Mandibular Body Fractures 

Updated: Nov 05, 2018
Author: Jose E Barrera, MD; Chief Editor: Arlen D Meyers, MD, MBA 

Overview

Background

Fractures of the mandibular body may be classified by anatomic location, condition and position of teeth relative to the fracture, favorableness, or type.

Body fractures occur between the distal aspect of the canines and a hypothetical line corresponding to the anterior attachment of the masseter. These fractures are proximal to the third molar.

Mandible fractures are also described by the relationship between the direction of the fracture line and the effect of muscle distraction on fracture fragments. Mandible fractures are favorable when muscles tend to draw bony fragments together and unfavorable when bony fragments are displaced by muscle forces. Vertically unfavorable fractures allow distraction of fracture segments in a horizontal direction. These fractures tend to occur in the body or in symphysis-parasymphysis areas. Horizontally unfavorable fractures allow displacement of segments in the vertical plane. Recent evidence demonstrates that there is no need to apply different treatment modalities to mandibular fractures regardless of whether the factures are favorable.[1, 2]

Body fractures often are unfavorable because of the actions of the masseter, temporalis, and medial pterygoid muscles, which distract the proximal segment superomedially. Additionally, the mylohyoid muscle and anterior belly of the digastric muscle may contribute to the unfavorable nature of this fracture by displacing the fractured segment posteriorly and inferiorly.

For patient education resources, see the Back, Ribs, Neck, and Head Center, Breaks, Fractures, and Dislocations Center, and Teeth and Mouth Center, as well as Broken Jaw and Broken or Knocked-out Teeth.

The image below depicts the vertical and horizontal forces acting on the mandible, as well as the relationship of muscle pull to fracture angulation.

Forces acting on the mandible and demonstration of Forces acting on the mandible and demonstration of the relationship between muscle pulls and fracture angulation. (A) Horizontally unfavorable. (B) Horizontally favorable. (C) Vertically unfavorable. (D) Vertically favorable.

Epidemiology

Frequency

In general, mandible fractures of the body, condyle, and angle have nearly the same incidence, while fractures of the ramus and coronoid process are rare. The literature suggests the following mean frequency percentages based on location: body (29%), condyle (26%), angle (25%), symphysis (17%), ramus (4%), and coronoid process (1%).

The mandible is involved in 70% of patients with facial fractures.

The number of mandible fractures per patient ranges from 1.5-1.8. Approximately 50% of patients with a mandible fracture have more than 1 fracture.

The multicenter, prospective European Maxillofacial Trauma (EURMAT) project found mandibular fractures, particularly condylar and body fractures, to be the most prevalent maxillofacial fractures in children. The study, which included 114 children aged 15 years or younger, reported 47 mandibular fractures, including 18 condylar fractures and 12 body fractures.[3]

A retrospective US study of pediatric mandibular fractures by Siwani et al found that among all types of mandibular fractures, including body fractures, patients most frequently incurred injury through motor vehicle accidents (52 patients, 43%), sports (24 patients, 20%), and assault (13 patients, 11%). The study, which involved 122 patients (216 mandibular fractures), all of whom were aged 18 years or younger, found that 11 patients (9%) had a history of attention deficit hyperactivity disorder (ADHD), 23 (19%) had a history of a non-ADHD mental disorder, 17 (14%) had asthma, 18 (15%) used tobacco, 13 (11%) used alcohol, and 11 (9%) used marijuana. The investigators suggested that the relatively high proportion of mental disorders and substance abuse found in this report could have treatment implications in pediatric mandibular fractures.[4]

Etiology

Vehicular accidents and assaults are the primary causes of mandibular fractures worldwide. The mandible fracture patterns of a suburban trauma center found that violent crimes such as assault and gunshot wounds accounted for the majority of fractures (50%), while motor vehicle accidents were less likely (29%).

Data from industrialized nations suggest that fractures have various causes, as follows:

  • Vehicular accidents - 43%

  • Assaults - 34%

  • Work-related causes - 7%

  • Falls - 7%

  • Sporting accidents - 4%

  • Miscellaneous causes - 5%

Assault most often causes mandible angle fractures.

Pathophysiology

Optimal mandible function requires maintenance of normal anatomic shape and stiffness (ie, resistance to deformation under load). Normal occlusion can be defined when the mesiolabial cusp of the maxillary first molar approximates the buccal groove of the mandibular first molar. Fractures result secondary to mechanical overload. Torque results in spiral fractures, avulsion in transverse fractures, bending in short oblique fractures, and compression in impaction and higher comminution. A fracture in which one cortex of the bone is broken while the other cortex is bent is termed a greenstick fracture.

Degree of fragmentation depends upon energy stored as a result of overload prior to the fracturing process. Therefore, wedge and multifragmentary fractures are associated with high-energy release.

