Retrograde arterialized venous flap: an experimental study

Reverse Flow Shunt Restricted Free Venous Flap for a Ring Avulsion Injury

Arterialized venous flaps can be an excellent option for reconstruction of digital defects. Previously, they remained unpopular owing to the high rate of venous congestion. Different techniques of restriction of the arteriovenous shunting have been described to mitigate this problem. In this article, the authors discuss a unique case whereby a reverse flow shunt restricted venous flap was used in an Urbaniak type III ring avulsion.

Retrograde Free Venous Flaps for Extremity Reconstruction: A Roadmap

Background and Objectives: Retrograde free venous flaps represent a separate entity among free venous flaps: their physiology is still unclear, but they provide an immediate visible refill after reconnection, with a similar behaviour to conventional flaps. Therefore, the dimensions and the indications of these flaps can be extended beyond what was previously believed, and they can be easily customized, including with respect to tendons and nerves. Nevertheless, they are still debated and regarded as unsafe. Materials and Methods: From 2012 to 2019, we performed 31 retrograde free venous flaps on 31 patients to reconstruct hands, digits, and in one case the heel. All the flaps were arterialized in a retrograde manner; the donor site was the forearm in 28 cases, the foot in 2 cases, and the calf in 1 case. We recorded the size, vein architecture, donor site, donor artery, donor morbidity, function for composite and non-composite flaps, immediate complications, late complications, survival rate, and the number of revisions. We recorded the hand function when appropriate. A total of 10 flaps were also intraoperatively studied with indocyanine green to monitor their hemodynamical behaviour. Results: All the patients were followed for an average of 8 months (6−15). The flap dimensions ranged from 6 cm2 to 136 cm2. All the flaps, except two that had complete necrosis, survived. Two flaps had partial necrosis. There was no correlation between necrosis and the size of the flap, with one case of necrosis and one of partial necrosis in the small flaps (<10 cm2). None of the cases with partial necrosis needed a new flap. Two flaps developed a late arterio-venous shunt that was ligated. Conclusions: The retrograde free venous flaps proved to be a useful tool for complex reconstructions of the hand and extremities. They can provide a large island of pliable skin and composite tissue with tendons and nerves, but surgeons must be aware of some caveats.

The Effect on Venous Congestion of Diverting Arterial Flow in the Arterialized Venous Flap

An arterialized venous flap is a cutaneous flap based solely on subcutaneous veins. The flap is perfused by nonphysiologic flow of blood from the vein into the peripheral tissue. This nonphysiologic perfusion limits the indications for an arterialized venous flap, and its postoperative complications make it an unpopular choice for reconstruction. When venous flaps are designed following the direction of venous valves (antegrade) in a flow-through fashion, the blood may bypass the peripheral tissue without perfusing the flap. A higher pressure within the efferent end of the vein impedes venous return from the peripheral tissue into this draining vein. Thus, venous congestion of the arterialized venous flap becomes inevitable. We describe our approach to designing an arterialized venous flap in which direct arteriovenous shunting is largely eliminated, thereby transmitting a higher pressure in the periphery of the flap while maintaining a physiologic venous pressure in the efferent vein. This restriction of shunting can be accomplished in a number of ways, depending on the venous pattern within the flap.

The use of indocyanine green angiography in arterialized-venous free flaps: case report and insight into flap vascular physiology

Arterialized venous flaps (AVFs) are an innovative option in hand reconstruction. Their exact vascular physiology and survival mechanisms remain unclear. We report on two hand reconstruction cases with AVFs. Indocyanine green laser angiography was used to assess vascular perfusion of the flaps. A notable change in flap perfusion was seen by 48 h post-operatively with normalization of shunting and progression to a diffuse perfusion pattern resembling traditional flaps. Flap survival was attributed to reversed shunting at the microvascular level occurring within the first 48 h post-operatively.

Using Free Arterialized Venous Flaps for Reconstructing Hand Defects

Hand and digit soft tissue defects are quite common and frequently require specialized reconstruction. When local flaps cannot be used to reconstruct a soft tissue defect, free flaps must be utilized. To overcome tissue volume and discrepancies in vessel diameter, arterialized venous free flaps from the forearm may provide an acceptable alternative. When using arterialized venous free flaps, surgeons should implement shunt restriction procedures to enhance flap viability.

