Compelling, controversial, and complicated. Thats how Kent Allen, DVM, of Virginia Equine Imaging, in The Plains, describes the equine back. The veterinary community continually debates equine back pain, which he said can be difficult to diagnose with standard approaches and imaging techniques.
Allen knows equine backs well. He has extensive experience treating high-performance horses in his practice and leadership roles at the Olympic, Pan American, and World Equestrian Games. Hes presented diagnostic and treatment methods for many International Society of Equine Locomotor Pathology (ISELP, for which he serves as vice president and executive director) modules around the world and at the American Association of Equine Practitioners convention.
Allen shared his back-pain workup and treatment recommendations with equine veterinarians at the 11th annual Northeast Association of Equine Practitioners (NEAEP) symposium, held Sept. 25-28, 2019, in Saratoga Springs, New York.
First Allen reviewed spinal anatomy, reminding veterinarians about variation in the thoracic and lumbar vertebrae running from the withers to the pelvis. Typically, horses have 18 thoracic (sometimes 19 and rarely 17) and six (occasionally five) lumbar vertebrae. He doesnt use markers on back radiographs to identify specific vertebrae, opting rather to look for the anticlinalthe vertebra at which the spine orientation changeswhich is usually the 15th thoracic vertebrae (T15, though occasionally T14).
T12 is usually the base of the withers, he explained, and the anticlinal is usually T15. Veterinarians can identify the thoracolumbar junction (between the thoracic and lumbar vertebrae) by looking at the change in rib curvature and the transverse processes, which are the protrusions from the sides of the vertebrae. Other helpful anatomical landmarks include the tuber coxaethe point of the hipwhich blocks veterinarians radiographic view of L4-6 (sometimes 5-6, he said). Thats also where articular processes begin to appear more upright.He pointed out the fused mammillary processes, where horses get arthritic change, off the articular processes and in the facet jointwhere the vertebral bodies come together.
We want to understand (the anatomy) before we start trying to diagnose it and treat it, he said, emphasizing that vets also must thoroughly understand the epaxial musculature, the multifidus muscle, longissimus muscle, intraspinous ligament (in which you can see some bony changes that arent usually associated with pathologydisease or damage), and the supraspinous ligament (which can be injured but usually a relatively minor issue thats easy to treat).
The multifidus, which attaches on the articular areas right beside the mammillary processes and reaches forward two or three vertebrae, is crucial because it is responsible for balancing and tensioning that back, he said. And, so, the more you fatigue or have pathology in the back and the more you get multifidus loss of the musculature, the more pressure and weight you put on the longissimus and the more the entire system fails.
Typical back problems Allen and his colleagues see in their practice include:
Bucking is common in horses with back pain, Allen said. Vets should ask themselves, Is it lame? Does the lameness have anything to do with the back (which is rare)? Usually its a decreased performance complaint.
Allen performs a detailed clinical exam on each horse fitting this description; he palpates the back and mobilizes its structures in a dynamic exam, watching the horse walk and jog. He emphasized that horses with back pain come in all shapes and sizes, and some might be very stoic and not show signs of problems until theyre performing at a very high level, sometimes even very late in their athletic careers.
These horses can jump, they can do their jobs, said Allen, citing an upper-level equine athlete he treatedone with significant overriding dorsal spinous processes that had gone undetected until the horse developed severe back pain late in his eventing career. Once we figured out his problem and gave him some pain relief, he looked a lot better doing his job.
Other horses are more demonstrative and will take your kneecap off if you press around on their backs, he said.
For horses not about to kick you in the kneecap, said Allen, he uses a surcingle weighted with 60 pounds to evaluate pain level while the horse is longed in a round pen. I get to see (the horse) move without the weighted surcingle and with the weighted surcingle without the riders influence, he said.
In videos he showed how a horse wearing the weighted surcingle stiffened, accentuating his lameness.
We use this a lot; we dont go through a day without putting this on several horses, he said.
Once Allen and his colleagues have determined without a doubt the horse is experiencing back pain, he turns to imaging, beginning with lateral radiographic views of the spine. He also uses nuclear scintigraphy (bone scans). But he cautioned that any imaging can reveal irrelevant dorsal articular remodeling. In other words, he and other veterinarians see damage in many backs that never creates pain.
