Comparison of Effective Use of Implanted Vascular Pedicles for Skin Flap Prefabrication: An Experimental Study

Prefabrication-a Vascularized Skin Flap Using an Arteriovenous LoopPrefabricated Flap With Arteriovenous Loop: An Experimental Study in Minipigs

BACKGROUND

Arteriovenous loops have a high potency to induce angiogenesis and are promising to solve the problem of scarce implanted pedicle sources and insufficient neovascularization in flap prefabrication. But there is a lack of large animal experiments to support their clinical application. Therefore, we aimed to explore the feasibility of prefabricating large flaps based on arteriovenous loops in pigs.

METHODS

Five minipigs were used. In the experimental group, a 10-cm-long ear vein graft was microanastomosed with the saphenous artery and vein to form an arteriovenous loop and implanted under the medial thigh flap. A month later, a 10×10 cm prefabricated flap pedicled with the arteriovenous loop was elevated and sutured in situ. In the control group, a 10×10 cm flap with no vascular pedicle was elevated completely and sutured in situ in the same position. The patency of the arteriovenous loop was evaluated by angiography 30 days after implantation, and the viability of flaps was assessed by macroscopic analysis 10 days after elevation. Three animals received arteriovenous loop flaps unilaterally and no-pedicle flaps unilaterally. Two animals received arteriovenous loop flaps bilaterally.

RESULTS

In the experimental group, no thrombi were exhibited in any arteriovenous loop. All 7 prefabricated flaps survived uneventfully. In the control group, 3 flaps were completely necrotic.

CONCLUSION

The arteriovenous loops with long interpositional venous grafts can be used as vascular pedicles to prefabricated large area and well-vascularized flaps. This approach can greatly expand the application of flap prefabrication.

Augmentation of Perforator Flap Blood Supply with Vascular Supercharge or Flap Prefabrication: Evaluation in a Rat Model

BACKGROUND

Vascular supercharge and flap prefabrication are two surgical maneuvers to improve flap blood supply. Although these techniques have been studied intensively, few studies have focused on the differences between supercharge and prefabricated flaps regarding their flap survival areas, vasculatures, and hemodynamics.

METHODS

In this study, 21 male Sprague-Dawley rats were divided into three groups as follows: group A, single perforator flap; group B, supercharge flap; and group C, prefabricated flap. Flap survival was measured 1 week after flap elevation. Indocyanine green angiography was applied to visualize flap vascularity and to analyze flap hemodynamics. Von Willebrand factor immunohistochemical staining was applied to assess the number of microvessels in the choke zone of the abdominal wall.

RESULTS

The flap survival areas were expanded significantly in the arteriovenous supercharge group and the vascular bundle prefabricated group compared with that in the single-perforator group (81.34 ± 8.12 percent and 75.51 ± 8.08 percent versus 46.27 ± 10.01 percent, respectively; p < 0.05). Hemodynamic analysis suggested that although a significant increase in arterial infusion could be achieved with flap prefabrication, the venous effusion of the prefabricated flap was the worst among the three groups, indicating greater susceptibility to compromised venous return. Active neovascularization was confirmed by an increased number of microvessels in group C. Specifically, the dilatation of choke vessels and the newly formed vessels of the prefabricated pedicle could be appreciated by indocyanine green angiographic mapping.

CONCLUSIONS

Both vascular supercharge and flap prefabrication can augment the blood supply of the perforator flap but by means of different mechanisms. Because a supercharge flap is less susceptible to venous compromise, it is suggested to first consider the use of vascular supercharging when feasible.

Prefabricated bone flap: an experimental study comparing deep-frozen and lyophilized-demineralized allogenic bones and tissue expression of transforming growth factor β

BACKGROUND

Extensive bone defects are still a challenge for reconstructive surgery. Allogenic bones can be an alternative with no donor area morbidity and unlimited amount of tissue. Better results can be achieved after allogenic bone preparation and adding a vascular supply, which can be done along with flap prefabrication. The purpose of this study was to evaluate demineralized/lyophilized and deep-frozen allogenic bones used for flap prefabrication and the tissue expression of transforming growth factor β (TGF-β) in these bone fragments.

METHODS

Fifty-six Wistar rat bone diaphyses were prepared and distributed in 4 groups: demineralized/lyophilized (experimental group 1 and control group 2) and deep freezing (experimental group 3 and control group 4). Two bone segments (one of each group) were implanted in rats to prefabricate flaps using superficial epigastric vessels (experimental groups) or only transferred as grafts (control groups). These fragments remained in their respective inguinal regions until the death that occurred at 2, 4, and 6 weeks after the operation. Semiquantitative histologic (tetracycline marking, cortical resorption, number of giant cells, and vascularization) and histomorphometrical quantitative (osteoid thickness, cortical thickness, and fibrosis thickness) analyses were performed. Transforming growth factor β immunohistochemistry staining was also performed.

RESULTS

Group 1 fragments presented an osteoid matrix on their external surface in all periods. Cartilage formation and mineralization areas were also noticed. These findings were not observed in group 3 fragments. Group 1 had more mineralization and double tetracycline marks, which were almost not seen in group 3. Cortical resorption and the number of giant cells were greater in group 3 in all periods. Vascularization and fibrosis thickness were similar in both experimental groups. Group 1 had more intense TGF-β staining within 2 weeks of study. Nevertheless, from 4 weeks onward, group 3 presented statistically significant stronger staining.

CONCLUSIONS

Although there are some differences between the preparation methods of allogenic bone, it is possible to prefabricate flaps with demineralized/lyophilized and deep-frozen bones.