Referral & Clinical

Trauma to Jaws

Jaw trauma is common in dogs and cats . Fractures to the jaws comprise 6% of all skeletal trauma surgery. New dental techniques, combined with standard surgical techniques, are often available to provide fracture repair without the need for invasive surgery.

With any jaw fracture it is absolutely essential to support the fracture site with a tape muzzle or soft Mikki muzzle as soon as possible. We frequently see cases where support has not been provided. As a result the weight of the fractured jaw pulls on the tissues and blood vessels making subsequent healing difficult if not impossible.

Normal orthopaedic techniques are tolerated very poorly by the jaws. There are a number of reasons for this. Firstly, most pins or plates are likely to damage the tooth roots and contribute to further pain and instability. Secondly, it is much more important to provide normal dental occlusion in order to allow the mouth to shut and return to normal function than it is to align the fragments accurately. Thirdly, these problems are often see in animals that already have significant dental disease. We see many cases where pins or wires have been drilled through tooth roots or the nasal cavity. This is not acceptable. Apart from the pain caused, the revsion surgery to remove these teeth desroyed by the pins can quadruple the time originlly taken to place them.

Case Example - pins used to stabilise fractures that damage teeth

This image shows pin damaged teeth subsequently removed by us. Note the pins holes in the radiograph of the mandible. The pins go through the root apices of the premolar 4 - just where the blood supply enters the pulp! Luckily the sensory nerves and major blood vessels in the inferior alveolar canal have not been damaged here.

These two radiographs are of the same dog. Note the pin tracks through the lower canine teeth effectively destroying them. The right side radiograph again shows a large pin hole (now infected) through the root apex of premolar 4 destrying the blood supply to the pulp and allowing the necrotic material to leak into the pin site.

Such damage is not necessary if care and due attention to teeth, blood vessels, sensory nerves and nasal turbinates is paid when selecting a treatment modality.

Inter-dental wiring combined with composite resin can be used to splint extensive fractures. Additionally, cats and small dogs lend themselves well to the bonding together of upper and lower canines to provide a stable environment for healing with the cat still being able to lap soft foods through the gap. Feeding tubes may be placed for initial nutritional support but can often be removed in 2-3 days.

Mandible Fracture - Dog

Libby fractured her right mandible in the mid-body rostral to the lower carnassial tooth (molar 1 - 409). There was complete separation in the mandible and the symphysis had also separated. A cerclage wire had been placed for the symphysis separation before referral.

An interdental wire was placed from just behind molar 2 up to the incisor area using the Stout Multiple Loop pattern. The interdental wire is not sufficient to provide stability for healing but holds the fargments together for splinting. Select wire that is trong enough but not so stiff that it is had to work with. Usually SWG22 or SWG24 is best.

A composite resin splint (ProTemp Garant or similar) is placed over the wire and teeth. If necessary the teeth can be acid etched to provide more adhesion. Composite resiin splints are best as they do not set with an exothermic reaction like acrylic . The heat from acrylic can damage the tissues and fry the dental pulp.

Important points - the splint MUST be finished smooth with a high speed diamond bur to ensure to damage to the adjacent soft tissues. Overhangs of the gingiva should also be removed and the splint glazed with a dentone bonding agent to provide a smooth surface. You shouild be able to run a latex rubber glove over it without catching. A rough splint will be very uncomfortable for the patient and cause large mucosal ulcers. Second point is that no part of the splint should be destabilised by tooth contact from the opposite jaw when the mouth is closed. In effect this means no splint on the buccal surface caudal to the lower carnassial as that is where the upper carnassial will occlude. In addition, splint should be removed to provide a space for the opposite canine tooth.

The above images show the healing of the mandible at 6 weeks postop. The splint and wire can be removed but care regarding toys etc is still important. At this point the health of the molar 1 (409) must be considered. The rostral (mesial) root was in the fracture line and it is probable that the blood supply to the pulp through the root apex has been lost resulting in ischaemic necrosis of the pulp. If this has happened the tooth either needs root filled (to remove the necrotic pulp) or extracated. Extraction is a very poor option as it can destabilise the original fracture site.

This radiograph is 20 weeks post op and shows good healing of the fracture site. At this stage there is no sign of toxin leakage from the pulp through the root apices of the molar 1. Radiographs of the contralateral lower left molar 1 are similar in morphology. Root canal treatment is not indicated at this stage and a further recheck is scheduled for one year postop.

Cat Mandibular Deviation

The case series shown below shows Phoebe the cat that presented with multiple head trauma. The referring practice had attempted to stabilise the jaws with wires. The effect of the wires being too tight was to destabilise the fractures further and leave sharp wires in the mouth damaging the soft tissues further. Neither of these provide satisfactory treatment.

The radiograph shows that, apart from the symphysis separation, there is no other significant fracture. Note, however, the deviation and shortening of the mandibles. This is common in cats once the powerful masticatory muscles re-align themselves following symphyisis separation. The red arrows show the condylar processes on the mandibles. Note the symmetry proving no TMJ luxation.

The jaws very often re-align under GA without difficulty. They just won't stay there! Our solution is to place a bonding agent between the upper and lower canine teeth using a cut-down drinking straw as a retainer. If there is a cerclage wire round the symphysis the cut end below the chin can be grasped with forceps to guide the jaws and hold them there while the material sets.

If the jaws stay aligned for 2-4 weeks the material can be removed. The result with Phoebe was excellent.

One word of advice when selecting wire for interdental wiring techniques or cerclage wires in feline symphysis separation. Many texts and journal articles advise the use of 20 SWG wire for cats. This is not necessary or desirable - 24SWG is far easier to use and plenty strong enough. Also, NEVER leave the cut ends in the mouth or exposed under the chin. Cat s love to rub their chins and a jagged end of a wire will cause unnecessary trauma.

The radiograph below shows an ellipse round a caudal mandible fracture in Harry The Cat - see photo above. Inter-canine bonding worked very well in this case with full healing in 4 weeks.

Many dogs with periodontal disease of the teeth suffer from pathological fractures of the mandible from minimal trauma. Lack of teeth can be a challenge but occlusion as a primary objective, with rapid return to function as a close secondary objective is still necessary. Flo (French Bulldog)was kicked by a horse and fractured her right mandible. The site was open and infected. This healed well with twin cerclage wires once the compromised teeth and infected tissue was removed. The radiographs below show her before and after surgery and the photograph is of her right mandible 6 weeks following wiring.

TMJ conditions are also common in trauma cases – particularly in high rise syndrome in cats. Luxation of the condyle is easily resolved but fractures of the condyle or zygomatic process of the temporal bone can be challenging to diagnose and resolve. CT scanning provides excellent imaging in these cases