An evidence-based study involving 3002 patients with mandibular fractures found that the presence of a lower third molar may double the risk of an angle fracture of the mandible.[5]

Presentation

History

Obtain a thorough history specific to preexisting systemic bone disease, neoplasia, arthritis, collagen vascular disorders, and temporomandibular joint (TMJ) dysfunction. Knowledge of the type and direction of the causative traumatic force helps determine the nature of injury. For example, motor vehicle accidents (MVAs) have a larger associated magnitude of force than assaults. As a result, a patient who has experienced an MVA most often sustains multiple, compound, comminuted mandibular fractures, whereas a patient hit by a fist may sustain a single, simple, nondisplaced fracture.

Knowing the direction of force and the object associated with the fracture also assists the clinician in diagnosing additional fractures.

Physical

Pertinent physical findings are limited to the injury site.

Change in occlusion may be evident on physical examination. Any change in occlusion is highly suggestive of mandibular fracture. Ask the patient how his or her bite feels.

Posttraumatic premature posterior dental contact (anterior open bite) and retrognathic occlusion may result from an angle fracture. Unilateral open bite is associated with a unilateral angle fracture.

Anesthesia, paresthesia, or dysesthesia of the lower lip may be evident. Most nondisplaced mandible fractures are not associated with changes in lower lip sensation; however, displaced fractures distal to the mandibular foramen (in the distribution of the inferior alveolar nerve) may exhibit these findings.

Change in facial contour or loss of external mandibular form may indicate mandibular fracture. A body fracture may cause the lateral aspect of the face to appear flattened. Loss of the mandibular body on palpation may be due to an unfavorable fracture. The anterior face may be displaced forward, causing elongation. In this case, the anterior mandible is displaced downward. Damage to the condylar growth center can cause retarded growth of the mandible and facial asymmetry in children.

Lacerations, hematoma, and ecchymosis are associated with mandibular fractures. Lacerations may provide diagnostic evidence of the type of fracture sustained. Hematoma and ecchymosis may alert the clinician to a mandibular fracture. Do not close facial lacerations before treating underlying fractures. Ecchymosis in the floor of the mouth is a diagnostic sign of a mandibular body or symphysis fracture.

Pain, swelling, redness, and localized heat are signs of inflammation evident in primary trauma.

Indications

Use the simplest means possible to reduce and fixate a mandibular fracture. Because open reduction carries an increased morbidity risk, use closed techniques whenever possible. Indications for closed reduction include (1) nondisplaced favorable fractures, (2) grossly comminuted fractures, (3) edentulous fractures (using a mandibular prosthesis), (4) fractures in children with developing dentition, and (5) coronoid and condylar fractures.

Indications for open reduction include (1) displaced unfavorable angle, body, or parasymphyseal fractures, (2) multiple facial fractures, (3) bilateral displaced condylar fractures, and (4) fractures of an edentulous mandible (with severe displacement of fracture fragments in an effort to reestablish mandible continuity).

Relevant Anatomy

The body or horizontal ramus of the mandible usually includes the third molar and is bounded anatomically from the distal symphysis to a line coinciding with the alveolar border of the masseter muscle.

Contraindications

Evaluate and monitor patients' general physical conditions prior to treating mandibular fractures.

Any force capable of causing a mandibular fracture also may injure other organ systems. Case reports have documented concurrent posttraumatic thrombotic occlusion of the internal carotid artery and basilar skull fractures.

Bilateral cervical subcutaneous emphysema, pneumothorax, pneumomediastinum, and spleen lacerations also have been associated with mandible fractures after trauma.

Patients should not undergo surgical reduction of mandible fractures until these issues are addressed.

 

Workup

Imaging Studies

See the list below:

  • CT scanning and plain radiography, including panoramic, lateral-oblique, posteroanterior, occlusal, and periapical views, may be helpful. However, the single most informative radiologic study used in mandibular fracture diagnosis is panoramic radiography.

  • Panorex provides the ability to view the entire mandible in one radiograph. However, it requires an upright patient, and it lacks fine detail in the TMJ, symphysis, and dental/alveolar process regions.

  • Plain radiography may be helpful.

    • The lateral-oblique view helps diagnose ramus, angle, or posterior body fractures. The condyle, bicuspid, and symphysis regions are often unclear.

    • Mandibular occlusal views demonstrate discrepancies in the medial and lateral position of body fractures.

    • Caldwell posteroanterior views demonstrate any medial or lateral displacement of ramus, angle, body, or symphysis fractures.

  • CT scanning also may be helpful in assessment of facial fractures.

    • CT scanning allows physicians to survey for facial fractures in other areas, including the frontal bone, naso-ethmoid-orbital complex, orbits, and the entire craniofacial horizontal and vertical buttress systems.

    • Reconstructions of the facial skeleton are often helpful in conceptualizing the injury.

