An extended dorsal island skin flap with multiple vascular territories in the rat: A new skin flap model

An animal experiment study on the application of indocyanine green angiography in the harvest of multi-angiosome perforator flap

Background

This study sought to explore the application value of indocyanine green angiography (ICGA) in the harvest of multi-angiosome perforator flap and the effect of low molecular weight heparin (LMWH) on the survival of postoperative flap.

Methods

Twenty-four SD male rats were selected to construct a three-angiosome perforator flap model with the unilateral iliolumbar artery perforator. They were randomly divided into two groups: the control group was injected with indocyanine green (ICG) into the femoral vein during the operation, and the fluorescence signal was collected and quantitatively analyzed using Real-Time Image Guided System to determine the intraoperative fluorescence imaging length. The experimental group was injected subcutaneously with LMWH (400 U/kg) after 0.5 h postoperatively, and the control group was injected with the same amount of normal saline. The injection was repeated at the same time each day from 0 to 7 days postoperatively. After the flap was sutured in situ, ICGA was performed at 0, 1, 3, 5, and 7 days postoperatively to observe the vascular structure of the two groups of flaps. The flap survival length of the control group was counted at 7 days postoperatively, and the correlation between the intraoperative fluorescence imaging length and the survival length at 7 days postoperatively was calculated. The proportion of distal necrosis of the flaps between the two groups was compared at 7 days postoperatively.

Results

The average length of intraoperative fluorescence imaging in the control group was 6.29±0.50 cm, and the survival length of the flap at 7 days postoperatively was 8.24±0.52 cm. The actual survival length was higher than the intraoperative fluorescence imaging length, with a ratio of 1.31±0.08. The difference was statistically significant (P<0.05). At 7 days postoperatively, the flap necrosis ratio of experimental group and control group were 10.92%±1.30% and 19.11%±1.19%, and the flap necrosis ratio of experimental group was lower than that of control group (P<0.001).

Conclusions

ICGA can locate the position of perforator, and can be used to predict and observe the length of distal survival of multi-angiosome perforator flap postoperatively. LMWH can promote the distal survival of flap and reduce flap necrosis.

Standardization of the Rat Dorsal Random Pattern (McFarlane) Flap Model and Evaluation of the Pharmacological Agents Aiming to Salvage Partial Flap Necrosis: A Systematic Review and a Meta-analysis

INTRODUCTION

Partial flap necrosis is a common complication after surgery. McFarlane flap model has been used for assessment of various agents' effects on random flap survival. The aim of this study was to review the methodology of studies using this flap model and reveal the most successful agents.

MATERIALS AND METHODS

PubMed, Scopus, and Web of Science databases were screened for words "McFarlane flap," "flap survival," and ("flap" and "rat") by using time limits between 1965 and 2019. A total of 71 original articles were reviewed. Dimensions and base (cranial/caudal) of the flap, treatment protocol, follow-up period, and survival rates were extracted. Modified survival rates were calculated. Coefficients of variation of cranial/caudally based control group flaps and most commonly used flap models were calculated to assess interstudy variability.

RESULTS

A total of 165 different treatment regimens were studied. One-hundred twelve regimens (67.9%) were found to increase flap survival. Most common flap dimensions were 9 cm × 3 cm, followed by 10 cm × 3 cm, 8 cm × 2 cm and 6 cm × 2 cm. Studies using caudally based flaps showed less interstudy variability, but survival rates were similar. Pentoxifylline, sildenafil, chlorpromazine, phenoxybenzamine, and phentolamine were reported to be successful in multiple studies.

CONCLUSIONS

There are numerous agents found to be effective for treatment of partial flap necrosis, but further clinical research is needed. To overcome standardization problems, use of commonly used flap dimensions with a caudal base and interpretation of results after 7 days of follow-up seems appropriate.

Percutaneous endoscopy in direct real-time observation of choke vessels in rat perforator flap model

Background

Most of the techniques used to investigate choke vessels are indirect. The aim of the present study is to assess the effectiveness of percutaneous endoscopy in direct real-time visualization of choke vessels in rat perforator flap models.

Methods

A classic perforator flap on the rat dorsum was designed (n = 12). An additional incision was made to place the percutaneous endoscope. Evans blue dye was injected from the common carotid artery to distinguish choke arteries from veins. Blood perfusion status was assessed using full-field laser perfusion imaging (FLPI) and the oxygen/carbon dioxide levels. Photographs of choke vessels were taken and compared at 1 h, 1 day, 4 days, and 7 days postoperation. The flap survival area was examined on day 7.

