Material and Methods: Sixteen Wistar rats were used. Tail vein graft 7.5 cm long was harvested. A 2x4 cm left groin flap was elevated pedicled on femoral artery & maintaining its original venous outflow. Graft was anastomosed end to side with right femoral artery & end to end with left femoral artery proximal to the flap pedicle. Thus the right femoral artery provided the inflow to the right leg and through the graft to the left groin flap and the leg. The venous outflow were left undisturbed. Blood flow was measured immediately and 5 days later using a doppler microprobe. On day 5 the left femoral artery was clamped distal to the flap pedicle to increase the resistance.

Results: One rat died and one had early thrombosis. Remaining flaps survived and all grafts were patent . Mean flow velocities are as follows. Day 1,Day5 Right femoral artery before anastomoses 10.5 cm/s left femoral artery before anastomoses 10.35 cm/s Right femoral artery proximal to anastomoses 7, 16.125cm/s Right femoral artery distal to anastomoses 4.625,9.625 cm/s left femoral artery distal to anastomoses 5.875, 13.3 cm/s Graft proximal 2.625, 6.875 cm/s Graft distal 2.5, 6.75 cm/s

Velocity and volume did not differ at the proximal or distal end of the graft. The mean velocity through the vein graft was significantly slower than the femoral arteries. On day 5 the velocity in the left femoral artery was similar to that in the proximal right femoral artery but more than the distal right femoral artery. Thrombosis was seen in all grafts within 10 minutes of clamping the left femoral artery distal to the pedicle.

Discussion: Many diabetic patients have a single patent vessel at the ankle level. Limb salvage in these patients is usually attempted by a proximal end to end anastomosis using a long vein graft. Failure of free flaps in not uncommon in distal anastomoses in the presence of poor collaterals. All vessels in this study thrombosed due to increased resistance showing that end-to-end anastomoses with high inflow can lead to graft failure. Conversely an end to side anastomoses has been shown to increase the distal outflow bed, decreasing the resistance and increasing graft flow and survival.