Anatomical understanding of target subcutaneous tissue layer for thinning procedures in thoracodorsal artery perforator, superficial circumflex iliac artery perforator, and anterolateral thigh perforator flaps

Background: Thinned perforator flaps, reported techniques, and degree of thinning differ by study. This study investigated the anatomy of subcutaneous tissue according to the varying fattiness and identified which component and how much of the subcutaneous tissue layer needed to be excluded to meet target flap thickness using computed tomography. Methods: Three stratified fattiness groups consisting of 30 donors were formed for thoracodorsal artery perforator, superficial circumflex iliac artery perforator, and anterolateral thigh flaps. Thickness of the superficial fat and the deep fat layers was measured at specific points in donor sites of the three flaps and the proportion of superficial and deep fat layers to exclude to reach the target flap thickness (4, 6, and 8 mm) was calculated. Result: The median proportion for the superficial fat layer varies depending on donor fattiness. The estimated percentage reduction of thickness after thin flap elevation along superficial fascia was approximately one-third of the whole layer. A variable proportion of each fat layer needs to be excluded to obtain required thinness and in very thick groups, part of the superficial fat layer must be removed to reach any of the target thicknesses for the three flaps. Conclusions: The present study demonstrated the frequent need for superficial fat layer manipulation when obtaining a thin perforator flap. To cope with various combinations of donor-site fattiness and different required thicknesses effectively, an appropriate thinning method should have increased adaptability, including the ability to control superficial fat layer thickness.