Free Pectoral Skin Flap in the Rat Based on the Long Thoracic Vessels: A New Flap Model for Experimental Study and Microsurgical Training

Development of a porcine training model for microvascular fasciocutaneous free flap reconstruction

BACKGROUND

In reconstructive surgery, improvements are needed in the effective teaching of free flap surgery. There is a need for easily accessible and widely available training without high financial costs or ethical concerns while still providing a realistic experience. Our aim was to develop an appropriate training model for microvascular flaps.

METHODS

We identified pig head halves as most appropriate regarding availability, cost, and realism. These accrue largely by the food industry, so no animals need to be sacrificed, making it more ethical from an animal welfare perspective. We evaluated the suitability as flap donor site and analyzed the vascular anatomy of 51 specimens.

RESULTS

Anatomical evaluation revealed a reliable and constant vascular anatomy, allowing the design of a flap model that can effectively illustrate the entire process of microvascular flap surgery. The process was divided into 6 key steps. The flap can be harvested after marking the vascular pedicle 5.3 cm from the lateral corner of the mouth. Skin island design and subsequent tissue dissection follow until a fasciocutaneous flap is raised, similar to a radial flap. Upon completion of flap harvesting, it can be freely transferred for defect reconstruction. Microvascular anastomosis can be performed on recipient vessels in the cervical region, and the difficulty can be individually adjusted.

CONCLUSIONS

The developed training model is a reasonable compromise in terms of surgical realism, availability, didactic value, and cost/time effectiveness. We believe it is a powerful and effective tool with high potential for improving surgical education and training.

Interleukin-6 from Adipose-Derived Stem Cells Promotes Tissue Repair by the Increase of Cell Proliferation and Hair Follicles in Ischemia/Reperfusion-Treated Skin Flaps

The most common postoperative complication after reconstructive surgery is flap necrosis. Adipose-derived stem cells (ADSCs) and their secretomes are reported to mediate skin repair. This study was designed to investigate whether conditioned media from ADSCs (ADSC-CM) protects ischemia/reperfusion- (I/R-) induced injury in skin flaps by promoting cell proliferation and increasing the number of hair follicles. The mouse flap model of ischemia was ligating the long thoracic vessels for 3 h, followed by blood reperfusion. ADSC-CM was administered to the flaps, and their survival was observed on postoperative day 5. ADSC-CM treatment led to a significant increase in cell proliferation and the number of hair follicles. IL-6 levels in the lysate and CM from ADSCs were significantly higher than those from Hs68 fibroblasts. Furthermore, a strong decrease in cell proliferation and the number of hair follicles was observed after treatment with IL-6-neutralizing antibodies or si-IL-6-ADSC. In addition, ADSC transplantation increased flap repair, cell proliferation, and hair follicle number in I/R injury of IL-6-knockout mice. In conclusion, IL-6 secreted from ADSCs promotes the survival of I/R-induced flaps by increasing cell proliferation and the number of hair follicles. ADSCs represent a promising therapy for preventing skin flap necrosis following reconstructive and plastic surgery.

Vascular architecture in free flaps: Analysis of vessel morphology and morphometry in murine free flaps

The aim of this study was to analyze the development of vascular architecture as well as vascular morphometry and morphology of anastomosed microvascular free flaps. Free pectoral skin flaps were raised in 25 rats and anastomosed to the femoral vessels in the groin region. CD31 immunohistology was performed after 3, 7 and 12 d (each 5 animals each) to analyze microvessel density (MVD), microvessel area (MVA) and microvessel size (MVS). Microvascular corrosion casting was performed after 7 and 12 d (5 animals each) to analyze vessel diameter (VD), intervascular distance (IVD), interbranching distance (IBD), and branching angle (BA). Further on, sprout and pillar density as hallmarks of sprouting and intussusceptive angiogenesis were analyzed. Pectoral skin isles from the contralateral side served as controls. A significantly increased MVD was found after 7 and 12 d (p each <0.001). MVA was significantly increased after 3, 7 and 12 d (p each <0.001) and a significantly increased MVS was analyzed after 3 and 7 d (p each <0.001). VD and IVD were significantly increased after 7 and 12 d (p each <0.001). For IBD, a significantly increase was measured after 7 d (p < 0.001). For IBA, sprout and pillar density, no significant differences were found (p each ≥0.05). Significant changes in the vascular architecture of free flaps after successful microvascular anastomosis were seen. Since there was no evidence for sprout and pillar formation within the free flaps, the increased MVD and flap revascularization might be induced by the receiving site.

