Mandible Body Fracture

Etiology

The etiology of body fracture includes personal violence/assault, vehicular accidents, falls, and sports activities.[2][1] Among all the factors, vehicular accidents are the most common cause (43%), followed by assaults (34%), falls (7%), and sporting accidents (4%).

Epidemiology

Various studies have reported that among all the mandibular fractures, the fracture of the mandible body accounts for almost 29% (with a range of 11 to 36%), followed by condyle and angle. In children, condylar and body fractures have been demonstrated to be the most prevalent maxillofacial fractures.[3] Body fractures are more prevalent among males than females.[1]

Pathophysiology

Mandibular body fractures usually occur between the distal aspect of the canine and a hypothetical line that corresponds to the region of anterior attachment of the masseter muscle. They may be classified based on the anatomic location, the direction of the fracture line, position of teeth relative to the fracture, and favorableness.[4][5] Based on the fracture line direction and the effect of muscle distraction on the fracture fragments, the body fractures can classify into two types (favorable and unfavorable). In favorable fractures, the bony fragments are drawn together by the muscle distraction, whereas in unfavorable fractures, the bony segments become displaced by the muscle forces.

These forces that render the fracture unfavorable are exerted by various muscles such as masseter, temporalis, and medial pterygoid muscle. These muscles distract the proximal bony segment in the superomedial direction. Moreover, two additional muscles (mylohyoid and anterior belly of digastrics) may also play a role in displacing the segments in the posterior and inferior direction.

History and Physical

History: A thorough history of the patient that includes any preexisting systemic bone disease, neoplasia affecting the bone, arthritis, collagen vascular disorders, and temporomandibular joint dysfunction must merit consideration. The nature of the injury and any additional fracture's presence is assessable by the type and direction of the causative traumatic force. The vehicular accidents tend to have a larger magnitude of the force that may result in multiple, compound, comminuted mandibular fractures compared to assaults that may result in a single, simple, nondisplaced fracture.

Physical: Intraorally, a change in occlusion may be apparent on physical examination. There may be anesthesia, paresthesia, or dysesthesia of the lower lip. This change in lower lip sensation generally occurs in displaced body fractures that are distal to the mandibular foramen (along with the distribution of the inferior alveolar nerve) and not seen in nondisplaced mandible fractures.[6][7]

In general, the common signs of a body fracture include laceration in the gingiva, step defect in the occlusion, and/or ecchymosis in the floor of the mouth. Ecchymosis in the mouth floor is a pathognomonic sign of a mandibular body fracture. The examiner should note the mobility in the fracture. To do so, use both hands to manipulate the mandible by placing the thumb on the occlusal surface of the teeth and fingers on the inferior border of the mandible. Then slowly and carefully, pressure should be placed between the two hands.[6][7]

Extraorally, there may be a change in facial contour due to loss of external mandibular form and skin abrasion. A body fracture often results in a flattened appearance of the lateral aspect of the face. On palpation of there is a loss of the mandibular body. An unfavorable fracture should be suspected. The anterior face may get displaced in the forward direction, resulting in elongation. In such cases, the anterior mandible becomes displaced in the downward direction. Other findings include lacerations, hematoma, and ecchymosis.

Evaluation

Evaluation of the body fracture is via radiographs using plain radiography (panoramic, lateral-oblique, posteroanterior, occlusal, and periapical views) and CT scan. The lateral-oblique view helps to diagnose posterior body fractures. Mandibular occlusal view and Caldwell posteroanterior view demonstrate the presence of medial or lateral displacement of body fractures. Among all the radiographs, the most informative is the panoramic radiograph. The entire mandible is viewable in a single plane along with various advantages such as simplicity of technique, cost-effectiveness, and low radiation exposure compared with CT or cone-beam computed tomography (CBCT). However, it is challenging to take a panoramic radiograph in a severely traumatized patient as it usually requires the patient to be upright position. Also, as it is a 2-dimensional image, it becomes difficult to appreciate buccolingual bone displacement.

When conventional 2- dimensional radiographs cannot give an accurate picture of the fracture, CBCT can be useful as it is highly sensitive in identifying fractures. Also, it provides better imaging quality and decreases the chances of interpretation error.[7][8]

Treatment / Management

There are two methods to treat mandibular body fractures, i.e., non-surgical conservative management and surgical management. Whether to treat the fracture using surgical or non-surgical means depends on the type, severity, and consequences of fracture. In non-surgical management, also known as closed reduction, maxillomandibular fixation (MMF) serves to stabilize the fracture.[9] It offers various advantages such as low cost as it does not require any surgical treatment and hospitalization, is a less invasive procedure, and low sensitivity to the professional experience. However, MMF should not occur in a non-compliant patient, patient with seizure disorders, severe pulmonary dysfunction, intellectual disability, psychosis, pregnancy, and multiple system injuries.  Indications for closed reduction include: 

1. Non-displaced favorable fractures
2. Presence of healthy dentition with sufficient teeth to obtain a stable occlusion 
3. Grossly comminuted fractures
4. Edentulous fractures
5. Fractures in children with developing dentition
6. Presence of adequate occlusion
7. Good facial esthetics and adequate open mouth

