A method for prevention of arterialized venous flap necrosis

Conditioning of microvascular venous flaps in rats

Venous-only perfusion flaps have not been used widely because of the associated high failure rate. Tissue conditioning offers a broad scope of techniques that can be applied pre-, peri-, or postoperatively to promote the adaptation of the affected tissue to any subsequent stress. This study aimed to assess the survival rates associated with a pure venous perfusion flap and investigate whether the timing of the vascular conditioning can affect free flap survival. Forty-four rats were included in the experiment. Group I underwent veno-arterial anastomoses with epigastric graft with pure venous perfusion without tissue conditioning. Groups II and III were pretreated for 7 or 14 days with ischemic conditioning. These groups were compared with a control group (group IV) of conventionally perfused flaps. After the initial surgery, all flaps were assessed clinically, photometrically, and by indocyanine green videoangiography. The flap success rates were 0% in group I, 49.97% ± 24.34% in group II, and 64.95% ± 20.36% in group III. The control group showed an overall survival of 89.3% ± 6.51%. With suitable conditioning, pure venous blood supply can provide adequate perfusion in the rat epigastric flap model. The timing of vascular conditioning appears to be critical for flap survival.

Unconventional Perfusion Flaps in the Experimental Setting: A Systematic Review and Meta-Analysis

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Background:

Unconventional perfusion flaps offer multiple potential advantages compared with traditional flaps. Although there are numerous experimental articles on unconventional perfusion flaps, the multiple animal species involved, the myriad vascular constructions used, and the frequently conflicting data reported make synthesis of this information challenging. The main aim of this study was to perform a systematic review and meta-analysis of the literature on the experimental use of unconventional perfusion flaps, to identify the best experimental models proposed and to estimate their global survival rate.

Methods:

The authors performed a systematic review and meta-analysis of all articles written in English, French, Italian, Spanish, and Portuguese on the experimental use of unconventional perfusion flaps and indexed to PubMed from 1981 until February 1, 2017.

Results:

A total of 68 studies were found, corresponding to 86 optimized experimental models and 1073 unconventional perfusion flaps. The overall unconventional perfusion flap survival rate was 90.8 percent (95 percent CI, 86.9 to 93.6 percent; p < 0.001). The estimated proportion of experimental unconventional perfusion flaps presenting complete survival or nearly complete survival was 74.4 percent (95 percent CI, 62.1 to 83.7 percent; p < 0.001). The most commonly reported animal species in the literature were the rabbit (57.1 percent), the rat (26.4 percent), and the dog (14.3 percent). No significant differences were found in survival rates among these species, or among the diverse vascular patterns used.

Conclusion:

These data do not differ significantly from those reported regarding the use of unconventional perfusion flaps in human medicine, suggesting that rabbit, rat, and canine experimental unconventional perfusion flap models may adequately mimic the clinical application of unconventional perfusion flaps.

Application of Concatenated Arterialized Venous Flaps in Finger Reconstruction

Venous flaps from the distal volar forearm are said to be suitable flaps for finger reconstruction. The pliability of the forearm venous flap makes it easy to follow the curvature of the finger contour. The thickness of the flap makes it appropriate as a flap for finger resurfacing. Following the venous network at the palmar forearm, diverse patterns of the venous flaps can be designed. This article describes the use of a 2-concatenated paddle, flow-through arterialized venous flap design for simultaneous resurfacing of 2 separate defects on a single digit. A technique that can be used to reduce postoperative venous congestion will be highlighted in this article.

Feasibility of type III venous flap in coverage of hand defects following trauma and burns

INTRODUCTION

venous flaps are alternative reconstructive option for coverage of defects. They are nourished by venous blood flow or by arterial blood flowing through the venous network. This study was conducted to assess the feasibility of venous flap in coverage of extremities defects following trauma and burns.

MATERIAL AND METHODS

Over a period of one year, 15 arterialized venous flaps were applied to skin defects of the hand. Postoperatively flap were monitored for survival and patients followed up for three months.

RESULTS

In patients with flap area ranging from 6 to 10 cm², all the 6 patients have complete survival (100%). In 11-15 cm² group 3 out of 5 patients have complete survival (60%) and 2 have partial survival (40%). In 16-20 cm² group 1 out of 3 have complete survival (33.3%) and 2 have partial survival (66.6%). In 21-25 cm² group there was only 1 patient who had complete necrosis. This study suggests that small venous flaps have better survival rate as compared to large flaps. Variable degree of congestion was present in all the patients in first post operative week which gradually disappeared in second week.

CONCLUSION

The venous flap is good alternate for reconstruction of the small defects of hand and digits. It is easy to designed and harvest. It is thin and pliable, without need to sacrifice a major artery at the donor site and with no limitation on the donor site.

Syndactylizing arterialized venous flaps for multiple finger injuries

Multiple soft tissue finger defects in different shapes and locations are usually difficult to manage. Such defects commonly involve tendons and bones. Palmar soft tissue defects may also lead to vascular compromise. In this retrospective report, we report the results of seven patients with multiple soft tissue finger defects that were covered by syndactylizing arterialized venous flaps. Six of the patients suffered hot-pressing machine and crushing injuries, one patient had a rolling belt injury. All patients presented with soft tissue defects on palmar or dorsal sides involving at least two digits. The palmar forearm was donor site for all patients. At least one afferent artery and two efferent veins were selected for the anastomosis. Lengths of afferent and efferent veins were long enough to perform healthy anastomosis outside the injury zone. The afferent vessels were anastamosed to the digital arteries with the largest possible diameter or to the common digital arteries to maximize flow. The efferent veins were anastamosed to dorsal veins. Separations of the digits were performed after three weeks by longitudinal incisions. The mean follow-up period was 12 months. None of our patients suffered a flap loss. Syndactylizing arterialized venous flaps may be used for composite or single tissue reconstruction for multiple finger defects with satisfactory cosmetic and functional outcomes.

