The most common causes of maxillofacial trauma in cats include falls from a height, car accidents, blunt trauma, iatrogenic injuries, and fights with other animals. The living environment (city vs. rural) may influence their incidence.
The origin, direction and force of the impact determine type, localization and number of lesions. Bone, soft tissues, teeth and palate may be affected concomitantly or not.
Other injuries, such as ocular and brain injuries, fractures of the long bones and joints, pneumothorax and pulmonary contusion, and abdominal trauma, may be present. A full clinical evaluation is therefore warranted in all trauma cases. Also, these patients should be medically stabilized, any life-threatening injuries addressed first. Analgesic and symptomatic treatment should be implemented as soon as possible. Placement of a nasogastric or esophagostomy tube may be indicated if treatment needs to be delayed.
Diagnostic imaging procedures, which inevitably require deep sedation or general anaesthesia, should be postponed until general anaesthesia can be safely performed. A basic radiographic screening of the skull, including a dorsoventral or ventrodorsal projection, a latero-lateral projection and right and left oblique projections, should be obtained. Intraoral views using nonscreen intraoral films are also very useful. However, CT is the gold standard diagnostic imaging procedure in maxillofacial trauma cases, as it has greater ability to identify lesions as compared to radiography.
Clinically, face symmetry, retropulsion of the eye globes, presence of oral or nasal hemorrhage, dental occlusion, integrity and mobility, range of motion of the mandible, integrity of the perioral and intraoral soft tissues and palate should be evaluated.
Soft tissue injuries may include ecchymosis (often a sign of underlying bone fracture or joint trauma and dislocation), erosion and laceration. Surgical curettage and direct suture of any mucosal or cutaneous laceration should be performed.
Dental injuries are present in up to 72% of maxillofacial trauma patients, with canine teeth, maxillary fourth premolar and mandibular first molar teeth being more commonly affected. Extraction of diseased and injured teeth should be performed with great care, to avoid any further displacement of bony fragments and trauma to the soft tissues. In fact, it is recommended to postpone extraction after bony healing, whenever possible (except in cases of severe periodontal disease, root fracture or teeth interfering with fracture reduction). In particular, any effort should be made to save teeth located along a bony fracture, as they favor anatomical reduction and fracture stabilization. They can also be used as anchor point for intraoral fixation devices. If periodontal disease is present, it should be addressed at the time of bony fixation. If endodontic disease is present, a temporary endodontic treatment may be performed at the time of bony fixation, and extraction or definitive endodontic treatment performed after bone healing.
Jaw fracture is a likely event following maxillofacial trauma. In feline patients, 11 to 23% of all fractures affect the maxillofacial region. The most commonly affected mandibular region is the symphyseal region, followed by the body of the mandible and the mandibular ramus. Diastasis along the midline of the hard palate is also frequent.
Early fracture reduction, re-alignment and adequate stabilization of bony fragments, rapid functional rehabilitation and atraumatic occlusion should be the main aims of treatment. Treatment should be performed as soon as possible (if vital and neurological parameters allow it), as a long delay in treatment may increase chances of infection of exposed fractures, tissue edema and surgical difficulties.
Proper dental occlusion is very important, because malocclusion may cause excessive leverage forces on the mandible, with an increased risk of nonunion healing, altered mandibular function and TMJ osteoarthritis. Also, in cats minimal mandibular displacement may cause an abnormal contact between the mandibular canine teeth and the maxillary tissues. Pharyngostomy or transmylohyoid intubations allow the evaluation of the dental occlusion during fracture repair.
Several different techniques may be used to treat jaw fractures in cats, including muzzle, cerclage wires, intraosseous fixation devices (interfragmentary wires, miniplates, etc.) and intraoral/interdental fixation devices (dental splinting and maxillomandibular fixation). Partial mandibulectomies and maxillectomies are sometimes necessary, in case of severely comminuted fractures.