The procedure involves the placement of Ivy loops using 24-gauge wire between two stable teeth followed by a smaller gauge wire to provide MMF between Ivy loops. Arch bars with 24- and 26-gauge wires are also frequently used. The arch bar provides additional stability by tension banding mechanism resulting in a second line of resistance. While placing arch bars, at least all the teeth in the affected quadrant of the mandible should be included. Encompassing the whole dental arch is not necessary. Arch bars are easy to place, have low cost, restore normal occlusion, and reduce the distraction of bone at the healing site. However, they require a second procedure for their removal and provide only semirigid fixation. In the case of an edentulous mandible, dentures can be wired to the jaw using circum-mandibular wires. But it has some disadvantages, including postoperative discomfort due to wires in the mandibular vestibule. Also, there is a risk of submental scar formation and damage to structures on the floor of the mouth.[10] (B3)

Alternatively, MMF screws are an option to fix the dentures. MMF screws are self-tapping screws placed in the sound bone in the vestibular regions anteriorly and posteriorly. They provide a bone anchor where elastics or wires can be placed for MMF when establishing the patient’s occlusion.[11][12] Arch bars can be placed in the denture, and intermaxillary fixation can be achieved. Gunning splints are another option in such cases.[13](B3)

On the other hand, in surgical management, i.e., open reduction and internal rigid fixation (IRF), the surgeon can visualize the fracture site easily and controls the reduction. There is the prompt recovery of the occlusion, maintenance of periodontal tissue, reconstitution of anatomic osseous morphology to its pre-surgery form, and return to early function (due to good nutrition and verbal communication).[14] However, it carries a risk of increased morbidity. Before undergoing any surgical treatment, a tooth in line of fracture may need extraction. Extraction is indicated when it is impossible or difficult to reduce the fracture due to the presence of the tooth or when the tooth has fractured roots, compromised periodontium resulting in mobility, or has an extensive periapical infection. However, the tooth may aid in guiding the reduction of fracture before extracting. After applying for the plate across the fracture, the reduction is confirmed, and the occlusion is checked. The plates and screws are then removed, the tooth extracted, and the plate reapplied by replacing the screws in the initial holes.

Surgical management can take place using an intraoral or extraoral approach, the choice of which depends mainly on the site and type of body fracture. Simple and fractures in the anterior segment with no or only slight dislocation should preferably have treatment using an intraoral approach.[15] This approach provides excellent access to the fracture site and allows observing the occlusion to reduce fracture and application of rigid fixation. The incision is placed in the vestibular region approximately 5 to 7 mm below the mucogingival junction to facilitate closure. This location also aids in the prevention of wound dehiscence. During an intraoral approach, care is necessary to avoid injuring the mental nerve.

On the other hand, the clinician can treat comminuted and fractures in the posterior segment with a high degree of dislocation using an extraoral approach as placing longer and stronger plates is difficult using the intraoral approach. An extraoral surgical approach is also a possibility with fractures that lie between the mandibular body's inferior and lingual aspects. Care is necessary to avoid injuring the marginal mandibular nerve.[16][17]

Indications for open reduction include:

1. Displaced unfavorable body fractures
2. Fracture of an edentulous mandible involving a severe displacement of fracture fragments to reestablish mandible continuity.

Postoperatively, patients should receive an analgesic. With the open reduction, antibiotic therapy covering gram-positive organisms is indicated. Wire cutters must remain at the bedside in case of vomiting. Reevaluation of the nutritional needs should also follow. In most adult mandibular fracture cases, intermaxillary fixation (IMF) is maintained for 4 to 6 weeks. In patients with a minimally displaced fracture in the tooth-bearing area, two weeks may be sufficient. After removing the wires, a radiograph is to ensure the union of the fracture.

Differential Diagnosis

Before treating mandibular body fracture, a thorough evaluation and monitoring of the patients' general physical conditions are necessary. The force that has caused mandibular body fractures may also injure other organ systems. There may occur concurrent posttraumatic thrombotic occlusion of the internal carotid artery or basilar skull fracture, bilateral cervical subcutaneous emphysema, pneumothorax, pneumomediastinum, and spleen lacerations after trauma. Therefore, patients should not be treated by surgical reduction of mandibular body fractures unless these issues are addressed.

Prognosis

Both closed and open reductions of mandibular body fractures lead to favorable results in terms of bony union. The treatment of dental injuries should be done concurrently with the fracture as the fractured teeth may become infected and jeopardize bone union. Hence, they require removal. As mandibular canines help to determine the occlusion, the clinician should preserve them, if possible. The management and prognosis of edentulous body fractures are often challenging due to advanced age and multiple comorbidities.

Complications

The most common complication is infection (resulting in malunion or non-union) or osteomyelitis. Contributing factors include:[18]

1. Oral sepsis
2. Teeth in the fracture line
3. Alcohol abuse and chronic disease
4. The prolonged time prior to treatment
5. Poor patient compliance,
6. Displacement of fracture fragments
7. Fracture of the plate 

Other complications include the delayed union of the fractured mandible. If the fracture of the body of the mandible is bilateral along with the parasymphyseal, or condylar fractures, the airway may get impaired. This impairment is due to the muscular action that pulls the distal mandibular segment backward, resulting in obstruction of the oropharynx by the tongue. There may also be nerve damage such as neuropraxia, in which function takes around 4 to 6 weeks to return, or neurotmesis, in which function may take around 18 months to return.