Fractures of the Small Metacarpal (Splint) Bones in Horses
Fractures of the second and fourth metacarpal (splint) bones are not uncommon. The cause may be from direct trauma, such as interference by the contralateral leg or a kick, but often accompany or follow suspensory desmitis and the resulting fibrous tissue buildup and encapsulation of the distal, free end of the bone. The usual site of these fractures is through the distal end, ~2 in. (5 cm) from the tip. Immediately after the fracture occurs, acute inflammation is present, usually involving the suspensory ligament. Lameness is typically noted (may be severe initially), which may recede after several days rest and recur only after work.
Diagnosis is confirmed by radiography. Ultrasound examination of the suspensory ligament may also be beneficial to determine a more accurate prognosis as well as guide a rehabilitation program. Surgical removal of the fractured tip and callus is the treatment of choice. Fractures involving the proximal one-third of the bone may require surgical stabilization of the bone to prevent carpal instability, particularly if the fracture involves the second metacarpal bone. Prognosis is based on severity of the associated suspensory desmitis, which has a greater bearing on future performance than the splint fracture itself.