[Experimental study and clinical use of the dorsal digital flag flap]

To investigate the survival mechanism of the dorsal digital flag flap, an animal experiment was undertaken in a monkey. Eight dorsal digital flag flaps were created and examined by clinical observations, laser Doppler and biopsy. Of them six flaps were proximal-based and two were distal-based. The results showed: 1. The flag flaps survived without purplish discoloration or blister formation when the length-width ratio reached 10:1; 2. The perfusion unit measured by laser Doppler flowmetry decreased on the second postoperative day and began to increase from the third day, and returned to or surpass the preoperative level on the fifth day; 3. Biopsies confirmed that there was no specific artery in the pedicle of the flag flap but a rich dorsal digital venous network. The results indicated that the flag flap is a venous flap. Its arterial perfusion passed through the perivenous vascular network of the pedicle while the venous drainage is through the dorsal digital veins. Based on this study, 20 venous dorsal digital flag flaps have been used for reconstruction of digital defects associated with exposure of bone or tendon in 12 patients. Satisfactory results were obtained in all cases.