Conventional myotomy
Endoscopic myotomy
What precisions concerning the site and length of myotomy could be expected from the present knowledge on the muscular structure of the lower esophageal sphincter?
D. Liebermann-Meffert, H.J. Stein (Munich)
When Ernst Heller, chief of surgery at the Sankt Georg's Hospital at Leipzig in Germany, performed the first successful surgical treatment for achalasia in 1913, he used for his technique of "extramucosal cardiomyotomy" the abdominal approach [1]. He pulled the stomach down into the abdominal cavity, first divided the external muscle layer longitudinally in the region of the functional obstruction, and then second, carefully incised the internal layer. The incision was relatively near the Magenstraße on the anterior wall, as seen in the pictures of surgical textbooks of his time. There is no clear information concerning the length of the myotomy, but Heller comments: "The sphincter is weak enough to allow food to pass and not to much, to prevent reflux" [1].
In 1990, a large part of the OESO meeting at Paris was dedicated to achalasia. The world experts expressed their opinion on the various aspects of this disease and its treatment.
There was a relative conformity that the main principle in the surgical management of patients with achalasia is the division of the musculature of the lower esophageal sphincter (LES), and there was consensus to perform a modified Heller's operation with myotomy of the anterior wall alongside the esophagogastric junction (EGJ), either via the transabdominal or the transthoracic route [2].
However, the debate went on about the proper length of the myotomy. The incision has been commonly recommended to begin at least 10 cm upward on the esophagus and to extend at least 3 cm onto the body of the stomach. Launois et al. proposed to use a mean esophageal myotomy of 7.6 ± 1.8 cm and to extend the gastric myotomy to 4.5 ± 1.5 cm [3]. Herewith, he could reduce the incidence of residual achalasia, but had to put up with increased reflux, known to occur with the extended myotomy [4].
The extension of the myotomy recommended previously is by far longer than the anatomical and functional sphincter measures [5-7] (Figure 1). The specific muscular arrangement of the LES and its corresponding thickening actually extend in the normal healthy condition for 3-4 centimeters upwards and pass beyond the distal end of the esophagus into the stomach wall for an other 1-2 centimeters (Figure 1).
The anatomical and the manometric LES, identified as high pressure zone, are precisely located at the esophagogastric junction. The area of the greatest muscular fiber concentration, maximum muscle thickness and maximum pressure, respectively, is in vivo in posterior lateral position [1, 6], which is the angle of His [5]. This rather confirms that the gastric sling fibers exert the antireflux effect of the sphincter [7]. Myotomy in the area of the lesser curvature, at place of the muscle clasps, therefore, is not expected to destroy the sphincteric function (Figure 2) and will preserve competence.
In order to preserve the function of the sphincter and to avoid reflux by its disruption, nowadays many esophageal surgeons limit the length of the gastric myotomy to 0.5 to 1.5 centimeter, respectively, so as not to destroy the muscular sling of the oblique gastric fibers [7-9]. Mattioli et al. [10] as well as Gozzetti et al. [11] question the benefit of this function preserving procedure. However, also still extending the myotomy far into the stomach, they take great care not to interfere with the sphincteric function of the gastric fiber sling and divide only the muscular clasps at the lesser curvature.
In summary:
- the LES crosses the EGJ exactly;
- the average thickening of the LES is 3.14 cm in length at the greater curvature (gastric sling) and 2.31 cm at the lesser curvature (clasps), from which 0.6 cm are located in the abdominal part of the LES. These lengths correlate with those of the high pressure zone of the LES;
- as the gastric sling represents the main anti-reflux effect, myotomy should be placed lateral to the clasps of LES to the anterior wall;
- from the anatomical point of view, extension of 1 cm onto the stomach seems an optimum and far enough.
Figure 1. Diagram showing the muscular thickening of the LES and its length measured in millimeters in 32 human specimens obtained from organ donors.
Figure 2. Recommended line of the esophagocardiomyotomy on anatomical base (dotted line) shown in a human dry fiber specimen. The external layer has been removed and the internal muscle layer with gastric sling fibers (1) and clasps (2) at location of the LES (3) are displayed.
References