[Experimental study of the mechanism on blood supply to delayed separated skin flap by ultrasonic Doppler].

In order to investigate the mechanism of blood supply to the delayed separated skin flap and the time and criteria for its transfer, 5 small-sized Banna pigs were selected to produce 14 skin flaps. In the experimental group the skin flap on one side was made from the middle of the back having an extra-thin steel sheet intervened between the flap and the soft tissue of the back whereas the flap on the opposite side without a steel sheet intervened was served as the self-control. The skin flaps were examined 3,7,10 and 20 days after the operation and 3,7 and 10 days after transfer, respectively, by (1) gross observation; (2) ultrasonic Doppler; (3) superficial skin temperature measurement and; (4) histomorphological examination. In the experimental group the survival rate of the flap was 100 percent whereas in the control group all of the flaps had necrosis from 30 to 50 percent after the flap being transfered. In the experimental group, the echo sound from the arterial blood flow from ultrasonic Doppler was heard at the pedicle 7 days after the operation, and as time elapsed, the echo sound spread distally, whereas in the controls no echo sound could be heard over the skin flap. There was significant difference statistically between the experimental and control groups in the temperature of the flaps while the flaps were being transferred (P < 0.01). The external diameters of the blood vessels in the central area of the skin flap were larger in the experimental group, 0.8 to 1.2 mm in comparison to 0.4 mm.