An epiglottic entrapment is an upper airway abnormality that can cause poor performance in athletic horses. A team of researchers from the University of Montreal recently developed a safer instrument for surgically correcting an entrapped epiglottis.
When a horse swallows food or water, the epiglottis (a movable, leaf-shaped piece of cartilage located at the base of the tongue and above the soft palate) covers the opening of the larynx to ensure that food and water do not enter the trachea, but instead pass into the esophagus. When a fold of tissue, called the aryepiglottic fold, folds into the epiglottis, the epiglottis becomes "entrapped." Clinical signs of epiglottic entrapment include noise on inspiration and/or expiration while exercising, poor performance, and, less commonly, headshaking.
"Two techniques are currently used (to correct an entrapped epiglottis): the transnasal axial division (a slice in the center of the tissue to relieve the entrapment) under general anesthesia using a hook bistoury--a long and narrow surgical knife--or releasing the entrapment with a laser (for which general anesthesia is not required)," said Mathieu Lacourt, DVM, of the University of Montreal, who along with colleague Marcel Marcoux, DVM, MS, worked to develop an improved bistoury.
With the addition of a shield that opens and closes over the blade, Lacourt and Marcoux's new bistoury protects the tissues in the esophagus and soft palate from being damaged by the sharp hook during treatment for an entrapped epiglottis.
Lacourt explained that both current treatments are used successfully despite each having drawbacks: "The transnasal axial division using the traditional hook knife is an effective and simple technique, and (physician-caused) injuries remain rare. Injuries of the nasal passage or the epiglottis are not severe or life-threatening consequences, but a laceration of the soft palate may induce dysphagia (difficulty swallowing) and accompanying pneumonia, which can be fatal. And the laser is used more and more, but requires specialized and expensive instruments and is demanding for the operator."
Lacourt and Marcoux's prototype of an improved bistoury was first completed in 2008. The original concept was to add a shield over the blade that opened and closed to protect the tissues in the esophagus and soft palate from being damaged by the sharp hook. Additionally, the improvements to the bistoury would allow the procedure to be completed safely with sedation rather than general anesthesia.
The team tested their instrument on eight Standardbred horses that presented at the University of Montreal with an epiglottic entrapment and they were able to resolve the entrapment successfully in all cases without general anesthesia. There were no recurrences after two weeks in any of the eight case horses. The normal recurrence rate with both the traditional hook bistoury and the laser is around 5%.
"The most important aspect of the procedure is to be able to cut the entrapment as (completely) as possible," Lacourt added. "As the new device is safer and has a larger diameter, the operator can place the device more easily in the best position to have a good incision thus reducing the level of recurrence.
"This instrument enables the veterinarian to practice a simple and effective technique under safe conditions on the standing horse" he noted. "The procedure takes 83 seconds, on average, and does not require specific skills or training. This technique eliminates the costs and risks related to the general anesthesia (with a traditional hook bistoury) and laser."
Lacourt noted that the instrument is now available for all practitioners to purchase.
The study, "Treatment of epiglottic entrapment by transnasal axial division in standing sedated horses using a shielded hook bistoury" was published in the Jan. 2011 edition of Veterinary Surgery. The abstract is available on PubMed.
Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.