Surgery for Dorsal Displacement of the Soft Palate

Dorsal displacement of the soft palate (DDSP) occurs when the palate partially obstructs the airway by becoming displaced on top of the epiglottis. This obstruction can affect breathing, especially during intense exercise. DDSP is known to be difficult to diagnose and treat. However, one viable option for treatment might be a combination of procedures during one surgery, according to Jennifer Smith, DVM, of the University of Pennsylvania's New Bolton Center. During the Soft Tissue Surgery session at the 2003 American Association of Equine Practitioners' convention, Smith discussed the combined use of the surgeries sternothyroideus myotomy, modified staphylectomy, and soft palate thermoplasty for effective treatment in Thoroughbred racehorses affected with DDSP.

Staphylectomy involves surgically resecting a small portion of the caudal edge  of the soft palate. Suggested benefits include the reduction of tissue for obstruction, a more rapid return of the displaced palate to its normal position, and/or stiffening of the palate from fibrosis and scar tissue formation, said Smith. Sternothyroideus myotomy involves cutting the sternothyroideus muscle, which prevents caudal retraction of the larynx and subsequent laryngopalatal dislocation. During soft palate thermoplasty, a carbon dioxide laser is used to make several parallel lines through the oral mucosa (mucous membrane) and the submucosa along the caudal  edge of the soft palate, creating a large area of fibrosis and stiffening of the palate.

In a study of 102 horses treated at Rood and Riddle Equine Hospital in Lexington, Ky., for DDSP using the combination surgery over a four-year period, 79 horses had a history of DDSP based on poor racing performance, characteristic noise production during exercise, or referral upper endoscopic examination findings, said Smith.  Information from lifetime race record was reviewed on 73 of the horses. It was found that 46 (63%) of the 73 horses that raced at least once before and after surgery improved their performance based on an increase in mean earnings per start. Mean earnings per start increased to $3,806 after surgery from $2,792 before surgery, and median earnings per start increased to $1,885 after surgery from $1,300 before surgery. The mean time before return to racing after surgery was 109 days.

The recovery times and race earnings were also compared based on the experience of the racehorse. Sixty-two percent of the experienced racehorses (horses which raced at least 3 times before and after surgery) improved in earnings postoperatively, whereas 65% of the inexperienced horses (horses which raced less than 3 times before or after surgery) improved postoperatively. Smith conjectured that the greater success of the inexperienced horses was due to a longer time before return to racing, which allowed more time for recovery. Experienced horses returned to racing after 86 days on average, compared to 132 days for inexperienced horses.

Smith said that the idea that the myotomy alone was the reason that the surgery was a success in 63% of the cases can be refuted by the fact that nine of the horses had been previously treated with a myotomy without success. Following that failed surgery, the combination surgery was used, with eight (88%) of the horses increasing their mean earnings per start after the surgery. "These findings lend further support to soft palate lasing as a useful treatment for horses with DDSP," she said.

"The success rate for this procedure (63%) is similar to the success rates reported for other surgical procedures used to treat horses with DDSP," Smith said. "Perhaps the improvement in performance of the Thoroughbred racehorses treated for DDSP by soft palate thermoplasty, modified staphylectomy, and sternothyroideus myotomy is caused by an alteration in soft palate structure and function. Thermal modification of connective tissue is a well-described phenomenon, resulting in tissue shortening, collagen contraction, and fibrosis. Based on the shrinkage observed in soft tissues during and after lasing of soft tissues, the lasing procedure used in our study could result in shortening or tightening of the caudal margin of the soft palate, thereby decreasing the likelihood of laryngopalatal dislocation."

For more on DDSP, see "Winning with Air."

About the Author

Sarah Evers Conrad

Sarah Evers Conrad has a bachelor’s of arts in journalism and equine science from Western Kentucky University. As a lifelong horse lover and equestrian, Conrad started her career at The Horse: Your Guide to Equine Health Care magazine. She has also worked for the United States Equestrian Federation as the managing editor of Equestrian magazine and director of e-communications and served as content manager/travel writer for a Caribbean travel agency. When she isn’t freelancing, Conrad spends her free time enjoying her family, reading, practicing photography, traveling, crocheting, and being around animals in her Lexington, Kentucky, home.

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