Jaw fractures are not uncommon in the horse and can occur for a number of reasons.
Trauma to the head is a typical cause. This could be blunt trauma, such as a kick, fall or collision, or injury caused when the horse pulls back suddenly while chewing or cribbing on a fixed object such as a feed manger or stable bars. This failure to let go of whatever it is he has clamped his teeth around can result in avulsion (pulling out) of the horse’s incisors, or more significant fractures of the mandible — the tapering lower half of the jaw.
Whatever the cause, these fractures are often immediately obvious or otherwise straightforward to diagnose. The damage may look extensive, yet repairs can be carried out relatively easily — usually with good cosmetic and functional results.
In some cases, there is no doubt a horse’s jaw is broken, especially if part of the structure is hanging loose. Additional clues include swelling, excessive drooling, inability to eat and a protruding tongue. Closer inspection may reveal bleeding, instability of part of the jaw and malalignment of the teeth and bones.
Some fractures are less evident, however, and may go unnoticed for a few days. A foul smell emanating from the horse’s mouth may be all that is apparent.
Definitive diagnosis can be accomplished with X-rays. Ultrasound may be useful for fractures in the cheek region of the mandible. For complicated fractures that may involve the temporomandibular joint, where the mandible and the maxilla (the upper jaw) articulate with one another, CT scanning may provide more diagnostic detail.
Treatment depends on the severity and location of the injury. Jaw fractures tend to heal well, for several reasons. There is good soft tissue covering, with an excellent blood supply. The bones are not weight-bearing, nor subjected to anywhere near the forces and loads of some others, such as bones in the leg. Any implants needed to repair a fracture are thus more than able to cope.
Surgery may not be necessary. Unilateral fractures, that involve just one half of the maxilla or mandible, will often heal on their own as long as the bones are not displaced and the injury is relatively stable. The intact half of the jaw acts as a splint, supporting the fractured area.
A displaced or bilateral fracture, affecting both sides, will require surgical correction and repair. Depending on the nature of the patient and the type of fracture, this may be performed in the standing horse using sedation and local anaesthesia — as in the case of Findus (see box, right).
A short general anaesthetic may be necessary, however, so it is sensible that anything other than a simple repair is carried out at an equine hospital rather than in a yard setting.
Intra-oral wiring is effective for fractures located in front of the cheek teeth — namely the incisors, the incisive bone and the very front of the lower jaw (termed the symphysis) and upper jaw (termed the premaxilla).
The site is thoroughly cleaned of any food, clotted blood or pieces of bone, and the fracture is “reduced”, so the broken parts are realigned. Stainless steel wire is then inserted around the teeth on either side of the fracture to anchor it together.
If the canine teeth, or “tushes”, are present, and the fracture is located in front of them, a notch can be cut into these hook-like teeth so a wire can be passed around them to hold the incisors in place. The wire can be wound around the second cheek teeth to provide more support — especially if the site of the break is behind both the incisors and canines.
The aim of any fixation is to align the fractured bones, creating a stable structure so the horse can eat and drink and healing can begin. Different wiring patterns can be used to stabilise almost any type of fracture in this area. With the wires in place and tightened, the ends are twisted, bent flat and often coated with acrylic to provide more security and to prevent discomfort.
A more involved fixation method is sometimes necessary, such as an internal repair using screws and plates alongside intra-oral wiring. This might be the case with a horse who has received a substantial kick on the chin, for example, which fractures the mandible and pushes the incisors back into the mouth. Intra-oral wiring may be used in conjunction with either a bone plate or a stabilising structure on the outside of the jaw, called an external fixator.
While the outcome is usually excellent, complications can arise. Jaw fractures are often open and contaminated, due to the unclean environment of the mouth. Internal fixation using bone plates can lead to infection and the prospect of implant removal after healing — involving more cost and the inherent risks associated with a second general anaesthetic.
It is important not to remove any teeth that have been loosened by the injury, as they may still be viable and recover. Some may have suffered severe damage, however, and will be beyond saving.
While the repair should restore the ability to eat and drink, a horse struggling with this will require hospitalisation for fluid therapy and nutritional support. Appropriate nursing and soft or sloppy meals should help until he can resume a normal diet.
Most cases recover quickly, however, with the horse requiring little more than painkillers and perhaps a short course of antibiotics.
Down to the wire
“I’d never seen an injury like it,” says trainer Jimmy Frost of the grotesque sight that greeted him when he looked in on Findusatgorcombe one morning in February 2017. “My first thought was that it would be the end of him. Surely we couldn’t mend that?”
It appeared that Findus, then five, had caught his bottom incisors in the stable bars and pulled back.
“All Jimmy saw was half of Findus’ face hanging off,” says owner Phill Meaden, who was called immediately with the news. “His lower jaw was split from front to back.”
Visiting vet James McIntosh, of South Moor Equine in Devon, continues: “Findus had suffered a rostral [meaning towards the incisors] mandibular fracture. We decided to operate in Findus’ stable to avoid the added trauma of transporting him to hospital. With the aid of painkillers and regional nerve blocks, we used stainless steel wire to close and stabilise the fracture.”
A piece of PVC tubing placed in Findus’ mouth allowed James easy access to the area, so he could drill small holes between the teeth to insert the wiring.
Trainer Jimmy recalls: “The horse stood quietly, but I was feeling quite queasy and the poor girl who was helping fainted. But hats off to James and the team. Everything went back into place and Findus was soon able to eat soft food and chopped-up hay.
“Healing was remarkably quick,” adds Jimmy, whose jump jockey daughter Bryony became the first female Grade One race winner in March on Frodon, and who also rides Findus. “Findus was out training in his ‘braces’ within a fortnight, first in a Hackamore and then a soft rubber bit, and won a race before the wires were finally removed.
“He’s still a bit wary around his mouth, but he has become a very consistent little chaser. He’s a dream horse — one of Bryony’s favourites.”
Ref Horse & Hound; 5 December 2019