Assessment in the rat of the hemodynamic effects of gradual expansion on vitality of the random zone of an axial island flap | [Valutazione nel ratto degli effetti emodinamici di una espansione graduale sulla vitalita della zona random di un lembo assiale ad isola]

The authors propose a new experimental model in the rat designed to planimetrically, microangiographically, histologically and histochemically assess the hemodynamic effects of gradual cutaneous expansion on vitality in the random zone of the abdominal axial flap, in order to establish if and how it influenced survival. 30 outbred male Wistar rats were divided into three groups: - Group 1 (control A, n = 10): a monopedicled abdominal flap was raised (7 cm long by 6 cm wide) of which half was axial and half randomly vascularized. - Group 2 (control B, n = 10): a monopedicled abdominal island flap was raised (7 cm x 6 cm) 14 days after insertion of a hollow silicons expander (6 cm long by 4 cm wide, nominal volume 60 cc), with a view to 'autonomizing' the flap. - Group 3 (study group, n = 10): a monopedicled abdominal island flap was raised (7 cm x 6 cm) after being expanded for 14 days (60 cc) with an expander identical to the one used in group 2. Planimetric assessment showed the following survival rates in the random zone: group 1: 61.8%, (SD 2.4); group 2: 74.2% (SD 3.6); group 3: 89.7% (SD 2.8). Microangiographic testing revealed the total absence of tracer in the random zone in group 1; the opening of arteriovascular connections in group 2 with tracer spreading to much of this zone; hypertrophy and vessel dilatation in group 3 with tracer spreading to entire flap. Histological sectioning of the random zone showed the presence in group 1 of areas of necrosis with vasal thrombosis extending to almost the entire surface. In group 2 these areas were only present in the more peripheral part, while in group 3 they were limited to the suture. In group 3 histochemical analysis indicated vasal ectasia with neoangiogenesis throughout the random zone. These results show that gradual expansion may amplify extension of the random zone of an axial cutaneous flap, thereby permitting exceptionally large flaps to be raised.