Experimental study of survival of pedicled perforator flap with flow-through and flow-end blood supply

The Effects of Angiosome Morphology on Choke Vessels and Flap Necrosis in a Rat Multiterritory Perforator Flap

BACKGROUND

Although the angiosome concept has been proposed for a long time, very few studies have been done on its morphology. Our study investigated the effects of angiosome morphology on choke vessels and flap necrosis in a rat multiterritory perforator flap.

METHODS

Seventy-two male Sprague-Dawley rats were randomly divided into 3 groups (n = 24/group). The flap contained the right iliolumbar, posterior intercostal, and thoracodorsal angiosomes (TDAVs), termed angiosomes I, II, and III, respectively. Only the posterior intercostal artery and iliolumbar vein were preserved in group 1, whereas only the posterior intercostal artery and vein were preserved in group 2, and only the posterior intercostal artery and thoracodorsal vein were preserved in group 3. Distances from angiosome II to angiosome I (II-I), angiosome II to angiosome III (II-III), angiosome I to the caudal side of the flap (I-caudal), and angiosome III to the cranial side of the flap (III-cranial) were measured. Arteriography, flap necrosis, average microvascular density, and vascular endothelial growth factor expression were evaluated.

RESULTS

The II-I distance was significantly greater than that of II-III (3.853 ± 0.488 versus 3.274 ± 0.433 cm, P = 0.012), whereas the distance of I-caudal resembled that of III-cranial (1.062 ± 0.237 versus 0.979 ± 0.236 cm, P = 0.442). The iliolumbar and posterior intercostal angiosomes were multidirectional, whereas the TDAV was craniocaudal and unidirectional. Seven days after the operation, the choke arteries had transformed into true anastomotic arteries. Flap necrosis was lowest in group 3, followed by group 2, and highest in group 1 (10.5% ± 2.4% versus 18.3% ± 3.5% versus 25.5% ± 4.6%, P < 0.01), whereas group 3 showed the highest microvascular density and vascular endothelial growth factor expression, in contrast to groups 2 and 1, with the lowest.

CONCLUSIONS

The choke vessel adjacent to the craniocaudal and unidirectional TDAV significantly blocked venous return. Increasing venous return may reduce the necrosis.

Effects of pharmacological delay with roxadustat on multi-territory perforator flap survival in rats

Roxadustat (FG-4592) is a specific hypoxia-inducible factor (HIF) prolyl hydroxylase inhibitor. We investigated the effects of FG-4592 pretreatment on survival and second choke vessels of multi-territory perforator flaps in rats. In total, 72 rats were divided into two groups (n = 36 each): the experimental (FG-4592) group and the control group. FG-4592 was administered orally as a single dose of 60 mg/kg every other day; the first drug solution was administered to the animals 7 days before the surgical procedure. On postoperative day 7, the surviving flap area was calculated. At 12 h post-surgery, in the second choke zone in the flaps, macrovascular hinges were compared by angiography and imaging, and microvascular changes were assessed by histology. Laser Doppler imaging was used to evaluate flap perfusion at the second choke zone at 12 h and 7 days after surgery. At 7 days after surgery, the flap survival area and perfusion were significantly greater in rats given FG-4592 compared with controls. At 12 h after surgery, the diameter of macrovascular and microvascular vessels, nitric oxide content, perfusion, and the protein levels of HIF-1α and inducible nitric oxide synthase were also significantly greater in FG-4592-treated rats than controls. In conclusion, pretreatment with roxadustat may improve initial flap survival and dilate the second choke zone vessels in a multi-territory perforator flap.

Which one is better for multi-territory perforator flap survival, central perforator artery or central perforator vein?

BACKGROUND

The survival of multi-territory perforator flap is associated with the position of the perforators. This study aimed to explore whether use of the central perforator artery or vein was better for flap survival.

METHODS

75 male Sprague-Dawley rats were randomly divided into three groups (n=25 per group). The flap contained the right and left iliolumbar, left posterior intercostal, and left thoracodorsal angiosomes, termed angiosomes Ⅰ to Ⅳ, respectively. The anastomosis between angiosomes Ⅱ and Ⅲ was termed choke 2. In experimental group 2, only the right iliolumbar vein and the left iliolumbar artery were preserved; in experimental group 1, only the right iliolumbar artery and the left iliolumbar vein were preserved; and in the control group, only the right iliolumbar artery and vein were preserved. On day-7 after the operation, the flap arteriography, intraluminal diameter, average microvascular density, vascular endothelial growth factor (VEGF) expression and flap survival were compared among groups. Moreover, the percentages of the angiosomes were measured.

