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The development of skin flap necrosis during the post-operative period A. Clinical necrosis on POD 3 and POD 7 were compared clinically for each rat, with 2 representative animals shown. Scale bars = 1 cm. B. Histological analysis of skin flaps at POD 7 biopsies. Resected tissues included blackcolored hardened areas (a), brown-colored areas (b), or normal-appearing areas (c). Each section was stained with H&E and observed using brightfield microscopy. Scale bars = 1 cm on the image of rat skin flap and 1 mm on the histological images.
Source publication
BACKGROUND:
The ability to predict the future viability of tissue while still in the operating room and able to intervene would have a major impact on patient outcome. Although several objective methods to evaluate tissue perfusion have been reported, none to date has sufficient accuracy.
METHODS:
In eight Sprague-Dawley rats, reverse McFarlane dor...
Contexts in source publication
Context 1
... chose a reverse McFarlane dorsal skin flap in rat (Figure 1) as the model is well validated, reproducible, and readily available for confirmation by other groups 25,26 . This model also produces a pattern of skin necrosis that progresses over 7 days (Figure 2A), as well as histological changes ( Figure 2B), which are consistent with those seen clinically in failed flaps. An important point is that animals must be followed until POD 7 because skin necrosis continues to mature between POD 3 and POD 7 ( Figure 2A). ...
Context 2
... chose a reverse McFarlane dorsal skin flap in rat (Figure 1) as the model is well validated, reproducible, and readily available for confirmation by other groups 25,26 . This model also produces a pattern of skin necrosis that progresses over 7 days (Figure 2A), as well as histological changes ( Figure 2B), which are consistent with those seen clinically in failed flaps. An important point is that animals must be followed until POD 7 because skin necrosis continues to mature between POD 3 and POD 7 ( Figure 2A). ...
Context 3
... model also produces a pattern of skin necrosis that progresses over 7 days (Figure 2A), as well as histological changes ( Figure 2B), which are consistent with those seen clinically in failed flaps. An important point is that animals must be followed until POD 7 because skin necrosis continues to mature between POD 3 and POD 7 ( Figure 2A). The necrotic area of the flap becomes either black and hardened or brown but not hardened. ...
Context 4
... necrotic area of the flap becomes either black and hardened or brown but not hardened. Histologically, blackened areas ( Figure 2B, a) displayed full-thickness necrosis of the skin including epidermis, dermis, skin appendages and subcutaneous fat, and underlying muscle while brown-colored areas ( Figure 2B, b) displayed necrosis of the epidermis, dermis, and appendages to the level of the mid dermis with inflammation. As expected, surviving skin had complete preservation of the epidermis, dermis, skin appendages, subcutaneous fat, and muscle ( Figure 2B, c). ...
Context 5
... necrotic area of the flap becomes either black and hardened or brown but not hardened. Histologically, blackened areas ( Figure 2B, a) displayed full-thickness necrosis of the skin including epidermis, dermis, skin appendages and subcutaneous fat, and underlying muscle while brown-colored areas ( Figure 2B, b) displayed necrosis of the epidermis, dermis, and appendages to the level of the mid dermis with inflammation. As expected, surviving skin had complete preservation of the epidermis, dermis, skin appendages, subcutaneous fat, and muscle ( Figure 2B, c). ...
Context 6
... blackened areas ( Figure 2B, a) displayed full-thickness necrosis of the skin including epidermis, dermis, skin appendages and subcutaneous fat, and underlying muscle while brown-colored areas ( Figure 2B, b) displayed necrosis of the epidermis, dermis, and appendages to the level of the mid dermis with inflammation. As expected, surviving skin had complete preservation of the epidermis, dermis, skin appendages, subcutaneous fat, and muscle ( Figure 2B, c). ...
Citations
... Although Doppler ultrasound is used to localize perforators, whose equipment is portable, it is unable to show the entire vascular network and its resolution is unsatisfactory. ICG is a Food and Drug Administration (FDA)-approved drug for angiography in microsurgery (15), with a maximum emission wavelength of approximately 800 nm. Thus, the clinically used fluorescence signal of ICG is approximately 800 nm, falling within the near-infrared I window (NIR-I, 700-900 nm) (16). ...
