Monday, July 14, 2014

Morrison: Utilize Support during Stall Time to Prevent Capsular Distortion in the Thoroughbred Racehorse's Foot

The following advice is provided by Scott E. Morrison, DVM of Rood and Riddle Equine Hospital in Lexington, Kentucky:

Foot problems can commonly cause horses to be scratched from a race, lose training days, overload other structures and have shortened careers.
Functionally adapted for speed and efficient use of energy, the Thoroughbred foot is light and lacks the mass for protection commonly seen in heavier boned breeds. The relatively thin walls and sole of the Thoroughbred foot make it more susceptible to trauma, injury and hoof capsule distortion.

Hoof capsule distortion refers to misshapen/imbalanced hooves such as flares, cracks, under-run, and collapsed and sheared heels. Distortions affect function and have been correlated with musculoskeletal injuries and lameness. Foot shape and balance are paramount to maintaining soundness and optimal performance.

Maintenance and development of a healthy functional foot are necessary for well-being and longevity of racehorses, and require a proactive approach including balanced shoeing and support.

The heel region is designed to impact the ground first and dissipate vibrations. This is usually the first part of the foot to display distortion since it is made up of soft, elastic structures. The toe is stiffer and designed to cut into the ground for traction.

Hoof capsule distortions occur slowly over time and result from long-term abnormal weight bearing. The most common imbalance encountered is feet shod with too much toe length and inadequate heel length. The center of the shoe’s weight bearing surface should line up with the center of the coffin joint which is aligned at the widest part of the sole. Balanced shoeing around the coffin joint helps to distribute force more appropriately over the hoof.

The foot has the ability to handle large impact forces without structurally collapsing. Most hoof capsule deformities (under-run, collapsed heels) develop slowly and result from long periods of constant low level loading.

Racehorses spend 22 or more hours a day standing in a straw-bedded stall, and most distortions likely occur while the foot is semi-static. During this period the foot is mostly dependent on its architecture for support.

Horses standing with little arch or sole support slowly fatigue the integrity of the capsule. The arch of the sole slowly flattens, the heel becomes under-run and folded inward, and the heel bulbs can become sheared. The insidious nature of hoof capsule distortions slowly compromise the foot, rendering it more susceptible to acute injury.

Providing support to the arch is very important, especially when the horse is standing for long periods. When exercising, the track surface packs into the sole and provides support. When in the stall, the hoof has little arch support and relies on the perimeter hoof capsule for support.

Using temporary arch supports bandaged onto the feet when stalled is often very helpful. These can be taken out when exercising. Other options include stabilizer plates and heartbars which are welded into the shoe. These provide support and protection while exercising, but do add weight to the foot and may affect the horse’s gait.

Various options are available for treating the distorted foot. Detecting a compromised hoof capsule, ensuring it is shod in a balanced manner and implementing one of the methods of support can help maintain or develop a functional sound foot.

This article appears courtesy of the University of Kentucky's Gluck Equine Research Center's Equine Disease Quarterly, Volume 23, Number 3, July 2014.

Note: Dr. Morrison presented an in-depth lecture on problems affecting the feet of American racehorses at the 2013 convention of the American Association of Equine Practitioners. The AAEP convention video library has Dr. Morrison's complete 40-minute lecture video and slides for sale. You can preview a sliver of the video at this link:
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