Hemodynamic Study of Three Patterns of Flaps on Rats with a Novel Panoramic Photographing Technique Involved

Sir: We read with interest the recent article entitled “Hemodynamic Study of Three Patterns of Flaps on Rats with a Novel Panoramic Photographing Technique Involved” by Zhuang et al.1 in Plastic and Reconstructive Surgery. We are impressed by the authors’ work in elucidating the hemodynamic characteristics of perforator, perforator-plus, and random flaps in a rat model. However, there are some points that merit discussion. In the article, a random group was achieved by ligating three perforators on one-half of the dorsal skin. However, these are not typical random flaps, as typical ones do not contain major vessels originally. Because the flaps were suddenly deprived of a major blood supply, they might need time to regain a normal supply equal to that of typical random flaps. However, flap necrosis may occur before compensatory vascular regeneration is completed. We feel that it might have been more appropriate to use modified McFarlane flaps in the random group of the same size as those used in the other two groups.2 The authors divided the necrotic portion and calculated the necrosis rate by using photographs, then concluded that there was no significant difference between perforator and perforator-plus flaps. However, the size of the necrotic area determined by gross observation may not be accurate. Obvious differences might be detected after a period longer than 7 days. To precisely evaluate the necrotic area, we suggest using fluorescein angiography3 or histologic examination. Moreover, histologic examination could have provided information about vascular caliber, function of endothelial cells, thrombus formation, and so on. As for observation of the morphologic evolution of vessels within the flaps, the authors detailed how to fix the flaps, but did not elaborate on how to fix the rats to prevent movement. Skin stretching caused by movement is one of the most important factors contributing to hemodynamic changes or vascular network formation. Moreover, inflammatory reactions resulting from trauma of suturing twice could also influence the outcome. Among recent techniques, laser speckle contrast imaging is a full-field method that can simultaneously provide both structural and functional information on blood vessels. In addition, an optical clearing agent can make the skin transparent; this method can be used to develop a switchable skin window for laser speckle contrast imaging of dermal blood flow,4 without skin stretching or a repeated operation. We appreciate the authors’ excellent work and request a reply to these comments. DISCLOSURE The authors have no financial interest to declare in relation to the content of this communication. There was no financial support of this communication. Zifei Li, M.D.Jie Luan, M.D., Ph.D.Plastic Surgery HospitalChinese Academy of Medical Science and Peking UnionMedical CollegeBeijing, People’s Republic of China