On a brilliant fall day in 2015, I cringed as I watched my then 7-year-old horse limp towards my veterinarian.
"What do you think?" I asked.
"I can inject that joint, but we’ll have to watch it," he replied.I went ahead with the steroid injection – watching tensely as the vet inserted a needle into my heavily sedated horse in the middle of a dusty barn aisle – and crossed my fingers. It helped initially, but two years later, my fearless adrenaline-junkie horse refused to jump. Time to call the vet again.
For an animal I had watched gleefully clear five-foot fences, the diagnosis was heartbreaking. A pasture injury in her early years triggered an inflammatory cascade that resulted in arthritis – at age 9. In a creature that can live 25 years or longer, career-ending diagnoses like these put horse owners in a tough position.
Whether they race, jump, show, or work cattle, horses – unlike most companion animals – have a job to do. When they can no longer fulfill their duties, their options – and those of their owner – are limited. Some can step down to less demanding work, others land coveted spots at therapeutic riding centers, and a precious few live out their lives as “pasture puffs” – beautiful, expensive lawn ornaments. Many owners do not have the resources to care for a retired horse in addition to a rideable replacement, so the retiree ends up on Craigslist, listed as “Free to good home!” with an uncertain, and possibly perilous, future.
My horse Callie has a permanent place in my backyard. After her diagnosis, I quit jumping, started her on medication, and switched to trail riding. Last year, Callie and I racked up 600 miles – but she is one of the lucky ones.
Why are leg injuries so devastating in horses? You may remember the story of Barbaro, the horse who won the Kentucky Derby but was eventually put down after breaking his leg in the Preakness Stakes. Horses have poor circulation in their lower legs, and they need to move around to keep their digestive systems functioning properly, so bedrest isn’t an option. Surgery suites large enough to accommodate horses are far less common than dog and cat sized facilities, and many procedures are performed in the stable, where maintaining a sterile surgical field is difficult.
While catastrophic injuries like Barbaro’s may never be treatable, milder issues like tendon, ligament, or joint damage can be remediated. A new multifunctional tool may soon be available for equine veterinarians: focused ultrasound. Focused ultrasound is similar to imaging ultrasound, but at higher intensities.
Clinical trials in humans and laboratory experiments in other animals have demonstrated that focused ultrasound can enhance the delivery of stem cells, increase collagen alignment and tensile strength in tendons, improve cell proliferation and tissue biomechanics in muscles and ligaments, and be used to perform neurectomies and temporary nerve blocks.
Focused ultrasound offers two significant advantages over traditional surgical approaches. It is noninvasive, thereby eliminating the difficulties of establishing and maintaining a sterile field in a barnyard. For animals like Callie that require lifelong injections, each one carrying a risk of infection, this is a major improvement. Additionally, focused ultrasound can be integrated with imaging ultrasound to provide diagnostic, therapeutic, and treatment monitoring capabilities in a single piece of equipment – a game changer for equine vets who often work out of a truck bed.
In human medicine, focused ultrasound has made a name for itself in the treatment of various types of cancer. It offers humans the same benefits it could offer horses diagnosed with sarcoids or melanoma – a noninvasive means of killing tumor tissue, with the added benefit of inducing a powerful immune response that could prevent recurrence or metastasis. While equine cancers are less common than sports injuries, there are few treatment options currently available, creating a clinical need focused ultrasound could fill.
The Focused Ultrasound Foundation is currently funding several veterinary clinical trials using focused ultrasound to treat dogs and cats, and it is interested in investigating equine applications as well. I hope for a future when focused ultrasound offers an alternative to veterinarians and horse owners alike. In the meantime, Callie and I will continue riding the trails until she tells me it’s time to retire.
Kelsie Timbie, PhD, is the Scientific Programs Manager and the Veterinary Program Director at the Focused Ultrasound Foundation.