The pathomechanism of posttraumatic edema of lower limbs: I. The effect of extravasated blood, bone marrow cells, and bacterial colonization on tissues, lymphatics, and lymph nodes.

Abstract

The mechanical injury of soft tissues and bones of lower extremities is frequently followed by long-lasting edema at the site of trauma and distally. The pathomechanism of this complication remains unclear. Venous thrombosis and interruption of lymphatics are considered to be the main etiologic factors. We propose a concept that protracted healing of injured tissues and bones with involvement of the regional lymphatic system (lymphatics and nodes) is responsible for persistence of edema. The events affecting the first (scavenging) phase of healing of traumatized tissues, such as hematoma, translocation of bone marrow cells to soft tissues, and colonization by microorganisms, and in particular their effects on lymphatics and lymph nodes, were studied. Mongrel dogs weighing 15-20 kg were used. Fresh blood or bone marrow cell (BMC) suspension was injected subcutaneously or intralymphatically into the paw. Strains of saprophyte bacteria residing on the skin surface were cultured and injected intradermally. Oil-contrast lymphography was performed before and after injections to evaluate the changes in lymphatics and nodes. Biopsy samples of paw skin, subcutaneous tissue, and regional lymph nodes (LN) were taken. The responsiveness of LN lymphocytes was studied in autologous mixed cultures with peripheral blood lymphocytes (PBL), BMC, and cultured bacteria. The PBL from subcutaneously injected blood were evacuated by the lymphatic route at a rate of 1-3%/6 hr. There was no thrombosis of lymphatic vessels or obstruction of LN sinusoids. The BMC evoked major inflammatory changes in both the skin and the LN. Bacteria caused local inflammation, dilatation of lymphatics, and destruction of node parenchyma. Autologous BMC and PBL stimulated LN lymphocytes in a 6-day culture. The responsiveness of lymph node lymphocytes to previously subcutaneously injected bacterial antigens was increased. The extravasated blood did not produce changes in skin, subcutaneous tissue, and lymphatics; however, it stimulated LN lymphocytes. The BMC and saprophyte bacteria caused major local and lymph node inflammatory response. All these factors may contribute to the local edema in the initial phases of healing of traumatized tissues.