Exostoses of the Second and Fourth Metacarpal Bones in Horses
Splints primarily involve the interosseous ligament between the large (third) and small (second) metacarpal (less frequently the metatarsal) bones. The reaction is a periostitis with production of new bone (exostoses) along the involved splint bone. Possible contributory factors include trauma from concussion or injury, strain from excess training (especially in the immature horse), faulty conformation, imbalanced or overnutrition, or improper shoeing.
Splints most commonly involve the second metacarpal bone. Lameness is seen only when splints are forming and is seen most frequently in young horses. Lameness is more pronounced after the horse has been worked. In the early stages, there is no visible enlargement, but deep palpation may reveal local, painful, subperiosteal swelling. In the later stages, a calcified growth appears. After ossification, lameness disappears, except in rare cases in which the growth encroaches on the suspensory ligament or carpometacarpal articulation. Radiography is necessary to differentiate splints from fractured splint bones.
Complete rest and anti-inflammatory therapy is indicated. Intralesional corticosteroids may reduce inflammation and prevent excessive bone growth. Their use should be accompanied by counterpressure bandaging. If the exostoses impinge against the suspensory ligament, surgical removal may be necessary.