Mandibular Fractures

Tags Force

Mandibular Fractures

Forces acting on mandible

· 2 main groups of muscles

1. muscles of mastication

2. hyoid muscles

· The muscles of mastication tend to displace posterior segments superiorly

· The suprahyoid muscles pull the anterior segments inferiorly.

· the lateral pterygoid muscles tend to pull the condylar head medially with high condyle fractures.

· Masticatory muscle function normally produces tension at the upper border of the mandible with compressive forces at the lower border.

· Proximal to the canine teeth in the area of the mandibular symphysis, the prevailing force varies with type of occlusal loading

· Alveolus and inferior border in this area of the mandible may be under compression or tensile forces at different times during the masticatory cycle, thus producing an overall torsion effect.

· Based on this, Champy define ideal lines of osteosynthesis.

· Posterior to the mental foramen a single plate is placed below the dental roots and above the inferior alveolar nerve.

· Anterior to the mental foramina two plates are necessary to neutralize the torsional forces.

Injury Pattern

Classified according

1. anatomic position

2. whether they are displaced, comminuted, or greensticked.

3. favorable or unfavourable

a. most ramus fractures are favourable

b. Symphyseal and parasymphyseal fractures tend to be vertically unfavorable and are displaced by the downward pull of the suprahyoid musculature.

c. High condylar fractures are considered unfavorable and are often displaced medially by the lateral pterygoid muscle.

Clinical

· Unilateral condylar fractures commonly present with a contralateral open bite and deviation to the ipsilateral side upon opening.

· Bilateral condylar fractures may present with anterior open bite and premature posterior contact.

Investigations

· Low Towne’s view - will clearly show the condylar processes of the mandible

· OPG – will diagnose 92 percent of mandible fractures

· CT – 99% sensitivity but will not provide the detailed information on dental occlusal relation that an OPG examination will.

· Cervical xrays

Management

Goals

1. to achieve anatomic reduction and stabilization

2. to reestablish pretraumatic functional dental occlusion

3. to restore facial contour and symmetry

4. to balance facial height and projection

Antibiotics

· essentially open fractures that should be considered contaminated, because of the oral flora, and many surgeons utilize prophylactic antibiotics

· recent randomized prospective study showed no difference in rates of wound infection in patients with an uncomplicated mandible fracture who received postoperative antibiotics versus those who received placebo

Management of teeth in line of fracture

· A loose tooth is not necessarily an indication for extraction

· Indications for tooth extraction

o comminuted or displaced fracture contains a tooth

o tooth root is fractured

o there is periodontal disease

o an abscess near the fracture line

o if the tooth is functionless because of lack of opposing teeth.

· The 3rd molar teeth is problematic – removing it will weaken the fixation but leaving it may lead to higher risk of infection.

· In general, it should be removed.

Conservative Management

1. undisplaced

2. normal occlusion

3. normal ROM

· 4 weeks of soft diet, oral hygiene

Closed Reduction

· nondisplaced or grossly comminuted fractures, fractures in the presence of mixed dentition or in the atrophic mandible, and fractures of the coronoid or condyle.

· Methods

1. Splints and dentures are occasionally used in children with mixed dentition or in edentulous patients. The splints or dentures are fixed to the mandible and maxilla by palatal screws or circumferential wires

o Gunning split or dentures in the edentulous mandible (height<2cm)

2. Intermaxillary fixation using arch bars, Ivy loops, or suspension screws. Occlusion can be maintained with either wires or elastics.

ORIF

· three basic types of internal fixation

1. compression plates

o remain controversial, as the plates are technically difficult to use and may cause malocclusion and there are no studies showing their superiority versus other fixation methods.

o If used alone, the DCP would cause compression at the inferior border with distraction and gapping at the superior border.

o The tension band principle (Champy technique) prevents this from occurring. A device such as an arch bar or miniplate can be placed on the alveolar or tension side of the mandible to restore anatomic alignment before the DCP is applied, allowing even compression along the entire length of the fracture.

o Compression plating of mandibular fractures may result in higher rates of complications, especially infections.

o Lag screws may be used for compression if the fracture line is favorable and if the fracture is noncomminuted.

2. semirigid fixation

o using a small plate with 1.5- to 2.0-mm unicortical screws.

o The advantages are the limited periosteal stripping of the fracture site needed. This technique relies on the forces of the strong jaw muscles to hold the fracture in place

o A locking plate may also be used in combination with a dental splint to add additional fixation if the comminution involves alveolar bone. Proponents of the locking plate point out that the placement of screws should not alter the reduction, but this has not been proven.