Background
Predicting flap viability benefits patients by reducing complications and guides flap design by reducing donor areas. Due to varying anatomy, obtaining individual vascular information preoperatively is fundamental for designing safe flaps. Although indocyanine green angiography (ICGA) is a conventional tool in intraoperative assessment and postoperative monitoring, it is rare in preoperative prediction.
Methods
ICGA was performed on 20 male BALB/c mice under five wavelengths (900/1,000/1,100, /1,250/1,450 nm) to assess vascular resolution after ICG perfusion. A “mirrored-L” flap model with three angiosomes was established on another 20 male BALB/c mice, randomly divided into two equal groups. In Group A, a midline between angiosomes II and III was used as a border. In Group B, the points of the minimized choke vessel caliber marked according to the ICG signal at 1,450 nm wavelength (ICG1450) were connected. Necrotic area calculations, pathohistological testing, and statistical analysis were performed.
Results
The vascular structure was clearly observed at 1,450 nm wavelength, while the 900 to 1,100 nm failed to depict vessel morphology. Necrosis was beyond the borderline in 60% of Group A. Conversely, 100% of Group B had necrosis distal to the borderline. The number of choke vessels between angiosomes II and III was positively correlated with the necrotic area (%). The pathohistological findings supported the gross observation and analysis.
Conclusion
ICG1450 can delineate the vessel structure in vivo and predict the viability of pedicled skin flaps using the choke vessel as the border between angiosomes.
... Some leaner rats may access the bottom of the flap even in the presence of the collar (Additional File 2, Fig. S9). To avoid animal self-mutilation issues, many researchers choose to create the dorsal flaps as in the classical 1965 McFarlane experiment [80][81][82][83][84]. However, one should note that dorsal flaps represent RPFs and thus a different flap healing model compared to the APFs. ...
Background
Some of the most complex surgical interventions to treat trauma and cancer include the use of locoregional pedicled and free autologous tissue transfer flaps. While the techniques used for these reconstructive surgery procedures have improved over time, flap complications and even failure remain a significant clinical challenge. Animal models are useful in studying the pathophysiology of ischemic flaps, but when repeatability is a primary focus of a study, conventional in-vivo designs, where one randomized subset of animals serves as a treatment group while a second subset serves as a control, are at a disadvantage instigated by greater subject-to-subject variability. Our goal was to provide a step-by-step methodological protocol for creating an alternative standardized, more economical, and transferable pre-clinical animal research model of excisional full-thickness wound healing following a simulated autologous tissue transfer which includes the primary ischemia, reperfusion, and secondary ischemia events with the latter mimicking flap salvage procedure.
Results
Unlike in the most frequently used classical unilateral McFarlane’s caudally based dorsal random pattern skin flap model, in the herein described bilateral epigastric fasciocutaneous advancement flap (BEFAF) model, one flap heals under normal and a contralateral flap—under perturbed conditions or both flaps heal under conditions that vary by one within-subjects factor. We discuss the advantages and limitations of the proposed experimental approach and, as a part of model validation, provide the examples of its use in laboratory rat (Rattus norvegicus) axial pattern flap healing studies.
Conclusions
This technically challenging but feasible reconstructive surgery model eliminates inter-subject variability, while concomitantly minimizing the number of animals needed to achieve adequate statistical power. BEFAFs may be used to investigate the spatiotemporal cellular and molecular responses to complex tissue injury, interventions simulating clinically relevant flap complications (e.g., vascular thrombosis) as well as prophylactic, therapeutic or surgical treatment (e.g., flap delay) strategies in the presence or absence of confounding risk factors (e.g., substance abuse, irradiation, diabetes) or favorable wound-healing promoting activities (e.g., exercise). Detailed visual instructions in BEFAF protocol may serve as an aid for teaching medical or academic researchers basic vascular microsurgery techniques that focus on precision, tremor management and magnification.
