Perforator Number Predicts Fat Necrosis in a Prospective Analysis of Breast Reconstruction with Free TRAM, DIEP, and SIEA Flaps

Sir: We are writing regarding the interesting article by Baumann et al., “Perforator Number Predicts Fat Necrosis in a Prospective Analysis of Breast Reconstruction with Free TRAM, DIEP, and SIEA Flaps,” in which some exciting clinical observations have been made that may shed further light on the physiology of deep inferior epigastric artery (DIEA) perforator flaps.1 However, we would like to clarify some important anatomical definitions made in the article that may have a substantial bearing on the ultimate interpretation of the findings. In their assessment of perforator flaps, the authors include the superficial inferior epigastric artery (SIEA) flap, describing the flap as a perforator flap and stating that the SIEA flap comprises “a single fasciocutaneous perforator.” We would like to make note of our anatomical findings of the SIEA, in which we assessed 500 studies of the SIEA with imaging.2 In our experience, the SIEA does not “uniformly” lie deep to the Scarpa fascia and in fact quite variably lies deep or superficial to the Scarpa fascia. Based on our studies, it would therefore not be appropriate to call the SIEA flap a perforator flap at all. As such, to include the SIEA in the same category as DIEA perforators is not appropriate, especially because even the SIEAs that are fasciocutaneous perforators may not be functionally equivalent to musculocutaneous perforators. The authors also describe the SIEA territory, stating that “SIEA flaps were included in this study as they comprise the same anatomic territory of lower abdominal skin and subcutaneous fat as muscle-sparing TRAM and DIEP flaps.” This is certainly not true, with multiple cadaveric dissection and angiographic studies,3,4 and clinical injection and immunofluorescence studies,2,5,6 all showing that the anatomical studies of the DIEA and SIEA are absolutely distinct from one another (Fig. 1).7 These studies have shown that the primary angiosome of the SIEA is the region between the linea semilunaris and the anterior axillary line, whereas that of the DIEA is between the linea alba and the linea semilunaris, although interindividual variability certainly occurs. This further emphasizes that for the scientific purposes of addressing the primary aims of the study by Baumann et al., it would be wise to exclude the data on the SIEA.Fig. 1.: Computed tomographic angiogram with volume-rendered technique reformat of the vasculature of the anterior abdominal wall, demonstrating the differences between angiosome territories of deep inferior epigastric artery perforators highlighted in blue (perforators >1 mm) and yellow (perforators <1 mm) and the SIEA highlighted in white. (Reproduced with permission from Rozen WM, Grinsell D, Koshima I, Ashton MW. Dominance between angiosome and perforator territories: A new anatomical model for the design of perforator flaps. J Reconstr Microsurg. 2010;26:539–545.A last note on the methodology used by the authors in assessing perforator anatomy concerns the authors stating that they counted the number of perforators intraoperatively, even where transverse rectus abdominis myocutaneous (TRAM) flaps were used. Furthermore, perforator size was assessed based on external diameters, as observed intraoperatively. Both of these techniques seem difficult to achieve with substantial accuracy for interpretation of results. In terms of counting perforator number in TRAM flaps, there may be many perforators within the included muscle that are simply not seen intraoperatively and missed in counting. We would suggest that the use of preoperative imaging may substantially improve the accuracy of this assessment. In our studies of the use of computed tomographic angiography, we have found a near 100 percent positive predictive value for assessing perforator number with the use of computed tomographic angiography.8,9 Of additional note, the use of the external diameter of perforators is a poor reflection of relative flow between perforators, as wall thickness varies substantially between individual perforators, as does relative flow between two perforators of the same external diameter. Again, the use of flow-dependent imaging may be useful as an objective measure of internal vessel diameter and relative flow, particularly with the use of color Doppler or duplex ultrasonography or contrast computed tomographic angiography or magnetic resonance angiography. Warren M. Rozen, M.B.B.S., B.Med.Sc., P.G.Dip.Surg.Anat. Iain S. Whitaker, M.B.B.Chir., Ph.D. Daniel Chubb, M.B.B.S., B.Med.Sc. Mark W. Ashton, M.B.B.S., M.D. Jack Brockhoff Reconstructive Plastic Surgery Research Unit Department of Anatomy and Cell Biology University of Melbourne Parkville, Victoria, Australia DISCLOSURE The authors have no financial interest to declare in relation to the content of this communication.