Mandibular and Maxillary Fractures

Mandibular and maxillary fractures refer to traumatic or pathological disruptions in the continuity of the mandible (lower jaw) or maxilla (upper jaw) in companion animals. These fractures are among the most common maxillofacial injuries in dogs and cats, often resulting from high-velocity trauma such as vehicular accidents, falls from heights, kicks, or bites. The mandible, being a U-shaped bone with a relatively thin body and ramus, is particularly vulnerable to fracture at specific anatomical sites, including the symphysis, premolar/molar region, and the condylar process. Maxillary fractures are less common but can involve the hard palate, zygomatic arch, and nasal bones. Surgical management aims to restore anatomical alignment, occlusal relationships, and masticatory function while minimizing soft tissue trauma and preserving neurovascular integrity. Treatment options range from conservative management for minimally displaced fractures to advanced surgical techniques such as interdental wiring, intraoral splinting, external skeletal fixation, and mini-plate osteosynthesis. The choice of technique depends on fracture location, displacement, comminution, patient size, and concurrent injuries. Successful outcomes require meticulous attention to dental occlusion, as malocclusion can lead to chronic pain, temporomandibular joint (TMJ) disease, and impaired feeding.

The primary etiology of mandibular and maxillary fractures in small animals is trauma, with motor vehicle accidents being the most common cause, accounting for up to 70% of cases. Other traumatic causes include falls from heights, kicks, blunt force trauma from objects, and bite wounds from other animals. Pathological fractures can occur secondary to underlying bone disease such as neoplasia (e.g., squamous cell carcinoma, osteosarcoma), severe periodontal disease, osteomyelitis, or metabolic bone diseases (e.g., hyperparathyroidism, nutritional secondary hyperparathyroidism). Iatrogenic fractures may occur during dental extractions, especially in small or fragile mandibles, or during aggressive manipulation of the jaw under anesthesia. Congenital or developmental abnormalities, such as craniomandibular osteopathy, can predispose to pathological fractures. In cats, maxillary fractures are often associated with high-rise syndrome (falls from significant heights). The anatomical vulnerability of the mandible is due to its relatively thin cortical bone, presence of tooth roots that weaken the bone, and the high biomechanical forces generated during mastication. The maxilla, being a more rigid structure, requires greater force to fracture, but fractures can extend into the nasal cavity, orbit, or hard palate, leading to additional complications.

Mandibular and maxillary fractures are common in both dogs and cats, representing approximately 3-6% of all fractures in small animal practice. Dogs are more frequently affected than cats, with a male predominance in some studies, likely due to increased roaming and trauma exposure. Young animals (less than 2 years old) are overrepresented, as they are more prone to vehicular trauma and high-energy injuries. Brachycephalic breeds, such as Pugs, Boxers, and Bulldogs, may have a higher risk of maxillary fractures due to their shortened facial bones and prominent eyes, while dolichocephalic breeds (e.g., Collies, Greyhounds) may be more susceptible to mandibular fractures due to longer, more slender mandibles. Toy and small breeds (e.g., Chihuahuas, Yorkshire Terriers) are particularly prone to mandibular fractures during dental extractions or minor trauma due to their thin mandibles. Working dogs, such as police and military dogs, may sustain maxillofacial fractures during apprehension or tactical operations. In cats, no specific breed predilection is noted, but outdoor cats have a higher incidence due to vehicular trauma and fights. The overall incidence of maxillofacial fractures in cats is lower than in dogs, but they are often more severe due to the high-energy nature of the trauma.

The pathophysiology of mandibular and maxillary fractures involves a complex interplay of biomechanical forces, tissue disruption, and subsequent healing processes. Fractures occur when the applied force exceeds the ultimate tensile strength of the bone. The mandible is subjected to bending, torsion, and shear forces during trauma, leading to characteristic fracture patterns. Direct trauma to the ventral mandible often results in symphyseal separation or fractures of the incisive region, while lateral forces cause fractures at the premolar/molar area, where the bone is weakened by tooth roots. High-energy trauma can produce comminuted fractures with significant displacement and soft tissue damage. The maxilla, being a pneumatic bone, fractures along lines of weakness, often involving the hard palate, nasal bones, and zygomatic arch. Fracture healing begins with the formation of a hematoma, followed by an inflammatory response, fibrocartilaginous callus formation, and eventual bony union. However, the oral cavity presents unique challenges to healing due to the presence of saliva, oral bacteria, and constant movement during mastication. Infection is a common complication, leading to delayed union or nonunion. Additionally, damage to the inferior alveolar nerve, which runs within the mandibular canal, can result in sensory deficits of the lower lip and teeth. Disruption of the temporomandibular joint (TMJ) can occur with condylar fractures, leading to chronic pain and restricted jaw movement. Systemic effects of trauma, such as hemorrhage, shock, and concurrent injuries (e.g., thoracic trauma, head trauma), can complicate the clinical picture and influence surgical timing.