RESULTS

The dilation of the choke 2 artery was most pronounced in experimental group 2, followed by experimental group 1, and, finally, the control group (p<0.05). Similar results regarding average microvascular density, VEGF expression, and survival rate were found among the three groups. The percentages of angiosomes Ⅰ to Ⅳ were 23.1%, 23.0±3.1%, 23.0±1.9%, and 31.0±3.1%, respectively.

CONCLUSIONS

Compared with the central perforator vein, the central perforator artery was more beneficial in enhancing flap survival. A multi-territory perforator flap with the central perforator artery could capture 3 angiosomes safely.

A Quantitative Evaluation of the Flow-Increasing Effect of Flow-Through Arterial Anastomosis in the Vascular Pedicle of Free Flaps: A Prospective Clinical Before-and-After Study

BACKGROUND

The clinical application of flow-through anastomosis has been reported in various studies; however, no studies have quantitatively evaluated and compared the actual hemodynamics in flow-through anastomosis and end-to-end anastomosis. This study quantitatively evaluated the blood inflow (volumetric flow rate) and vascular resistance (pulsatility index) of flow-through arterial anastomosis using an ultrasonic flowmeter, and compared these values with those of end-to-end anastomosis in actual clinical settings. In addition, factors affecting the outcomes have also been examined.

METHODS

Twenty-eight patients who underwent free flap reconstruction after tumor resection were subjected to flow-through arterial anastomosis and flow examination. First, in the end-to-end state, the proximal anastomotic site was measured. This was followed by the opening of the distal arterial clamp, and measurement was then continued (in the flow-through state).

RESULTS

In flow-through arterial anastomosis compared with end-to-end anastomosis, the volumetric flow rate was significantly increased (18.9 ± 14.1 ml/minute versus 6.0 ± 6.3 ml/minute) and the pulsatility index was significantly decreased (5.2 ± 3.7 versus 13.6 ± 10.2), when comparing paired data. Multiple regression analyses revealed that a perforator flap (versus a musculocutaneous flap) was independently associated with both reduced volumetric flow rate and increased pulsatility index in end-to-end anastomosis, and that hypertension was independently associated with an increased pulsatility index in end-to-end anastomosis. However, no factors in flow-through anastomosis were significantly associated with those values.

CONCLUSION

In terms of blood flow and vascular resistance, flow-through arterial anastomosis was considered to have promising quantitative effects and should be performed when the conditions of both the donor and recipient vessels meet the requirements.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, IV.

Astragaloside IV improves angiogenesis under hypoxic conditions by enhancing hypoxia‑inducible factor‑1α SUMOylation

Improving angiogenic capacity under hypoxic conditions is essential for improving the survival of skin grafts, as they often lack the necessary blood supply. The stable expression levels of hypoxia‑inducible factor‑1α (HIF‑1α) in the nucleus directly affect the downstream vascular endothelial growth factor (VEGF) signaling pathway and regulate angiogenesis in a hypoxic environment. Astragaloside IV (AS‑IV), an active component isolated from Astragalus membranaceus, has multiple biological effects including antioxidant and anti‑diabetic effects, and the ability to provide protection from cardiovascular damage. However, the mechanisms underlying these effects have not previously been elucidated. The present study investigated whether AS‑IV promotes angiogenesis via affecting the balance between ubiquitination and small ubiquitin‑related modifier (SUMO) modification of HIF‑1α. The results demonstrated that persistent hypoxia induces changes in expression levels of HIF‑1α protein and significantly increases the proportion of dysplastic blood vessels. Further western blotting experiments showed that rapid attenuation and delayed compensation of SUMO1 activity is one of the reasons for the initial increase then decrease in HIF‑1α levels. SUMO1 overexpression stabilized the presence of HIF‑1α in the nucleus and decreased the extent of abnormal blood vessel morphology observed following hypoxia. AS‑IV induces vascular endothelial cells to continuously produce SUMO1, stabilizes the HIF‑1α/VEGF pathway and improves angiogenesis in hypoxic conditions. In summary, the present study confirmed that AS‑IV stimulates vascular endothelial cells to continuously resupply SUMO1, stabilizes the presence of HIF‑1α protein and improves angiogenesis in adverse hypoxic conditions, which may improve the success rate of flap graft surgery following trauma or burn.