Graphical Abstract
... Although normalization enhances reliability and validity by reducing influencing factors, intensity-related parameters are depleted. These absolute parameters, such as maximum intensity, could be useful in the assessment of tissue viability, as was shown in several studies [18,72,101]. Furthermore, normalization of time-intensity curves in areas with low fluorescence intensity (for example within tissue necrosis), i.e., magnifying the signal to 100%, might lead to fluttering of the curves, making them noninterpretable. ...
Purpose
Incorrect assessment of tissue perfusion carries a significant risk of complications in surgery. The use of near-infrared (NIR) fluorescence imaging with Indocyanine Green (ICG) presents a possible solution. However, only through quantification of the fluorescence signal can an objective and reproducible evaluation of tissue perfusion be obtained. This narrative review aims to provide an overview of the available quantification methods for perfusion assessment using ICG NIR fluorescence imaging and to present an overview of current clinically utilized software implementations.
Methods
PubMed was searched for clinical studies on the quantification of ICG NIR fluorescence imaging to assess tissue perfusion. Data on the utilized camera systems and performed methods of quantification were collected.
Results
Eleven software programs for quantifying tissue perfusion using ICG NIR fluorescence imaging were identified. Five of the 11 programs have been described in three or more clinical studies, including Flow® 800, ROIs Software, IC Calc, SPY-Q™, and the Quest Research Framework®. In addition, applying normalization to fluorescence intensity analysis was described for two software programs.
Conclusion
Several systems or software solutions provide a quantification of ICG fluorescence; however, intraoperative applications are scarce and quantification methods vary abundantly. In the widespread search for reliable quantification of perfusion with ICG NIR fluorescence imaging, standardization of quantification methods and data acquisition is essential.
... 9 It has already been used for various indications, including image guidance in oncologic surgery, intraoperative perfusion measurement of bowel anastomosis to predict leakage, location of perforator vessels in reconstructive surgery, and quality control for coronary artery bypass surgery. [10][11][12][13][14][15][16][17][18][19] Indocyanine green (ICG) is one of the two fluorescent dyes approved for clinical use by the Food and Drug Administration and is confined to vascular components, making it feasible for skin perfusion assessment through either an intravenous or intra-arterial route. 11,20,21 The toxicity of ICG is low, with a reported incidence of allergic reactions in 1 of 10,000 patients. ...
Objective
In the diagnosis of peripheral artery disease (PAD), the ankle-brachial index plays an important role. However, results of the ankle-brachial index are unreliable in patients with severe media sclerosis. Near-infrared (NIR) fluorescence imaging using indocyanine green (ICG) can provide information about tissue perfusion and has already been studied in oncologic, reconstructive, and cardiac surgery. For patients with PAD, this technique might give insight into skin perfusion and thereby guide treatment. We performed a systematic review of the literature on the use of NIR fluorescence imaging in patients with PAD.
Methods
PubMed, MEDLINE, Embase, and Cochrane were searched for articles and abstracts on the application of NIR fluorescence imaging using ICG as fluorescent dye in patients with PAD. Our search strategy combined the terms “fluorescence,” “ICG,” or synonyms and “peripheral artery disease” or synonyms. The extracted data included fluorescence parameters and test characteristics for diagnosis of PAD.
Results
Twenty-three articles were found eligible for this review using 18 different parameters for evaluation of the fluorescence signal intensity. NIR fluorescence imaging was used for four main indications: diagnosis, quality control in revascularization, guidance in amputation surgery, and visualization of vascular structures. For the diagnosis of PAD, NIR fluorescence imaging yields a sensitivity ranging from 67% to 100% and a specificity varying between 72% and 100%. Significant increases in multiple fluorescence parameters were found in comparing patients before and after revascularization.
Conclusions
NIR fluorescence imaging can be used for several indications in patients with PAD. NIR fluorescence imaging seems promising in diagnosis of PAD and guidance of surgeons in treatment, especially in patients in whom current diagnostic methods are not applicable. Further standardization is needed to reliably use this modality in patients with PAD.