Role of Arterial Perfusion in Early Survival of Arterialized Venous Flaps: A Mechanism Study and Clinical Application

BACKGROUND

The arterialized venous flap (AVF) is appropriate as a flap for hand and foot resurfacing meet the aesthetic demands in the same time. However, the inconsistency of survival rate limited its popularization in clinical settings. The purpose of this study was to investigate the role played by the caliber and location of the artery.

METHODS

Arterialized venous flaps were designed on the abdomen of New Zealand rabbits, and the animals were randomized into 3 groups and 2 groups in experiment 1 and 2, respectively. In experiment 1, the artery flow was restricted with vascular staplers of different calibers. In experiment 2, the artery was anastomosed with the afferent vein in the center or at the margin of the flap. Blood perfusion state, water content, epidermal metabolite levels, and flap survival status were observed in both experiments. Furthermore, outcomes of 12 patients received AVF to resurface soft tissue defects in the digits, hands, and feet between January 2016 and February 2018 were analyzed.

RESULTS

In experiment 1, compared with the control group, groups with restricted artery showed poor results regarding blood perfusion state, water content, epidermal metabolite levels, and flap survival status. In experiment 2, group with the afferent vein in the center of the flap showed better results mentioned previously. All the flaps survived uneventfully in this study. Two flaps partially failed (20% of the flap area) because of insufficient perfusion. Generally, larger caliber and center-located vein helped the survival of AVF.

CONCLUSIONS

Experimental findings suggested that increased arterial perfusion and center-located vein are beneficial for the survival of AVF. Clinical series proved the findings previously. The problem of inconsistency of AVF can be partially solved by increasing arterial perfusion and dissecting afferent vein into the center of flap, and still, further studies are needed to shed light on the mechanism behind.

[Repair of soft tissue defect of fingers with modified arterialized venous flap]

Objective

To summarize the effectiveness of modified arterialized venous flaps in repairing soft tissue defect of fingers.

Methods

Between January 2017 and April 2018, 16 patients with soft defects of fingers were treated. There were 12 males and 4 females, with an average age of 41 years (range, 24-74 years). One case was resulted from resection of cicatricial contracture and 15 cases was caused by mechanical strangulation. The defects located at thumb in 3 cases, index finger in 5 cases, middle finger in 4 cases, ring finger in 2 cases, and little finger in 2 cases; and at the palmar aspect in 4 cases, and dorsal aspect in 12 cases. The size of defect ranged from 3 cm×2 cm to 10 cm×3 cm. All flaps were harvested from the palmar aspect of the ipsilateral forearm. The distal ports of the two veins were ligation. Partial fat was eliminated and the all connecting minute branches between the two veins were ligation under microscope in order to achieve the thorough shunt restriction. Then the flaps were positioned over the recipient site without inversion. The size of flap ranged from 3.5 cm×2.5 cm to 10.5 cm×3.5 cm. All donor sites were directly sutured except that 1 case was recovered with free skin graft.

Results

All flaps survived entirely except that 1 case happened vein crisis. Three flaps demonstrated mild-to-moderate venous congestion without any treatment and the swelling of flaps gradually subsided after 1 week. Skin grafting at donor site survived and all incisions healed by first intension. Thirteen patients were followed up 8-16 months (mean, 11 months). The textures and appearances of the flaps were satisfactory. At last follow-up, the mean size of the Semmes-Weinstein (SW) monofilament test of the flaps was 4.01 g (range, 2.83-4.56 g); the mean static two-point discrimination of the flaps was 12 mm (range, 6-20 mm).

Conclusion

Modified arterialized venous flaps with thoroughly restriction of arteriovenous shunting can offer decreased congestion of venous flaps and improve survival rate. Better effectiveness can be achieved by using this flap to repair soft tissue defect of finger.

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.

Reverse Flow Shunt Restricted Arterialized Venous Free Flap

Several technical modifications have been described to avoid complications of venous flaps. The authors describe a technical variation of the venous flap to reduce the risk of venous congestion and the likelihood of shunting, thus increasing venous flap reliability.

Venous flaps for coverage of traumatic soft tissue defects of the hand: a systematic review

A PRISMA-guided systematic review was performed of all published cases that detail the use of venous flaps for soft tissue reconstruction of the hand following trauma. Outcome measures examined included flap survival rates, venous congestion, and return to theatre. Database searches were performed on Medline, Embase, AHMED, CINAHL. A total of 381 articles were identified. Data were extracted from 45 articles that met inclusion criteria. A total of 756 flaps were described and their data analysed. A total of 75% of flaps were arterialized and 25% were pure venous flaps. There was no difference in survival rate for arterialized or pure venous flaps. Unplanned return to theatre occurred in 5.3% due to flap compromise or necrosis. Early venous congestion was present in 60% of cases. Total early failure requiring re-operation occurred in 19 flaps (2.5%) of cases. Venous flaps offer a versatile and well-tolerated reconstructive option. Early venous congestion is common, but can be managed non-operatively.

