STERNOTHYROHYOIDEUS MYECTOMY OR STAPHYLECTOMY FOR TREATMENT OF INTERMITTENT DORSAL DISPLACEMENT OF THE SOFT PALATE IN RACEHORSES - 209 CASES (1986-1991)

The efficacy of sternothyrohyoideus myectomy (SM) and staphylectomy as treatments for intermittent dorsal displacement of the soft palate wa s evaluated in 209 racehorses (126 Thoroughbreds, 83 Standardbreds). T he 2 most common complaints weve respiratory tract noise (75% of house s) and exercise intolerance (51% of horses). Stopping, defined as the inability to finish the race at racing speed, was reported in 40% of t he horses. Endoscopy at vest revealed evidence of abnormal epiglottic anatomy (hypoplasia or flaccidity) in 51% of the hones and abnormal so ft palate function in 36% of the horses. Race records were available f or 149 (77 Thoroughbreds, 72 Standardbreds) horses. The sex distributi on consisted of 38% sexually intact males, 20% geldings, and 42% femal es, with a mean age of 3.4 years. Sixty-nine houses underwent staphyle ctomy, with a mean of 16 weeks to first start after surgery. Eighty ho rses underwent SM, with a mean of 10 weeks to first start. Sternothyro hyoideus myectomy was performed on significantly move (P < 0.05) Thoro ughbreds than Standardbreds, and staphylectomy was performed on signif icantly (P < 0.0001; chi(2) = 39.56) more Standardbreds than Thoroughb reds. After surgery, most horses (74%) had no change in class; however , more moved up in class (17%) than down (9%). On the basis of compari son of earnings for 3 starts before surgery with that for 3 starts aft er surgery, successful outcome was obtained in 60% of the horses (35 T horoughbreds, 13 Standardbreds) that received SM and in 59% of the hor ses (11 Thoroughbreds, 30 Standardbreds) that received a staphylectomy . The likelihood of achieving a successful outcome was greatest in hou ses with total earnings between $5,000 and $25,000. This difference wa s only significant, however, wizen this group was compared with those houses with total earnings of less than $5,000 (P = 0.048; chi(2) = 3. 89). Presurgical endoscopic findings were not significantly associated with the outcome after surgical treatment.