Dental splints have the mechanical advantage to be placed on the tension side (alveolar margin) of the fracture. They are simple to apply, do not require soft tissues dissection, are well tolerated by patients and are relatively cheap. The main indications for their use include symphyseal separation, simple transverse fracture of the body or incisive area of the mandible, and maxillary fractures. Comminuted fractures (with severe bone loss), fractures in young animals (with developing teeth) and caudal mandibular fractures may represent contraindication to the use of splinting techniques.
The acid-etch splinting technique is used. First, soft tissue curettage and suture are performed. Then the teeth to be included in the splint are scaled and polished. A cerclage wire is applied around the dental crowns, reducing and stabilizing the bony fracture (the interdental wire also increases mechanical retention of the resin). The teeth are acid etched for 15 seconds, and a dental resin is applied to completely cover the wire, while bony fragments are maintained in reduction. Materials with a low exothermic temperature reaction, such as cold autopolymerizing composite resins, should be chosen to minimize the risk of thermal pulpitis. A minimum amount of resin should be used, to limit splint's size and temperature raise during polymerization. The splinting material should be placed on the lingual side of the mandibular teeth and on the vestibular side of the maxillary teeth, to minimize occlusal interference. Appropriate fracture reduction and splint placement should be confirmed radiographically. The splint should finally be smoothened with an abrasive bur, and proper occlusion checked before recovery.
The splint is removed from 2 to 6 weeks after placement, based on type and severity of bony injury, following radiographic confirmation of bone healing. It should be initially separated at the level of the fracture, and stability of the bony fragments evaluated manually. If stable, the resin (and wire) is gauged with a bur and then gently lifted from the dental surfaces. This should be done with great care, to minimize the risk of injury of the dental crowns.
Maxillomandibular fixation (MMF) may be used to treat caudal mandibular fractures and recurrent temporomandibular luxation. The same steps described for the dental splints are followed, but the resin is applied between maxillary and mandibular canine teeth, either uni- or bilaterally, to fix the mandible in position. The mandibular opening after placement should be about 2 cm, to allow spontaneous nutrition and water consumption. However, the placement of an esophagostomy tube may be indicated to allow proper nutrition. Altered thermoregulation, difficulties eating and swallowing, aspiration pneumonia and temporomandibular ankylosis (in case of intra-articular fracture) are all potential complications of MMF. Splinting time should therefore be as short as possible. It is important to note that tracheal intubation may be impossible to perform when the splint is place, and that splint's removal may have to be performed under injectable anesthesia. Other options for MMF include labial reverse suture through buttons, and bignathic encircling and retaining devices (BEARD). The first technique entails the use of nylon sutures passed full thickness through the right upper lip, the rostral mandibular soft tissues, and the left upper lip. Buttons are placed on the cutaneous side to decrease suture tension. BEARD involves the use of a nylon leader line tunneled subcutaneously around upper and lower jaws and tightened ventrally with crimps.
These devices are easily removed in case of complications, simply by cutting the Nylox sutures.
Particularly in high rise syndrome, traumatic palatal defects often develop along the midline, with diastasis at the level of the intermaxillary suture. By manually re-apposing the bony fragments, the palatal defect may be reduced to a point that sometimes surgical treatment is not necessary. However, if an oronasal communication persists, direct suture of the mucosal margins is rarely successful, as tension develops along the suture line and dehiscence is frequent. The uni- or bilateral Von Langenbeck technique or the use of mono-pedunculated flaps are effective surgical options in these cases.
References
1. Bar-Am Y, Polard RE, Kass PH, et al. The diagnostic yield of conventional radiographs and computed tomography in dogs and cats with maxillofacial trauma. Vet Surg. 2008;37:294–299.
2. Bennett JW, Kapatkin AS, Marretta SM. Dental composite for the fixation of mandibular fractures and luxations in 11 cats and 6 dogs. Vet Surg. 1994;23:190–194.
3. Bonner SE, Reiter AM, Lewis JR. Orofacial manifestations of high-rise syndrome: a retrospective study of 84 cats (2000–2010). J Vet Dent. 2012;29:10–18.