LEVEL OF EVIDENCE

II.

The position of 'shunt restriction' along an arterialized vein affects venous congestion and flap perfusion of an arterialized venous flap

Restriction of arteriovenous (AV) shunting has been shown to enhance peripheral perfusion and also reduce venous congestion of an arterialized venous flap. Thus, this study is designed to investigate the effect of 'shunt-restriction' location on venous congestion and flap perfusion in a 'shunt-restricted' arterialized venous flap (AVF).

METHODS

Abdominal flaps based on the thoracoepigastric vessels of Sprague-Dawley rats were raised. The inferior epigastric vein was repaired to the femoral artery in order to create an AVF. The superior epigastric vein was preserved for drainage. Microcirculation and laser Doppler flowmetry results were compared between AVFs with 'shunt restriction' at a proximal third (SR-proximal) distance and 'shunt restriction' at a distal third (SR-distal) distance.

RESULTS

Bidirectional sluggish flow was detected at the proximal part of venous flaps in both groups. Unidirectional normal flow was observed in more capillaries of the distal flaps in the SR-proximal group. In the middle of the flaps, blood flow was sluggish and intermittent in the veins and was absent in most capillaries of the SR-distal group. The flow was prompt and unidirectional in more capillaries of the SR-proximal group. Using laser Doppler flowmetry, the average perfusion of the whole SR-proximal flaps was found to be higher than that of SR-distal flaps (p = 0.017). The average flux at the middle and distal portions of the SR-proximal group was significantly higher than those of the SR-distal group (p = 0.049).

CONCLUSION

'Shunt restriction' at the proximal third of the AV shunt resulted in enhanced perfusion and reduced venous congestion in an AVF.

Treatment of unfavourable results of flexor tendon surgery: Skin deficiencies

We recently reported a small study at the Federation of European Societies for Surgery of the hand, which was entitled ‘What is secondary flexor tendon surgery’? This study concluded that ‘secondary flexor tendon surgery’ was a generic name encompassing a multitude of pathologies. Between 10% and 15% of cases exhibited pathology of the skin and subcutaneous fat and required flap reconstruction of these tissues. Skin replacement may be used prophylactically at primary surgery or become necessary at secondary surgery after release of scar contractures, to achieve cover of vital structures. The long-term problem of skin deficiency relating to flexor tendon function is one of loss of extension from longitudinal scar shortening of the integument, even if the flexor tendons are primarily concerned with bending the digits, not straightening them. This loss of extension can only be tolerated in a hand to a certain degree without significant loss of function. This paper is largely an analysis of the flaps available and suitable for different degrees of skin deficiency and at different places along the course of the flexor system. It attempts to dispel the idea that ‘any flap will do’ provided the flexors are adequately covered.

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.

Retrograde arterialized free venous flaps for the reconstruction of the hand: review of 14 cases

PURPOSE

Although the literature is encouraging with regard to the survival rate of arterialized free venous flaps, previously reported difficulty in healing owing to early venous congestion and subsequent epidermolysis continues to prevent their widespread application. We report 14 arterialized free venous flaps for primary reconstruction of the hand, with inflow in the arterialized vein running against the valves.

METHODS

Between February 2010 and May 2012, we performed 14 arterialized free venous flaps, each of which included at least 2 veins running in parallel. The arterialized vein was anastomosed in a retrograde manner, with the inflow running against the valves. All flaps were customized with regard to dimension, shape, quality of skin, pedicle length, vessel size, inclusion of additional anatomical structures, and donor site. The flaps were used to cover small, medium, and large defects; 2 flaps were larger than 100 cm(2). Three flaps were injected with indocyanine green on the table after harvesting, to visualize the vascular tree of the flap. These 3 flaps were then monitored with systemic indocyanine green injection and an infrared camera for 3 days postoperatively.

RESULTS

All but 1 flap survived. Venous congestion and epidermolysis were observed in 2 small flaps. The flaps injected with indocyanine green displayed a ramified vascular tree with no arteriovenous flow-through phenomenon.