Emergency Repair of Severe Limb Injuries With Free Flow-Through Chimeric Anterolateral Thigh Perforator Flap

BACKGROUND

Complex limb trauma often involves both soft tissue and vascular defects, and is challenging for surgeons. The traditional musculocutaneous flap cannot achieve a 3-dimensional wound repair. Here we report our experience with a single-stage reconstruction and revascularization performed on complex extremity injuries using a free flow-through chimeric anterolateral thigh perforator (ALTP) flap.

PATIENTS AND METHODS

Seventeen patients (16 men; aged 19-55 years) with complex soft tissue defects attended our hospital from January 2010 to November 2017. All patients underwent reconstruction based on free flow-through chimeric ALTP flap for complex injuries in their extremities. The wound size ranged from 16 × 8 to 45 × 30 cm. The injured artery was flow-through anastomosed with the descending branch of the lateral femoral circumflex artery to regain blood flow. The muscle flap was used to fill the deep dead space on the injury site. The skin and fascial flaps were used for superficial cover. The donor site defects were sutured directly in 6 patients; simultaneous skin grafts were applied in the remaining 11 patients.

RESULTS

The ALTP flaps survived in 15 patients. Failure necessitated limb amputation in 2 patients. Six patients received both skin and fasciae flaps; 11 received flaps comprising the skin, fasciae, and vastus lateralis muscle. Partial necrosis after skin grafting was observed in 11 patients, and the wounds healed either by dressing change (1 patient) or second skin graft (10 patients). All donor sites healed without complications. All patients were followed up for 5 to 60 months (mean, 21.8 months).

CONCLUSIONS

The flow-through chimeric ALTP flap can be used for 1-stage reconstruction of 3-dimensional soft tissue defects and vascular gap. It is feasible for managing complex injuries of both the upper and lower extremities in emergency settings.

Comparison of arterial supercharging and venous superdrainage on improvement of survival of the extended perforator flap in rats

BACKGROUND

Arterial supercharging and venous superdrainage have been the commonly used vascular augmentation techniques for resolving partial loss of flaps in reconstructive surgery. It remains controversial which one of them is more effective in improving flap survival. The purpose of this study was to compare the effect of distal venous superdrainage and arterial supercharging on the survival of an extended dorsal perforator flap in rats.

MATERIALS AND METHODS

Sixty Sprague-Dawley rats were randomly divided into three groups (n = 20 in each group). An extended dorsal perforator flap with the size of 3 × 12 cm based on the deep circumflex iliac artery and vein was elevated in each rat. In arterial supercharging group, the thoracodorsal artery was retained as the distal supercharging vessel; In venous superdrainage group, the thoracodorsal vein was retained as the distal superdrainage vessel. In control group, no other arteries and veins were retained except the main vascular pedicle. On the seventh day after operation, the survival area of flap was calculated as a percentage of viable area to the total flap. Vascular changes in the choke zones were assessed by angiography. Microvascular density and diameter were assessed via immunohistochemistry staining of CD31 on the fifth day after operation.

RESULTS

The flap survival area in arterial supercharging group was significantly higher than that in venous superdrainage group (98.9 ± 0.8% vs. 81.5 ± 3.5%, p < .001). By gross observation, the extent of dilation of choke zone vessels in venous superdrainage group was smaller compared with that in arterial supercharging group. The density of CD31-positive vessels and the diameter of choke zone vessels in arterial supercharging group were significantly larger than that in venous superdrainage group (23.4 ± 4.6 mm^-2 vs. 13.1 ± 4.2 mm^-2 , p < .05; and 37.5 ± 5.8 μm vs. 27.8 ± 4.9 μm, p < .05).

CONCLUSION

Compared with venous superdrainage, distal arterial supercharging in the potential territory resulted in better survival of an extended dorsal perforator flap in a rat model.

