Lameness Diagnostics
by: Karen Briggs
June 2004 Article # 5201

We're Going Live

Imagine an X ray machine that shows you not a static image, but a live and continuous view of the bony innards of your horse. That's the fluoroscope, a hand-held scanner shaped like a large C, which displays its findings on a TV monitor as it's manipulated around your horse's leg.

Fluoroscopy generally lacks the sharp detail achievable by high-end X ray units, but it makes up for that by providing instantaneous images that aren't affected by slight movements by the horse. Furthermore, using a fluoroscope is fairly cost-effective. At Kleider Veterinary Services in Langley, British Columbia, Nick Kleider, DVM, finds that scanning an entire leg with the fluoroscope often works out to approximately what it would cost to do static X rays of a single joint. That's a huge bonus if you're working with a mystery lameness and haven't been able to zero in on one location.

"I use the fluoroscope routinely in lameness diagnostics," says Kleider. "I've had the unit for about a decade now, and I would find it very difficult to run my practice without it! What you lose in resolution is made up for by the panoramic view it provides, of any part of the horse you can fit in between the arms of the fluoroscope, right up to the stifle."

Often Kleider uses the fluoroscope on mystery lamenesses before, or instead of, blocking the limb. He finds it a less invasive way to narrow down the location of the problem. Then, if the fluoroscopic image isn't sufficiently detailed to tell the whole story, he employs conventional radiographs to bring the lameness into sharper focus.

 "It's great for hind-end lamenesses in particular--especially subtle ones with no discernible swelling or heat," says Kleider. "The 360-degree view can help you view each individual joint in the hock, for example. Then you can identify which angle you need to radiograph to make a definitive diagnosis. Or you can do a motion study by taking the leg and flexing it while you're scanning--that can highlight articular fractures, like in the proximal sesamoids, for example.

"About 50% of the time (the fluoroscope) can show you the problem and save the owner a lot of time and money," he adds.

Kleider found there was something of a learning curve to interpreting fluoroscopic images at first, since they're the reverse of X rays. "White is black and black is white," he says. "But it's so quick to use--sometimes you can reveal a problem in three seconds."

That fluoroscopy hasn't become a more mainstream part of equine veterinary practice surprises Kleider a little, considering the prominent role it plays in his diagnostic strategy. "It's very under-rated!" he says. "I guess that it never really got popular because the equipment is easily damaged. It was originally advertised as portable, but when I took it to the track I found it was too fragile--I was always replacing parts. Now I just keep it at the clinic and scan on an outpatient basis. And I do sedate the horse because it's such an expensive piece of equipment."

Concerns about radiation exposure might have dissuaded some practitioners from employing fluoroscopes, but according to Kleider, the amount of radiation emitted by a fluoroscope is very low compared to conventional X rays. Protection against radiation exposure is still necessary, but he has yet to encounter any difficulties in more than 10 years of use.

One thing the fluoroscope isn't good at is scanning the hoof. "Usually the resolution you get isn't great, and it's difficult to maneuver the arms to get a good image unless you pick up the foot. But it's a great monitoring tool during surgery on bone chips--you can get an instant view of the joint and see whether you've gotten all of the fragments before you close. And I find it's wonderful for repairing fractures to see where I should position the screws. It's so much faster than developing X rays."

 With the addition of some injectable contrast dye, fluoroscopy can also be used to check that a temporary nerve block has gone where it's supposed to go. "You get an instant yes or no on the needle placement, which can be a very good control," Kleider says.

 "And it's very client-friendly, because it's digital imaging," he adds. "You can freeze-frame the images--you lose a little resolution, like a videotape when it's put on pause, but it's still good enough to see in most cases. And you can save the whole scan to a disc. Clients love it because they can get a copy and play it on their own computers."