retrospective analysis of racehorses treated by a modified laryngoplasty relative to cohorts. Since performance outcome is measured differently in many studies, the reader should be cautious in making direct comparisons amongst studies. One common deficit in many studies is the short term performance analysis. We evaluated horses over several years and looked at quarterly earnings. Our data indicate that the horses treated by modified laryngoplasty earn as much over time, and compete as long or longer than their cohorts. While laryngoplasty may never be the perfect procedure, if the goal is to create a stable partially abducted arytenoid, methods as described above to improve the probability of achieving this goal could be employed. The only potential disadvantage of this technique is if the appropriate degree of abduction is not achieved, there will be a limited time of opportunity to change the position of the arytenoid before a joint ankylosis ensues. If several months after surgery the horse exhibits significant aspiration, or on the other extreme a lack of adequate abduction, repeat laryngoplasty is unlikely to be an effective option for surgical correction. An arytenoidectomy would be recommended. Other potential reasons for limited improvement in performance after laryngoplasty do not just revolve around structural stability, but involve dynamic function. There is evidence that the horse with limited resting abduction after laryngoplasty can often undergo further dynamic collapse of the affected arytenoid, or have other soft tissue structures obstructing the airway during strenuous exercise. If there is not adequate abduction of the left arytenoid it is common that the left aryepiglottic fold and/or the right vocal cord will deviate axially during inspiration and result in partial obstruction and noise. If the arytenoid is poorly abducted it is likely that the left arytenoid will undergo further dynamic collapse during exercise. Resting evaluation of the arytenoid cannot predict stability under exercising conditions accurately. There is also experimental evidence that horses, after laryngoplasty, may not have gross evidence of aspiration, but can have microscopic contamination of their lower airway. The impact of this lower airway contamination on performance is unknown, but it is easy to speculate that it could initiate a complex of lower airway inflammation that does impact gas exchange. Given the challenge of obtaining a positive outcome with laryngoplasty, other alternative treatments of cordectomy, ventriculectomy, arytenoidectomy, or reinnervation have been considered as viable treatment options. These different surgical options are tailored more to the use of the horse and the degree of laryngeal dysfunction. Arytenoidectomy is generally reserved for chondropathies and reinnervation has limited success, but www.faep.netâ€
vocal cordectomies can still be successful in select cases of laryngeal dysfunction. The vocal cordectomy (sometimes in conjunction with the ventriculectomy) is reserved for horses that maintain some abduction capability and that are not racehorses. The goal is to minimize noise production for show horses. It is rarely recommended as a sole treatment for a racehorse. Vocal cordectomy can be performed in the standing horse with transendoscopic laser resection or via laryngotomy (standing or anesthetized). While bilateral ventriculocordectomy is advocated by some clinicians to decrease abnormal noise, and can be performed successfully with traditional surgery, it should not be attempted with transendoscopic laser surgery at one time because it will likely lead to ventral scar/webbing formation in the larynx. The value of a ventriculectomy is arguable. If the vocal cord is completely resected, the ventriculectomy likely has little benefit.
Pre operative photo of laryngeal hemiplegia.
Selected References:
Post operative photo after
modified laryngoplasty. Ahern B, Parente E: Mechanical evaluation of the equine laryngoplasty. Vet Surg 315 39:661-666, 2010. Brown J A, Derksen F J, Stick J A, et al 2003 Ventriculocordectomy reduces respiratory noise in horses with laryngeal hemiplegia. Equine Veterinary Journal 35(6):570-574 Dahlberg JA, Valdes-Martineez A, Boston RC, Parente EJ. Analysis of conformational variations of the cricoid cartilages in Thoroughbred horses using computed tomography. Equine Veterinary Journal in press 2010. Dixon P M, McGorum B C, Railton D I, et al 2003A. Long-term survey of laryngoplasty and ventriculocordectomy in an older, mixed-breed population of 200 horses. Part 1: Maintenance of surgical arytenoid abduction and complications of surgery. Equine Veterinary Journal 35:389-396 Parente EJ, Birks E. Habecker P. A modified laryngoplasty approach promoting ankylosis of the cricoarytenoid joint. Veterinary Surgery 40:204-210, 2011. Radcliffe C, Woodie J, Hackett R, et al: A comparison of laryngoplasty and 300 modified partial arytenoidectomy as treatments for laryngeal hemiplegia in 301 exercising horses. Vet Surg 35:643-652, 2006. Witte T, Mohammed H, Radcliffe C, et al: Racing performance after combined 262 prosthetic laryngoplasty and ipsilateral ventriculocordectomy or partial 263 arytenoidectomy: 135 Thoroughbred racehorses competing at less than 2400 m 264 (1997-2007). Equine Vet J 41:70-75, 2009.
Eric J. Parente, DVM, DACVS ++ Dr. Parente is an Associate Professor of Surgery at New Bolton Center, University of Pennsylvania, School of Veterinary Medicine. He has specialized in performance evaluations and upper respiratory surgery. ++ He earned his veterinary degree from Cornell University, completed his internship at Rood and Riddle Equine Clinic, and then his surgical residency at New Bolton Center. ++ Dr. Parente received his board certification from the American College of Veterinary Surgeons in 1994 and continues to be an active member on various committees, as well as a presenter at its annual symposium. ++ He is internationally recognized as a respiratory surgeon and is well published in both texts and journals.
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