A Pain in the Back

A Pain in the Back

Photo: Anne M. Eberhardt/The Horse

New diagnostic technologies and treatment modalities have revolutionized how veterinarians address equine back pain

As recently as 10 to 15 years ago, equine back pain was usually dismissed as a secondary clinical sign of a hind limb problem. But with the advent of more sophisticated and powerful diagnostic technology and a better understanding of equine back pain as a problem in and of itself, veterinarians are making great strides in managing the problem more effectively. Many horses with deteriorating performance attributable to chronic back pain have been able to return to competition at a high level.

Locate the Problem

According to Kent Allen, DVM, of Virginia Equine Imaging, in Middleburg, the three major causes of back pain in horses are:

1. Kissing spines;
2. Osteoarthritis of the dorsal articular processes--the small joints located toward the top and to either side of the vertebrae; and
3. Muscular pain, such as from a short-lived sprain or a gait asymmetry, or secondary to bony pain in the area.

Conformation characteristics contribute to the development of kissing spines. In horses suffering from this condition, the vertebrae's dorsal spinous processes are spaced too closely, or even curve at the top and overlap. At rest and without stress to the spinal column, they don't touch or cause pain. But as a horse's workload or weight-bearing increases, the processes can grate against one another.

"As a horse starts moving and flexing his back more, they start rubbing together and you get proliferative new bone and all the things that go on with bony inflammatory disease," Allen says. "Then you start getting more of an arthritic process, whereas before you just had a malformation."

Dorsal articular arthritis occurs in the joint spaces between the dorsal aspects of the vertebrae and is fairly common in horses. Arthritis along the bottom of the vertebrae, or spondylosis, is a rarer diagnosis.

Back pain in horses typically is recognized first by the rider. Under saddle, an affected horse commonly will display a deterioration in performance, an unwillingness to move forward, and general discomfort. Clinical signs on the ground might include pain upon back palpation, cold-backed behavior, and having difficulty holding up the feet during shoeing. Severe chronic back pain can even cause horses to become violent in their avoidance behavior (e.g., rearing and/or bucking).

Clinical observation is the veterinarian's first step to diagnosing the source of back pain. "Anything that causes chronic pain in a horse's back starts leading to muscle atrophy (wasting) of the back muscles, which can be evaluated visually," says Allen. "Most horses have a convexity in the epaxial (topline) muscles. Horses with chronic back pain will have or develop a concavity (due to atrophy) there."

Chronic pain also can cause muscle spasms and stiffness--even if the source is skeletal--and subsequently the muscle in spasm atrophies. "Muscles can either spasm because they're trying to protect that area, or they have reflex pain because of the inflammation around that joint," says Kevin Haussler, DVM, DC, PhD, assistant professor at Colorado State University's College of Veterinary Medicine & Biomedical Sciences. A careful exam, including a detailed back palpation, can help the vet isolate areas of pain and muscle spasm.

Veterinarians can also rule out a primary foot or limb lameness that might be ¬responsible for the back pain by performing systematic nerve blocking of the front and hind legs. During this process he or she injects a local anesthetic to numb a particular region and observes whether the level of pain improves. At the conclusion of clinical evaluation, the veterinarian might turn to a variety of diagnostic machines to help further pinpoint the problem.

Radiography (X ray) with a high-powered machine at a clinic is key to imaging the spine, which is buried under layers of muscle. Good-quality radiographs can help a vet diagnose skeletal problems from the withers to about two-thirds of the way down the lumbar (lower back) region.

Nuclear scintigraphy, or bone scan, has also become a valuable tool in diagnosing spinal problems and allows imaging of the pelvis and other skeletal structures.

And thanks to research by Jean-Marie Denoix, DVM, PhD, of Centre d'Imagerie et de Recherche sur les Affections Locomotrices Equines, in France, ultrasound has become another key tool for imaging the equine back. "We've learned from Dr. Denoix's use of ultrasound to evaluate the spinal joints to compare the left and right sides at each vertebral level to see arthritic changes," explains Haussler.

Break the Cycle

Treating back pain post-diagnosis follows a simple principle: Stop the pain and then build muscle strength in the affected area. But vets are rethinking the traditional back pain treatment method of using non-steroidal anti-inflammatories (NSAIDs), which Allen says are "spectacularly ineffective on most equine back problems, muscular or bony." Muscle relaxants can help with muscle spasms, but if the pain trigger is skeletal relief will be temporary.

