Ain't Doin' Right Diagnostics

Many horses can be off in their performance, yet not show clinical signs of lameness. There might be no answers after the customary diagnostic work-up, leaving veterinarian and owner scratching their heads and looking for the next stop in the quest for a diagnosis.

Carl Kirker-Head, MRCVS, Dipl. ACVS, Marilyn M. Simpson Chair in Equine Medicine of Tufts University School of Veterinary Medicine, explained the phenomenon of subtle or obscure lameness as one that is difficult to see or define consistently.

"Subtle lameness, to each of us, might be a different thing in terms of its severity and presentation," he said. "The lameness might appear to switch from one leg to another; it may come, it may go. The horse who is 'off ' is just marginally unsound and frequently doesn't respond to the usual course of treatment."

Exploring an obscure lameness can be expensive, inconclusive, and trying, and is not always appropriate. Patience on the part of the owner and veterinarian are key, along with the understanding that even if the cause of the mysterious lameness is found, it isn't guaranteed to respond to treatment. However, many times it proves worthwhile, as in the following case.

Sitting on the desk of Jay Merriam, DVM, at his Massachusetts Equine Clinic in Uxbridge is a photo of a black dressage horse. The picture is signed by the rider, "Thanks for the trip to Barcelona."

At 13, the horse was considered too old to send to the Olympics by his trainer. The warmblood's condition exemplified Merriam's description of subtle lameness--a horse previously capable of working at a certain level no longer performing up to par. "It's lameness more noticed by the rider than by the visible eye," Merriam said.

The horse was sent to Merriam because of chronic underperformance as an FEI-level dressage horse. He had been diagnosed with a bone chip in the ankle, and had had some hyaluronic acid treatments and minor shoeing changes. Although not obviously lame, the horse wouldn't engage or take the right lead.

The bone chip wasn't the cause of the underperformance, as previously was thought. Following a conventional evaluation, farrier John Jarosz looked at the warmblood with Merriam, using specific X rays and measurements for balance and hoof angle. The horse had become unbalanced with sheared heels in front, a long toe, and side-to-side wall imbalances.

"I couldn't have successfully treated this horse without having the feet corrected," said Merriam.

However, over the years, the horse also had become imbalanced in the back, pelvis, and hock due to his feet. In the back, there was inflammation in the dorsal spinous processes. The pelvis was tilted left because of one foot being longer than the other behind. (For a dressage horse, the feet need to be even so they move symmetrically.)

A commitment from the owner for long-term treatment was necessary; this multi-focus affliction couldn't be treated all at once. The owner went to the clinic from Maine every six weeks to get the horse re-evaluated. The gelding was re-shod, and had a bone scan done at Tufts so Merriam could make sure he wasn't missing anything in treating the back pain by acupuncture. After a year, the horse was short-listed for the Olympic team and went to Barcelona as an alternate in dressage.

Case Two

A success story illustrating the extensive diagnostic options available for horses involves a 3-year-old Morgan mare seen at Tufts by Kirker-Head in October 1997. The horse had jumped off the trailer when loaded following purchase. There was swelling in the left hock, and the horse was given phenylbutazone (Bute) and cold hosed. Prior to going to Tufts, it was seen by a veterinarian, with X rays and a fluid sample taken and antibiotics administered. The analysis of the sample showed an increase in the number of white blood cells consistent with the inflammation present.

At Tufts, a fluid sample confirmed acute inflammation. An ultrasound showed a slight tear in the lateral/collateral ligament of the left hind leg. The Morgan was diagnosed as having synovitis, probably traumatic in origin. She was sent home for 14 days of stall rest with hand walking, hydrotherapy, Bute, and Tribrissin antibiotic for 10 days.

She was re-presented with lameness two months later at Tufts after having pasture turnout. She could readily bear weight on the hind limb and, for the most part, was able to take normal steps without demonstrating lameness, but every four to five strides she would be three-legged lame (non-weight-bearing on that foot). The hock remained swollen around the tibiotarsal joint, and in view of the case history, a fluid sample of the joint was repeated, showing moderate inflammation. (A sample with a protein level of two and 500 cells per unit of fluid is normal. The previous reading after the initial injury and during inflammation showed a protein level of four, with 12,000 cells per unit. The present sample had a protein count of 3.2, with 3,000 cells per unit.)

