Overground Endoscopic Findings Following Prosthetic Laryngoplasty for Management of RLN

Laryngoplasty has long been reported to be a very successful technique in horses that are not used for racing, but results in racehorses have been generally more modest. Whilst the mechanical causes of laryngoplasty failure have been previously discussed by many authors, it is only recently that post-operative exercising endoscopy has been used as a tool to ascertain exactly why horses that are perceived to be surgical failures still make respiratory noise or have dynamic airway obstruction that may contribute towards poor performance.

The published papers that report overground endoscopic findings in horses that have had prosthetic laryngoplasty (usually in conjunction with left ventriculocordectomy or vocal cordectomy) include 2 retrospective studies1,2 that evaluated horses that were returned to the clinics due to perceived continuing noise or poor performance post-operatively, and 2 prospective studies3,4 that attempted to follow up a cross-section of horses that underwent laryngoplasty (i.e. not limited to surgical ‘failures’).

All studies found an alarmingly high prevalence of dynamic upper respiratory abnormalities, even in horses that were reported to be a ‘success’ by the owners. True arytenoid instability i.e. failure of the laryngoplasty suture to hold the arytenoid in a fixed position was more prevalent in the studies evaluating surgical ‘failures’, which is probably not surprising. The jury is currently out as to whether horses with poor post-operative abduction grades are more likely to have arytenoid instability than those with good post-operative abduction. However, all studies reported a wide range of upper respiratory abnormalities, many of which are not intuitively attributable to the laryngoplasty procedure. Due to the variability in reporting or in categorisation of abnormalities by different authors, not all 151 horses can be included in each category.  [...]