Rat ear reattachment as an animal model

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.

Drug-Induced Atrial Fibrillation Complicates the Results of Flap Surgery in a Rat Model

The relationship between atrial fibrillation (AF) and flap survival has not been fully characterized. Therefore, the goal of this study was to investigate the effect of AF on survival areas of pedicled flap and survival rates of free flap in an experimental rat AF model. An aconitine-induced rat AF model was established without intubation anesthesia. Survival areas of the pedicled rectangular epigastric flap were compared between AF rats (n = 7) and control rats (n = 7), and survival rates of the free epigastric flap were compared between AF rats (n = 10) and control rats (n = 10). Animals that died during the study or in which AF was not induced were excluded from study. A total of 64 rats were assessed in this study. Atrial fibrillation was induced with a success rate of 77.8% (21/27) throughout the study. Pedicled flap survival area was significantly higher in controls (75.1 ± 9.0%; n = 7) than that in AF animals (55.7 ± 13.0%; n = 7) (P < 0.01, nonpaired Student t test). Free flap survival rates were 80% in controls and 40% in AF animals (P = 0.07, χ² test). This is the first study to develop an aconitine-induced model of AF in rats. Atrial fibrillation has a detrimental effect on survival areas of the pedicled flap and survival rates of the free flap.

A reverse-flow composite flap in the rat

Reverse-flow flaps are currently particularly used for the reconstruction of defects of the distal part of the extremities. Despite their common usage there have been many reports of postoperative complications, especially resulting in partial or total flap necrosis. There is insufficient knowledge of flap haemodynamics, physiology and wound healing properties in reverse-flow flaps. Development of the proper experimental models is needed to investigate these issues. The purpose of this study was to describe a new reverse-flow flap model in the rat. A total of 20 adult Wistar rats weighing 200-250 g were used in this experiment. In five rats, the vascular anatomy of the auricle of the rat was determined by anatomic dissection and microangiography. In the experimental group (N=5), 1x1 cm reverse-flow composite flaps were harvested as a semi-island shape, based on the distal course of the medial branch of the anterior auricular artery. In the control group, consisting of five rats, the flap was designed and raised based on the proximal course of the medial auricular artery, again in a semi-island shape. In the remaining five animals, a square-shaped composite tissue of the whole layer of the auricle, 1x1 cm in size, was harvested dividing all the bases circumferentially. The composite tissue was replaced in situ. While the former was considered a conventional antegrade-flow flap subgroup, the latter was designated as a graft subgroup. All flaps were replaced in situ. The survival of the flap was evaluated on postoperative day 7 by direct observation and microangiography. The skin island of all the reverse-flow flaps and conventional antegrade-flow flaps survived completely giving a success rate of 100%, whereas all grafts in the control group underwent complete necrosis. Microangiographic studies revealed the vascularity of the reverse-flow and antegrade-flow flaps, identifying the course of the auricular arteries. In conclusion, with its evident advantages of easy to design and harvesting, reliable survival pattern and consistent vascular structure, our new flap model will provide a means for future studies on flap haemodynamics, physiology in reverse-flow flaps.

Rat Penis as a Replantation Model

The aim of this study is to assess the feasibility of rat penile replantation as a new microsurgical training model. The study was performed in 2 parts. ANATOMIC STUDIES: Fifteen Wistar albino rats were used to study and document the penile vascular anatomy. In 5 rats, dissections were performed after colored silicone injections, while 5 rats were operated under anesthesia to develop the strategy of flap elevation. In the remaining 5 rats, microangiographic study was performed with silicone-lead oxide mixture. FLAP STUDIES: As flap studies in 5 rats, penis were elevated based on right-side internal pudendal artery and internal pudendal vein and resutured. In 6 rats, penis were elevated as free flaps, and in 3 rats the penis were implanted in right thigh of the rats being the femoral artery and vein recipient. In the remaining 3 rats, penis were resutured in their original place, with saphenous artery and vein being the recipient and rerouted to the pubic region. At postoperative fifth day, the penis were examined for viability, and selected ones were histologically examined. Rat penis has a dual blood supply from bilateral internal pudendal arteries. Venous drainage is via both crural veins and dorsal vein. One side of the internal pudendal artery and anastomotic vein (branch of pudendal plexus) may be used as the vascular pedicle of the flap. Rat penis may be successfully elevated as a free flap and also may be replanted in its original place.