In fact, several good studies show there are a lot of orthopedic back problems in horses that show no pain in the back, he said. And so youre left wondering if these horses have pathology and theyre not back sore, then what the heck are you doing X raying them and bone scanning them if theres no correlation between the imaging and the clinical? And the answer is, its really hard to figure it out.
You have got to tie the clinical to the imaging, he added, telling veterinarians to first ask themselves in back pain cases how the injury happened. (Researchers) proved years ago that kissing spines without a doubt is developmental, and it worsens with time. Now, no one has really proven one way or another about the facet arthritis, but I suspect its the exact same thing.
Whether a horse experiences and shows pain from the pathology depends on what the horse is asked to do, he said. For example, in one study veterinarians found severe bone pathology in a group of racehorses euthanized for reasons besides back pain. But, had the horses all become jumpers, many might have exhibited pain they didnt show as racehorses, he reasoned.
The question is, does the horse have the developmental abnormalities, which most of the time were never going to know, is it old enough to have this problem, does it have a job that is going to exacerbate the problem? he said. And, then, you as clinicians can start putting the picture together.
Additionally, Allen said he and his colleagues commonly see horses that are both lame and back sore, generally for separate problems requiring treatment.
Once Allen has confirmed the pathology in the back is, in fact, the cause of the pain, he applies the following treatments:
Secondary treatments include light ridden or in-hand work for short periods. In fact, Allen said its key to avoid long rest periods, opting instead to avoid muscle wasting by returning horses to work.
Extracorporeal shock wave therapy is a big part of his treatment approach. What were really doing with it is quite different from what were doing with treating a proximal suspensory (ligament injury in the leg), he said. There, were trying to stimulate all kinds of healing pathways . Here (with backs) what were trying to do is downregulate pain receptors normal bone has very few pain receptors in it, but arthritic bone has a lot.
We tend to use 1,000 to 2,000 pulses, depending on whether we know where the problem is, and typically we repeat it at five- to six-month intervals, but its variable depending on the patient, he added. Weve been very successful with managing these upper-level athletes with ESWT.
Allen and his colleagues commonly use ESWT and mesotherapy synergistically if the back injury is soft-tissue-related only.
As for other treatment approaches, Allen referenced a study Denoix et al. conducted with the bisphosphonate tiludronate disodium (Tildren). It maybe wasnt the greatest in statistical significance, but 80% of the horses treated with Tildren showed improvement by Day 60, compared with 50% of the control group, he said. So definitely on arthritis in that area, this is a study that you can point at and say, Well, theres a rationale for giving these horses Tildren.
Allen said while several studies support acupuncture for treating backs, this approach as well as chiropractic dont last very long. They last about three weeks, he said. We need something that lasts months and months, or longer.
In an unpublished study Allen and his colleagues looked at 314 horses presented for back pain. Of those, 57 were also presented for lameness. When veterinarians examined the horses, they considered only 32% as lame, but 92% as positive to back palpation and 90% as having a positive response to the weighted surcingle. Some other notes he made:
I dont understand why we want to rush to do surgery because you can manage these horses very effectively with medical therapy, he said. Medical management of back pain and pathology is very successful at keeping these horses going and going at their level of work, not dropping down and doing something lesser.
Theres one exception to that the horses that have already presented with avoidance behavior, he added. And if that avoidance behavior includes bucking the riders off now you have a physical problem and a mental problem. Once that horse has decided that his default response to back pain is bucking the rider off, you can treat that horse and you can be very successful. But what you dont know is at what moment four months from now thats all going to wear off and that horse is going to turn into a horse trying to be the star of the Calgary Stampede.
His biggest take-home message? Veterinarians must see horses with back pain in the field, diagnose them, and start medical management early. If you wait till they start bucking, the prognosis plummets, he said.
The (combination of) technology and the education is there to do it now, he added. It wasnt 15 years ago, but it is now. And, so, you can X ray the dorsal spinous processes, you can have (horses) sent to a clinic and you can X ray the entire spine and know what youre looking at, you can do bone scans, and you can learn to ultrasound these articular processes and the osteoarthritis. These horses dont have to keep going, and you have to educate your riders that when this horse starts getting back sore, weve got to see it and weve got to figure it out.
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Equine Back Pain: Dr. Kent Allen's Bag of Diagnostic and Treatment Tricks - TheHorse.com