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Six Auxiliary Traction Techniques: Making Endoscopic Mucosal Dissection Simple

2022-04-20 Author: Views: 0

Endoscopic mucosal dissection (ESD) has become a widely accepted minimally invasive treatment for early gastrointestinal cancer because of its high complete resection rate and good safety. The basic operation is divided into three steps: submucosal injection, circular incision of surrounding mucosa and stripping of submucosal tissue.

For some lesions in difficult parts of ESD treatment, repeated submucosal injection is usually adopted. Although it provides a limited surgical field for subsequent stripping operation, the operation time is long and increases the risk of bleeding and perforation. Another simple scheme is to try to adjust the patient's position according to the direction of gravity, so as to obtain the ideal tension on the stripping surface and provide a good operation field of vision, but the patient's optional position is limited, which limits the use effect.

Therefore, the key to solve the above problems is how to obtain a good "surgical field" and realize safe and accurate cutting and stripping operation.

Inspired by surgical traction technology, various endoscopic assisted traction technologies came into being. According to the source of traction, it can be roughly divided into internal traction and external traction; According to the composition of the traction device, it can be divided into metal clamp wire joint traction technology, metal clamp elastic ring joint traction technology, S-O metal clamp traction technology, magnetic anchor technology, etc.

This paper summarizes the advantages and disadvantages of various related traction technologies, in order to provide reference for clinical choice.

Combined traction technology of metal clamp wire

At present, it is widely used in the operation of esophagus, stomach, duodenum and colon. The technical points are as follows:

1. In vitro, the silk thread was ligated between the two clamping arms of the metal clip, and the metal clip was fixed and clamped on the lesion with the cut edge through the endoscopic treatment channel (Fig. 1a). Light wire pulling is used to maintain moderate tension, so that the focus can be fully lifted, and then complete stripping can be carried out. However, due to its limited traction direction, it is difficult to apply force to the opposite side (anal side) of the lesion.

2. Later, some scholars improved the above method, that is, fix another metal clip on the opposite mucosal wall of the first metal clip, and bypass the wire tied to the first metal clip from here to produce a "pulley block" effect, in order to obtain the anal tension (Fig. 1b).

3. Another more direct way is to fix the second metal clip and silk thread on the contralateral mucosa at the same time, so as to generate tension from the opposite side of the stripped tissue, as shown in Fig. 1C. However, there are still deficiencies in this method. First, the silk thread itself can only provide directional tension; Second, the silk thread itself has no shrinkage. With the increase of stripping surface, the tension of silk thread will decrease, and its function will weaken or disappear.

The principle of this method is relatively simple, the operability is good, and the materials are relatively easy to obtain. Silk thread, nylon thread and dental floss can be used as stay wire materials. A randomized controlled study showed that compared with traditional ESD, it shortened the operation time and reduced the number of submucosal injection, but there might be metal clipping problems during simultaneous interpreting.

Combined traction technology of metal clip elastic ring

Compared with the traction ring in the body, it can provide an elastic force for the traction ring in the body. Because there is no need to provide external force, it can not be limited by the anatomical position and the size of digestive tract lumen. It is especially suitable for the difficult position of ESD operation.

The material used by the elastic ring has been widely used in clinic, such as O-ring of esophageal vein curve ligation device, surgical sterile gloves, etc. its nature is stable in the body and will not produce allergic reaction.

In practice, the medical elastic ring is tied on one arm of the metal clip with 3.0 silk thread outside the body, and then stored in the release sheath together with the metal clip (Fig. 2a); After pre separating the mucosa in vivo, the metal clip was fixed at the edge of the lesion, and the side arm of the second metal clip was fixed at the opposite edge of the lesion through the elastic ring (Fig. 2b-c); The superficial mucosa of the lesion was turned out due to elasticity, exposing the visual field (Fig. 2D).

After operation, the auxiliary instruments and specimens were recovered. Considering that the elastic ring should be stored in the sheath in advance and easy to operate in the later stage, the ideal radius of this ring after folding and unfolding is divided into 2 mm and 5 mm, and the silk thread used for ligation is red, so as to compare with the surgical background.

Relying on the magnetic force generated by the magnetic field to provide traction at different angles, directions and sizes for ESD operation is a very creative idea. Bind a small magnet to a metal clip or the ligation line between two metal clips, fix it with a single / dual channel endoscope, locate it, and use another magnet to generate magnetic force outside the body to pull the whole stripping process.

This technology has undergone many improvements since its invention. The types of magnets can be divided into electromagnet, samarium cobalt rare earth permanent magnet and neodymium rare earth magnet. The latter is the magnetic material of current magnetic force. Coating on the surface of magnet can prevent human tissue from being allergic to nickel. The shape of the external magnet can be square, cylindrical or dish, while the internal magnet is a ring that is easy to bind. The anchor points of magnet can be divided into single anchor point and double anchor point, and the latter has a wider field of vision (Fig. 4).

It should be noted that since the generation of magnetic force between magnets is usually related to its volume and distance, the volume or number of external and internal magnets should be increased during ESD operation on the posterior wall of gastric body, but the increase of the number of magnets may hinder the visual field of operation.

At present, the external magnet used in the magnetic anchor traction technology has been equipped with a standard telescopic arm (SFC Co Ltd, fa-m-vc2) to reduce the workload of assistants. The average time of platform assembly is only 4 minutes, and the operation time is shorter than that of the control group. However, the price of the whole system is expensive, and the relevant research is only limited to the stomach of animals, which needs to be confirmed by further research.

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