Hernia DOI 10.1007/s10029-012-0981-7
ORIGINAL ARTICLE
An animal model to train Lichtenstein inguinal hernia repair J. Rosenberg • I. Presch • H. C. Pommergaard J. Burcharth • M. Bagot d’Arc
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Received: 20 December 2011 / Accepted: 9 August 2012 Ó Springer-Verlag 2012
Abstract Purpose Inguinal hernia repair is a common surgical procedure, and the majority of operations worldwide are performed ad modum Lichtenstein (open tension-free mesh repair). Until now, no suitable surgical training model has been available for this procedure. We propose an experimental surgical training model for Lichtenstein’s procedure on the male and female pig. Methods In the pig, an incision is made 1 cm cranially to the inguinal sulcus where a string of subcutaneous lymph nodes is located and extends toward the pubic tubercle. The spermatic cord is located in a narrow sulcus in the pig, thus complicating the procedure if operation should be done in the inguinal canal. The chain of lymph nodes resembles the human spermatic cord and can be used to perform Lichtenstein’s hernia repair. Results This experimental surgical model has been tested on two adult male pigs and three adult female pigs, and a total of 55 surgeons have been educated to perform Lichtenstein’s hernia repair in these animals. Conclusions This new experimental surgical model for training Lichtenstein’s hernia repair mimics the human inguinal anatomy enough to make it suitable as a training model. The operation facilitates the training in the positioning and fixation of the mesh and can be performed numerous times on the same pig. It is therefore a useful
J. Rosenberg (&) H. C. Pommergaard J. Burcharth Department of Surgery, Herlev Hospital, University of Copenhagen, Herlev Ringvej 75, Herlev 2730, DK, Denmark e-mail:
[email protected] I. Presch M. Bagot d’Arc Baxter Innovations GmbH, Wagramerstr. 17-19, 1220 Vienna, Austria
training method for inexperienced surgeons to obtain experience in aspects of the Lichtenstein procedure. Keywords Hernia Inguinal Training Education Animal model Background Inguinal hernia repair is one of the most frequent surgical procedures performed by the general surgeon [1]. Nearly 800,000 operations for inguinal hernias are performed yearly in the United States alone. One of the most frequently used and validated techniques for inguinal hernia repair is the Lichtenstein procedure, that is, an open tension-free mesh repair [2, 3]. Surgical training models are important means to gain sufficient surgical skills. This is especially important for this type of operation since many are performed by residents. Currently, only two models exist, one on the rabbit [4], which is limited due to the small size of the animal. The other model, on the male pig [5], is limited due to differences in anatomy between the male pig and humans. Furthermore, there are no good realistic commercially available computer simulation models for this operation. Therefore, a good experimental model for training in Lichtenstein inguinal hernia repair is needed, which is comparable to humans with respect to both anatomy and size. We present a new animal model in both female and male pigs, which simulates the human inguinal male anatomy. Methods A normal landrace pig, approximately 30–40 kg in weight, was used for the model. The pig was fully anesthetized and
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Hernia Fig. 1 Dissection of the spermatic cord in a male pig. The spermatic cord in male pigs is placed deep in a narrow sulcus, which complicates the Lichtenstein procedure. (The urinary catheter and the cross show the midline)
placed on its back and a classical oblique incision was made in the inguinal area. Although the male pig has a spermatic cord, this retracts if the pig has been castrated and it is placed in a very narrow sulcus between the thigh and the lower abdominal musculature (see Fig. 1). In the female pig, there is no well-defined anatomic structure in this inguinal area that resembles the spermatic cord. For the new model, an incision 1 cm cranially to the normal inguinal incision (the sulcus) is made. An oblique incision is made extending 8–10 cm from the pubic tubercle (see Fig. 2). In this position, in the subcutaneous tissue, the superficial (subcutaneous) inguinal chain of lymph nodes is placed [6–8], and this can be easily dissected to resemble a normal spermatic cord in humans (see Fig. 2). This chain of superficial inguinal lymph nodes extends down close to the pubic tubercle, and it is therefore possible to place a polypropylene mesh on the pubic tubercle, continuing beneath the lymphatic chain with the two tails of the mesh around the chain in the cranial area, perfectly mimicking a Lichtenstein preparation in humans. Obviously, there is no inguinal ligament in this area since it is in the subcutaneous plane; however, the mesh can still be sutured to a tissue layer mimicking the clinical situation in humans (see Fig. 3). The model is also suitable for training the use of fibrin sealant for mesh fixation in this area (see Fig. 4). All animals were killed after the experiment. The use of animals for surgical training was approved by the Government of Lower Austria (Niedero¨sterreichische Landesregierung), St. Po¨lten, Niedero¨sterreich.