    • CT scanning is also ideal for condylar fractures, which are difficult to visualize.

 

Treatment

Medical Therapy

Patients with isolated nondisplaced or minimally displaced condylar fractures may be treated with analgesics, soft diet, and close observation. Patients with coronoid process fractures may be treated similarly. Additionally, these patients may require mandibular exercises to prevent trismus. If the fractured coronoid restricts mandible movement, medical therapy is contraindicated. Use prophylactic antibiotics for compound fractures. Penicillin remains the antibiotic of choice.

Surgical Therapy

Techniques for closed reduction and fixation of the dentulous mandible vary.

Closed reduction and fixation

Placement of Ivy loops using 24-gauge wire between 2 stable teeth, with use of a smaller-gauge wire to provide maxillomandibular fixation (MMF) between Ivy loops, has been successful. Arch bars with 24- and 26-gauge wires are versatile and frequently are used. In an edentulous mandible, dentures can be wired to the jaw with circummandibular wires. The maxillary denture can be screwed to the palate. Arch bars can be placed and intermaxillary fixation (IMF) achieved. Gunning splints also have been used in this scenario.

Open reduction and internal fixation

Multiple approaches to open reduction and internal fixation (ORIF) exist.[6, 7] Consider fracture location, nerve position, and skin crease lines when choosing the appropriate approach.

Intraoral versus extraoral approach to body fractures

The intraoral approach may be used in fractures with no or only slight dislocation. This approach allows sufficient exposure in the anterior part of the horizontal ramus. The molar area may require additional stab incisions to place screws for plate fixation. With an intraoral approach, exercise caution to avoid injuring the mental nerve.

The extraoral approach is necessary with fractures that have a high degree of dislocation or comminution because placing longer and stronger plates is difficult via the intraoral approach. Extraoral approach is also undertaken with fractures lying between the inferior and lingual aspects of the body. Give special attention to the marginal mandibular nerve. General anesthesia is indicated in both intraoral and extraoral approaches.

Transverse fracture line without displacement

Two 4-hole miniplates (2.0) may be used. Use monocortical screws for the superior plate. Place bicortical screws for the inferior mandibular border. Placing a superior plate helps neutralize tensile forces. In addition, a dental splint may be placed just underneath the tooth root apices. The splint must span at least 3 teeth on either side of the fracture. Recently, the treatment of mandibular fractures (symphysis, parasymphysis, and angle) with 3-dimensional plates provided 3-dimensional stability and carried low morbidity and infection rates.[8] The only probable limitations of 3-dimensional plates were excessive implant material due to the extra vertical bars incorporated for countering the torque forces.

Transverse fracture line with displacement

In this type of fracture, undertake wider surgical exposure. Reduction in the superior aspect of the placement may be secured with a tension-band splint or a 2.0 miniplate in the alveolar crest or tensile area.

Fix the inferior border with a 2.4 compression plate as seen in the image below. Stronger male patients may require a reconstruction plate with bicortical screws at this site.

Oblique fracture lines, which have wider surface area, may be fixed with 3 lag screws or a combination of lag screws and plates as seen in the image below.

(A) An oblique fracture of the body fixed with 1 l (A) An oblique fracture of the body fixed with 1 lag screw, in combination with a compression plate at the inferior border and a dental splint for tension. (B) A fracture of the mandible body with a basal triangle. (C) Open reduction and adequate fixation using a miniplate at the superior border and a reconstruction plate at the inferior border. (D) Postoperative radiograph demonstrating fixation. An open hole in the reconstruction plate lies between the triangle and the corpus.

Fractures of the basal triangle

The basal triangle may be reduced and fixed with a reconstruction plate at the mandible base. Lag screws may be used to fix comminuted segments to the plate or adjacent bone. Reduce the tensile aspect of the fracture with a 2.0 miniplate and monocortical screws or a tension-band splint as seen in the image above.

Comminuted fractures

Reduce and approximate fragments with lag screws or 1.5/2.0 miniplates. Bridge fragments with reconstruction plates.

Preoperative Details

Approach mandibular fractures methodically. Patients rarely die from mandibular fractures. Perform diagnosis and treatment in an orderly and efficient manner. Use prophylactic antibiotics for compound fractures. Evaluate nutritional needs.

Intraoperative Details

The primary goal of treatment is to reestablish occlusion. Function is compromised with malunion. Most mandibular fractures can be treated by closed reduction. Nondisplaced favorable fractures can be managed by closing with IMF alone. Arch bars or Ernst ligatures may be placed and supplemented with autopolymerizing resin.

Three separate techniques for rigid fixation of the mandible have been developed: (1) the bicortical Luhr system, using vitallium plates; (2) the Arbeitsgemeinschaft für Osteosynthesefragen/Association for the Study of Internal Fixation (AO/ASIF) system of stainless steel compression or reconstruction plates with bicortical screws;[9] and (3) the Champy miniplate technique placed along the "line of ideal osteosynthesis," using monocortical screws.