Results

The average survival rate of perforator flaps was 70.1 ± 10.8%. The choke arteries but not choke veins were stained blue after injection of Evans blue dye. The choke arteries constricted instantly after surgery, dilated to a maximum diameter on postoperation day 4, and returned to the preoperation status on day 7. The choke veins dilated instantly after the operation, reached their largest diameters on postoperation day 4, and remained dilated on day 7. The behaviors of choke vessels were consistent with the FLPI results and oxygen/carbon dioxide statuses.

Conclusion

Percutaneous endoscopy can provide direct real-time visualization of choke vessels in living rat perforator flap models and enable the identification of choke arteries and veins. This novel technique represents an ideal platform for investigating choke vessels in perforator flap models.

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.

Comparison of contraction rates of epigastric and extended dorsal island skin flaps in rats

Flap surgery is a wide field in plastic and reconstructive surgery practice and experimental research is needed to improve surgical success. These research is often performed on rats. Rat is a loose-skinned animal and contraction of skin flaps on rats is an underestimated condition. Besides this variable contraction of survived and necrotic tissues may mislead calculations and results. In this study, contraction patterns of epigastric and dorsal island skin flaps were investigated to identify this phenomenon. Forty-two male Sprague-Dawley rats were divided into four groups. Eleven epigastric flaps with unilateral pedicles, 11 epigastric flaps with bilateral pedicles, 10 extended dorsal island skin flaps with unilateral pedicles, and 10 extended dorsal island skin flaps with bilateral pedicles were prepared. Total, necrotic and viable flap areas were calculated from standardized photographs which were taken daily. The animals were placed on marked papers and image processing software was used the calculate flap areas from the photographs. Respect to these daily flap areas, the contraction rates in epigastric flaps were highly significant. The area loss in necrotic tissues were faster than the viable areas. Compared to the epigastric flaps, the contraction was not significant in extended dorsal island skin flaps flap groups. In conclusion, the rat extended dorsal island skin flap is a more reliable model for experimental flap research, which is resistant to contraction, when compared to the epigastric skin flap model.

A new lateral thoracic artery perforator flap design with multiple vascular territories in rats

BACKGROUND

To describe a new design for an extended lateral thoracic artery (LTA) perforator flap and investigate its anatomical, dynamic, and potential territories.

MATERIALS AND METHODS

To assess vascular territories, rats were randomized according to LTA perforator flap type into the surgical groups A, hemidorsal island flap; B, entire dorsal island flap; and C, reduced-size dorsal island flap.

RESULTS

On postsurgical day 7, the surviving flap areas were 95%, 92%, and 89% in groups A, B, and C, respectively. Necrosis most commonly occurred in the contralateral LTA territories in groups B and C. The immunoreactivities of intercellular adhesion molecule 1 and vascular endothelial growth factor receptor 2 in dynamic territories, as choke vessel markers, were increased.

CONCLUSIONS

We clarified the LTA perforator flap nomenclature and defined its pedicle course and anastomosing patterns; furthermore, we demonstrated that the LTA perforator did not anastomose with its counterpart because of its unidirectional, oblique, and craniocaudal course. The LTA perforator flap was found to be a good model comprising multiple vascular territories and exhibiting continuous necrosis.

An Ideal Flap Alternative for Closure of Myelomeningocele Defects: Dorsal Intercostal Artery Perforator Flap

BACKGROUND

Dorsal intercostal artery perforator (DICAP) flap is an ideal flap to be used for posterior trunk defects since it leads to lower donor-site morbidity and shorter operative times, offers easy surgical planning, and uses a reliable and easily identifiable artery.

MATERIALS AND METHODS

The study retrospectively reviewed 52 patients with meningomyelocele defects that were closed with DICAP flap between January 2007 and May 2015.

SURGICAL TECHNIQUE

Each of the 4th to 12th posterior intercostal arteries can be used as dorsal perforators. The dominant direct cutaneous perforators derive from the 4th, 5th, 6th, 10th, and 11th posterior intercostal arteries. These perforators are located 5 cm medial to the spinous processes of the thoracic vertebrae and can be easily identified.

CONCLUSION

Dorsal intercostal artery perforator flap is a reliable flap alternative for the defects seen in neonates, including myelomeningocele, oncologic resections, burn defects, and radiation burns since it is a thin flap and offers easy surgical planning and shorter operative times.

Effects of Venous Superdrainage and Arterial Supercharging on Dorsal Perforator Flap in a Rat Model

Objective

To comparatively assess the effects of venous superdrainage and arterial supercharging on dorsal perforator flap survival.

Materials and Methods

Sixty male Sprague-Dawley rats (450–550g) were randomly divided into three groups (n = 20), including control group (Control) and experimental groups A (venous superdrainage, Exp. A) and B (arterial supercharging, Exp. B). At postoperative day 7, survival areas of the flaps were evaluated and all animals underwent angiography. Laser Doppler was used to evaluate flap perfusion from 0h to 7days after surgery. Histology with hematoxylin and eosin staining was used to count microvessels. Tissue of “Choke vessels”was excised for quantification of hypoxia inducible factor-1α (HIF-1α) and vascular endothelial growth factor (VEGF) by western blot assay at 6h and 7days after surgery.

