Quantitative regression analysis of the cutaneous vascular territories in a rat model

High-pressure infusion improves multi-territory perforator flap viability via choke artery dilation: A preliminary study in a rat model

BACKGROUND

Multi-territory perforator flaps have become the preferred option for the repair and reconstruction of large soft tissue defects. Although methods (e.g., pharmacological agents, mechanical stimulation, and thermal stimulation) were developed to open choke vessels to improve flap survival, the flap necrosis rate is still as high as 28.8%. The authors hypothesized that high-pressure infusion might enhance flap viability by dilating choke arteries intraoperatively in a rat model of multi-territory perforator flap.

METHODS

Two-month-old male Sprague-Dawley rats were randomized into two groups (n = 32 each). During the multi-territory perforator flap elevation based on the right superficial epigastric angiosome, one group received continuous high-pressure infusion (mean pressure, 250 mmHg; duration, 1 min) of an isotonic heparin sodium solution (12,500 U/L) via the artery in the pedicle, whereas the other group received no infusion. At 7 days postoperatively, arteriography was performed; endothelial nitric oxide synthase (eNOS) and vascular endothelial growth factor (VEGF) expression and microvascular density were evaluated by western blot and histology, respectively; and flap survival was compared. Moreover, intraluminal diameters were examined at 1 day and 7 days postoperatively using hematoxylin and eosin staining, and coagulation function was assessed immediately postoperatively.

RESULTS

High-pressure infusion significantly promoted the dilation of choke arteries at 1 day and 7 days postoperatively. It also increased eNOS and VEGF expression, flap survival, and microvascular density. The coagulation function remained unaffected.

CONCLUSIONS

High-pressure infusion allowed intraoperative and postoperative dilation of the choke arteries that enhanced the viability of multi-territory perforator flaps in rats.

Differences between novel hybrid mode flaps and traditional perforator flaps at the level of metabolites using LC-MS

The multi-territory perforator flaps are widely used in plastic surgery. However, partial necrosis flap in the potential territory remains a challenge to plastic surgeons. We raised a novel "hybrid nourished mode" (HNM) flap based on the multi-territory deep inferior epigastric perforator (DIEP) flap to improve flap survival. Thirty-two rabbits were randomly divided into DIEP and HNM groups. Untargeted metabolic mechanisms between the DIEP and HNM groups were performed using LC-MS under the filter criteria of fold change >20.0 times or <0.05, and variable importance in projection (VIP) value was set at ≥1, P < 0.05. Between the two groups, flap survival, perfusion, microvasculature, histopathology, and immunohistochemistry of CD31 were assessed on post-operative day 7. We screened 16 different metabolites that mainly participated in biosynthesis of secondary metabolites, aminoacyl transfer RNA biosynthesis, phenylalanine metabolism, arginine and proline metabolism, among others. The results of the HNM flaps were higher than those of the DIEP flaps (P < 0.05) in the aspects of flap survival, flap perfusion, and microvasculature. Compared with the DIEP flaps, HNM has a stronger advantage in tissue metabolism. This study provided us with a better understanding and strong evidence in terms of metabolites on how HNM achieves the survival of large multi-territory perforator flaps.

Trans-Cinnamaldehyde Increases Random Pattern Flap Survival Through Activation of the Nitric Oxide Pathway

Background

The application of random pattern skin flaps is limited in plastic surgery reconstruction due to necrosis. Trans-cinnamaldehyde has antibacterial, anticancer, and antioxidant properties. In this study, we aimed to investigate the effect of trans-cinnamaldehyde on skin flap survival and its possible mechanism regarding nitric oxide.

Materials and Methods

One hundred forty male Sprague-Dawley rats were randomly divided into seven groups (n = 20 each group). After the dorsal flap was raised, different doses of trans-cinnamaldehyde (10, 20, and 30 mg/kg) were immediately given by oral gavage in the three different groups. To assess the possible involvement of the nitric oxide system, N^G-nitro-L-arginine methyl ester (L-NAME, a nonselective nitric oxide synthase inhibitor) was used in this study. All flap samples were incised on postoperative day 7.

Results

Our results showed that flap survival was increased significantly in the 20 mg/kg (P < 0.001) trans-cinnamaldehyde (TC) group compared to the control group or 30 mg/kg TC group. This protective function was restrained by coadministration of L-NAME with 20 mg/kg TC. The results of histopathology, laser Doppler, arteriography mediated with oxide–gelatine, and fluorescent staining all showed a significant increase in capillary count, collagen deposition, angiogenesis, and flap perfusion. Immunohistochemistry results revealed a significant increase in the expression of CD34, eNOS, and VEGF.

Conclusion

Trans-cinnamaldehyde increased flap survival through the nitric oxide synthase pathway and contributed to angiogenesis. A concentration of 20 mg/kg trans-cinnamaldehyde was recommended in this study.

The feasibility and survival mechanism of a large free flap supported by a novel hybrid perfusion mode

OBJECTIVES

In this study, we presented a novel hybrid perfusion mode in an attempt to provide a new strategy to improve the survival of an extended large flap and discuss its possible mechanisms.