CONCLUSIONS

Arterialized free venous flaps with retrograde arterial flow offer thin and pliable coverage that fits easily around the contours of the hand. They are easy to harvest, with little donor site morbidity. Tendons or nerves can be incorporated for reconstruction of composite defects.

CLINICAL RELEVANCE

Our series suggests the possibility of routine use of a free venous flap with retrograde arterial flow for reconstruction of the hand.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

The effect of hemodynamic remodeling on the survival of arterialized venous flaps

Objective

To evaluate the effect of hemodynamic remodeling on the survival status of the arterialized venous flaps (AVFs) and investigate the mechanism of this procedure.

Materials and Methods

Two 7 x 9 cm skin flaps in each rabbit (n=36) were designed symmetrically in the abdomen. The thoracoepigastric pedicle and one femoral artery were used as vascular sources. Four groups were included: Composite skin grafts group and arterial perfusion group were designed in one rabbit; AVF group and hemodynamic remodeling group by ligation of the thoracoepigastric vein in the middle were outlined in another rabbit. Flap viability, status of vascular perfusion and microvasculature, levels of epidermal metabolite and water content in each group were assessed.

Results

Highly congested veins and simple trunk veins were found using angiography in the AVF group; while a fairly uniform staining and plenty of small vessels were observed in the hemodynamic remodeling group. The metabolite levels of the remodeling group are comparable with those in the arterial perfusion group. There was no statistically significant difference in the percentage of flap survival between the arterial perfusion group and hemodynamic remodeling group; however, significant difference was seen between the AVF group and the hemodynamic remodeling group.

Conclusions

Under the integrated perfusion mode, the AVFs are in an over-perfusion and non-physiological hemodynamic state, resulting in unreliability and unpredictability in flap survival; under the separated perfusion mode produced by remodeling, a physiological-like circulation will be created and therefore, better flap survival can be expected.

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.

The physiology, microcirculation and clinical application of the shunt-restricted arterialized venous flaps for the reconstruction of digital defects

Reconstruction of digital defects using the venous flap offer several advantages but remained unpopular owing to levels of venous congestion rates. We performed animal studies to test the hypothesis that an arterio-venous shunt increases pressure for peripheral flap perfusion and decreases venous congestion. Using an abdominal adipofascial flap model in six male Sprague-Dawley rats, microcirculation was modified as follows: type I - arterial flap; type II - flow-through arterio-venous flap (AVF); and type III - shunt-restricted AVF. In type I flaps, blood flow was observed to be unidirectional in both arterioles and venules. In type I flaps, blood flow was observed to be unidirectional in both arterioles and venules. In type II flaps, blood flow oscillated without a dominant direction and came to a standstill. In type III flaps, blood flowed proximally in a reverse direction whereas distally, flow was similar to type I flaps. In a clinical series, 21 patients received a total of 22 shunt-restricted AVFs. All 22 clinical flaps survived; four flaps suffered epidermolysis but recovered without full thickness loss.

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.

Gravitational retrograde venous perfusion--a technique for limb extremity salvage when microvascular arterial repair is not possible

Occasionally in plastic surgery immediate microvascular arterial repair is not possible. This occurs when distal vessels in the extremities are extensively damaged or thrombosed. If there is some intact venous anatomy it may be possible to maintain adequate perfusion for viability using a gravitational retrograde venous perfusion technique, until collateral arterial supply develops. We have used this technique successfully in three cases--blast injury to the hand, extensive digital thromboembolism and a devascularised sole of foot. This technique involves elevating and lowering the limb at 30 min intervals for 5-7 days. Elevation results in venous drainage and pallor of the limb and dependency results in venous congestion confirming retrograde venous flow. In the authors' experience ischaemic necrosis was inevitable in these cases without the use of this new technique. We have attempted to explain this phenomenon by way of retrograde venous perfusion in association with high venous pressure and high oxygen tension.

Clinical application of the retrograde arterialized venous flap

Retrograde arterialized venous flaps were applied to skin and soft-tissue defects in 13 patients with an average age of 34.4 years. Ten defects were located on the hand, and three on the lower leg. All flaps were harvested from the flexor aspect of the forearm; they ranged in size from 2 x 1 to 11 x 7 cm. There was venous congestion with superficial epidermolysis in six flaps, but not in the other seven. Partial skin necrosis in two of the lower-extremity flaps necessitated secondary skin grafts. Our results suggest that retrograde perfusion enhances blood flow in the periphery of arterialized venous flaps and gives good results in terms of flap survival, especially on the upper extremity.