Animal models in plastic and reconstructive surgery simulation-a review

BACKGROUND

The use of live and cadaveric animal models in surgical training is well established as a means of teaching and improving surgical skill in a controlled setting. We aim to review, evaluate, and summarize the models published in the literature that are applicable to Plastic Surgery training.

MATERIALS AND METHODS

A PubMed search for keywords relating to animal models in Plastic Surgery and the associated procedures was conducted. Animal models that had cross over between specialties such as microsurgery with Neurosurgery and pinnaplasty with ear, nose, and throat surgery were included as they were deemed to be relevant to our training curriculum. A level of evidence and recommendation assessment was then given to each surgical model.

RESULTS

Our review found animal models applicable to plastic surgery training in four major categories namely-microsurgery training, flap raising, facial surgery, and hand surgery. Twenty-four separate articles described various methods of practicing microsurgical techniques on different types of animals. Fourteen different articles each described various methods of conducting flap-based procedures which consisted of either local or perforator flap dissection. Eight articles described different models for practicing hand surgery techniques. Finally, eight articles described animal models that were used for head and neck procedures.

CONCLUSIONS

A comprehensive summary of animal models related to plastic surgery training has been compiled. Cadaveric animal models provide a readily available introduction to many procedures and ought to be used instead of live models when feasible.

Adipose-Derived Stem Cells Protect Skin Flaps against Ischemia/Reperfusion Injury via IL-6 Expression

Flap necrosis is the most frequent postoperative complication encountered in reconstructive surgery. We elucidated whether adipose-derived stem cells (ADSCs) and their derivatives might induce neovascularization and protect skin flaps during ischemia/reperfusion (I/R) injury. Flaps were subjected to 3 hours of ischemia by ligating long thoracic vessels and then to blood reperfusion. Qtracker-labeled ADSCs, ADSCs in conditioned medium (ADSC-CM), or ADSC exosomes (ADSC-Exo) were injected into the flaps. These treatments led to significantly increased flap survival and capillary density compared with I/R on postoperative day 5. IL-6 levels in the cell lysates or in conditioned medium were significantly higher in ADSCs than in Hs68 fibroblasts. ADSC-CM and ADSC-Exo increased tube formation. This result was corroborated by a strong decrease in skin repair after adding IL-6-neutralizing antibodies or small interfering RNA for IL-6 ADSCs. ADSC transplantation also increased flap recovery in I/R injury of IL-6-knockout mice. IL-6 was secreted from ADSCs through signal transducer and activator of transcription phosphorylation, and then IL-6 stimulated angiogenesis and enhanced recovery after I/R injury by the classic signaling pathway. The mechanism of skin recovery includes the direct differentiation of ADSCs into endothelial cells and the indirect effect of IL-6 released from ADSCs. ADSC-CM and ADSC-Exo could be used as off-the-shelf products for this therapy.

A Model of Free Tissue Transfer: The Rat Epigastric Free Flap

Free tissue transfer has been increasingly used in clinical practice since the 1970s, allowing reconstruction of complex and otherwise untreatable defects resulting from tumor extirpation, trauma, infections, malformations or burns. Free flaps are particularly useful for reconstructing highly complex anatomical regions, like those of the head and neck, the hand, the foot and the perineum. Moreover, basic and translational research in the area of free tissue transfer is of great clinical potential. Notwithstanding, surgical trainees and researchers are frequently deterred from using microsurgical models of tissue transfer, due to lack of information regarding the technical aspects involved in the operative procedures. The aim of this paper is to present the steps required to transfer a fasciocutaneous epigastric free flap to the neck in the rat.