A prospective randomized clinical trial comparing 2.0-mm locking plates with 2.0-mm standard plates in the treatment of mandible fractures found the statistically significant difference between the plates. In addition, mandible fractures treated with 2.0-mm locking plates and 2.0-mm standard plates have similar short-term complication rates.

With multiple facial fractures, treat mandibular fractures first because the mandible is the foundation on which facial bones can be laid. Perform intraoral surgery prior to an extraoral approach. IMF time varies according to type, location, number, and severity of fracture. Generally, 6 weeks of IMF are prescribed, although this is only an empiric approximation.

Treat dental injuries concurrently with the fracture. Fractured teeth may become infected or jeopardize bone union and should be removed. Mandibular cuspids help determine occlusion and should be preserved, if possible.

The management of edentulous body fractures is challenging. Patients are typically advanced in age and present with multiple comorbidities. The tendency to do less should be avoided. Ellis et al reported on a 17-year experience of treating 32 atrophic mandibles and found that a more aggressive approach for managing fractures produced healing in all patients and, in the end, may be more "conservative" than a less aggressive approach.[10] These fractures were treated through an extraoral approach with rigid internal fixation. Immediate bone grafts were used in 23 of the 32 patients.

Postoperative Details

Administer analgesic medications in the postoperative period. With open fractures, use antibiotic therapy covering gram-positive organisms. Keep wire cutters at the bedside in case of vomiting. Reevaluate nutritional needs.

Follow-up

Maintain IMF for 4-6 weeks, tightening wires every 2 weeks. After wires are removed, a Panorex radiograph is usually obtained to ensure fracture union.

Complications

Complications following mandibular fracture repair are rare. The most common complication is infection or osteomyelitis. Contributing factors include (1) oral sepsis, (2) teeth in the fracture line,[11] (3) alcohol abuse and chronic disease, (4) prolonged time prior to treatment, (5) poor patient compliance, (6) displacement of fracture fragments, and (7) fracture of the plate. Material analysis of AO plates used in mandible fractures revealed titanium plate fracture in 4 out of 110 mandibular reconstructions.[12] The plate fracture was most common in angle-type plates because of constriction on the internal side of the plate.

Outcome and Prognosis

Both closed and open reductions of mandibular fractures cause favorable results for bony union. In a study of 922 mandibular body and angle fractures treated with an intraoral approach without IMF, solid bony union was achieved in more than 99% of patients.[13]

Rarely does a second fracture following additional assault or vehicular accident occur. However, when it does happen, the cause for the second fracture is usually an assault, with 90% related to alcohol intake. Angle, body, and parasymphysis regions of the mandible were the most common sites to be involved in the first occasion.

In a study with 10 cases, an internal rigid fixation procedure was performed for the treatment of a secondary fracture. In the recurrent injuries, none of the fractures occurred at exactly the same anatomical site. Fractures were either in the neighboring side or in the contralateral side of the previously healed area of the mandible. On the second occasion, angle fractures were common, but body and subcondylar fracture rates increased. At second presentation, the complication rate increased from 23.1% to 53.8% and most commonly involved malocclusion.

Future and Controversies

Controversy exists over open versus closed reduction for angle fractures. Traditionally, MMF has been the mainstay of treatment. Plating techniques have revolutionized open reduction as a treatment modality.

Advantages of closed reduction include proven efficacy, low complication rate, and short operating time. This technique may be performed as an office procedure. Disadvantages include long fixation (ie, 3-6 wk), poor nutrition associated with MMF, risk of TMJ ankylosis, and airway problems.

Advantages to ORIF include earlier mobilization and nearly exact bone fragment reapproximation. Disadvantages include increased treatment cost and need for operating room time.

Another controversy involves disposition of teeth located in the fracture line. In the postantibiotic era, infection of involved teeth is less troublesome. Many teeth may be retained, and they can be useful in reduction and stabilization of fractured segments. Extract teeth if they prevent proper reduction and fracture stability or if they have significant periodontal disease or caries.[14]

The use of miniplates for treatment of mandibular fractures has been controversial. A recent study using 0.55 mm-thick miniplates with 1.2 mm monocortical miniscrews showed that 2-point fixation with microplates is appropriate for the internal fixation of simple, isolated mandibular fractures.[15] Its advantages include a high adaptability to the fracture site, occlusal self-adjustment, a minimal mass effect, and a relatively strong holding power of 2-point fixation. In 54 patients, 8 complications were found, including 7 patients with a double fracture, including mild malocclusion (n = 3), paresthesia (n = 3), asymptomatic delayed union (n = 1), and asymptomatic plate fracture (n = 1).