Reply: Hemodynamic Study of Three Patterns of Flaps on Rats with a Novel Panoramic Photographing Technique Involved
As suggested in the comment, the most widespread model for a random flap is the modified McFarlane flap on the middle back of the rat that does not require ligation of major perforators when harvested. Actually, we were familiar with the random flap model before this study.2 The reason we do not adopt this model is the intention to locate the three types of flaps on the same site so that more comparability among flaps can be achieved, and our prior understanding that because there is no specific perforator in the pedicle, the flap can be termed a “random flap.” We have no idea whether there is a considerable difference of vascularization between a typical random flap and the “man-made” random flap suddenly deprived of a major blood supply as described by us, which might be worthy of further future investigation.
As for the calculation of the necrosis rate of the flap, the method of dividing the size of the darkened area by the size of the full flap adopted by us is the most common and convenient one as described in many relevant articles.3,4 Also, the 7-day length is a typical observation phase as described in numerous relevant articles. If the observation length is prolonged, scar will gradually form over the darkened area and fall off, with the result that distinguishing between the viable and necrotic tissues is more difficult. Although using fluorescein angiography may be a good method for calculating the necrosis rate, the equipment needed is not available in many research units, thus limiting its popularity. Also, when it comes to using histologic examination for determination of the necrosis rate, we have no idea how this could work because only a tiny piece of tissue could be harvested for histologic examination each time.
As far as the new photography technique is concerned, the rats are anesthetized before undergoing image collection and thus no fixation of the rats is required. Skin stretching and inflammatory reactions resulting from suturing twice could be avoided if image capture is carried out only immediately after surgery and at the end of the observation phase. As suggested by the comment, we read with interest the article regarding the laser speckle contrast imaging combined with an optical clearing agent that could provide simultaneous structural and functional information about vessels in the skin.5 We do agree that this method is indeed a good method that can be used for future study of flap vasculature. However, this method has potential disadvantages (e.g., the chemical agents that render the skin transparent may have adverse effects on the vascular biology, and the speckle contrast imaging device is a very expensive device that is available in only a few research centers). Despite the potential advantages of our photography technique, it is a method that can be tried in nearly any laboratory with the need for capturing high-quality dynamic vascular images in the study of flaps. In a word, we are truly appreciative of the insights and opinions from Li and Luan, which will inspire us to find the direction of our future study.