If the vet rules out skeletal issues as the source of pain and the problem is purely muscular, he or she might pursue acupuncture and chiropractic modalities. Allen notes, however, that "most muscle problems, just like muscle problems in human backs, are going to be of a temporary nature. If it's truly purely a muscle problem, most of those will fade away."

Saddle fit and rider balance are the most common causes of simple muscle pain and can be addressed with a veterinarian, trainer, and/or saddle fitter's help. Neuromuscular conditions such as polysaccharide storage myopathy and exertional rhabdomyolysis (tying-up) can also affect the back muscles and should be ruled out.

But if the inflammation and pain are rooted in the spine itself, the source of the pain must be addressed to solve the problem. "For you to be successful in these more chronic back problems over the long haul, you need longer term pain relief because that's the only way you're going to break the pain-spasm cycle," explains Allen.

Breaking this pain-spasm cycle long enough to allow the horse's muscles to develop and strengthen in the area of chronic pain is key. Rest is often counterproductive for back problems, because the lack of exercise accelerates muscle loss. "The reality is that no one is going to make kissing spines or osteoarthritis go away in a back," Allen says. "What we are going to do is break the pain-spasm cycle, return the horse to a workload and make it as comfortable as possible, and start the muscles growing back and trying to get the muscles to protect the area of the back that has the chronic problem we're dealing with."

New Horizons

According to both Allen and Haussler, treating the inflammation and pain caused by arthritis and kissing spines can start with applying alternative modalities such as acupuncture, chiropractic manipulation, and mesotherapy, which involves a vet inserting a series of small needles that stimulate the mesoderm, or the middle layer of skin, to help alleviate pain. At the 2010 American Association of Equine Practitioners (AAEP) Convention, Haussler presented a study in which he and colleagues measured the effects of spinal manipulation as compared to spinal mobilization chiropractic techniques. The results of the study demonstrated that manipulation and mobilization both increased spinal mobility, with mobilization being most useful for treating acute pain without overstretching or injuring soft tissues, and manipulation helping relieve chronic neck and back pain. Published research supporting other alternative methods' efficacy, however, is limited.

Extracorporeal shock wave therapy (ESWT) is another recent technology that might help relieve bony back problems. Also at the 2010 AAEP Convention, Allen presented on back pain treatment options, noting that ESWT is one of the most effective therapies performed at his clinic for pain management. "It's completely noninvasive, and if you know where you're treating, you don't need to use a large number of shocks," he says. "You can treat either kissing spines or dorsal articular process arthritis with it."

Injections into the vertebral joint spaces can also alleviate pain. The gold standard of quelling the inflammatory response involves using corticosteroids, but Allen has also had success with injectable tiludronate (Tildren). "We've used it in a lot of backs with lots of bony inflammatory problems and it's a drug that--by the nature of its suppression of osteoclastic (destructive) activity on the bone--it's going to calm bony inflammation bodywide," Allen says. Tildren is not yet FDA-approved for use in the United States; however, approval is pending. Currently it must be pre-approved and imported from Europe.

Veterinarians can treat kissing spines by administering joint injections either with or without ultrasound guidance if they have pinpointed the problem's location. Injections to treat dorsal articular arthritis, however, should be ultrasound-guided. Allen cautions that while these treatment modalities can be effective, accurately diagnosing the problem is still essential.

Some vets have treated kissing spines surgically, removing the impinging areas of the spinous processes, but it's a drastic procedure. "I'd be concerned about removing pieces of bone from the back and causing instabilty," Haussler says. "I think most vets manage these issues quite well now conservatively with corticosteroids, strengthening exercises, and acupuncture."

Strong Backs Are Healthy Backs

As previously mentioned, once the pain-spasm cycle has been broken it's time to strengthen the back. A course of rehabilitative exercises is essential to a treatment's success. Before embarking on an under-saddle conditioning program, consider and address saddle fit and rider balance. Then, build the muscles around any skeletal problems to help stabilize the area and reduce stress on the vertebral joints.

With pain management and strength building in the back, most horses can overcome what just a decade ago was a puzzling and misunderstood problem. "With this more modern approach to back problems, the neat part about it is that we take a lot of horses who would have been retired or a poor performer, and with a little care and work, you can get these horses back to being comfortable again and successful participants in their sports," says Allen.

About the Author

Molly Sorge

Molly Sorge is an equine journalist from Rother Glen, Va. She is also a contributing writer for The Chronicle of the Horse.

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