[A simple classification system for all skin flaps]

The arterial quality of a skin flap largely depends on the vascular connections to the surrounding tissue. We can differentiate three typical vascular structures underneath the body's surface: large supporting vessels running parallel to the body's surface, transporting vessels (perforators) with a segmental vascularization and leading to horizontal (reticular) nets of distribution. These structures can be found at the subcutaneous plane, all septofascial planes, and the vascular pattern of the muscles. All three structures can provide sufficient blood to partially separated and mobilized skin areas (flaps). Each skin flap can be classified by the type of enclosed tissue (subcutis, fascia, muscle) and the type of blood supply (axial, segmental, reticular). The quality of blood flow within a skin flap is not disturbed by separation and mobilization if the vascular continuity to the supporting horizontal vessels stays intact. This is the case in socalled axial pattern flaps (the supporting vessel is elevated with the flap) and in segmental pattern flaps (here continuity stays intact with the supporting vessel in deeper layers). In contrast, reticular pattern flaps are characterized by a decreased quality of blood flow (sensible to pressure and tension) because they lack a direct connection to the supporting vessels. Most skin flaps show a complex organization of their vascular structure: they either have a parallel support by several structures (improved quality of blood circulation) or they contain several structures in sequence within their longitudinal axis (decreased quality of blood circulation). This structural analysis does not take into account the hemodynamic conditions and their influence on the quality of blood circulation which are predisposed by the width and the amount of vessels.