The impact of automatic retractors on the esophagus during anterior cervical surgery: an experimental in vivo study in a sheep model

Abstract

<jats:sec> <jats:title>Object</jats:title> <jats:p>Postoperative dysphagia is a well-recognized complication of the anterior surgical approach to the cervical spine. However, its incidence and etiology remain unknown. The aim of this study was to investigate the impact of automatic retractor use on the esophagus and to describe the related pathological changes that might occur during cervical spine surgery.</jats:p></jats:sec> <jats:sec> <jats:title>Methods</jats:title> <jats:p>A single-level cervical discectomy was performed via an anterior approach in 16 skeletally mature female sheep. Continuous retraction was applied with an automatic retractor system during surgery. The sheep model was chosen because of anatomical similarities to the human esophagus. The esophageal tract in every animal was examined using contrast radiographic examination. Eight animals were killed 3 days after the operation (Group 1). The remaining sheep were killed 4 weeks after the operation (Group 2). The esophagi were removed for histopathological study, which was performed using H &amp; E and Masson trichrome staining. The changes in esophageal innervation were examined with nicotinamide adenine dinucleotide diphosphate–diaphorase histochemical staining.</jats:p></jats:sec> <jats:sec> <jats:title>Results</jats:title> <jats:p>Only 1 animal (a Group 1 sheep) demonstrated any postoperative radiographic abnormality. In Group 1 sheep, histopathological study of the esophagi at the treated level revealed edema between the muscular fibers in the outer longitudinal and inner circular layers of the muscularis propria. At some points, obvious signs of vascular congestion, vascular damage, and inflammation were observed. In the Group 2 animals, there was mild-to-moderate fibrosis extending from the outer surface of the esophagus to the longitudinal layers of the muscularis propria in the area to which retraction had been applied. Enzyme-histochemical staining revealed the presence of normal myenteric plexus and ganglion cells, and nitrergic innervation in all parts of the esophagus wall.</jats:p></jats:sec> <jats:sec> <jats:title>Conclusions</jats:title> <jats:p>The results of this study demonstrate that direct pressure induced by the medial retractor blade on the esophagus wall leads to local injury. Postoperative dysphagia in human patients who have undergone anterior cervical spine surgery could be a clinical manifestation of this phenomenon.</jats:p></jats:sec>

Milk Temperature Influences Esophageal Motility in the Newborn Lamb

“…Previous in vivo studies have demonstrated similarities between the ovine and human esophagus with respect to thickness and histological structure [3]. This led us to hypothesize that the newborn lamb is a relevant model for swallowing studies in certain neonatal conditions.…”

Framework Surgery for Treatment of Unilateral Vocal Fold Paralysis

“…72 Moreover, patients presenting after anterior cervical disk fusion procedures may complain of solid food dysphagia, presumed to be caused by pharyngeal plexus injury. 73,74 This condition may not improve with intervention and, therefore, affected patients must be counseled regarding realistic expectations. 75 …”

Absence of Effect of Nasal Continuous Positive Airway Pressure on the Esophageal Phase of Nutritive Swallowing in Newborn Lambs

“…However, transposition of the present results from newborn lambs to human infants must be made with caution. Indeed, anatomical differences with regards to the extent of striated muscle along the esophagus (upper third only in humans vs. entire esophagus in the sheep) [28], as well as bolus propagation velocity (5 to 10 times slower in humans vs. sheep) [19], are noticeable. On the other hand, there are clear similarities between the two species, including the presence of well-determined upper and lower esophageal sphincters recorded by manometry in the lamb (personal unpublished results), the fact that the preruminant lamb is monogastric in the first week of life [29] and the presence of spontaneous gastroesophageal refluxes, with several characteristics close to the human infant [19].…”