Results

In the Exp. A group, almost all flaps survived (98.2±1.6%); in the Exp. B and control group, survival areas accounted for 78.8±8.5% and 60.3±7.8%, respectively (P <0.001). In addition, Exp. A animals showed improved anastomosis of choke vessels 2 compared with the Exp. B and Control groups. Furthermore, flap blood flow and partial pressure of oxygen in the Exp. A group were significantly higher compared with values obtained for the Exp. B and Control groups, from 6 hours to 7 days after surgery. More microvessels were found in the Exp. A group (11.65±1.33) than in Exp. B (9.25±0.34) and control (7.25±0.91) animals on POD 7. The relative expression level of HIF-1α and VEGF were significant at 6h and 7days after surgery.

Conclusions

Venous superdrainage in rat dorsal perforator flap is more effective than arterial supercharging in promoting flap survival, and could effectively alter hemodynamics in the microcirculation and stimulate blood vessel formation.

Delay by Staged Elevation of Flaps and Importance of Inclusion of the Perforator Artery

"Surgical delay" is aimed at increasing blood flow to adjacent angiosomes by opening choke vessels, to obtain larger and more reliable flaps. We hypothesized that staged elevation (delay) from distal to proximal, in addition to preservation perforator artery near the base will improve survival. Thirty-two Sprague-Dawley rats were divided into 4 groups and 3x8cm caudal McFarlane flaps were elevated. In "delay" groups the 3 × 4 cm distal part was elevated and sutured back, with complete elevation (3 × 8 cm) after 4 days. The deep circumflex iliac artery (DCIA) at the base was either preserved or transected. The groups were: group A (Delay/DCIA preserved), group B (Delay/DCIA transected), group C (No Delay/DCIA preserved), group D (No Delay/DCIA transected). The percentage of surviving flap area was measured after 7 days with digital planimetrics. Statistics were done with ANOVA and unpaired T-test. The survivals were: 98.44 ± 3.13 %(group A), 69.33 ± 5.51 %(group B), 76.50 ± 8.91 %(group C) and 52.89 ± 3.15 %(group D). Delay lead to a greater degree of survival whether the arteries were preserved (p = 0.002) or transected (p = 0.01). In groups where the DCIA was preserved, the delay lead to a greater area of survival (p = 0.002). Inclusion of arteries lead to a greater degree of survival whether delay was performed (p = 0.003) or not (p = 0.005). Necropsy showed that the DCIAs were dilated bilaterally when preserved with vascular arcades reaching all viable areas. When the DCIA was transected, the gluteal perforators were dilated bilaterally with the vascular arcades reaching all viable areas. Staged elevation is an effective method of delay in both random and rando-axial flaps. When this is combined with preserving the perforator artery, survival rates are further enhanced.

The effect of platelet rich plasma on angiogenesis in ischemic flaps in VEGFR2-luc mice

To improve skin flap healing, one promising strategy in reconstructive surgery might be to optimize platelet rich plasma (PRP) bioactivity and the ischemia-altered expression of genes. We studied both the effect of PRP on ischemic flaps, and whether in vivo bioluminescence imaging (BLI) is a suitable method for the longitudinal monitoring of angiogenesis in surgical wounds. Axial murine skin flaps were created in four experimental groups. In vivo measurements of VEGFR2 expression levels were made every other day until the 14th day. The local VEGF level and microvessel density were quantified on the 14th day via ELISA and immunohistochemistry, and flap survival rates were measured. We demonstrated that PRP and induced ischemia have a beneficial influence on angiogenesis and flap healing. Combining the two resulted in a significantly robust increase in angiogenesis and flap survival rate that was corroborated by bioluminescence imaging of VEGFR2 activity. This study shows that angiogenic effects of PRP may be potentialized by the stimulus of induced ischemia during free flap harvesting, and thus the two procedures appear to have a synergistic effect on flap healing. This study further demonstrates that BLI of modulated genes in reconstructive surgery is a valuable model for longitudinal in vivo evaluation of angiogenesis.

