Cross-site anastomosis for a free flap with a long pedicle in the rat

We describe a simple and reliable technique for tunneling of the vascular pedicle of the free flap with a long pedicle, that may otherwise cause twisting and/or kinking of the pedicle. There are two modifications of the technique. In the cross-groin anastomosis modification, using a haemostat in a blunt manner, a suprapubic subcutaneous tunnel is created between two groin regions. The vascular pedicle of the flap is pulled and passed through this tunnel to the contralateral region. While the anastomoses are done on one site, the flap is inserted to the contralateral groin. In the second modification ('groin anastomosis-cross dorsum flap insert procedure'), the flap is transferred to the dorsum of the rat at approximately the same level of the groin. Using a haemostat, a large subcutaneous tunnel safe enough for the pedicle is created between the groin region and the rat dorsum lateral to the hip region. The anastomoses are done in the groin region, and the flap is inserted on the dorsum. This technique was used in 16 animals, with a free cutaneous maximus muscle musculocutaneous flap transfer based on the axillary vessels being done in eight animals; and a posterior thigh perforator-based flap based on the popliteal vascular pedicle in the remaining eight. Both groups had a pedicle length of approximately 4 cm, with a 100% survival rate. In conclusion, the technique is simple, reliable, and can be easily carried out without necessitating special procedures. It provides a straight course for the vascular pedicle with tension-free anastomosis by appropraitely adjusting the distance of the vascular anastomosis and flap insertion site.