Several intrinsic and extrinsic factors predispose animals to mandibular and maxillary fractures. Intrinsic factors include anatomical variations such as brachycephalic conformation, which alters the distribution of forces and increases the risk of maxillary fractures. Small breed dogs have inherently thin mandibles, making them more susceptible to fractures during dental procedures or minor trauma. Age is a significant factor; young animals have a higher incidence due to their active behavior and immature bone, while older animals may have weakened bone due to periodontal disease or neoplasia. Underlying systemic conditions such as hyperparathyroidism, Cushing's disease, or chronic kidney disease can compromise bone density. Nutritional deficiencies, particularly calcium and vitamin D, can lead to metabolic bone disease. Extrinsic factors include high-energy trauma from vehicular accidents, falls, and fights. Iatrogenic factors, such as excessive force during dental extractions or improper use of dental elevators, are preventable causes. Poor management practices, such as allowing dogs to ride unrestrained in vehicles, increase the risk of trauma. Additionally, prior surgeries or radiation therapy to the head can weaken the bone and predispose to pathological fractures.

Clinical signs of mandibular and maxillary fractures vary depending on the location and severity of the fracture. Common signs include pain on opening the mouth or palpation of the jaw, swelling of the face or jaw, drooling (ptyalism), and reluctance to eat or drink. Malocclusion is a hallmark sign, with the teeth not aligning properly when the mouth is closed. There may be visible displacement of the jaw, asymmetry of the face, or crepitus on palpation. Oral bleeding, lacerations of the gingiva, and exposed bone may be present. In cases of maxillary fractures, signs may include epistaxis, facial swelling, epiphora (excessive tearing), or exophthalmos if the orbit is involved. Neurological deficits, such as facial nerve paralysis or loss of sensation in the lower lip, can occur if the inferior alveolar nerve is damaged. Animals may exhibit abnormal jaw movements, such as opening the mouth with a deviation to one side, indicating TMJ involvement. In severe trauma, systemic signs of shock, such as tachycardia, pale mucous membranes, and hypothermia, may be present. A thorough oral examination under sedation or anesthesia is essential to assess the extent of the fracture and dental occlusion.

Differential diagnoses for mandibular and maxillary fractures include: 1) Temporomandibular joint (TMJ) luxation or fracture, which presents with similar signs of malocclusion and pain, but can be differentiated by radiography or CT showing joint abnormalities. 2) Craniomandibular osteopathy, a non-neoplastic proliferative bone disease affecting young dogs, which causes bilateral mandibular and tympanic bulla swelling, but radiographs show characteristic periosteal new bone formation. 3) Osteomyelitis of the mandible or maxilla, which may present with swelling, pain, and draining tracts, but is usually associated with chronic infection and can be differentiated by imaging and culture. 4) Neoplasia of the oral cavity, such as squamous cell carcinoma or osteosarcoma, which can cause pathological fractures; biopsy and imaging are necessary for diagnosis. 5) Severe periodontal disease, which can lead to bone loss and pathological fracture, but is typically more chronic and associated with dental calculus and gingivitis. 6) Myositis of the masticatory muscles, which causes pain and difficulty opening the mouth, but does not cause malocclusion or crepitus. 7) Salivary gland disease, such as sialocele, which can cause facial swelling but is usually fluctuant and not associated with malocclusion. 8) Foreign body penetration, which can cause localized swelling and pain, but imaging may reveal a radiopaque object. 9) Tetanus, which can cause trismus and difficulty opening the mouth, but is associated with systemic signs and a history of wound infection. 10) Congenital abnormalities, such as mandibular prognathism or brachygnathism, which cause malocclusion but are not associated with trauma or pain.

