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Use of Earthworms for Microsurgery Training
15 December 2008 (online)
Microsurgery procedures are widely used in reconstructive surgery after trauma defects, tumor ablation, replantation, and organ transplantation and also in experimental surgery. Training in microsurgery is an exhaustive and expensive process and thus poses a challenge to poorer countries to create and sustain special centers for these training programs. Also, the ethics of using living animals in experimental procedures continues to be challenged, which increases the costs of the last stages of microsurgery training.
In this context, alternative models that make less use of animals are welcome, but many proposed artificial models are sophisticated and can increase costs significantly.  Less expensive solutions using biological tissues that are normally discarded, such as human placenta, omentum, abdominoplasty material, and others, are also described,  but those materials are not widely available, and the training center must be linked to a hospital source. Other options include the use of fresh dead animals, like discharged rats from other experiments, or normally commercialized animal parts for food, like chicken and pig parts.   The challenge arises especially during the intermediate stages of training, after the training with latex gloves and silicon tubes, when the trainee must become familiar with organic tissues and with tubular architecture and yet avoid the use of living animals until the very end of the training program. Alternatives to help diminish costs or save animal lives are discussed all the time . 
We believe that each institution with a microsurgery training laboratory center must explore the many possibilities of training models and create a personalized training protocol that takes into consideration both its possibilities and restrictions. Our training laboratory is physically distant from the hospitals of our institution, thus making it difficult to use human discarded tissues. We face a very strong policy against the use of superior living animals for educational purposes. We also cannot use expensive synthetic materials due to financial restrictions. In this context we propose the use of common earthworms (Fig. ) as an intermediary step in our training to simulate vascular anastomosis before we use live rats.
Figure 1 Source of earthworms.
In our technique, common earthworms are cut into 1- to 2-cm pieces. Internal organs and contents are removed by washing with water and longitudinal crushing by hand (Fig. [2A]). Care must be taken in the force applied so as not to destroy the tubular wall of the animal. Longer pieces are difficult to clean, leading to wall rupture.
After preparing the tubular segments, they are fixed to a microvascular clamp (Fig. [2B]) and divided, ready for the training of end-to-end anastomosis (Fig. [2C]). End to lateral anastomosis can be also simulated and trained using two tubular segments. Different diameters can be obtained according to the sizes of the earthworm selected, and anastomosis of different diameter structures using several adjustment techniques can be performed.
Figure 2 (A) Earthworm segments prepared for training. (B) Macroscopic aspect of the training model in practice. (C) Trainee surgeon during a training session with an earthworm model. (D) Earthworm piece prepared and ready to start exercise under magnification fixed on microvascular clamp. (E) Magnified aspect of the cut piece of earthworm just before starting the anastomosis training. (F) Magnified aspect of anastomosis after complete half-diameter suture, showing a satisfactory simulation of vessel exercise.
We are using the earthworms in the last year of training cards before exercises using living rats. We note the obvious improvement of the trainees' skills reflected in the quality of the anastomosis performed on the earthworms (Fig. ). The first trainees using this technique, however, did not complete the microsurgery training card, so it was impossible to measure the difference in the time spent for training, or in the number of rats used to achieve the full skill required. Nevertheless, the capacity of performing training anastomosis and the similarity of the structure of the earthworm segment and the blood vessels are undeniable (Fig. [2F]).
Figure 3 Progression on the quality of the anastomosis with training. (A) First anastomosis attempt with the earthworm model made by the trainee surgeon. (B) Anastomosis aspect after first month of training. (C) Improvement of quality after 2 months of training (eight sessions).
In the future it will be possible to evaluate the benefits of this new training model using parameters such as time spent on training, number of rats used, and the costs of the training course, and to compare it with other methods proposed in the literature. 
For now, we can conclude that the use of earthworms as a new microsurgery training model is possible and provides an interesting alternative to the standard training cards employed before the use of living animals. It can reproduce many anastomosis exercises and improve trainee skills effectively. It is inexpensive and easily available worldwide. Furthermore, it can probably reduce the use of living mammals in microsurgery training programs.
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Gustavo Mantovani, M.D.
R. Leonardo C. Varandas, 50, apto 68, bloco 6, Morumbi 05705-180
Sao Paulo, SP-Brazil