Regardless of ultrasound findings before treatment, sacroiliac (SI) joint patients receiving intraarticular methylprednisolone were more than four times more likely to get back to athletic work than those injected with triamcinolone, said Katie Ellis, DVM, MS, an equine sports medicine and rehabilitation clinician in the University of Georgia’s Department of Large Animal Medicine, in Athens.
“When horses show clinical signs of pain or dysfunction coming from the SI region, it might be worthwhile to try to treat that joint without doing the SI ultrasound,” Ellis said.
As a practitioner, previously at Colorado State University in Fort Collins, Ellis had performed multiple transrectal and transcutaneous ultrasounds to diagnose SI pathologies (disease or damage). But horses don’t always tolerate transrectal exams well, and they can be dangerous for the veterinarian if the horse reacts violently to the procedure, she said. So Ellis questioned the diagnostic procedure’s usefulness in these cases.
“My goal was to see whether it was worthwhile to do these ultrasounds, or if we should just treat the signs,” she said.
Ellis and her fellow researchers investigated 106 cases of horses receiving ultrasound imaging to diagnose SI pain and ultrasound-guided corticosteroid injections into the SI joints. The horses had been treated at Colorado State University’s teaching hospital between 2009 and 2018. The scientists contacted the horses’ owners and requested they participate in a survey about how their horses had fared since starting corticosteroid therapy.
Forty-two owners completed the survey. Responses indicated 62% of the horses had returned to their previous level of performance or higher, Ellis said. Meanwhile, 4% of the horses returned to a lower level of work, and 28% didn’t return to work.
The results showed no correlations with initial diagnostic ultrasound examination findings, she said.
“We found that, at least with our group of horses, there was really nothing on ultrasound exam that helped determine if the horse was going to respond positively or negatively to corticosteroid injection,” said Ellis.
The results were surprising, she admitted, particularly regarding certain pathologies. “I really thought maybe if there were some changes in the lumbosacral discs—which we see quite frequently—that maybe the worse those changes were, the less likely horses would be to respond, because those seem to be the more painful horses,” she said. “But that wasn’t the case.”
Medication choices made a dramatic difference, she added. Methylprednisolone was 4.2 times more likely to lead to a return to previous level of performance than triamcinolone, her results revealed.
That might be because methylprednisolone provides a longer response, she said. It might also be how the SI area reacts to the drug. “Some regions just respond better to methylprednisolone than others,” Ellis said.
Methylprednisolone treatment can lead to a positive drug test in performance horses, Ellis added. While the Fédération Equestre Internationale (FEI) recommends a 28-day withdrawal period, Ellis said injections into the SI joint would require an even greater elimination time because it remains in the region longer.
Although further studies involving more horses should be done to confirm the findings, Ellis said the investigation has already influenced the way she treats horses with SI pain.
“This has changed how I approach these horses, for sure,” she said. “It’s never wrong to do the imaging. But it may not change what you end up doing with that patient, and it might not help figure out if a horse is going to respond to the injections or not. So perhaps it’s worth just trial-treating them and seeing how they respond.”
The study, “Retrospective analysis of horses with ultrasound evaluation of the sacroiliac region and response to local corticosteroid injection,” was published April 29, 2021, in the Journal of Equine Veterinary Science.