A sport-horse veterinarian outlines common causes, diagnostic methods, and treatment options
Reprinted from the May 2016 Issue of USDF Connection
By Jennifer O. Bryant
In dressage, we may be more concerned with our horses’ backs than riders in any other equestrian discipline. A horse whose back is stiff, tight, or sore can’t perform at his best, and trying to sit the trot on such a back is murder on the rider.
We employ all sorts of things to help our horses’ backs be comfortable—from massage to fancy cushioned saddle pads—but what’s actually causing the pain? Back lameness can have numerous causes, according to Grant D. Myhre, DVM, who gave a talk on the subject at the 2015 Adequan/USDF Annual Convention in Las Vegas. Here are key points from his presentation.
What we call “back lameness” may stem from problems related to the horse’s spine, or it can have to do with the soft tissues, said Myhre, the owner of Myhre Equine Clinic in Rochester, NH, a multi-veterinarian practice offering services ranging from diagnostics and imaging to surgery and rehabilitation.
Examples of spine-related problems include scoliosis (abnormal curvature of the spine) and arthritis. A poorly fitting saddle can cause soft-tissue pain. The SI joint can have a subluxation—a spinal misalignment visible as a “hunter’s bump.” A horse with a subluxated SI joint “can become sound, or it can become a chronic problem,” Myhre said.
Sometimes back lameness is a symptom of some other issue, such as in a case of internal-organ pain manifesting as a sore or tight back, Myhre said. And some back issues aren’t pain-related at all, such as in “shivers” and other neurologic problems.
Diagnosis Can Be the Greatest Challenge
“If we can diagnose it and we can change the course, then we can make the horse better,” Myhre said. Diagnosis may require a bit of detective work on the veterinarian’s part.
Myhre frequently begins by testing to see whether there is an inflammatory component to the lameness. “I’ll try an NSAID (nonsteroidal anti-inflammatory drug)—say, one gram of bute morning and evening—for a week” unless ulcers are an issue, he said. “If it gets better on an anti-inflammatory, it’s an inflammatory problem. Then it’s reversible.”
And if the NSAID doesn’t work? “We in the US like to block things out—to know that’s the area with pain,” said Myhre, referring to the way many leg and foot lamenesses are pinpointed. But “in the back, that’s very difficult to do.” Some veterinarians will block the sacroiliac joint—SI disease is a common cause of back lameness, Myhre said—“but I’ve had horses almost go down from that. I think there are better diagnostic methods without the danger of that.”
Myhre’s own diagnostic toolbox includes a complete physical exam, including rectal palpation. He’s found that a low-tech assessment—fingernails into a “response area”—is “a subjective test but a very good test” of problems in the SI region. “I can generate more response to the SI area than any other place. If I can’t get them to move, it tells me they’re reluctant to move because they’re in pain someplace.”
As an aside, Myhre mentioned that Lyme disease, which frequently gets the blame for all sorts of oddball symptoms in horses, “rarely causes lameness.” Living as he does in New Hampshire, which he said has the highest incidence of Lyme in the country, Myhre conducted a study using the Lyme-diagnostic SNAP test, which he said has a 96-percent accuracy rate. Of the 100 horses studied, one-third tested positive for Lyme disease but “none had lameness associated with Lyme.” The affected horses “responded to treatment, but it was more of an attitude change—they mellowed and felt better. I think Lyme is more of a lower-grade problem; it does not cause lameness very often.”
“I would do a bone scan on every horse, every lameness if I could.” —Grant D. Myhre, DVM
After Myhre’s clinical exam has identified a suspected problem area, he’ll move on to structural imaging to learn what’s going on beneath the horse’s skin. Examples of structural imaging include ultrasound, radiographs, and MRI; but “the best method of imaging I’ve found is nuclear scintigraphy,” he said, displaying a photo of a nuclear-scan image revealing a fractured rib cage. Radiographs may be sufficient to diagnose such problems as “kissing spines,” in which the upward-projecting spinous processes rub or touch. Besides causing pain, kissing spines can also lead to arthritis or desmitis (inflammation of the ligaments).
Methods of treating back lameness are as varied as the causes.
Myhre will inject problem SI joints—doing so requires a rather wicked-looking 10-inch curved needle— with anti-inflammatory agents such as steroids or the joint-health product Adequan.
Another option for fighting bone-related back lameness is the drugs known as bisphosphonates, which help to retard bone loss. In the equine world, the two best-known bisphosphonates are Osphos and Tildren; Myhre prefers Osphos, calling Tildren “less researched.” Both products were approved for horses only for the treatment of navicular syndrome; their use to treat back lameness is currently off -label, but “we’re starting to use it on some backs. The bone process is similar, so I would expect that [the results] would be similar.”
“I don’t believe in injecting joints prophylactically,” Myhre added. “Steroids can cause damage, especially when overused.”
Some therapies, especially those available without a prescription, are counterirritants: “They stimulate nerves that take away the sensation of deeper pain.” Some injectable products, as well as many topicals and products that use heat or cold, also fall into the counterirritant category. (The prescription topical Surpass is an NSAID.) Such products may provide some relief, but they “rarely heal anything,” Myhre said.
Kissing spines may require a different treatment approach. Myhre has removed interfering dorsal spinous processes surgically. Another option is shock-wave therapy; Myhre said he has had success with monthly shockwave treatments. Shock-wave therapy is a so-called mechanical form of treatment; other treatments that have been used in combating equine back pain are chiropractic, acupuncture, massage, laser therapy, and electrical stimulation, he said.
A wide range of other lamenesses can cause secondary back discomfort, Myhre said. Suspensory-ligament strains, arthritic hocks, OCD—all have to be addressed in order for the back problem to improve.
If the problem is deeper, surgery may be required. Myhre has operated to remove bladder stones, kidney stones, enteroliths, and granulosa cell tumors on mares’ ovaries, any of which can cause back pain.
A Whole-Horse Approach
Back lameness is a real problem, and it’s not always a quick fix. If you’ve ruled out saddle-fit issues and other external culprits, then it’s probably time to call in a veterinarian with a comprehensive knowledge of potential causes, experience in diagnosing back-lameness causes, and access to the latest treatment modalities. A savvy sport-horse veterinarian is your best all