... Giunta et al. suggested that a fluorescence perfusion index of less than 25% indicates skin necrosis while viable tissue has values exceeding 40%. 29 Monahan et al. published similar data, reporting a "grey zone" between 25% and 57% in which ICGA is unable to accurately determine perfusion, 30 while Wada et al. 31 use a fluorescence threshold between 40 and 50% to determine viable tissue in rats. Gorai et al. suggest resecting mastectomy flaps at a fluorescence value below 34%. ...
Background
Indocyanine green angiography (ICGA) is slowly replacing conventional methods of evaluating perfusion during flap surgery. Microcirculatory changes during flap elevation create a marked state of hypoperfusion intraoperatively leading to ICGA underestimation of tissue viability and consequent resection of viable tissue. We propose a novel method of flap warming to induce maximum vasodilation before performing ICGA to increase accuracy in assessing perfusion.
Methods
Submental flaps harvested on a single perforator were created in 8 pigs. ICG angiography was performed in the intraoperative phase (ICGA-C), after inducing maximum vasodilatation by warming the flap at 42 °C (ICGA-W) and at 24H postoperative (ICGA-24). By setting a fluorescence threshold of 33% as indicative of necrosis, the flap surface deemed viable by ICGA was measured for ICGAC, ICGAW and ICGA24. The results were then compared to the actual flap survival observed clinically at 7 days.
Results
The mean of ICG-C predicted flap survival (FS-C = 49.17%) is 12.97% lower than the mean of actual flap survival on postoperative day 7 (FS = 62.14%). The mean difference between ICG-W and ICG-24 predicted flap survival (FS-W and FS-24) and actual flap survival in the postoperative day 7 (FS) is lower, 3.13% and 2.15%, respectively. Average perfusion recovery over 24 h was 10.83% (FS-24–FS-C).
Conclusions
Conventional intraoperative ICGA underestimated perfusion in all cases. Warming the flap intraoperatively and achieving maximum vasodilation mitigates the effects of vasoconstriction and mimics the microcirculatory environment encountered at 24 h. Performing angiography after induced vasodilation improves ICGA assessment of flap perfusion.
... When planning a reconstruction with a superficial fascia-preserving flap, some modalities can be used to anticipate the proportion of necrosis and to prepare or modi-fy the plan. Indocyanine green and fluorescence images can precisely predict tissue viability [20]. With precise planning using CT angiography and color Doppler imaging, we are confident that surgeons can minimize flap morbidity. ...
Elevating thin flaps has long been a goal of reconstructive surgeons. Thin flaps have numerous advantages in reconstruction. In this study, we present a surgical method for elevating a thin flap and demonstrate the safety of the procedure. A retrospective review was performed of the electronic medical records of patients who underwent thin flap elevation for lower extremity reconstruction from April 2016 to September 2016 at the Department of Plastic Surgery of Asan Medical Center. All flaps included in this study were elevated above the superficial fascia. A total of 15 superficial circumflex iliac artery free flaps and 13 anterolateral thigh free flaps were enrolled in the study. The total complication rate was 17.56% (n=5), with total loss of the flap in one patient (3.57%) and partial necrosis of the flap in four patients (14.28%). No wound dehiscence or graft loss at the donor wound took place. Elevation above the superficial fascia is not inferior in terms of flap necrosis risk and is superior for reducing donor site morbidity. In addition to its safety, it yields good aesthetic results.
Background
Some of the most complex surgical interventions to treat trauma and cancer include the use of locoregional pedicled flaps and free autologous tissue transfer. While the techniques used for these reconstructive surgery procedures have improved over time, flap complications and even failure remain a significant clinical challenge. Animal models are useful in studying the pathophysiology of ischemic flaps, but when repeatability is a primary focus of a study, conventional in-vivo designs, where one randomized subset of animals serves as a treatment group while a second subset serves as a control, are at a disadvantage instigated by greater subject-to-subject variability.