The diagnostic algorithm for mandibular and maxillary fractures begins with a thorough history and physical examination, including assessment of the animal's overall stability and any concurrent injuries. After initial stabilization, a complete oral examination is performed under sedation or general anesthesia to evaluate dental occlusion, identify fractures, and assess soft tissue damage. Radiography is the primary imaging modality, with standard views including lateral, ventrodorsal, and oblique projections of the skull. Intraoral radiographs may be obtained for better detail of the dental arcade. For complex fractures, computed tomography (CT) is recommended to provide three-dimensional assessment of fracture configuration, displacement, and involvement of the TMJ or nasal cavity. CT is particularly useful for surgical planning and for detecting subtle fractures not visible on radiographs. In cases where neurological deficits are present, advanced imaging such as MRI may be indicated to assess nerve damage. Diagnostic arthroscopy of the TMJ can be performed if joint involvement is suspected. Laboratory tests, including complete blood count, serum biochemistry, and coagulation profile, are performed to assess overall health and surgical risk. Blood gas analysis may be indicated in trauma patients to evaluate acid-base status. In cases of suspected infection or neoplasia, fine-needle aspiration or biopsy may be performed. The diagnostic algorithm should be systematic and tailored to the individual patient, ensuring that all injuries are identified and appropriately managed.

Laboratory findings in animals with mandibular and maxillary fractures are often nonspecific but can provide valuable information for perioperative management. A complete blood count may reveal leukocytosis due to stress or infection, and anemia if there has been significant blood loss. Serum biochemistry may show elevated liver enzymes or creatinine due to concurrent trauma or shock. Coagulation parameters, including prothrombin time (PT), activated partial thromboplastin time (aPTT), and platelet count, should be assessed to rule out coagulopathies, especially in animals with head trauma. Blood gas analysis can identify metabolic acidosis or hypoxemia, which may require correction before surgery. In cases of suspected osteomyelitis, bacterial culture and sensitivity testing of bone or exudate are essential. Synovial fluid analysis is not typically performed unless TMJ involvement is suspected; in such cases, arthrocentesis may reveal inflammatory changes. Inflammatory biomarkers such as C-reactive protein (CRP) and serum amyloid A (SAA) may be elevated in acute trauma or infection. Urinalysis is important to assess renal function and rule out concurrent urinary tract trauma. Overall, laboratory findings are supportive rather than diagnostic, and imaging remains the cornerstone of diagnosis.

Imaging plays a crucial role in the diagnosis and surgical planning of mandibular and maxillary fractures. Standard radiography includes lateral, ventrodorsal, and oblique views of the skull. Lateral views are useful for assessing the mandibular body and ramus, while ventrodorsal views evaluate the maxilla, hard palate, and zygomatic arch. Oblique views help to visualize the temporomandibular joint and the mandibular condyles. Intraoral radiographs provide high-detail images of the dental arcade and are essential for evaluating tooth root involvement and alveolar fractures. Radiographic findings include radiolucent fracture lines, displacement of bone fragments, and step defects in the cortical margin. In maxillary fractures, opacification of the nasal cavity or frontal sinuses may indicate hemorrhage or fluid accumulation. Computed tomography (CT) is the gold standard for complex fractures, providing three-dimensional reconstructions that allow precise assessment of fracture configuration, comminution, and displacement. CT is particularly valuable for evaluating the TMJ, orbital fractures, and fractures involving the nasal cavity. Magnetic resonance imaging (MRI) is reserved for cases with suspected soft tissue or nerve injury, such as inferior alveolar nerve damage. Ultrasonography may be used to assess soft tissue swelling or abscess formation. In cases of suspected vascular injury, angiography or CT angiography can be performed. Advanced imaging modalities have significantly improved the accuracy of fracture classification and surgical planning, leading to better outcomes.

