Micro-anastomosis of 0.3-0.4 mm vessels after cold ischemia using a rat model of toe-to-thumb transplantation.

Anastomoses of vessels of less than 0.5 mm in diameter remain a challenge from the technical aspect. Clinically such anastomoses are necessary for replantation of the distal digit in adults and whole digits in children. Survival data for replantation of these parts after prolonged ischemia have not yet been reported. Since a rat foot has an anatomic structure similar to the human hand, we used 40 rats as models of toe-to-thumb transplantation to study the survival rates of transplanted toes after various periods of cold ischemia (4 degrees C) of the amputated part. While a 100% success rate was achieved following immediate transplantation of the amputated digits (control group), the survival rates were 87.5, 75, 75, and 62.5% after transplantation of digits cooled for 24, 48, 72, and 96 hours, respectively (groups 2-5). No exact ischemic time limit was demonstrated. The results suggest that, in this model, optimal digital replantation results are achievable even after a 24 hour period of cooling preservation.