Proposed pathway and mechanism of vascularized lymph node flaps

Objective To investigate the pump mechanism and pathway of lymph transit in vascularized lymph node flaps. Background Microsurgical treatment of lymphedema with vascularized lymph node transfer can improve signs and symptoms of disease, but the pathways and mechanisms of these flaps warrant further exploration. Methods (Animal model) 72 flaps were raised in 18 rats: 36 groin flaps contained lymph nodes (LN), 36 deep inferior epigastric artery perforator flaps did not (non-LN). Indocyanine green (ICG) was added into normal saline (NS), 1%, 3%, 5%, 7% and 10% albumin. Three rats were assigned to each group. LN and non-LN flaps were submerged in solution and surveyed for venous fluorescence. In the 7% albumin and NS groups, volumetric change of solution was measured. (Human model) A similar experiment was performed in humans using five submental LN flaps. Results (Animal model) Fluorescence was detected in the venous pedicle of LN flaps submerged in 5%, 7% and 10% albumin, and half of flaps submerged in 3% albumin. Fluorescence was not detected in LN node flaps submerged in ICG-containing NS or 1% albumin solution. Fluorescence was not detected in non-LN flaps. There was greater volume reduction with LN flaps than non-LN flaps (p < 0.001). (Human model) Fluorescence was detected in the venous pedicle of all flaps immersed in lymph. Conclusions ICG fluorescence was detected in the venous pedicle of rat and human LN flaps submerged in lymph or albumin when the concentration was greater than 3%. Based on these results, a pathway for lymphatic uptake is presented.