Revascularization of Arterialized Venous Flaps through a Total Retrograde Reverse Blood Flow: Randomized Experimental Trial of Viability

Background:

Arterialized venous flaps (AVFs) have been used for reconstruction of soft tissue defects throughout the body. Several different revascularization models have been performed, but venous drainage through the arterial system has not been studied. In our total retrograde reverse blood flow (TRRBF) perfusion model, the arterial blood flow enters through the venous system and venous drainage exits through the arterial system.

Methods:

We developed a novel experimental model in rabbit ears to evaluate the capacity of TRRBF perfusion pattern to allow AVF viability. The ears were assigned to 3 groups: group 1, total devascularization without revascularization (n = 3); group 2, TRRBF (n = 12); and group 3, conventional AVF (n = 12). The ears were observed during a 30-day follow-up period, and clinical serial assessment of edema, cyanosis, and necrosis was performed. Tissue oxygenation was determined at the beginning and end of the follow-up. Histological analysis was performed.

Results:

Necrosis was found in 3/3 (100%) ears in group 1, 3/12 (25%) in group 2, and 0/12 (0%) in group 3 (95% CI, 0.505–0.994; P = 0.0001). In group 2, edema was higher (5/12, 41.66%) than in group 3 (0/12, 0%) (95% CI, 0.0135–0.65; P = 0.041). Cyanosis and venous congestion was of greater intensity and duration in group 2 than in group 3 (10.33 ± 4.51 vs 4.5 ± 2.06 d).

Conclusions:

Although evolution is torpid and prolonged in ears with TRRBF, 9/12 (75%) survived, suggesting that TRRBF can be used as a rescue method.

Clinical applications of venous flaps in the reconstruction of hands and fingers

In recent years, the venous flap has been highly regarded in microsurgical and reconstructive surgeries, especially in the reconstruction of hand and digit injuries. It is easily designed and harvested with good quality. It is thin and pliable, without the need of sacrificing a major artery at the donor site, and has no limitation on the donor site. It can be transferred not only as a pure skin flap, but also as a composite flap including tendons and nerves as well as vein grafts. All these advantages make it an optimal candidate for hand and digit reconstruction when conventional flaps are limited or unavailable. In this article, we review its classifications and the selection of donor sites, update its clinical applications, and summarize its indications for all types of venous flaps in hand and digit reconstruction.

Optimizing the arterialized venous flap

BACKGROUND

Outcome of arterialized venous flaps is quite varied. The authors' initial experiments showed that a good vascular bed contributes significantly to survival of the flap. In continuation of these experiments, this study aimed to understand the influence of architectural variations on flap outcome.

METHODS

Fasciocutaneous flaps were designed on the ears of New Zealand rabbits, and the animals were randomized into four groups having flaps that used the larger anterior marginal vein (1.3 mm) or the smaller central vein (0.6 mm) for arterial inflow, with or without isolation of the flap from its bed with a silicone sheet. Flaps were observed for area of flap survival and vasculature was assessed by microangiography.

RESULTS

Using the smaller central vein for arterial inflow (n = 15), arterialized venous flaps had an excellent outcome, with good flap survival in 100 percent of the animals (survival of >85 percent of flap area), and a mean flap survival area of 99.4 +/- 1.6 percent. Even when neovascularization was prevented by isolation of the flaps (n = 14), 92 percent of central vein flaps showed good survival, with a mean flap survival area of 93.3 +/- 7.3 percent, which was significantly better than that of anterior marginal vein flaps (n = 22), which showed good flap survival in only 27 percent of the animals (mean flap survival area, 76.4 +/- 12.1 percent).

CONCLUSIONS

Survival of arterialized venous flaps is optimized by using smaller-caliber veins for inflow and reserving larger-caliber veins for outflow. This regulates inflow and avoids high blood pressure, and arterialized venous flaps behave as physiologic flaps do, by not relying on neovascularization for survival.

Pre-arterialisation of an arterialised venous flap: clinical cases

Many factors affecting the survival of arterialised venous flaps have been elucidated, both experimentally and clinically. The survival of large arterialised venous flaps has been reported, with varying results. Large arterialised venous flaps with preformed arteriovenous fistulae at the donor sites have been successfully performed in experimental animals. We report the results of repair of skin defects in the extremities with arterialised venous flaps in eight patients. The arteriovenous shunts were created at the donor sites at least 2 weeks before the flaps were harvested. The flap sizes ranged between 4 x 4cm and 9 x 10 cm. Flap survival was between 93% and 100% of the surface area, as shown by digitalised scanning. In addition to the known advantages of venous flaps, such as less bulk, preservation of the main arteries and ease of harvesting, pre-arterialisation makes designing the flap easier due to the noticeable superficial veins. Pre-arterialisation, when used in carefully selected cases, did not prolong the hospital course of the patients.