Summary & discussion and future perspectives the duration of IR injury. PFL always occurred in a distal to central pattern, and it could occur in all zones. In contrary to other experimental models, the ischemia period in our study was relatively short. Usually, an ischemia period of 6–8 hours is used in IR injury studies.18‐20 Our study is the first to our knowledge that even a short ischemic period using an experimental model could induce IR‐related PFL. This is also observed in clinical studies where relatively short but incremental ischemic period led to an increase of flap‐related complications in DIEP flaps.21,22 Considering the pattern of PFL, a more physiological zone classification in flaps such as TRAM and DIEP flaps is proposed. The previous classification introduced by Hartrampf et al.23 and later modified by Holm et al.,24 dividing the flap in four perfusion zones, is considered obsolete and should not be used. A more physiologic perfusion classification is introduced by dividing the flap into three zones: a central zone, a zone that is vulnerable to IR injury, and a zone of distal ischemia. The size of the central zone is variable and may be affected by several (modifiable) factors. 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 (chapters 4–6). 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. 119
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