Away from the racecourse, the most common cause of fracture is a one-off traumatic injury — typically a kick from another horse, a road traffic accident or a collision with a solid object.
A sharp kick to an area with minimal muscle padding can be catastrophic, with locations such as the cannon bone and the inside of the leg above the hock and knee being particularly vulnerable. What can look like a small wound at first glance can hide some serious underlying bone damage.
It is important to be aware that not every broken bone results in a non-weight bearing, swinging leg lameness. If the initial trauma causes a crack or chip in the bone, the horse will be sore but will usually still be able to bear some weight on the limb.
The risk of the damaged leg falling apart increases hugely if any such injury is left unrecognised and untreated. If the horse puts pressure on a cracked bone, especially if moving at speed or struggling to stand, the bone will fail calamitously and the leg will shatter irreparably into pieces.
Even if the horse is not particularly lame, it is vital that a traumatic kick wound or a possible stress fracture is treated with extreme care. The horse should be box rested and veterinary assistance sought.
It is always better to investigate any such injury, rather than wait and see. Painkillers such as bute can mask pain, allowing the injured horse to stress the potential fracture to the point of failure. Once a simple crack in the bone is identified, there is a reasonable chance that a period of box rest, combined with a gradual return to work, will result in complete healing within four to six months.
Modern diagnostic techniques such as digital radiography, ultrasonography and bone scans mean that many fractures can be identified before they have had a chance to progress. Yet horse size can hinder both diagnosis and treatment of potential fractures. X-ray machines are not always powerful enough to obtain diagnostic images of the upper limbs in larger horses, but portable ultrasound machines can be useful.
There may be a need to transport the horse to an equine hospital to make a specific diagnosis, but this might be unreasonable on welfare grounds if he is extremely lame. There may be a risk of displacing a fracture further by moving him, yet without travelling him it may be impossible to establish the cause of what could be a severe lameness.
Compromises are required. Sometimes it is possible to splint a horse to make him comfortable enough to travel, given time and the appropriate equine ambulance transport with a gentle ramp and a competent driver.
Effective first aid immediately after the injury has a huge effect on the final outcome, which means restricting the whole horse and the injured limb from moving to reduce further damage. The aim with a lower limb injury is to stabilise the joint above and below with an adequate splint.
Some fractures can be treated routinely with impressively high success rates, given an appropriately skilled hospital team and good facilities.
Considerable scientific veterinary evidence is being accumulated to assess how different fractures are best managed, and whether surgery is necessary or if a horse can heal with splints and box rest.
One recent study looked at horses with fractures of the radius, the large forelimb bone between the knee (or carpal joint) and elbow. Radial fractures are fairly common yet challenging to manage successfully.
Previous work has shown that provided the fracture does not go all the way across the bone, and/or the bone is not displaced, then the outlook, with conservative treatment (namely box rest, cross-ties and full limb support bandaging) is reasonable. If the fracture fragments have displaced or the fracture involves a large open wound and therefore infection, the prognosis is worse.
Researchers reviewed the survival rates of horses with radial fractures, along with the risk factors associated with fractures managed either conservatively or surgically. They included 54 horses in their retrospective study, 13 of which were euthanised on admission due to the severity of the fracture or financial constraints of the owner.
Of the remaining 41 horses, 14 had incomplete fractures and were managed conservatively with Robert Jones bandages (a large support bandage) and splints. Twelve of these survived until they could be discharged. The other 27 had complete fractures that were repaired surgically — 15 of these survived to discharge.
The two conservatively managed horses that were euthanised developed supporting-limb laminitis. Of the surgical cases that did not survive, two were euthanised following recovery from anaesthesia. The others developed surgical site infections (and these were associated with open fractures) or suffered failure of the surgical repair.
Risk factors tied to surgical failure were age (older horses were less likely to survive); surgical duration (procedures taking more than 168 minutes were less likely to have a successful outcome), and surgical site infection (that trended toward a decreased survival rate).
The take-home message is that younger horses, and older horses with incomplete fractures, tend to have a good prognosis for recovery. Horses with open fractures are more likely to develop surgical site infection, which is associated with a poor prognosis for survival.
One factor not included in this study but reviewed elsewhere, is the size of the horse. Essentially it would appear that in a full-size adult horse (weighing more than 300kg) the outlook for surgical repairs of such fractures is not good. In foals and little ponies, there is less weight to manage, and the chances of repair and recovery are greater.
Globally, horses are benefiting from the accumulation of data now increasingly available, which is assisting vets in their decision-making with regard to the options for fracture repair. The terms “challenging” and “tricky” appear far too often, however, in describing case management.
Writing as a vet summoned to see such emergencies, it would seem that the horse-owning world is divided into two: those who believe that every equine fracture requires immediate euthanasia, and those who consider that a horse with any injury — however awful — must be saved.
It is worth making yourself aware of the scientific facts, so you are in a position to make a rational decision should your horse ever sustain such an injury.
Ref Horse & Hound; 27 April 2017