Rat dorsal paired island skin flaps: a precise model for flap survival evaluation

Rectangular flaps on the rat or mouse dorsum are frequently used for flap survival elongation research. However, since rectangular flaps are purely random, the survival rate varies among individuals. A reliable animal flap model with low individual variation is desirable for flap survival research, especially in the angiogenic field. We investigated the survival rate of paired flaps in the rat dorsum containing 3 vascular territories in each flap, and determined their usefulness for flap elongation research. Two symmetrical adjoining rectangular flaps (11 x 3 cm each) were drawn on the rat dorsum. Two days after material injection, flaps were elevated with only the deep circumflex iliac vessels as the vascular pedicle. Flaps were immediately sutured back and the flap survival area was measured 7 days after the operation. The control group (n = 9) had saline solution injected in both flaps. The bone marrow group (n = 8) had bone marrow injected in the right flap, and saline solution injected in the left flap. In the control group, the survival rate of the paired flaps was not statistically different (right flap, 89.0+/-5.6%; left flap, 89.3+/-4.5%). In the bone marrow group, the survival rate between the bone marrow injected flap (89.9+/-3.7%), and the saline flap (84.8+/-4.3%) was statistically different. The rat dorsal paired island skin flap model shows low difference in flap survival rate and uses an internal control. This is a suitable model for flap survival elongation research.

Dipyrone increases the blood flow of arterial dorsal skin flaps

BACKGROUND

Findings have shown that dipyrone has a beneficial effect on skin flap survival. A pharmacologic explanation for this effect points to its vascular smooth muscle-relaxing effect. This study evaluated the effect of dipyrone on blood flow and thus survival of rat random dorsal skin flaps.

METHODS

For this study, 27 male Wistar albino rats were randomly assigned to control (treated with sterile saline) and treatment (treated with dipyrone 100 mg/kg) groups. A random dorsal skin flap measuring 4 x 10 cm was raised in each animal. The edges of the flap were sutured back into their original place. Dipyrone treatment continued at 100 mg/kg per day during the 7-day observation period. Blood flow was recorded by laser Doppler preoperatively (baseline), immediately after the flap was sutured back to its original position (acute), and on postoperative day 7. The degree of necrosis was evaluated by the grid method on day 7. Mean percentage necrosis and minimum laser Doppler readings were compared between the two groups.

RESULTS

A significant increase in blood flow was observed in the dipyrone group at the acute phase but not on postoperative day 7. The percentage of the necrotic area was lower in the treatment group. However, it did not reach the significance level (p = 0.09).

CONCLUSION

Dipyrone significantly increases [corrected] skin blood flow at the acute phase of flap elevation although the necrotic area does not reach the significance level.

A novel murine island skin flap for ischemic preconditioning

BACKGROUND

Ischemia reperfusion injury is a well-known phenomenon affecting skin flap viability. One method to improve flap viability is ischemic preconditioning. Previous murine flap models used random flaps. We developed a single pedicle island skin flap which allows us to create true ischemia by clamping the single pedicle. Our first aim was to describe a novel murine skin flap model with a definable, reproducible injury. Our second aim was to test the usefulness of this model by demonstrating mitigation of injury via ischemic preconditioning.

MATERIALS AND METHODS

Dorsal lateral thoracic artery pedicle island skin flaps (3.5 x 1.5 cm) were elevated in 39 male C57/BL6 mice: a Control group (n = 7), 10 h of ischemia (n = 21), and Preconditioning (2 cycles of 20 min ischemia: 20 minutes reperfusion) + 10-h ischemia (n = 11). After flap elevation, a silicon sheet barrier was placed. The axial pedicles were occluded, and the flaps were inset with 6-0 prolene. In all mice, ischemia was followed by 1 wk of reperfusion. At 1 wk, percent necrosis was measured and an analysis of variance was performed.

RESULTS

The percent of flap necrosis was 1.1% +/- 1.11% in controls. Animals that were subjected to 10 h of ischemia developed 33.14% +/- 7.23% necrosis. Preconditioned animals that underwent 10 h of ischemia demonstrated a 43% reduction in necrosis (18.82% +/- 5.68%). There was a statistically significant difference among all groups (P < or = 0.001).

CONCLUSION

Rat models have been the standard for skin flap experiments. We have developed a novel murine single pedicle island skin flap model with reproducible injury. This model has numerous advantages, including ease of handling, low cost, appropriateness for biomedical studies, and the availability of genetically altered animals. We also confirmed this model's usefulness in a study of mitigation of ischemia reperfusion injury through ischemic preconditioning.

An ameliorated skin flap model in rats for experimental research

There is a disagreement in the experimental design of random skin flaps owing to their vascular inconsistency. The definition of a reliable axial-pattern skin flap model is needed. The purpose of this study was to describe a new skin flap model to deal with entire drawbacks of existing random and axial pattern skin flap designs. This was accomplished by creating paired skin flaps including both skin and vascular pedicle on the dorsum of the same rat. This design was suitably termed as rando-axial flap. The present study offers a simple and reliable skin flap model with following advantages: (1) it has a predictable necrosis area, (2) it reveals a larger survival area (75 +/- 5%) when compared to other flaps in this study (Mann-Whitney U-test, p<0.001), (3) the vascular pedicle is consistent, (4) control and study flaps are placed on the same animal (5) it can be converted to a random, an axial or a free flap.