mechanical trauma.
Trauma, defined as 50% of the minimal energy needed for tibia fracture (3.7 J/g), was applied to the leg of hairless mice. Intravenously injected fluorescein isothiocyanate–dextran 150 kDa and Rhodamine-6G were used for intra-vital fluorescence microscopy of blood vessels. Lymphatics were stained with fluorescein isothiocyanate–dextran injected into the footpad. A computer-assisted analysis system allowed measurement of the functional capillary density (FCD), vessel diameters, velocity of blood flow, and edema value expressed as extravasation index (EV). The percentage of slowly rolling and sticking leukocytes in postcapillary venules was estimated.
At the site of injury, trauma resulted in significant reduction of FCD in skin, subcutaneous tissue, and striated muscle. There were no significant differences in the vessel diameter (skin subcutaneous and muscle arterioles and venules, and superficial saphenous artery and vein) or velocity of blood flow (subcutaneous tissue and muscle venules). The EV increased significantly in muscle venules and was higher in muscles, subcutaneous tissue, and superficial saphenous veins than in controls (nonsignificantly). An increased percentage of slowly rolling and sticking leukocytes was noted in the superficial saphenous vein at the site of injury and proximal to it. The lymphatics remained patent, with faster visualization and increased summarized cross-sectional areas in traumatized extremities.
Early changes occurring in soft tissues in response to mechanical injury were characterized by reduction in FCD of skin and muscles, and less in subcutis; increased EV, reflecting leakage of macromolecules; increased percentage of slowly rolling and sticking leukocytes; maintenance of lymphatic vessel continuity; and increased lymph formation and flow rate.
From the Institute for Surgical Research (G.S., A.V., D.N., K.M.) and Department of Orthopedics (A.V.), Klinikum Grosshadern, Ludwig-Maximilians-University, Munich, Germany, Clinic for Maxillofacial and Plastic Surgery (D.N.), Knappschaftskrankenhaus, Bochum-Langendreer, Germany, Department of Surgical Research and Transplantology (G.S.), Medical Research Center, Polish Academy of Sciences, and Department of Orthopedics and Traumatology (G.S.), Medical Academy, Warsaw, Poland.
Submitted for publication June 4, 2000.
Accepted for publication May 16, 2001.
Address for reprints: Grzegorz Szczesny, MD, Department of Surgical Research and Transplantology, Polish Academy of Sciences, 5 Pawinskiego Str., 02-106 Warsaw, Poland; email: firstname.lastname@example.org.