A novel model to evaluate the learning curve in microsurgery: Serial anastomosis of the rat femoral artery

INTRODUCTION

Microsurgery training is an essential component of the plastic surgery residency program.

Although many non-living animal models have been proposed as a suitable alternative to the living model ^1–4, they don’t allow to reproduce many of the factors that normally occur during a microsurgical dissection and anastomosis, such as bleeding and vessel spasm, as well as they prevent the surgeon to check the anastomosis by performing a patency test. Therefore the live rat animal model is still indispensable. In bibliography, many living rat animal models have been reported, consisting in the performance of several exercises, such as flaps or transplants, but all of them imply the use of a high number of animals allowing the use of one vessel only for one exercise. We propose a simple method to evaluate the surgeon’s microsurgical skills during the training, consisting in the performance of 4 anastomosis in a row. This allows to exploit as much as possible the same vessel and it leads to an amplification of the trainee surgeon’s mistakes, helping the novice surgeon to assess his microsurgical level and to improve his capacity.

MATERIALS AND METHODS/SURGICAL TECHNIQUE

The experiment was approved by the Ethics Committee at St. Anne University hospital in Brno and performed under standard conditions (i.e., temperature 24°C to 25°C, light conditions, sterility).

A total number of 30 Wistar-albino Rats, weighting approximately between 300–350 g, were used in this study. The rats were intraperitoneally anesthetized using ketamine (75−95 mg/kg) and xylazine (5−8 mg/kg) solution. Euthanasia was performed with intracardiac phenobarbital administration. Both femoral arteries of each rat were used, giving a total of 60 vessels with a diameter ranging from 0.9 to 1.1 mm.

In order to obtain as much space as possible, it is mandatory to completely expose the femoral artery, from the inguinal ligament up to the ending of the vessel in the saphenous artery, through an accurate ligature of every vessel that branches off from the femoral artery up to the genicular descending artery.

The microvascular technique used was the simple-interrupted suture in 10-0 nylon, according to the standard method of Acland⁵, and anastomoses were performed in a proximal-distal fashion.

After each procedure, the surgical field was irrigated with a topical 10% magnesium sulphate solution to reduce the risk of vessel spasm⁸.

Once the femoral artery was completely prepared, the first author performed serial anastomoses to a maximum of 4 (Fig. 1).

This model has been used on 60 femoral arteries by a single surgeon who had no previous microsurgical experience (G. L.).

Following accomplishment of each anastomosis, patency was checked by a standard patency test after 10 minutes (Fig. 2). Each microsurgical session was concluded every time the surgeon achieved a negative patency test, indicating the vessel’s occlusion. The test results were then collected in relation to the number of anastomoses in a row in a table, calculating the patency rate. The higher was the number of patent anastomoses, the greater was the patency rate.

RESULTS

Patency rate was 96.6% (n=58) for a single anastomosis; 63.3% (n=38) for 2 anastomoses in a row; 36.6% (n=22) for three anastomoses in a row and 18.3% (n=11) for 4 anastomoses in a row (Fig. 3)

The results of each femoral artery procedure are summarized in Table 1.

DISCUSSION

The use of a rat model in microsurgery training dates back to the early 1960’s, when pioneers, such as Lee ⁷, identified the necessity of low cost surgical models that could meet the clinical needs of the day. The rat model, but in particular the rat femoral artery, is definitely the most frequently used in microsurgical training for its easy dissection, for the optimal exposure of the vessel and for its dimensions (0.7–1.1 mm). This is essential in order to learn to tackle every possible difficult situation in surgical practice.

Various factors contribute to the difficulty of performing several anastomoses in series:

1. Incorrect stitches distribution along the margins, instead of parallel arrangement with regards to the blood flow direction;
2. Twisting of the vessel between each anastomosis;
3. Repeated traumatic pinching of vessel’s margins;
4. Increase of the platelet deposit downstream of each anastomosis;
5. Limitation of the clamping space;
6. Awkward surgical field;
7. Gradually increasing stress to the surgeon.

All these factors are the typical mistakes performed by the novice surgeon, who doesn’t realize, at the beginning of its training, the importance of avoiding them during a microsurgical suture. This exercise shows the errors amplification, this way leading the surgeon to correct himself.

We have found that patency test was resulted positive after achieving four anastomoses in a row only during the latest microsurgical sessions. These results show how the surgeon gradually improved his skills, reaching a plateau in the learning curve at the end of his microsurgical training, in which the risk of errors is much lower.

The training of a novice microsurgeon is a step-by-step process. Starting from simple exercises such as end-to-end suture of the femoral artery, the trainee will be able to perform a more advanced practice like the rat kidney autotransplantation or the epigastric free flap⁷. All the living models for microsurgical training reported in bibliography improve the microsurgical skills increasing the difficulty in the vessel dissection or decreasing the vessel’s size but none of them highlights the typical mistakes that a novice surgeon does at the beginning of its training.

In our opinion, this model helps the novice surgeon to assess his microsurgical level and to improve his capacity in performing an anastomosis through an exercise consisting in creating 4 anastomoses in a row. Indeed, this leads to an amplification of the trainee surgeon’s mistakes, which add up to each other as the anastomoses are performed. However, further studies need to be conducted in order to increase the sample.

Moreover lately many studies focus on the research of suitable non-living models, this leading to the costs reduction and the animal preservation. The performance of serial anastomoses on the same artery avoids the animal waste, working on the same vessel as much as possible.

The surgeon’s technique and the accuracy in placing the stitches are the most important factors in determining the patency of serial anastomoses, as demonstrated by the learning curve effect observed in Table 1. Thus, this model can be used to evaluate the progress of a plastic surgery resident in his microsurgical training.

CONCLUSION

Considering the most common mistakes performed by the microsurgeon at the beginning of his microsurgical training, we believe that this model helps the novice surgeon to assess his microsurgical level and to improve his capacity in performing an anastomosis through an exercise consisting in placing 4 anastomoses in a row.

Corresponding Author:

Serena Tamburino, M.D.

Department of Plastic Surgery, University of Catania

Cannizzaro Hospital

Via messina 829, 95100 Catania

Italy

E-mail: serenatamburino@hotmail.com