With more than 1,000 pounds of mass traveling at 35 miles per hour, the demands placed on each tendon and ligament in an equine limb can seem overwhelming.
Although they usually work together in harmony, even the fittest Thoroughbred can experience over-extension of a soft tissue. One of the most common (and difficult) soft tissue injuries is the strain of a ligament, the strong connective tissue band that connects bone to bone.
Ligaments are stabilizing structures that help hold bones together and keep them from overextending.
Ligament injuries can occur in both the forelimbs and the hind limbs, with the suspensory ligament being one of the primary sites of ligament failure. The suspensory ligament holds the back of the equine ankle in place and prevents overextension of the fetlock during the weight-bearing phase of a horse's stride.
The International Equine Veterinarian Hall Of Famer believes that tendon and ligament injuries in racehorses have increased over the past few years, and he suspects the advent of artificial surfaces could have contributed to a perfect storm of factors influencing the injury rate.
“Equine practitioners started to notice that soft tissue injuries became more common,” Bras says. “This this was due to many variables that affected the conditions of the [track] surface and the effect on the horses.”
Add this to the hoof issues Thoroughbreds are known for, such as thin walls and soles, and low heel/long toe, and there could be a predisposition to soft tissue injuries.
“Otherwise, these types of injuries [tendon and ligament strains and tears] seem to be more common in sport horses due to the extended careers beyond racing and types of discipline they inhered as a second career, such as hunter jumpers, eventers and/or dressage,” Bras says.
Ultrasound and MRI are the most common diagnostic tools that are used, as well as therapeutic shoeing to treat soft tissue injuries. For this treatment method to work well, the veterinarian and farrier must understand the forces at play on the injured structures, Bras says.
“The purpose of therapeutic shoeing,” he says, “is to decrease the tension and stress on the [injured] structures while allowing them to heal appropriately.”
A horse isn't built to spend the many weeks of his recovery lying down, so the farrier's job is to disperse the forces the leg will take to prevent further stress to the injured area. This varies depending upon the injury location. Bras says that an injury to the deep digital flexor tendon is commonly approached with a shoe with an elevated heel, which is thought to decrease the tension on the tendon. The last phase of stride is where the deep digital flexor tendon takes the most strain, so adding a break over modification to the shoe would facilitate range of motion in hopes of decreasing the stress forces and tension in the tendon.
A different strategy is at work when relieving stress from ligaments.
“A horse with a suspensory injury [is shod] where the shoe would ideally allow the heels to sink in more in the deep footing, decreasing the stress on those specific structures,” Bras says. “A horse diagnosed with a collateral ligament [injury] is treated with a wider-web branch shoe on the side of the injury to support that ligament when in soft footing.”
The type of footing a horse is recovering in also dictates the farrier's strategy. These types of supports are most helpful for horses dealing with deep footing, like the type that would be found in a stall, Bras says.
Soft tissue injuries usually take approximately 90 days for primary healing, but experts usually suggest horses wait longer (6 months to a year), to bring the horse back to the previous level of work.