Cytology and histopathology are primarily indicated when there is suspicion of an underlying pathological process, such as neoplasia or osteomyelitis. Fine-needle aspiration (FNA) of any mass or swelling associated with the fracture can be performed to obtain samples for cytological evaluation. Cytological findings may include inflammatory cells (neutrophils, macrophages) in cases of infection, or neoplastic cells in cases of malignancy. Histopathological examination of bone biopsies is essential for definitive diagnosis of tumors such as osteosarcoma, chondrosarcoma, or squamous cell carcinoma. Histological features of osteosarcoma include malignant osteoblasts producing osteoid, while squamous cell carcinoma shows nests of squamous epithelial cells with keratin pearls. In cases of osteomyelitis, histopathology may reveal necrotic bone, inflammatory infiltrate, and bacterial colonies. Special stains, such as Gram stain for bacteria or immunohistochemistry for tumor markers, can aid in diagnosis. In cases of craniomandibular osteopathy, histopathology shows proliferative periosteal bone with a mixed inflammatory infiltrate. Biopsy should be performed with caution to avoid further weakening of the bone, and samples should be obtained from the fracture site or any abnormal tissue. Cytology and histopathology are not routinely performed for simple traumatic fractures but are essential when pathological fracture is suspected.

Treatment of mandibular and maxillary fractures aims to restore normal occlusion, provide stability for bone healing, and minimize complications. Conservative management may be considered for minimally displaced, stable fractures, particularly in young animals, using a soft diet and activity restriction. However, most fractures require surgical intervention. Surgical options include: 1) Interdental wiring, which involves passing wire around adjacent teeth to stabilize the fracture; this is suitable for symphyseal fractures and some body fractures. 2) Intraoral splinting, using acrylic or composite splints applied to the teeth to immobilize the fracture; this is non-invasive and effective for certain fractures. 3) External skeletal fixation, using pins and connecting bars placed percutaneously; this is useful for comminuted or infected fractures. 4) Internal fixation with mini-plates and screws, which provides rigid stabilization and is ideal for complex fractures, especially in the maxilla and ramus. 5) Cerclage wire or interfragmentary wire fixation for simple fractures. 6) In cases of severe comminution or bone loss, bone grafting may be necessary. The choice of technique depends on fracture location, patient size, and surgeon preference. Preoperative management includes stabilization of the patient, administration of broad-spectrum antibiotics, and pain management. Postoperative care involves a soft diet, oral hygiene, and restricted activity. Complications such as malocclusion, nonunion, infection, and implant failure must be monitored. Physical rehabilitation, including passive range of motion exercises, may be recommended to maintain TMJ function.

The prognosis for mandibular and maxillary fractures is generally good to excellent with appropriate treatment. The overall success rate for surgical repair is high, with reported union rates exceeding 90% in dogs and cats. Factors that influence prognosis include the severity of the fracture, presence of concurrent injuries, timing of surgical intervention, and the experience of the surgeon. Simple, minimally displaced fractures have an excellent prognosis, while comminuted fractures involving the TMJ or with significant bone loss have a guarded prognosis. Complications such as malocclusion, nonunion, osteomyelitis, and implant failure can negatively impact outcomes. Malocclusion is a common complication, occurring in up to 20% of cases, and may require additional corrective procedures. Nonunion is rare but can occur if fixation is inadequate or infection develops. The prognosis for return to normal function, including eating and grooming, is excellent in most cases. Long-term follow-up is recommended to monitor for late complications such as TMJ arthritis or tooth root abscesses. With proper surgical technique and postoperative care, the majority of animals achieve full functional recovery.

Postoperative follow-up for mandibular and maxillary fractures is essential to ensure proper healing and detect complications early. Immediate postoperative care includes monitoring for pain, swelling, and oral bleeding. Antibiotics are typically continued for 7-10 days postoperatively. A soft diet is recommended for 4-6 weeks to reduce stress on the fracture site. Oral hygiene, including gentle rinsing with chlorhexidine solution, should be maintained. Sutures or external fixator pins should be checked regularly for signs of infection or loosening. Radiographic evaluation is performed at 4, 8, and 12 weeks postoperatively to assess bone healing. At 4 weeks, early callus formation should be visible; at 8 weeks, bridging callus is expected; and at 12 weeks, the fracture should be clinically stable. Implant removal may be recommended after complete healing, especially for external fixators or cerclage wires, but internal plates can often be left in place. Activity restriction is advised for 6-8 weeks, with gradual return to normal activity. Physical therapy, including passive range of motion exercises for the TMJ, may be beneficial. Long-term follow-up at 6 months and 1 year is recommended to monitor for late complications such as malocclusion, TMJ disease, or tooth root abscesses. Owners should be educated on the signs of complications and the importance of regular veterinary check-ups.

