Deep Digital Flexor Tendon Injuries in Sport Horses

FEI-certified veterinarian, Duncan Peters, DVM, MS, heads the Sport Horse Program at Hagyard Equine Medical Center in Lexington, Kentucky. In this second part of the series he explains how this common type of sport horse injury happen, how it’s treated and how it may affect your horse’s career:

“DDFT DAMAGE

The deep digital flexor tendon runs down the back of the leg and behind the heel to attach to the bottom of the coffin bone (the bone that underlies the hoof wall at the front). Its main job is to flex the leg, but it also plays a support role at the heel, where the tendon fibers fan out to pass over the navicular bone.

Injuries in the lower section of this tendon, from mid-pastern into the foot, are common for sport horses. The tendon stretches taut when your horse weights his foot and at the moment of breakover, when his weight passes over the toe and the heel begins to lift. If the stress is too great, fibers may tear or pull away from the coffin bone. This section of the tendon may also become chronically inflamed and thickened from repeated stress; a condition called tendinitis.

Most at risk

Jumping and work at speed can overload the tendon because the DDFT stretches to the max as your horse pushes off at the gallop or after landing from a jump. Mechanics of conformation or poor shoeing may contribute – a horse who has long toes and low heels puts extra stress on the lower part of this tendon during breakover.

Signs

Lameness varies. Sometimes there’s heat, swelling and sensitivity at the back of the pastern or above the heel, but you may not see these signs if the injury is down in the foot.

Tendon injuries can be hard to pinpoint in the foot. Local nerve blocks will tell your vet that your horse is sore in his heel but not whether the problem is the tendon, the navicular bone or some other structure. Ultrasound scans will reveal tendon damage higher up but are not so helpful within the hoof capsule. Magnetic resonance imaging, available at some major clinics, shows these injuries well.

Action

Tendons are a lot like ligaments and heal in the same way, that is, slowly.

• Follow the steps outlined in the suspensory section: cool down, rest, hand-walking and a gradual return to work, based on the program your veterinarian sets out.
• Shoeing changes (such as rolled or rockered toes to ease breakover) may be part of the program.
• If the problem is tendinitis, your veterinarian may suggest an injection of anti-inflammatory medications into the tendon sheath (covering).
• Regenerative therapies, such as stem cells and platelet-rich plasma, are being used to improve healing in torn tendons and ligaments alike. These treatments theoretically help the tissues heal stronger, but they don’t shorten the layup and rehab time.

Outlook

DDFT injuries can sideline horses for varying amounts of time. If your horse has a very mild strain, he may be back in work in six to eight weeks. For a tear, think months – it’s not uncommon for horses to be laid up eight months or more. Doing too much, too soon, is a recipe for reinjury.

A healed tendon, like a healed ligament, is never quite as strong as it was before the injury. The question is always: Will it hold up? The answer depends on how severe your horse’s injury was to begin with, how well it healed and what your expectations are for his future performance.” [1]

[1] https://practicalhorsemanmag.com/health-archive/5-common-sport-horse-injuries-11606