New X rays revealed no significant prob-lem; nuclear scintigraphy (a bone scan) em-ploying soft tissue and bone phase evaluations revealed increased uptake of radioisotope in the bone phase on the medial and proximal left hock, indicating bone remodeling in response to injury. A high-detail X ray subsequently showed subtly increased bone density in the distal tibia corresponding with the hot spot diagnosed on the bone scan.

In hopes of learning more, a computer tomographic scan (CT scan) was performed to reveal greater detail about the subtle changes in bone density. The CT scan showed a cyst-like lesion (bone defect) of the distal tibia, 8 millimeters in diameter and possibly communicating with the hock joint. It had irritated the surrounding bone and caused the remodeling detected by the bone scan and X ray. The use of a CT scan to diagnosis this unusual type of change in the hock, termed a "subchondral cyst-like lesion" was a new development in equine science, and Kirker-Head and his colleagues reported this in the veterinary literature in 1996.

Having precisely located the lesion, surgical intervention became a possibility. An arthroscopy was performed to determine the condition of the hock joint and to find out if the cyst communicated with it. It did not, ruling out the possibility of accessing the cyst from the joint.

Instead, the vets used intraoperative fluoroscopy to image the bone in multiple dimensions in order to choose the optimal surgical approach from outside the joint. The cyst was drilled and debrided, and a sample of its contents showed no infection. Bone cement impregnated with Amikacin antibiotic was inserted into the defect that lay beneath the articular cartilage, which would have otherwise collapsed without support.

The Morgan was sent home with instructions for passive range of motion exercises and a gradual increase in hand walking. Hyaluronic acid was recommended, plus Cosequin, Bute, and a continuation of antibiotics for 10 days.

Four months later, she showed grade one lameness at the walk and grade two lameness following hock flexion at Tufts, which "isn't unusual," says Kirker-Head. "Bone takes four months to heal, and remodeling at six months post-surgery is not unusual," he says.

In 1999, she was completely sound and in competition.

Case Three

In the array of Western diagnostic options--ultrasound, bone scan, thermography, and CT scanning--there is an American obsession with diagnosis, Merriam comments. The Chinese, who primarily use acupuncture, don't even have that word, he said. "We think if we can name it, we can treat it. (We think) increasing the clarity of the diagnosis will improve the diagnosis," he said, "but there are some horses that have obscure lameness, and they never receive a (definitive) diagnosis yet they can be treated successfully."

One example is a 15-year-old Quarter Horse, a former event horse currently used for low-level dressage and trail riding. The gelding had a recurring left front foot problem; he was shortening his stride around corners and would take an off step every so often in ring work. His left front foot was radiographed, but showed no changes. He didn't block for navicular, but did become sound when the whole foot was blocked. Merriam recommended corrective shoeing and floating the outside wall to restore balance.

Liz Maloney, DVM, of Equine Therapies in Sherborn, Mass., suggested using an EDSS (equine digit support system) shoe. This wide-web aluminum shoe allows for quicker breakover. Maloney also suggested shortening the toe, relieving the strain on the back of the foot, and taking pressure off the navicular bone.

The gelding had been sound for only two weeks following previous shoeings; with the EDSS shoe, there was an eight-week period without the lameness returning.

Maloney notes that common lameness often goes in diagonal pairs. As the Quarter Horse began to bear more weight on the treated left front foot, the right hind, previously questionable, had begun to show pain. The left front had become more sore while protecting the right hind, and now that the left front was no longer sore, the lesser right hind lameness became more apparent. He was given Adequan, with a recommendation to inject the hock for arthritis in the spring when on a consistent work schedule.

Paying For Information

Kirker-Head says that the extent to which the owner is willing to explore an obscure unsoundness can be determined by finances; some owners will put themselves in debt to find out what is wrong with a horse.

"When I appreciate there might be financial implications, I try to factor that into helping the owner make the decision," he says. While it's not the veterinarian's business, he says, "You do have to point out to them where it's going to leave them, and how they may be able to invest their money better in a new horse, rather than risk it on what often is a very risky venture."

Many times patience is what determines whether the owner finds out the cause of a subtle lameness. "How committed is the horse owner to getting the horse back to totally normal?" asked Merriam, "and how happy is the horse in doing what he's doing?"

For those who finally figure out the cause of a subtle lameness, Merriam cautions that, "a lot of horses even then only have a limited response to appropriate therapy." But for those who reach a resolution, "going through the process can be extremely rewarding when you get back on track."

About the Author

Andrea Reynes

Andrea Reynes is a free-lance journalist specializing in horses and the human-animal relationship. She has an animal care business in Lincoln, Mass.

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