Angiogenic and anti-inflammatory properties of azadirachtin A improve random skin flap survival in rats

Random skin flaps are widely used to repair tissue defects. However, the distal flap regions are prone to ischemic necrosis, limiting clinical applications. Azadirachtin A, a fruit extract from the neem, improves tissue blood supply and metabolism, reduces cell swelling, promotes tissue healing, and prevents venous thrombosis. We explored whether it enhances random skin flap survival. Fifty-four Sprague-Dawley rats were divided into control, low-dose, and high-dose Azadirachtin A-treated groups using a random number table. We used an improved version of the McFarlane technique to create flaps. On day 2, superoxide dismutase and malondialdehyde levels were measured. Tissue slices prepared on day 7 were stained with hematoxylin and eosin. The expression levels of vascular endothelial growth factor (VEGF), toll-like receptor 4 (TLR4), nuclear factor kappa-B (NF-kB), interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) were immunohistochemically assayed. Microcirculatory blood flow was measured via laser Doppler blood flowmetry. Flap angiography was performed using the lead-oxide gelatin injection technique. And the azadirachtin A groups exhibited a greater mean flap survival area, an improved mean blood vessel density, a greater blood flow, and higher superoxide dismutase and VEGF levels, especially at the high dose. Azadirachtin A markedly reduced the levels of TNF-α, IL-6, IL-1β, TLR4, and NF-kB. These findings suggest that azadirachtin A promotes random skin flap survival by improving the blood supply, reducing tissue inflammation, and inhibiting flap ischemia reperfusion injury.

Effects of arterial blood supply and venous return on multi-territory perforator flap survival

This study aimed to design arterial ischemic and venous congested areas on the same multi-territory perforator flap, assessing the effects of arterial blood supply and venous return on flap survival. Totally 68 rats were randomly divided into the experimental (Exp) and control (Con) groups. In the Exp group, flaps were based on left superficial epigastric artery and right superficial epigastric vein. In the Con group, flaps were based on the left superficial epigastric artery and vein. Immediate postoperative ink-gelatin angiography, epidermal metabolite levels detection, tissue edema measurement, survival rate evaluation in half of the flaps and average microvessel density assessment were performed. Blood in the Exp group flowed through most angiosomes, but only flowed around pedicled vessels in the Con group; metabolite levels of left halves in the Con and Exp groups were comparable with those of right halves. Angiosomes with high water contents occurred in the Exp group. Survival rates of left halves in the Con and Exp groups were higher than those of right halves, and more microvessels were found in the left ventral areas of both groups compared with the right ventral area in the Exp group. These findings revealed that on the same multi-territory perforator flap, arterial blood supply, affected by venous return, is a prerequisite for flap survival.

The Effect of Leonurine on Multiterritory Perforator Flap Survival in Rats

BACKGROUND

Leonurine (Leo), a natural active compound of Leonurus cardiaca, has been shown to possess various biological activities. However, it is not known whether Leo promotes perforator flap survival.

METHODS

In this study, a perforator flap was outlined in the rat dorsum. The rats that survived surgery were divided randomly to control and Leo groups (n = 36 per group). Flap viability, flap perfusion, and level of protein linked with oxidative stress, cell apoptosis, and angiogenesis were evaluated.

RESULTS

Relative to control group, the Leo group showed significantly higher the flap survival percentage (70.5% versus 90.2%, P < 0.05) and blood perfusion (197.1 versus 286.3, P < 0.05). Leo also increased 1.8-fold mean vessel density and upregulated 2.1-fold vascular endothelial growth factor protein expression compared with the control group, both of which indicate increased angiogenesis. Moreover, it significantly inhibited apoptosis by lowering caspase-3 activity. Superoxide dismutase expression was remarkably elevated in Leo group compared with the control group (56.0 versus 43.2 U/mg/protein, P < 0.01), but malondialdehyde quantities were significantly lower in the Leo group compared with control group (41.9 versus 57.5 nmol/mg/protein, P < 0.05).

CONCLUSIONS

Leo may serve as an effective drug for improving perforator flap survival in rats via antioxidant and antiapoptotic mechanisms and promotion of angiogenesis.

A Preliminary Study of the Effects of Venous Drainage Position on Arterial Blood Supply and Venous Return within the Conjoined Flap

Background:

Conjoined flap viability is associated with arterial blood supply and venous return. This study aimed to assess the effects of venous drainage position on arterial blood supply and venous return within the conjoined flap.