Results We used this model on five different occasions, in three female pigs and two male pigs. In all cases, it was feasible and the anatomic preparation was uneventful. Using this
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Fig. 2 An incision is made 1 cm cranially to the standard inguinal incision. The chain of superficial inguinal lymph nodes is visible. The superficial inguinal chain of lymph nodes is dissected to resemble the spermatic cord
model, we trained a total of 55 surgeons in the performance of Lichtenstein hernia repair using fibrin sealant for mesh fixation. We got only positive feedback from the trainees, but since feedback was not obtained in structured forms and only orally, we cannot report it systematically.
Discussion We have described a new model for the training of Lichtenstein hernia repair using the pig. Instead of using the normal spermatic cord in the male pig, we dissected the superficial inguinal chain of lymph nodes in the inguinal area, which is placed more superficially than the spermatic cord. In this way, the operative training more closely simulates the human situation with a flat back wall of the inguinal area.
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Fig. 3 The polypropylene mesh is placed on the pubic tubercle, continuing beneath the lymphatic chain, and then placed with the two tails around the chain in the cranial area, perfectly mimicking a Lichtenstein preparation in humans
The surgeons’ experience and technical ability is an important prognostic factor for the patient’s outcome [9]. It has been shown that practice of the surgical technique improves the outcome of the surgical procedure [1, 9]. Relatively inexperienced surgeons can obtain good surgical results with Lichtenstein’s technique if they are properly trained [1, 10]. Today, patients expect that the surgeon is experienced in the specific surgical procedure that he/she is performing, and a useful animal training model may improve the surgeons’ experience. When training specific surgical techniques, knowledge on tissue handling and texture is essential. In this regard, animal models are superior to other forms of surgical training models including computer simulation. The pig in particular is excellent for this type of surgical training since its anatomy is comparable to humans’. To perform an anatomically correct Lichtenstein operation on a male pig, one needs to mobilize the spermatic
cord, which is located very deep in a muscular sulcus; hence, this operation is limited to male pigs, ideally not castrated, and is difficult to perform and not comparable to human anatomy. In our animal model, we used the superficial inguinal chain of lymph nodes as a substitute for the spermatic cord. The anatomic location of this chain of lymph nodes better simulates the anatomic location of the human spermatic cord. The technique of using the superficial inguinal chain of lymph nodes can be used on both male and female pigs. This is important because of better availability of female pigs, as in Denmark for instance, where we only have access to female pigs for surgical training. A model of Lichtenstein’s surgical technique exists in rabbits [4]. However, there are several limitations in performing Lichtenstein repair in a rabbit, most importantly the very small size of the animal and different anatomy compared with humans. Depending on different traditions in different countries, it may not be easy to use animals for surgical training. It is therefore a good idea to develop new artificial models for training in, for example, hernia repair. In Denmark, we have easy access to pigs for surgical training; however, it is not normal to train on male pigs since they often are killed immediately after birth. Our presently described experimental model is feasible in the female pig, and numerous surgeons can perform a Lichtenstein repair in the same pig before killing the animal, which can also be used to create various models of ventral hernia repair as onlay, sublay/ retromuscular, or preperitoneal. After each mesh placement, the mesh can be removed and the procedure can be done over again. Furthermore, simultaneous operation on both sides of the pig can be performed. There are, however, also drawbacks with this model. It facilitates the training in the positioning and fixation of the mesh, but does not permit training in the treatment of the hernia sac, identification of nerves, and calibration of the deep inguinal ring. Thus, it cannot replace other training principles for open
Fig. 4 This model is also suitable for training the use of fibrin sealant for mesh fixation
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inguinal hernia repair, such as the hands-on training situation in patients. It has been shown that virtual reality is an excellent tool in training laparoscopic skills [11, 12]. If simulating an open surgical procedure on a laparoscopic simulator, there is an obvious disadvantage, since the person is using laparoscopic instruments and movements. This is necessary since equipment for detection of hand movements is not yet available. This is why open surgical techniques are very difficult to train by simulation. A virtual reality Lichtenstein simulation program exists [13]. However, this technique relies on the use of laparoscopic instruments and is therefore less comparable to the actual clinical situation. In conclusion, a new experimental animal model for training Lichtenstein inguinal hernia repair has been developed using a subcutaneous chain of lymph nodes as a model for the spermatic cord in humans. The model uses live tissue in pigs to simulate human anatomy. This model is excellent for educating inexperienced surgeons in the Lichtenstein procedure.
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