Results
We present a novel, economical, and standardized pre-clinical animal model of excisional full-thickness wound closure and healing using axial pattern flaps that incorporates an anatomically named vascular pedicle. In this bilateral epigastric fasciocutaneous advancement flap (BEFAF) model, which simulates an actual clinical procedure of autologous tissue transfer, one flap heals under normal and a contralateral flap - under perturbed conditions or both flaps heal under conditions that vary by one within-subjects factor. Although we describe step-by-step methodological approach how to create such flaps as well as collect, process, and analyze flap survival data in larger size rodents, specifically, the rats (Rattus norvegicus), the BEFAF model is transferable and could be implemented in any mammalian species. We also stress the importance of taking and presenting high resolution histological stain images of the flaps that are indispensable for diagnostic result interpretation in the full-thickness wound healing studies.
Conclusions
BEFAFs may be used to investigate the spatiotemporal cellular and molecular responses to complex tissue injury and interventions simulating clinically relevant flap complications (e.g., secondary arterial, venous, or mixed ischemia) and therapeutic or surgical treatments (e.g., flap delay) in the presence or absence of confounding risk factors (e.g., substance abuse, irradiation, diabetes) or favorable wound-healing promoting activities (e.g., exercise). This technically challenging but feasible reconstructive surgery model eliminates inter-subject variability, while concomitantly minimizing the number of animals needed to achieve adequate statistical power. BEFAF also serves as an aid for teaching basic vascular microsurgery techniques that focus on precision, tremor management and magnification.
Skin grafting is one of the most frequently performed surgical procedures in dermatology. Nevertheless, the failure rate is still quite high, which can cause a huge burden for patients and the health care system. Early interventions, like salvage surgery, can rescue the grafts that are going to fail. Therefore, real-time and objective monitoring of skin grafts and flaps is crucial to guide clinicians for an evidence-based treatment. This can be achieved by modern sensor applications using advanced techniques in nanotechnology and material science. This review provides an overview on current challenges for the further development of (bio-)sensors for monitoring the uptake of implanted skin grafts and skin flaps. Special interest has been given to invasive/non-invasive as well as wearable/implantable applications. In addition, the adaptation of recent developments in alternative sensing systems with physical, optical and electrochemical transducers for the continuous monitoring (intra- and post-operative) of skin transplants has been discussed.
The use of skin flaps to fill large defects is a key surgical technique in reconstructive surgery, effective real‐time in vivo imaging for flap design and use is urgent. Currently, fluorescent imaging in the second NIR window (NIR‐II; 1000–1700 nm) is characterized by non‐radiation, less expensive and higher resolution in comparisons with the first NIR window (NIR‐I; 700‐900 nm) and other traditional imaging modalities. In this article, we identified the location and numbers of perforators and choke zone via NIR‐II imaging. Then, eight abdominal perforator flaps were established and evaluated the perfusion zones at special time points. Finally, after eight pedicled flaps establishment, NIR‐II imaging was used to guide the optimal timing for division of flap pedicle. The results showed that NIR‐II fluorescence imaging with indocyanine green (ICG) can reliably visualize vascular supply, which makes it to be an accurate and in vivo imaging approach to flap clinical design and use. This article is protected by copyright. All rights reserved.
Background
Flap necrosis is a feared complication of reconstructive surgery. Current methods of prediction using Indocyanine green (ICG) lack specificity. IntegriSense750 is a fluorescence agent that binds sites of vascular remodeling. We hypothesized that IntegriSense750 better predicts flap compromise compared to ICG.
Methods
Fifteen mice underwent lateral thoracic artery axial flap harvest. Mice received an injection of ICG (n = 7) or IntegriSense750 (n = 8) daily from postoperative days (POD) 0–3 and were imaged daily. Mean signal-to-background ratios quantified the change in fluorescence as necrosis progressed.
Results
Mean signal-to-background ratio was significantly higher for IntegriSense750 compared to ICG on POD0 (1.47 ± 0.17 vs. 0.86 ± 0.21, p = 0.01) and daily through POD3 (2.12 ± 0.70 vs. 0.96 ± 0.29, p < 0.001).
Conclusions
IntegriSense750 demonstrates increased signal-to-background ratio at areas of flap distress compared to ICG which may increase identification of flap necrosis and improve patient outcomes.