This flap is based on the superficial epigastric artery and vein, which originates from and drain into the femoral artery and vein, respectively. On average the caliber of the superficial epigastric vein is 0.6 to 0.8 mm, contrasting with the 0.3 to 0.5 mm of the superficial epigastric artery. Histologically, the flap is a composite block of tissues, containing skin (epidermis and dermis), a layer of fat tissue (panniculus adiposus), a layer of striated muscle (panniculus carnosus), and a layer of loose areolar tissue.

Succinctly, the epigastric flap is raised on its pedicle vessels that are then anastomosed to the external jugular vein and to the carotid artery on the ventral surface of the rat's neck. According to our experience, this model guarantees the complete survival of approximately 70 to 80% of epigastric flaps transferred to the neck region. The flap can be evaluated whenever needed by visual inspection. Hence, the authors believe this is a good experimental model for microsurgical research and training.

Twelve tips for postgraduate or undergraduate medics building a basic microsurgery simulation training course

Microsurgery is used in a variety of surgical specialties, including Plastic Surgery, Maxillofacial Surgery, Ophthalmic Surgery, Otolaryngology and Neurosurgery. It is considered one of the most technically challenging fields of surgery. Microsurgical skills demand fine, precise and controlled movements, and microsurgical skill acquisition has a steep initial learning curve. Microsurgical simulation provides a safe environment for skill acquisition before operating clinically. The traditional starting point for anyone wanting to pursue microsurgery is a basic simulation training course. We present twelve tips for postgraduate and undergraduate medics on how to set up and run a basic ex-vivo microsurgery simulation training course suitable for their peers.

Modified free pectoral skin flaps in rats

Various types of murine free flaps have been developed for microsurgical training and research. We present a new modification of the free pectoral skin flap in Sprague-Dawley rats. Twelve free pectoral skin flaps were raised according to the standard protocol except that we deviated from it by transecting the common thoracic vessels at the origin of the axillary vessels and anastomosing them end-to-side to the femoral vessels in the groin. This reduced operating time and complications as well as postoperative morbidity and mortality. Overall, it simplified the procedure considerably and therefore made the model more attractive to beginners in microvascular surgery.

Comparative study of different combinations of microvascular anastomosis types in a rat vasospasm model: versatility of end-to-side venous anastomosis in free tissue transfer for extremity reconstruction

BACKGROUND

There have been many studies comparing the patency rates of end-to-end and end-to-side microvascular anastomoses in both arteries and veins. Most of them failed to demonstrate a significant difference. The purpose of this study was to compare three different combinations of microvascular anastomoses in a rat vasospasm model, and determine which type of anastomosis is the most tolerant to vasospasm.

METHODS

Ninety Wistar rats were divided into three groups (n = 30 for each). In each group, a free pectoral skin flap was elevated and microsurgically transferred to the anterior cervical region. In group 1, end-to-end anastomoses were performed on both arteries and veins, in group 2 end-to-side anastomoses were performed on arteries and end-to-end anastomoses were performed on veins, and in group 3 end-to-end anastomoses were performed on arteries and end-to-side anastomoses were performed on veins. After revascularization, vasospasm was induced with topical epinephrine. Flap survival was assessed on day 3, and the success rates of the three groups were compared.

RESULTS

The flap success rate was 73.3% (22 of 30) in group 1, 66.7% (20 of 30) in group 2, and 96.7% (29 of 30) in group 3. The differences between groups 1 and 3 and between groups 2 and 3 were statistically significant. Overall, venous thrombosis was much more frequent than arterial thrombosis.

CONCLUSIONS

In a rat epinephrine-induced vasospasm model, venous thrombosis was much more frequent than arterial thrombosis. The type of arterial anastomosis did not affect the success rate, but end-to-side venous anastomosis had a higher success rate than end-to-end venous anastomosis.