Evaluation of an intercostal myoneurovascular transposition as a lower esophageal neosphincter.

Previous work has shown promising results for an intercostal myoneurovascular transposition in the prevention of gastroesophageal reflux following esophagectomy. A first study evaluated the intercostal transposition procedure and compared it with the Nissen fundoplication using a rabbit model of gastroesophageal reflux. Group A underwent partial cardiomyectomy to produce gastroesophageal reflux. Group B underwent cardiomyectomy, and intercostal transposition around the gastric cardia. Group C underwent Nissen fundoplication and cardiomyectomy. All animals had preoperative and 1-week and 4-week postoperative intraesophageal manometry and pH studies. At the 4-week interval, macroscopic and microscopic esophageal histopathology was assessed. The mean change in values from preoperative to 4 weeks postoperative were compared. Group B showed significantly lower reflux time (P < 0.001) and grade of esophagitis (P < 0.005), and significantly greater average lower esophageal sphincter basal pressure (P < 0.001) and abdominal length of sphincter (P < 0.01) when compared with Group A. There was no statistical significance between the results of Group B and Group C. A second study assessed whether reflux was prevented by an anatomical structure, or a muscle flap acting in a physiological manner. At autopsy, the ten rabbits from Group B underwent removal of the intercostal wrap, and the right 11th intercostal muscle as a control. There was a significant difference in the quantity of viable muscle tissue between muscle flaps and controls (P < 0.001), the muscle flaps having generally little viable muscle left 4 weeks after surgery. A further experiment to evaluate this result found that loss of muscle tissue was due to excessive stretch and not due to damage of the intercostal neurovascular bundle during mobilization. Two groups of animals underwent electromyographic studies. The first group underwent recordings of all intercostal muscles. The second group underwent intercostal transposition around the gastric cardia, and insertion of recording electrodes into the muscle flap. The electromyographic activity of the muscle flap was recorded at 0, 2, and 4 weeks after surgery. The second group demonstrated activity in the muscle flaps simultaneous with diaphragmatic contractions. This activity, although much reduced, was still present 4 weeks after surgery. These studies showed that the intercostal transposition and Nissen fundoplication procedures are equally effective in preventing experimental gastroesophageal reflux. The antireflux properties of the intercostal transposition were possibly the result of anatomical buttressing of the gastroesophageal junction, and not due to a fully viable contracting muscle flap.