Fractures of the metacarpal and metatarsal condyles (cannon bone), and proximal phalanx (long pastern bone) are of the most common fractures in racehorses. These fractures extend from the metacarpophalangeal / metatarsophalangeal (fetlock) joint surface into the adjacent epiphyseal bone, and from here can propagate into the diaphysis (central area of the bone). If the fracture emerges through any aspect of the bone it is said to exit, and this feature is used to define a ‘complete fracture’. Those fractures which do not exit are termed incomplete. When a fracture is complete, there is no longer a bridge to hold the two fragments of bone together and the fracture may become displaced.
Certain types of fractures in horses are amenable to surgical repair in the standing sedated patient. To be considered for repair this way, the following criteria must be met:
- the fracture must be incomplete
- there must be no displacement of the fracture
- the patient must be temperamentally suitable
To enable fracture repair standing, the distal (lower) limb must be anaesthetised such that the horse cannot feel anything during surgery. This also means the horse no longer protects the limb and instead bears full weight through it, making careful handling of the patient imperative during this phase. A stable level of deep sedation is required to minimise patient movement, and this is delivered by drip through an intravenous catheter. Once both of the above are achieved, surgery is performed in exactly the same manor as when the horse is under general anaesthesia.
Standing repair of fractures avoids the inherent risks associated with general anaesthesia (for more information about risks of anaesthesia follow this link). The cost of treatment is also reduced by avoiding anaesthesia costs. Balancing the reduced risks of general anaesthesia, there is a greater risk of patient movement and potential for breaking instruments when performing surgery. For the same reasons there is also a greater risk of breaks in sterility.
NEH surgeons Ian Wright and Matt Smith both have extensive experience of fracture repair in horses, and in appropriate cases routinely perform fracture repair surgery in standing sedated patients. If you would like more information about standing repair of fractures please contact either Ian Wright or Matt Smith in the hospital on 01638 782020.