MATERIALS AND METHODS

A 14 × 10 cm flap was designed on the rabbit abdomen. Ninety-six rabbits were randomly divided into three groups based on the flap perfusion mode: control group I (CON 1, physiological perfusion mode with bilateral deep inferior epigastric vascular pedicles intact), control group II (CON 2, physiological perfusion mode with single deep inferior epigastric vascular pedicle intact), hybrid nourished group (physiological perfusion as in CON 2 combined with arterialized venous nonphysiological perfusion mode, referred to as a hybrid perfusion mode). Flap survival, status of vascular perfusion, microvasculature, histopathology, expression of CD34, eNOs, VEGF and metabolic status of the flaps by LC-MS were assessed in each group.

RESULTS

The results of "hybrid nourished" flaps were similar to the traditional flaps in terms of flap survival, level of vascular perfusion and microvasculature except the status of metabolites.

CONCLUSIONS

The feasibility of this novel hybrid perfusion mode will greatly extend the indications of flap transfer and efficiently improve the survival reliability of large flaps. In a sense, this mode will be an ideological emancipation for the field of flap surgery.

Rip 1-dependent endothelial necroptosis participates in ischemia-reperfusion injury of mouse flap

BACKGROUND

Ischemia reperfusion injury plays an important role in free flap necrosis. However, the detailed mechanism is not clear, and effective methods for improving the survival rate of skin flap are still lacking.

OBJECTIVE

To investigate the regulation and functional link between necroptosis and ischemia-reperfusion injury of mouse flap.

METHODS

We established a mouse ischemia-reperfusion injury flap model and a cell Oxygen Glucose Deprivation (OGD) model intervened with Necrostatin-1. The mouse flap tissues were harvested in vivo for histological immunofluorescence analysis and western blotting analyses. The HUVECs cells with various treatments in vitro were assessed by using Transwell assay, tube formation assay, cell counting kit-8 analysis and flow cytometry. A Rip3-knockout cell line and a TNFR1-knockout cell line were generated from HUVEC cells using the CRISPR-Cas9 technology and were subsequently used to explore the related mechanisms.

RESULTS

The expression of p-Rip3 is positive in both mouse and cell culture models. When necroptosis is completely or partially inhibited in vivo, damaged tissues are repaired with better efficiency. The cells treated with Necrostatin-1 in vitro exhibit faster migration, proliferation and better tube formation. Deficiency of TNFR1 can block the necroptosis pathway by blocking the phosphorylation of Rip3 in HUVEC OGD/ROG model. Meanwhile, the levels of APJ, HIF-1α, and VEGF are reduced when necroptosis is inhibited by Necrostatin-1.

CONCLUSION

TNFR1 mediates Rip1/Rip3 in ischemia-reperfusion injury. Inhibition of necroptosis attenuates the ischemia-reperfusion injury of flap and may enhance hypoxic tolerance of HUVECs and vascular homeostasis through regulation of the HIF-1α signaling pathways.

Saphenous Artery Perforator Flaps in Minipigs: Anatomical Study and a New Experimental Model

This study describes the anatomy of the saphenous artery (SA) perforators in minipigs and the development of a new animal model. First, the anatomic characteristics of the SA and perforators in minipigs were examined after latex-lead oxide perfusion. Subsequently, the right hind limbs of 10 minipigs were used to generate capillary perforator flaps (group A; utilizing the SA and 5.5 cm of deep fascia above the knee), while all perforators of the left hind limbs were reserved (group B). Four additional minipigs were used to evaluate SA perforator flaps with capillary perforators plus sarcolemma and a small amount of muscle (group C). Preoperative and postoperative CTA of both hind limbs confirmed that all perforators were ligated in groups A and C. The average length of the SA was 14.86 ± 0.76 mm. The diameters of the SA at initiation, the medial tibial condyle, and the medial malleolus were 1.73 ± 0.15 mm, 1.50 ± 0.12 mm, and 1.30 ± 0.13 mm, respectively. There were 7.09 ± 1.16 perforators per hind limb, with an average diameter of 0.40 ± 0.13 mm (range, 0.10-0.78 mm), and the majority (96.2%) had a diameter >0.2 mm. The survival rates of the flaps in groups A, B, and C were 32 ± 39%, 100%, and 60.2 ± 17%, respectively. The position of the SA in minipigs is constant, its diameter is relatively large, and it has many perforators, allowing it to be used as a reliable model of perforator flaps, including capillary perforator flaps.

Effect of a nondominant perforator on multiterritory perforator flap survival in rats

BACKGROUND

During flap surgery, the dominant perforator is usually selected as the pedicle. This study investigated the effect of a nondominant perforator on multiterritory perforator flap survival.

METHODS

The deep circumflex iliac artery perforator flap (DCIA flap) and intercostal artery perforator flap (ICA flap) were performed (n = 12). Only the pedicle was different between the two flaps. The DCIA flap was based on the right and peripheral DCIA with three dynamic and two potential perforasomes. The ICA flap was based on the right and central ICA with five dynamic perforasomes. All adjacent perforators were ligated except the pedicle. On postoperative day 7, flap viability, angiography findings, and perfusion were compared.