Methods:

Fifty-four rats were divided randomly into three groups (n = 18 per group). In experimental group 2, only the right intercostal posterior artery and the left iliolumbar vein were maintained; meanwhile, only the right intercostal posterior artery and the left intercostal posterior vein were preserved in experimental group 1. The control group had only the right intercostal posterior artery and vein preserved. The distances between angiosomes were measured. At 7 days after surgery, flap survival was evaluated, lead oxide–gelatin flap angiography was performed, and average microvessel density was assessed by hematoxylin and eosin staining, and lactate levels were assessed.

Results:

The distance between angiosomes I and II was the shortest, whereas angiosomes I and III were most distant (p < 0.05). At 7 days after surgery, survival rates in experimental group 2 and experimental group 1 were both 100 percent, whereas 86.5 ± 1.6 percent of controls survived. Furthermore, angiogenesis was more obvious in experimental group 2 than in experimental group 1 and controls. Moreover, lactate levels were lower in experimental group 2 (7.47 ± 0.17 mM) and experimental group 1 (8.03 ± 0.31 mM) compared with control values (9.98 ± 0.37 mM; p < 0.05).

Conclusion:

Changes in position of venous drainage might cause continuous arterial high-pressure perfusion and venous superdrainage, which improves flap survival.

Effects of curculigoside A on random skin flap survival in rats

Necrosis in distal areas of random skin flaps remains a challenging issue. Curculigoside A (CA), one of the main bioactive phenolic compounds, has been reported to induce angiogenesis in vitro by increasing proliferation, tube formation, and migration. In addition, CA was shown to increase vascular endothelial growth factor (VEGF) expression. In this study, we investigated the potential use of CA as a novel candidate to enhance the viability of the ischemic skin flap. A modified McFarlane flap was used as a surgical model in Sprague-Dawley rats. Three groups of rats were treated as follows: the control group received 0.9% saline orally, while rats in the two treatment groups were administered 10 mg/kg or 20 mg/kg CA orally for 7 days, respectively. On day7, the mice were killed, and tissue samples were collected for hematoxylin and eosin staining and immunohistochemical examination, while laser Doppler imaging and oxide-gelatin angiography were performed to assess angiogenesis. Kits for the analysis of superoxide dismutase (SOD) and malondialdehyde (MDA) were used to verify the oxidative stress level. Treating animals with CA significantly increased the surviving portion of the flaps. VEGF and SOD expression and microvessel development were markedly increased, and the MDA level was reduced, in the CA treatment groups. Histological studies demonstrated that CA promoted angiogenesis and attenuated inflammatory cell numbers. These findings indicated that CA increases random skin flap survival.

[Application of free anterolateral thigh Kiss flap in repair of large scalp defect after malignant tumor resection]

Objective

To investigate the effectiveness of free anterolateral thigh Kiss flap in repair of large scalp defect after malignant tumor resection.

Methods

Between December 2012 and December 2016，18 patients with large scalp defect after malignant tumor resection were treated. There were 16 males and 2 females with an average age of 52.6 years (range, 43-62 years). There were 17 cases of squamous carcinoma and 1 case of dermatofibrilsarcoma protuberan. The size of scalp defect ranged from 15 cm×10 cm to 17 cm×12 cm after resection of tumors. The scalp defects were repaired with the free anterolateral thigh Kiss flap. And the size of flap ranged from 15 cm×6 cm to 20 cm×8 cm. The skull was completely resected in 2 cases, and repaired with Titanium mesh. The sizes of skull defects were 12 cm×10 cm and 10 cm×8 cm. The donor site was sutured directly.

Results

Eighteen flaps survived with primary healing of wounds; and healing by first intention was obtained at the donor sites. One patient died because of intracranial metastasis at 5 months after operation, and no local recurrence occurred in the other 17 patients. The follow-up time ranged from 6 months to 4 years (mean, 26.6 months). The results of both appearance and function were satisfactory, without ulceration during follow-up. No obvious scar was found at donor sites and no obvious impairment was observed after harvesting free anterolateral thigh flap.

Conclusion

Large scalp defects after malignant tumor resection can be effectively repaired by free anterolateral thigh Kiss flap. The donor site can be sutured directly, without skin grafting, thus avoiding the secondary donor site.