The extensor tendon sheaths are balloon-like spaces enclosed by a thin membrane. They contain a small amount of synovial fluid (egg yolk-consistency fluid that provides lubrication and nutrition to the tendon). These tendon sheaths are located on the fronts and sides of high motion areas in the limb.
Wounds introduce bacteria into this space, which can quickly colonize and create infection. The infection is particularly difficult to control because it is within this closed space.
Wounds to the front of the limb around the carpus and hock may involve the extensor tendon sheaths. Involvement of these structures completely changes the management of the wound and so it is critical to make the diagnosis early. Luckily, however, because these structures do not have weight bearing function (the extensor tendons only swing part of the limb forward), lameness is usually not severe.
Most horses that have infection of extensor tendon sheaths have severe swelling localized to a specific area near a joint. They often are reluctant to walk but will bear weight on the limb. The fact that the horse is usually not critically lame allows for the time necessary to treat these stubborn infections.
Veterinary diagnosis is through examination, ultrasound and sampling and testing of the synovial fluid for infection. Treatment involves hospitalization with aggressive flushing and medication of the tendon sheath, and may require surgical procedures.
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Prognosis & Relevant Factors
Prognosis is fair to good with early detection and aggressive treatment. The length of time from wounding to diagnosis and treatment is most important. Once infection is well established in the nooks and crannies of the tendon sheath, treatment becomes very difficult.
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