Successful Treatment of Persistent Dorsal Displacement of the Soft Palate and Evaluation of Laryngohyoid Position in 15 Racehorses

Authors: K. F. Ortved, J. Cheetham, L. M. Mitchell and N. G. Ducharme
Source: Equine Veterinary Journal
Publisher: Equine Veterinary Journal Ltd.

Abstract:

Reasons for performing study: Caudal descent of the larynx has been proposed to be associated with intermittent dorsal displacement of the soft palate (DDSP) as it leads to a loss of the seal between the epiglottis and soft palate but further investigation of this theory is required.

Objectives: To evaluate laryngohyoid position of horses with persistent DDSP in comparison to horses with intermittent DDSP and evaluate the outcome of treatment.

Hypotheses: Horses with persistent DDSP have a different laryngohyoid position compared to those with intermittent DDSP. Horses with persistent DDSP can be returned successfully to racing with a laryngeal tie-forward procedure.

Methods: Medical records of 15 racehorses presented for persistent DDSP between 2002 and 2007 were reviewed. Age, sex and breed matched horses diagnosed with intermittent DDSP were used as a comparison group. Treatment of all horses was performed by laryngeal tie-forward, 8/15 horses with persistent DDSP had a subsequent laser staphylectomy. Preoperative laryngohyoid position was compared between the 2 groups using a radiographic reference system. Surgical effect on position was assessed by comparing pre- and post operative radiographic measurements. Outcome was assessed by return to racing and comparison of pre- and post operative race earnings ($).

Results: Thirteen of 15 horses with persistent DDSP returned to racing. Seven of 15 horses were treated with laryngeal tie-forward alone while 8/15 horses were also treated with a laser staphylectomy. Horses with persistent DDSP had a more caudal larynx (ossification of the thyroid cartilage) (13 mm, P = 0.014), a more caudal (10 mm, P = 0.044) and dorsal (7 mm, P = 0.01) basihyoid bone, and a more dorsal thyrohyoid-thyroid articulation (10 mm, P = 0.002) than horses with intermittent DDSP.

Conclusion sand potential relevance: Racehorses with persistent DDSP can be treated successfully by laryngeal tie-forward or by laryngeal tie-forward followed by laser staphylectomy. Horses with persistent DDSP have a more caudal larynx and more caudal and dorsal basihyoid bone than horses with intermittent DDSP.