The splint bones are located at both sides of the cannon bone. These are called II and IV Metacarpal (in the front limbs) or metatarsal (in the back limbs) bones. They support the lower row of carpal/tarsal bones.
The location of the II and IV metacarpal and metatarsal bone, make them particularly vulnerable to fracture, this are known as split fractures. This area is prone to receive direct trauma such as kicks. In particular, the fourth metatarsal is more prone to fracture than the second. In other occasions, the fracture might happen in association to suspensory desmitis.
The splint bone fractures can be open or closed. Occasionally, a discharge track or lameness can be found and guarantee investigation. Ultrasound and/or x-ray will suffice to diagnose a splint bone fracture.
The treatment will depend on the type of fracture.
· If the fracture does not affect stability, is non-infected, and is simple (the bone fragments are relatively unified) then treatment is generally conservative with heavy supportive bandaging and a period of enforced rest (12-14) weeks with regular radiographic re-evaluations to assess the quality of healing before embarking on a controlled exercise programme following conformation of satisfactory healing.
· Clean fractures of the mid- distal body, where avulsion or poor healing quality is suspected guarantee surgical management. The distal fragment or callus will be removed removal of but always leaving the proximal end intact. Usually, these horses can return to a normal life relatively quickly.
· On the other hand, if the fracture is comminuted, the treatment might be more complicated as it is likely to find associated osteitis, osteomyelitis or bone sequestrum.
· The fractures of the proximal third of the split bones are most difficult to treat. The literature recommends that no more than the distal two thirds of the split bone should be removed as this can cause great instability within the carpus/ tarsus. In these cases, the use of plates and screws might be required. Complications such as osteoarthritis, avulsion of the proximal end or callus are common in this type of fractures.
In the vast majority of cases, the prognosis for return to previous work is good, it can vary from 3weeks to 6 months, irrespective of whether the treatment employed has been surgical or conservative. Suspensory ligament damage will influence the prognosis, ultrasonographic evaluation of the suspensory early on in diagnosis and treatment is advisable as well as regular lameness evaluations during the recovery course.