RESULTS

Even though the diameter of DCIA (mm) was larger than that of ICA (0.49 ± 0.03 vs. 0.4 ± 0.04; p < .05), the ICA flap survival rate (%) was higher than that of DCIA flap (99.5 ± 0.7 vs. 83.8 ± 3.9; p < .001). Based on a dominant perforator, a necrotic area was observed in the potential perforasomes of the DCIA flap. The choke vessels between the anatomical and dynamic perforasomes dilated postoperatively in the two flaps, whereas the others did not. The perfusion (PU) differences between the DCIA and ICA flaps in the dynamic perforasomes were nonsignificant (average, 342.4 ± 9.1 vs. 347.3 ± 7.3; p > .05).

CONCLUSION

Increasing the number of dynamic perforasomes had no effect on flap survival, even based on a nondominant perforator. And the pedicle position affected 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.

Basic Perforator Flap Hemodynamic Mathematical Model

Background:

A mathematical model to help explain the hemodynamic characteristics of perforator flaps based on blood flow resistance systems within the flap will serve as a theoretical guide for the future study and clinical applications of these flaps.

Methods:

There are 3 major blood flow resistance network systems of a perforator flap. These were defined as the blood flow resistance of an anastomosis between artery and artery of adjacent perforasomes, between artery and vein within a perforasome, and then between vein and vein corresponding to the outflow of that perforasome. From this, a calculation could be made of the number of such blood flow resistance network systems that must be crossed for all perforasomes within a perforator flap to predict whether that arrangement would be viable.

Results:

The summation of blood flow resistance networks from each perforasome in a given perforator flap could predict which portions would likely survive. This mathematical model shows how this is directly dependent on the location of the vascular pedicle to the flap and whether supercharging or superdrainage maneuvers have been added. These configurations will give an estimate of the hemodynamic characteristics for the given flap design.

Conclusions:

This basic mathematical model can (1) conveniently determine the degree of difficulty for each perforasome within a perforator flap to survive; (2) semiquantitatively allow the calculation of basic hemodynamic parameters; and (3) allow the assessment of the pros and cons expected for each pattern of perforasomes encountered clinically based on predictable hemodynamic observations.

Vascular anatomy and clinical application of the free proximal ulnar artery perforator flaps

Background:

There is a dearth of detailed published work on the anatomy of ulnar artery perforators. The objective of this study was to fully document the vascular basis of the free proximal ulnar artery perforator flap and report its use in reconstruction of the hand.

Methods:

(1) The ulnar artery perforators were studied in 25 fresh cadavers and 10 cast preparations. Cadavers were injected with lead oxide for 3-dimensional reconstruction. The origin, course, and distribution of the ulnar artery perforators were comprehensively documented. (2) Between August 2011 and January 2013, 29 free proximal ulnar artery perforator flaps were utilized for reconstruction of soft-tissue defects of the hand in 25 patients. Flap size varied from 3.5 × 2.0 cm to 24.0 × 4.0 cm, with a consistent thickness of approximately 3 mm.

Results:

(1) There were 7 ± 2.0 ulnar artery perforators. The average external diameter was 0.6 ± 0.2 mm. Each perforator supplied an average area of 26 ± 7.0 cm². Extensive anastomoses were found between the ulnar artery perforators and multiple adjacent source arteries. (2) All flaps survived. The clinical results were satisfactory after 10.2 ± 5.3 months of follow-up. The flaps were considered cosmetically acceptable by both patients and doctors.

Conclusions:

The main advantage of the proximal ulnar artery perforator flap is that it is a thin flap that is ideal for upper extremity reconstruction, either as proximally or distally based local perforator flap or as a free flap. The donor site is excellent, and the vascular anatomy is very consistent.

Can we consider standard microsurgical anastomosis on the posterior tibial perforator network? An anatomical study

PURPOSE

The main vessels in an injured leg can be spared with perforator-to-perforator anastomosis. However, supermicrosurgery is not a routine procedure for all plastic surgeons. Our objective was to establish if the diameter of the perforators of the leg could allow anastomosis with standard microsurgical procedures.

METHODS

Twenty lower legs harvested from ten fresh cadavers were dissected. Arterial and venous vessels were injected with colored latex. The limbs were then dissected in a suprafascial plane. All the perforating arteries of a diameter >0.8 mm were located and their external diameter, the number and external diameter of the venae comitantes were reported.

RESULTS

We found at least three tibial posterior artery perforators with diameters >0.8 mm per leg with a mean external diameter of 1.1 mm and one vena comitans in almost all cases (96 %). The vena comitans was usually bigger than the perforating artery with a mean diameter of 1.6 mm. After statistical analysis, we were able to locate two main perforator clusters: at the junctions of the upper two-thirds of the leg and of the lower two-thirds of the leg.

CONCLUSION

The low-morbidity concept of perforator-to-perforator anastomosis can apply to posterior tibial artery perforators without using supermicrosurgical techniques. This is of high interest for open leg fractures where main vessels could be injured. We hope that the results of our study will incite surgeons to consider sparing of main vessels for coverage of open leg fractures whether surgical teams master supermicrosurgery or not.

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.