Establishing a Composite Auricle Allotransplantation Model in Rats: Introduction to Transplantation of Facial Subunits

BACKGROUND

Allografts from cadaveric sources may be an alternative for replacing the missing auricle. In this report, the technical aspects of orthotopic composite auricle allotransplantation and an effective short-term immunosuppression protocol in a rat model are described.

METHODS

A total of seven transplantations were performed in the experimental group. The donors were Brown Norway (RT1(n)) rats and the recipients were Lewis (RT1(1)) rats. In the pilot study, 11 isotransplantations (Lewis to Lewis) were performed in either heterotopic (n = 4) or orthotopic (n = 7) locations to establish the surgical technique. Composite auricle allografts were harvested and transplanted based on the posterior facial vein, the external carotid artery, and the great auricular nerve. A plastic square mold sutured over the transplants was used to prevent mechanical trauma to the transplants. Cyclosporine A initiated as 16 mg/kg/day for 2 weeks and tapered to a dosage of 8 mg/kg/day for another 2 weeks was the only immunosuppression regimen.

RESULTS

All allografts survived with perfect viability for the follow-up period of 30 days. There were no signs of rejection, infection, or graft-versus-host disease, although significant weight loss was observed resulting from the immunosuppressive treatment. However, signs of rejection started 4 to 6 days after cessation of the cyclosporine A treatment, including edema, localized epidermal desquamation, and erythema formation that eventually progressed to necrosis within 11 to 14 days. The histologic outcomes were well correlated with the macroscopic appearance.

CONCLUSIONS

It is feasible to elevate and transplant the composite auricle in rats as a single neurosensorial facial subunit. A tapered dose of cyclosporine A from 16 mg/kg to 8 mg/kg allows maintaining allograft survival for 30 days across a strong major histocompatibility complex barrier. This model is reliable and reproducible and has the potential to be used for future immunologic studies to prevent or to induce transplantation tolerance.

Surgical technique for vascularized ear transplantation in mice

Traditionally, the mouse nonvascularized skin graft has been widely used in organ transplant research. There are, however, several limitations with this model, the main one being the different immune response of vascularized vs. nonvascularized grafts. We have recently developed a vascularized, orthotopic ear transplant model in mice. This model has several advantages that make it a useful tool to study many aspects of transplantation. The donor operation consists of harvesting the ear with intact arterial and venous pedicles. The arterial pedicle is dissected down to the common carotid artery with ligation of all branches except the auricular artery. The venous pedicle is based on the jugular vein with preservation of the auricular veins draining into the posterior facial vein. In the subsequent recipient operation, the graft is transplanted into an orthotopic position using the common carotid artery for arterial inflow and the jugular vein for venous outflow. We performed 16 such transplants (6 isografts, 5 allografts, and 5 xenografts), with a success rate of 94% (15/16). The donor operation time was 1.5 hours and the recipient operation time was 2.5 hours. The total time for anastamosis was 45 +/- 5 minutes. Serial biopsies were obtained on days 3, 5, and 7, and correlated with gross findings. In summary, this study illustrates that it is technically possible to transplant a mouse ear graft. The main advantage of this model is that it is a vascularized graft that can be visibly observed and easily biopsied, thus allowing for good correlation between gross and histological findings after transplantation. We plan to use this model further to study in detail the rejection patterns in an allograft and xenograft setting.

A new vascularized skin transplant model in rats

The aim of this work was to develop a vascularized skin transplantation model in the rat to allow comparison of the immunological events with those of classic free skin grafts and vascularized organ grafts. Seventy-nine syngeneic transplants were performed using inbred Wistar and PVG rats to develop the model. Epigastric skin flaps were taken with a vascular pedicle of common femoral artery and vein and implanted on the back of the neck. The graft vessels were anastomosed end-to-end and end-to-side to the recipient common carotid artery and external jugular vein with interrupted 10-0 nylon sutures under an operating microscope. A high success rate (11 of 11) was achieved in the final method developed, with light microscopy confirming normal skin structure in the flaps following transplantation. The advantages of the model include comparable skin size to that commonly used for nonvascularized skin grafts, while the physiology in terms of blood supply is similar to that of vascularized organ grafts; the grafts are visible with free access for biopsy; and the size of the graft can easily be varied to allow studies concerning antigen load.