Extrinsic Vascular Pathway Preservation Improves Survival in a Rat Three-Territory Flap Model Based on the Deep Circumflex Iliac Artery

Abstract

arious extended flaps have been widely used in clinical settings; however, unexpected necrosis remains common in the distal portion of the flap. 1,2 In 2013, a review of 693 articles on 17,096 deep inferior epigastric perforator flaps showed that the flap necrosis rate was 0% to 11%. 3 Similarly, a 2015 retrospective study of 45 patients who underwent extended thoracodorsal artery perforator flap surgery for breast reconstruction reported that the distal flap necrosis rate was 13%. 4 A retrospective study on 150 patients who underwent extended circumflex scapular flap for neck burn reconstruction from 1986 to 2015 reported a distal flap necrosis rate of 15%. 5 Various therapeutic modalities have been used to augment tissue perfusion and improve flap Background: Extended flaps are commonly applied for large defects. However, a postoperative flap necrosis incidence of 11% to 44% remains a major complication. Previous clinical studies have shown that maintaining the extrinsic vascular pathway (EVP) can increase the survival area of extended flaps. The authors hypothesized that preserving the EVP would improve flap survival by reducing blood resistance within the vascular territory. Methods: Twenty-four adult male Sprague-Dawley rats were used. Tissue samples were obtained from eight untreated rats as a baseline control. Three-territory flaps were elevated in the remaining 16 rats. The EVP was preserved or ligated. Flap perfusion was assessed immediately using indocyanine green angiography. Rats were euthanized on day 7. The flap survival area was measured using Adobe Photoshop. Hematoxylin and eosin staining, CD31 immunostaining, and Western blot analysis of vascular endothelial growth factor protein expression were used to quantitatively assess vasodilation and angiogenesis in choke zones. Results: Indocyanine green angiography revealed that blood could flow through the preserved EVP and perfuse the third vascular territory of the flap. EVP preservation significantly increased flap survival area (86.3%, 19.3% difference; P < 0.001), promoted vasodilation (5.0/choke zone, 3.0/choke zone difference; P = 0.013) and angiogenesis (29.3/mm 2 , 14.3/mm 2 difference; P = 0.002), and increased vascular endothelial growth factor expression (0.6, 0.2 difference; P = 0.067) in the second choke zone. Conclusions: EVP preservation improves flap survival in this rat three-territory flap model. Further investigation in large-animal models is required for clinical translation.