Dynamic Equine Laryngeal Prosthesis
Date
2017
Authors
Ahern, Benjamin John
Editors
Advisors
Franklin, Samantha
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Thesis
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Abstract
The respiratory system of horses is the major limiting factor for athletic performance. As such, any respiratory impairment can have a considerable effect on athletic performance. A common site for this impairment to occur is the upper respiratory tract with laryngeal collapse being the most common form in horses. The recurrent laryngeal nerves in the horse are the longest nerves in the body and prone to degenerative axonopathy. This is termed recurrent laryngeal neuropathy (RLN) and results in neurogenic atrophy of the cricoarytenoideus dorsalis (CAD) muscle. Loss of function of the CAD leads to dynamic laryngeal collapse when exposed to the negative airway pressures produced during exercise. As a result, RLN is a common cause of reduced athletic performance in horses. Currently the most commonly performed treatment for RLN in horses is a static prosthetic laryngoplasty. This procedure has a relatively poor success rate in performance horses (ranging from 50-70%) and high complication rate of between 26-43%.1-4 Two of the major complications are dysphagia and loss of abduction. In general, many of the complications can be attributed to either under or over abduction of the arytenoid and static laryngoplastic fixation. The objective of the research reported here was to develop a laryngoplasty system that allowed for alteration of the degree of arytenoid abduction post-operatively. This thesis outlines the successful development of such a device. Initially, the existing standard laryngoplasty procedure was examined mechanically and a variety of prototypes were developed and evaluated. Subsequently, we selected the final dynamic laryngoplasty system (DLPS) for further evaluation. After optimising the position of attachment to the arytenoid using an anchor, the prototype device was mechanically tested under static loading, cyclic and ramp (single linear loading) to failure conditions. This study found the device was able to cause effective shortening of a suture loop with minimal cyclical loss and was able to resist ramp testing sufficiently to justify further evaluation. Additional in vitro testing was performed using cadaveric larynges and demonstrated that the DLPS was able to cause effective increases in arytenoid abduction within the confines of equine laryngeal anatomy. The final in vitro study tested the ability of the DLPS to achieve and maintain arytenoid abduction during testing using a static airflow model with a flow rate of 55L/sec which was consistent with previously published research. After completion of the in vitro studies an in vivo proof of concept study was performed. This demonstrated that the device could be effectively delivered via a standing procedure under sedation and allowed for selective alteration in arytenoid abduction at 7 days post-operatively.
School/Discipline
School of Animal and Veterinary Sciences
Dissertation Note
Thesis (Ph.D.) -- University of Adelaide, School of Animal and Veterinary Sciences, 2017
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