Fractures of the splint bone are quite commonly seen in horses and can occur anywhere along the length of the bone. Usually the horse will be lame and there will be heat, swelling or a wound in the affected area. Fractures in the lower half of the bone are usually seen in performance horses and occur at exercise. The interosseous ligament that attaches the splint bone to the cannon becomes less pliable with age and increased weight bearing can result in fracture of the bone, usually at its thinnest part 1-2 inches above the end or ‘button’. In some case the suspensory ligament may also be affected as it lies very close to the splint bones at the back of the cannon.
Fractures in the upper half of the bone are often traumatic in origin and usually have an associated wound and infection. These may be the result of a kick or other trauma and often affect the lateral or outside splint bone. Generally, the higher the fracture is in the bone, the more serious it may be, especially if there are multiple fragments, an open wound or if it is affecting the knee or hock joints.
Splint bone fractures may be suspected based on examination of the horse but xrays are needed for accurate diagnosis. Sometimes an ultrasound scan is also carried out as this allows assessment of soft tissue damage as well. If the fracture is not displaced, is closed (no wound) and does not affect the knee or hock joints then treatment is likely to involve a period of box rest and bandaging. If the fracture is more complicated, either because it is higher up the bone, is affecting the joint, is open (there is a wound) or there are multiple fragments then surgery may be required. This may involve removal of one or more fragments of bone or in some cases larger sections of the bone are removed and a plate is used to stabilise the remaining portion.
Horses with splint bone fractures often do very well with appropriate treatment. The prognosis is worse with open fractures, especially when they occur higher up in the bone or have joint involvement.