Response of the perforator vessel to the varying volumes of expansion of tissue expander implanted at the base of rabbit s1 perforator based dorsal flap

Purpose: The purpose of this study is to determine the effect of expansion of the rabbit S1 perforator based dorsal flap to the blood flow from the pedicle and vessel diameter via color Doppler ultrasound, to the thickness of the tunica media and tunica adventitia via histopathological examination and to the vascularity of the flap via angiography. Material and Methods: We used color Doppler ultrasound to measure the peak systol flow velocity, end diastolic flow velocity, middiastolic flow velocity, mean flow velocity, resistivity index, pulsatility index and diameter of the right and left S1 perforators of 12 New Zealand rabbits. Tissue expander were implanted at the left sides and right sides were used as control group. 4 of the expanders were inflated to 150cc, 4 of the expanders were inflated to 200cc and 4 of the expanders were inflated to 250 cc. After 3 weeks of expansion, period we repeated color Doppler ultrasound examination and compared the results. After the monobloc harvesting of experiment and control flap, we made angiography of the flaps and compared the vascularity. We took biopsies from the the perforator arteries of experiment and control group and we compared the thickness of tunica media and tunica adventitia. Results: The diameter of the perforator vessel increased with tissue expansion at both experiment and control groups. The increase of vessel diameter was more evident at experiment group. Rezistivity index decreased at the experiment group and increased at the control group. Pulsatility indexes changed at neither experiment nor control group. At the angiographies, there is notable increase of the vascularity of experiment group's flaps. There is no difference between the thickness of the tunica media and tunica adventita layers of the experiment and control group. Conclusion: With tissue expansion of a perforator flap, the diameter of the perforator vessel increases, rezistivity index decreases and pulsatility index does not change. At the adjacent angiozom of the expanded flap, vessel diameter increases and rezistivity index decreases. These changes at the adjacent angiozom can be the result of an adaptation which occurs in order to incline blood flow to the expanded tissue through the choke anastomosis which are opened as aresult of tisuue expansion. The vascularity increases when a perforator flap is expanded. Tissue expansion does not make any change at the thickness of tunica media and adventitia layers of the perforator vessel. Key Words: perforator flap, tissue expansion, color Doppler ultrasound, perforator diameter, resistivity index