“Never use only clinical assessment to estimate the progress of a laminitic horse,” began Ric Redden, DVM, moderator of the laminitis Sunrise Session on Dec. 7 and founder of the International Equine Podiatry Center in Versailles, Ky. “X rays and venograms (images of blood flow in the foot) are essential.” He went on to discuss cases where horses had little to no blood flow in the feet but weren’t very lame, and contrasted this with horses which were still very lame but for which imaging showed that their feet were recovering. The implication was that the horse’s outward presentation can often contradict what’s really going on inside the foot.

Since venograms are relatively new to many veterinarians’ diagnostic arsenals, technique for taking them was discussed. Redden described in detail his procedure for taking venograms and the radiographic views he prefers. He strongly suggested that attendees interesting in learning venogram technique “go buy a $20-100 horse at the stockyard and do about 12 venograms on him. Look at the anatomy. He probably won’t be normal, but he might be more normal than a laminitic horse. If you learn your technique on a laminitic horse, you run the risk of misinterpreting the data you receive, and of not producing the optimum results with your technique. There is a learning curve for this procedure. There are all kinds of problems you can have with the technique as well with a very lame horse that has compromised blood flow, fragile vessels, edema, etc. It’s a tough way to learn the procedure.”

He also encouraged veterinarians to learn the technique first, before worrying about interpreting the films. “Don’t jump to conclusions until you’ve polished your technique,” he advised. “You could have a loose tourniquet and perivascular leak (puncturing the vessel twice, resulting in contrast media concentrating at the injection site instead of perfusing throughout the foot) causing misinterpretation of what’s going on in that foot…Telltale signs of these problems are quite obvious on venograms.”

Describing further polishing of venographic procedure, he advised attendees to rock the horse’s foot to allow perfusion of the anterior laminae (which doesn’t occur during weight bearing). He added that this helps mechanically open the vessels, enhancing perfusion. “It’s important to get total perfusion of the laminae and the front of the foot,” he said. “And if you have therapeutic shoes on the horse, don’t take them off for the venogram,” meaning that if the horse will be wearing these shoes, you need to see what blood flow is with them on.

Co-moderator Bruce Lyle, DVM, a primary equine practitioner in Aubrey, Texas, said that the toughest thing for him in getting started with venograms was to gain the confidence that he’d get information from them that would change his outlook and treatment of a case. He now uses venograms often in combination with thermograms, and added that he thinks the venogram is one of the most exciting diagnostic tools in the veterinarian’s arsenal.

“With a venogram, you can tell when the syndrome is getting worse even when the horse looks the same,” Redden added. “Then you know to keep from turning the horse out, putting him on a trailer, etc. Using a venogram can give true meaning to the word ’stability’.” He also recommended keeping a normal venogram around for comparison’s sake in educating owners and farriers.

Aside from the imaging benefit, attendees discussed the finding that venograms improve blood flow in the foot. “The contrast media is extremely hypertonic (concentrated),” Redden explained. “Perhaps it helps remove some of that edema (fluid swelling) from the tissues, reducing compression on the blood vessels.” When asked about how frequently a venogram could be done on a horse for this effect, he answered that he would do one whenever indicated.

Measuring and Assessing Feet

Quantification of hoof parameters was also discussed, including sole depth, the horn-laminar zone (H-L zone, distance between the hoof wall and the apex or tip of the coffin bone), coronary band-extensor process (CE, the vertical distance between the coronary band and the extensor process of the coffin bone, or the very top of the coffin bone where the extensor tendon attaches), and palmar angle (angle the wings of the coffin bone make with the ground).

Redden expresses the H-L zone as a paired measurement, by measuring it just below the extensor process and again at the end of the coffin bone. Thus, he would get a measurement of about 15 mm/15 mm for a normal light-boned horse (wider zones are common in larger horses, such as draft horses, aged Thoroughbreds, and many Standardbreds). A hoof in which the lower H-L zone measurement increases over time to surpass the upper measurement is slowly rotating.

It was mentioned that hardworking horses can reinforce the H-L zone, making it wider. “This just emphasizes the fact that the horse’s foot is an amazingly adaptive structure,” said one attendee.

The CE measurement often equals zero in normal horses, but up to about 15 mm can be normal as well. “It’s important to establish a starting point with an X ray,” explained Redden. An increase in this number indicates a sinking bony column, which is often big trouble.

He also expresses sole depth plus cup when present, with the sole depth over the cup depth. This measurement is made from the apex or tip of the coffin bone vertically to the shoe surface or ground surface if the horse is barefoot. Thus, a foot with a 15 mm/3 mm sole depth has 15 mm of sole and a 3 mm cup. Redden notes that the minimum amount of sole required for sole protection is 15 mm, and less than that tends to make a horse sore and can compromise circulation regardless of breed or intended use.

Shoeing the Laminitic Horse

Shoeing methods were briefly discussed, mostly centering on Redden’s “rock and roll” or “platano” (Spanish for the banana shape) therapeutic shoe, which has a curved ground surface. This design allows the horse to stand at whatever hoof angle is most comfortable. “A flat shoe with a rockered toe only helps when the horse moves,” he said. “The platano shoe in effect massages the circulation, as I feel that the (blood) pump of the foot is tension from (flexor) tendon pressure and release. It allows the foot to be self-adjusted and perfused 24 hours a day whether the horse is moving or not.

“Maybe we need to concentrate on treating them as they sleep, not as they race,” he added. “This helps them grow a lot of sole.”

About the Author

Christy M. West

Christy West has a BS in Equine Science from the University of Kentucky, and an MS in Agricultural Journalism from the University of Wisconsin-Madison.

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