Effects of Heel Nails on the Hoof

At the University of California, Davis, researchers used cadaver limbs loaded in a hydraulic press to determine the effects of being barefoot and three different nailing patterns (two toe nails; two toe and two quarter nails; and two toe, two quarter and two heel nails) on hoof wall surface strains, deformation and expansion under loads that simulated full weight bearing at the walk, trot and canter.

Nine limbs transected across the middle of the radius of nine horses were used, and the shoeing treatment utilized a Queen’s Plate XT. Rosette surface strain gauges (six) and markers (14) were attached to the hoof and lower limb to measure the magnitude and direction of surface strains as well as movement of the limb and hoof wall.

As expected, fetlock extension increased significantly with increased loading but did not vary by treatment. Hoof expansion approximately doubled at the trot compared with the walk and at the canter compared with the trot. The heel area showed the largest hoof wall expansion, which increased with increasing loads, and expansion in the quarters was great proximally compared with distal measurements. More palmar-placed nails (quarter and heel nails compared with toe nails) decreased expansion of the heels, and heel nails (compared with toe nails) changed hoof wall deformation during loading. The authors suggest in the live horse this could change hoof conformation over time resulting in underrun heels and increased risk of injury.

— Dahl VE et al. Animals 2023:13:1872

Viagra for Arthritis

A collaboration of researchers from four universities in Sweden conducted a blinded, randomized controlled trial with a new treatment combination of sildenafil (the active ingredient in Viagra), mepivacaine (a numbing anesthetic like Novocain) and glucose as a disease-modifying drug for arthritis. Twenty standardbred trotters mildly affected by naturally occurring arthritis in the carpus (knee joint) were treated with the experimental treatment or a commonly used corticosteroid (betamethasone) as a control.

No side effects were reported for the combination treatment. Measured biomarkers for arthritis, as well as flexion test scores, improved in the combination treatment group compared with the betamethasone control group. In addition, the experimental treatment improved gait quality at the trot. This first study evaluating the combined treatment product suggests it is safe and may be effective for early, mild cases of arthritis in horses.

— Skiödebrand E et al. Osteo Cart Open 5 2023:100381

Exercise with Restricted Blood Flow as Therapy

Exercise with restriction of blood flow is commonly used in human orthopedic rehabilitation. The process is to selectively restrict blood flow to a limb using a special tourniquet, then have the patient perform low-intensity exercise. This results in increased strength and muscle development as if the patient had performed high-intensity exercise.

Researchers at Colorado State University experimented using Doppler blood pressure monitoring to examine the typical pressures needed to produce the desired blood flow occlusion and to see whether this technique produced signs of lameness or was safe to use in horses. They exercised four horses daily with blood flow restricted to one forelimb and evaluated them for lameness on days 0, 28 and 56.

There were no significant differences in the mild lameness detected between the treated and untreated limbs. Similarly, the study detected no complications such as blood clots or skin irritations. The pressures needed to achieve blood flow occlusion varied significantly between horses and between limbs in the same horses. It appears this technique can be safely used on horses, but occlusion pressures may need to be tailored to each individual and monitored during treatment.

— Johnson SA et al. EVJ 2022;55:872-883

Ice Cold Therapy for Laminitis

Continuous ice-cold therapy to the hooves is recognized as effective for the prevention and early treatment of acute laminitis by modifying the inflammatory response and preventing tissue damage. Researchers at the University of Saskatchewan in Canada reviewed 19 publications that evaluated different methods of applying cold therapy for laminitis, including the pros and cons of each. Methods range from low-tech approaches such as standing horses in tubs, bags, or boots containing an ice water slurry to wraps that apply cold gel packs, boots, or compression wraps that circulate ice water and refrigeration systems designed to cool the lower limb.

Treatment should be applied at the earliest signs of laminitis or, preferably, when the inciting risk event has occurred (e.g., grain overload or colitis) but before clinical signs develop. The hoof wall surface temperature must be cooled to below 50 degrees Fahrenheit and maintained at this temperature for 24 to 48 hours after other signs of the inciting cause have resolved. This can take as long as 3 to 5 days. Continuous cooling during the treatment period is recommended over intermittent cooling as the latter can cause vasodilation, which is to be avoided.

Wet methods such as standing horses in a tub, bag, or boot filled with an ice water slurry are effective but labor intensive and require a large, continuous supply of ice, as much as 400 pounds per day to ice all four feet. Swelling of the immersed portion of the limbs is not uncommon but tends to resolve after the treatment is completed. More serious complications, such as cold injury to the skin, are more likely to occur with methods that use ice applied directly to the skin without mixing with water.

Some high-technology methods that cool the leg above the hoof or use gel packs do not achieve the necessary reduction in hoof wall temperature. Those that circulate or simply hold ice water around the limb in an insulated boot seem to achieve a good result more efficiently, but there is still room for a safer, more practical and effective method.

— Lavado RA et al. The Vet J 300-02 2023:106016