Introduction: Unconventional perfusion flaps (UPFs) are reconstructive options characterized by being perfused exclusively by veins. In UPFs at least one of the afferent veins of the flap is anastomosed to a feeding vessel. Usually, this feeding vessel is an artery, and the UPF is called an arterialized venous flap (AVF). If the feeding vessel is a vein, the UPF is called a venous flap (VF). The efflux of blood is ensured in most cases by the continuity of one or more of the UPF’s veins with neighboring veins. Although UPFs present several potential advantages relatively to conventional perfusion flaps, they have rarely been mentioned in the clinical literature, due to reported high necrosis rates, particularly in the presence of infection, and due to a poor understanding of their underlying physiologic mechanisms. Methods: We performed systematic reviews and meta-analyses on the clinical and experimental used of UPFs. Followingly, we studied in detail the vascular anatomy of the ventrolateral aspect of the rat’s abdomen. Using this knowledge, we improved a model of a conventional flap (CF) harvested from the epigastric region of the fat. Subsequently, we developed an optimized a model of AVF in the abdomen of the rat. We, then, evaluated the effect of transfecting the optimized model with human beta defensin genes (BD-2 and BD-3) to increase flap survival in the presence of Pseudomonas aeruginosa infection and of a foreign body. Moreover, we compared the efficacy of arterialized neurovenous flaps (ANVFs) with other nerve conduits to reconstruct a 10-mm-long median nerve gap in an ischemic environment in a rat model. Followingly, we performed cadaveric studies to assess pertinent aspects of the anatomy and histology of anatomical regions commonly used to harvest UPFs. Finally, we used some of the information gathered to treat a teenager with an ulnar artery and nerve composite defect at the forearm level. Results: We estimated an overall survival rate of UPFs of 89.5% in the clinical context and of 90.8% in the experimetal setting. Clinically, there was a positive correlation between the rate of postoperative infection and the need of a new flap (Pearson coefficient 0.405; p=0.001). Blood supply to the abdominal integument of the rat was more dependent on axial vessels, comparatively to humans. Venous valves were clearly observed in this region. The free epigastric CF and the homologous optimized AVF presented survival rates of nearly 100%, and 76.86 ± 13.67%, respectively. Transfecting the AVF model with BD-2 and BD-3 increased flap survival, and decreased biofilm formation. ANVFs produced more complete and faster recovery than nerve grafts, for most of the parameters used to assess nerve regeneration. Anatomical and histological studies revealed that large subcutaneous veins were surrounded by doublings of the superficial fascia. Moreover, veins were placed at different depths, with the largest ones being deeply placed and the smallest more superficially placed. Finally, it was noted that superficial cutaneous nerves, routinely used as autologous nerve grafts, were closer to sizeable superficial veins than to arteries and respective comitante veins of significant caliber. UPFs could be tailored to specific defects by including either skin, subcutaneous tissue, tendons, nerves, muscle fascia and/or bone in variable combinations. The used of an ANVF in a teenager allowed the successful reconstruction of both the arterial and nerve defects. Conclusion: Although many question remain to be answered relatively to UPFs physiology, optimization, and indications, there seems to be enough evidence to support their use in the realm of integumentary and nerve reconstruction.
|Publication status||Published - 2018|