Microcirculation Study of Rabbit Ear Arterial and Venous Flow-Through Flaps Using a Window Chamber Model

Abstract

Venous flaps are used widely for finger reconstruction because they provide thin tissue, and the flap harvest is associated with less donor-site morbidity. The viability of the venous flap, however, is not as good as that of the ordinary perfused skin flap, and its microcirculation is questionable according to various indirect observations and hypotheses in the literature. Using a window chamber model in a rabbit ear, both arterial and venous flow-through flaps were studied. Factors evaluated were flap viability, flap weight, flap circulation as assessed by laser Doppler flowmetry, and direct observation of the microcirculation. Statistical analysis was performed using the two-sample t test. There was no statistically significant difference in viability between arterial and venous flow-through flaps (p = 0.661). The arterial flow-through flap had better perfusion than thevenous flow-through flap, as measured by laser Doppler perfusion studies (10.40 perfusion units [PU] vs 4.50 PU). However, no statistically significant difference was noted (p = 0.0717). Flap weight assesseed 1 week after surgery and oxygen saturation measured immediately after surgery showed significant differences between the arterial and venous flow-through flaps (p = 0.0001 and 0.0279). These datasuggest that the arterial flow-through flap is subjected to more congestion becauseof the abnormal flow pattern seen, andpossibly because of a superior inflow or nutritional status found in these flaps. Using vital microscopy, direct evaluation of the microcirculation was performed. A to-and-fro phenomenon was noted in both arterial and venous flow-through flaps,which was followed by a reversed direction of flow in part of the microvasculature. With both types of flaps, the blood was directed eventually from the postcapillary venules to the capillaries, through the terminal arterioles, and then to the arterioles. These findings may be explained partially by the normal physiologic pressure gradients present in the microvasculature of these flaps. In this study, direct observation of the microcirculation was used as well as other objective measures to determine the flow patterns and clinical behaviors found in these types of flaps. A model in a rabbit ear for the study of venous and arterial flow-through flaps is described, and clinical correlations are discussed.