Chapter 7 The size of the central zone is variable and may be affected by several (modifiable) factors (Table 7.3). These are the perforator location and size and number of true vascular interconnections between adjacent angiosomes within the flap. This central part is probably not affected by a short ischemic period and because there is no delay in perfusion in this region and ischemic period is maintained within the tissue tolerance and recovers quickly after reperfusion. This central part is hypothesized to have an axial pattern blood supply and is probably not affected by flap complications. The region adjacent to the central zone is the zone that is affected by the relatively short ischemic period and delayed perfusion, as shown in our previous studies.30,33,34 This paracentral region probably has a more random pattern blood supply compared with the central zone and variable perfusion, depending on the number and size of choke vessels. Even more distal is a zone that has inadequate perfusion on the flap pedicle and can be expected not to be viable, certainly not when exposed to any additional trauma such as IR injury, and is thus destined to undergo necrosis. Table 7.3 Possible influencing factors on zones A, B, and C. Intrinsic vascular anatomy Dominance of various perforators Vascular interconnections between adjacent angiosomes Dominance of superficial venous system Surgical expertise Decision making: number and size of perforator(s) Atraumatic surgical technique Ischemia period Additional venous drainage Patient factors Flap size obesity ASA* classification *ASA = American Society of Anesthesiologists The choice of perforator can be guided by preoperative CT angiogram; this felicitates the decision‐making process, and dominance of the superficial system can be judged preoperatively.8,35 However, a final judgment whether the blood flowing through the perforator will be adequate to sustain the flap has to be made clinically.20 Despite tremendous progress in flap design and anatomy knowledge, preoperative mapping, and venous drainage augmentation procedures, a more biochemical/ pharmacologic intervention may be an important next step in the further refinement of free tissue transfers, such as the DIEP flap, although much work still lies ahead because possible successful interventions reducing or eliminating PFL and/or FN also have to be evaluated for clinical safety in patients and in oncological follow‐up. 108
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