Anatomy of the Forelimb
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The majority of equine
tendon and ligament injuries occur in the metacarpal (foreleg), metatarsal
(hind leg) and pastern regions. The superficial digital flexor tendon (SDFT)
and suspensory ligament (SL) are the most commonly affected structures. The
SDFT is located just under the skin surface, followed by the deep digital flexor
tendon (DDFT) , inferior check ligament and suspensory ligament. In the pastern
region, the SDF and DDF tendons are also evaluated as well as the distal sesamoidean
ligaments (straight and oblique) While this brochure focuses on these regions,
the principles are similar for any musculoskeletal injury. Ultrasound can also
be utilized to diagnose injuries in other areas such as the shoulder, stifle,
fetlock, sacroiliac and pelvic region. |
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How do I know my horse has a tendon or
ligament injury?
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The clinical signs
of a tendon or ligament injury can be quite varied. Acute injuries are often
characterized by heat, swelling and pain on palpation of the affected structure.
Lameness can range from mild to severe and may be somewhat transient, sometimes
lasting only a few days. Chronic injuries often result in persistent thickening
of the tendon or ligament and an intermittent or persistent lameness. |
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Swelling of the Superficial Digital
Flexor Tendon
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Swelling of the Inferior Check
Ligament
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What should you do if you think your horse
has a tendon or ligament injury?
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Your initial goal
is to reduce inflammation. Support bandages, twice daily cold
water hosing or ice will help to reduce heat and swelling. Anti-inflammatories
should be given under the direction of your veterinarian. Your horse
should be confined to a stall until ultrasound confirms the presence
of an injury. |
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What do we evaluate on ultrasound?
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Normal tendons and ligaments
demonstrate a homogeneously echogenic (evenly white) appearance on ultrasound
when viewed on cross-section. Fiber pattern is evaluated by placing the transducer
parallel to the tendon/ligament fibers. Normal tendons/ligaments demonstrate
a long linear fiber pattern. Ultrasound machines are equipped with calculation
packages so that we can measure the size of the tendon or ligament. |
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Mild
Tear of the Superficial Digital Flexor Tendon |
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Moderate
Tear of the Superficial Digital Flexor Tendon |
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Severe
Tear of the Superficial Digital Flexor Tendon |
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Injured tendons and ligaments
demonstrate an increased cross-sectional area (size), decreased echogenicity
(a black or gray appearance) and a disrupted fiber pattern. The above images
demonstrate the appearance of an acute mild, moderate and severe tear of the
superficial digital flexor tendon. |
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Tendon and Ligament Healing
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Most tendon and ligament injuries require 9-12
months for optimal healing. Key to the success of returning your horse to work
is regular ultrasound exams to check the progress of healing throughout his
or her rehabilitation. Injured tendons/ligaments should demonstrate an improved
size, echogenicity and fiber pattern at each recheck exam, as seen in the two
images below. This horse sustained a severe tear of his superficial digital
flexor tendon as seen on the left image. The image on the right shows significant
evidence of healing with an improved echogenicity and fiber pattern. |
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Severe Acute Superficial
Digital Flexor Tendon Injury |
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5 Months Later:
Marked Improvement of the Injury |
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However, some injuries are slower to demonstrate
evidence of healing on ultrasound. This is often the case with suspensory ligament
and deep digital flexor tendon injuries. The images below illustrate a horse
with a persistent lesion of his suspensory ligament after four months of layup.
In this situation, a horse may be allowed to progress in his rehabilitation
as long as there is no evidence of new injury and the horse is not demonstrating
any signs of lameness. |
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Severe Acute Suspensory Ligament
Injury |
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4 Months Later:
Lesion is Still Easily Visible |
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Rehabilitation
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Initially, stall rest
with handwalking is required. Your horse should not have access to unrestricted
exercise such as pasture or arena turnout during the first 4-6 months. The injured
tendon or ligament cannot withstand sudden heavy loading during this time and
is highly susceptible to reinjury. An example of a controlled
exercise program is described below. By gradually loading the tendon/ligament
in increasing amounts, you are stimulating the tendon/ligament to heal to the
best of its ability. It is important to remember that your horse's program may
deviate from this program, depending on the structure involved, severity of
initial injury and progression of healing. |
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Controlled Exercise Program
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0-60 days - handwalking
- 60-90 days - 5 minute trot/jog
- 90-150 days - 10-15 minute trot/jog
- 150-210 days - 20-25 minute trot/jog
- 210-240 days - canter 5 minutes / gallop 1 mile
every other day (racehorse)
- 240-270 days - canter 10 minutes / gallop 1 mile
every day (racehorse)
- 270-300 days - low jumping / short breeze (racehorse)
- 300-330 days - normal jumping / breezes (racehorse)
- 330-360 days - competition
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Recheck ultrasound
exams are performed every 60 days to assess healing and to prevent reinjury.
Ultrasound can detect evidence of tendon or ligament damage before
a new injury occurs. In this case, the horse’s exercise level is reduced to
prevent further injury. It is important to remember that horses should not advance
in their exercise program without re-evaluation by a veterinarian. |
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Prognosis—Will my horse be able to return
to his job?
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Rehabilitation
of tendon and ligament injuries is a long and sometimes
frustrating process. However, many horses are able to successfully
return to showing, racing, trail riding, etc.
Your horse's prognosis depends on many factors, including the
structure involved and the severity and extent of the initial
injury. For example, a 20% tear of the deep digital flexor tendon
yields a much poorer prognosis than a 20% tear of the superficial
digital flexor tendon. |
Current and intended
use of your horse also plays a role. For example, a Thoroughbred
racehorse with a 30% tear of his superficial digital flexor tendon may
not return to racing, but could become a successful hunter. On the other
hand, a light trail horse with the same injury will likely be able to
return to trail riding. |
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Perhaps the most important factor is patient
and owner compliance. Some horses and owners tolerate confinement
better than others. The rehabilitation program requires patience and
commitment. It can be difficult to work with a fit horse that is suddenly
not able to exercise. In these cases, it is important to work with your
veterinarian to develop a plan that works for you and your situation.
In the end, this plan will give you the best chance to have your horse
return to his preinjury level of competition or function. |
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Large Animal Ultrasound Service
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Veterinary Medical Teaching Hospital
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University of California, Davis
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Davis, CA 95616
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Phone: 530-752-0290
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Faculty: Mary Beth Whitcomb, DVM (Section Head)
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Betsy Vaughan, DVM
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Intern: Wade Tenney, DVM
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Technician: Lindsay Graham
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