Clinical pearls for managing mandibular and maxillary fractures include: 1) Always assess dental occlusion before and after surgical repair; malocclusion is a common complication that can be prevented by careful alignment of the teeth. 2) Use intraoral radiographs to evaluate tooth root involvement and ensure that no root fragments are left in the fracture line. 3) In symphyseal fractures, use a figure-of-eight wire around the canine teeth or a pin and wire technique to stabilize the symphysis. 4) For maxillary fractures, be aware of the infraorbital canal and avoid damaging the infraorbital nerve. 5) In cats, the mandible is particularly thin; use small implants and avoid excessive periosteal stripping. 6) Consider the use of a transcondylar pin for condylar fractures to maintain joint function. 7) Use a tension band wire on the ventral aspect of the mandible to counteract distracting forces. Pitfalls to avoid include: 1) Failing to address concurrent injuries, such as thoracic trauma or head trauma, which can be life-threatening. 2) Inadequate fixation leading to instability and nonunion. 3) Over-tightening wires or screws, which can cause bone necrosis. 4) Penetrating the tooth roots during pin placement, leading to endodontic disease. 5) Not providing adequate postoperative analgesia, which can lead to decreased food intake and poor healing. 6) Ignoring the importance of dental occlusion, which can result in chronic pain and TMJ disease. 7) Using inappropriate implant size for the patient, especially in toy breeds. 8) Failing to recognize and treat osteomyelitis, which can lead to implant failure and chronic infection.

Perioperative pharmacological protocols for mandibular and maxillary fractures are based on Plumb's Veterinary Drug Handbook. Prophylactic antimicrobials are indicated to prevent infection, especially in open fractures or when implants are placed. A common protocol is cefazolin (22 mg/kg IV) administered 30 minutes before incision and repeated every 90 minutes during surgery. Postoperatively, amoxicillin-clavulanate (13.75-22 mg/kg PO q12h) or clindamycin (10-15 mg/kg PO q12h) may be continued for 7-10 days. Pain management is crucial; opioids such as hydromorphone (0.05-0.1 mg/kg IV or IM q4-6h) or buprenorphine (0.01-0.02 mg/kg IV or IM q6-8h) are used in the immediate postoperative period. Nonsteroidal anti-inflammatory drugs (NSAIDs) such as carprofen (2.2 mg/kg PO q12h) or meloxicam (0.1 mg/kg PO q24h) can be used for 3-5 days, but caution is advised in animals with renal or hepatic disease. Local anesthetic blocks, such as a maxillary or mandibular nerve block with bupivacaine (1-2 mg/kg), can provide excellent intraoperative and postoperative analgesia. A constant rate infusion (CRI) of lidocaine (25-50 mcg/kg/min) or ketamine (0.5-1 mg/kg/hr) may be used for multimodal analgesia in severe cases. Muscle relaxants such as methocarbamol (20-40 mg/kg PO q8h) may be used to reduce jaw muscle spasms. Chondroprotectants such as polysulfated glycosaminoglycan (4.4 mg/kg IM or SC twice weekly) may be considered for TMJ involvement. All drug dosages should be adjusted based on the patient's individual needs and concurrent conditions.

The surgical management of mandibular and maxillary fractures in small animals has been extensively studied. A landmark study by Boudrieau (2012) reviewed the use of mini-plate osteosynthesis for mandibular fractures, reporting high success rates with rigid fixation and early return to function. Another study by Lascelles et al. (2003) compared different fixation methods for symphyseal fractures, finding that a combination of pins and wire provided superior stability. A retrospective study by Kitshoff et al. (2013) evaluated the outcome of maxillary fractures in dogs and cats, concluding that surgical treatment with mini-plates or external fixation resulted in excellent functional outcomes. The use of computed tomography for surgical planning has been shown to improve accuracy and reduce complications (Soukup et al., 2015). A systematic review by Verstraete et al. (2016) emphasized the importance of dental occlusion and the need for meticulous surgical technique. The AO Veterinary Expert Group has published guidelines for the treatment of maxillofacial fractures, recommending the use of locking plates for improved stability. Recent studies have also investigated the use of patient-specific 3D-printed implants for complex fractures, showing promising results (Winer et al., 2017). Overall, the evidence supports early surgical intervention, rigid fixation, and careful attention to occlusion for optimal outcomes.