3. reconstruction plate

o form of internal surgical splint.

o serve to buttress fragments against displacement and to absorb the functional load while healing occurs.

o particularly useful for the treatment of multiple segmental fractures. The fracture segments are held together with wires or miniplates. The reconstruction plate is than contoured and secured with two screws in each stable lateral segment. The segmental fragments are then secured to the plate.

Treatment by site

Body

· usually buccal sulcus incision

· occasionally external Risdon incision

· inferior plate ± arch bar as tension band

Angle

· Prone to fracture due to 3rd molar, thin bone and lever action

· carry the highest surgical complication rate of all mandibular fracures

· best treated with ORIF due to tendency for displacement of the proximal segment.

· Best result and least complication with single, noncompression, 2.0 miniplate placed through an intraoral approach

· A transcutaneous approach may be required for screw placement

· More complications are seen with more rigid fixation

Symphysis

· 2 plates required for parasymphyseal fractures

· Care to avoid the mental nerve

· Lag screws good for this area

Ramus and Coronoid

· Most are treated conservatively

Mandibular condyle

Classsification (Lindahl)

1. Fracture level

Condylar head (intracapsular)
Neck – thin region below the head
Subcondylar – from sigmoid notch to the posterior border of the ramus just below the neck of the condyle

2. Displacement at fracture level (relation to condyle to mandible)

Angulation with medial override
Angulation with lateral override
Angulation without override
Fissure (no contact)

3. Position of the condylar head to articular fossa

No displacement
Slight displacement
Moderate displacement

d. Dislocation (head usually anteromedial)

· Medial angulation of the condylar fragment with lateral override at the fracture level was the typical fracture in adults

· Angulation without override the characteristic fracture in growing individuals.

· Medical override occurred both in children and in adults and seemed to be the result of more severe trauma to the chin.

Bilateral condylar fracture: medial Angulation with Lateral Override

Medial angulation, no override

Closed vs Open Approach

· Controversial, many studies have not shown benefit in terms of mobility, joint problems or occlusion

· proponents of open reduction are critical of the conservative treatment approach, and believe that temporomandibular joint dysfunction has been underreported and that there may be a higher incidence of traumatic arthritis, decreased range of motion, and malocclusion than previously suspected in closed reduction series.

· With conservative treatment, patients will often deviate with maximal opening and has some loss of definition of the jawline at rest

· higher incidence of shorter posterior facial height on the side of injury and more tilting of the occlusal and bigonial planes toward the fractured side.

Benefits of ORIF

More consistent occlusal results
Greater postoperative condylar mobility
More consistent facial symmetry

Strong indications for ORIF (Zide)

1. displacement into the middle cranial fossa

2. impossibility of obtaining dental occlusion by closed reduction

3. lateral extracapsular displacement of the condyle

4. presence of a foreign body

5. open fracture with potential for fibrosis.

6. Displacement of the proximal fragment of 30 degrees or more from the axis of the ascending ramus.

7. Shortening of the ascending ramus with telescoping of the fragments with concomitant open bite.

8. Dislocation of the condylar head from the temporomandibular fossa.

Relative indications for ORIF

1. bilateral or unilateral condylar fractures with a midface fractures

2. comminuted symphysis and condyle fracture with tooth loss

3. displaced fracture resulting in open bite or retrusion in mentally retarded or medically compromised adults who would not tolerate intermaxillary fixation

4. displaced condylar fractures in the edentulous or partially dentate mandible with posterior bite collapse

Absolute indications for conservative management

1. In nondislocated fractures

2. intracapsular fractures of the condylar head,

3. condylar fractures without functional disturbances

4. condylar fractures in children

Closed treatment

· will normally consist of a delay while swelling and spasm settle, followed by MMF with elastic guidance, not rigid, for 1-6 weeks.

ORIF

· Open Approaches

1. transparotid, retromandibular

§ 17% transient facial nerve palsy, 7% hypertrophic scar

· Endoscopic

1. Transcutaneous endoscopic assisted

2. Transoral endoscopic assisted

§ Lower risk of facial nerve palsy, imperceptible scar

§ High learning curve

§ higher rate of hardware loosening, leading to reoperation in at least one study

§ higher rate of nonunion, refracture, and possibly malocclusion

Complications

4 types of complications

1) those arising in the course of proper treatment

2) those caused by inadequate/inappropriate treatment(

3) those due to surgical failure

4) those that result from no treatment.

Nonunion (2.4%)

· normal bony union of the mandible takes place over 4 to 8 weeks, depending on the age of the patient

· The radiographic appearance is one of sclerotic bony margins and a gap where bone has not bridged the fracture site.

· Many of these fibrous nonunions will eventually convert to a bony union.

· Mandibular body has the highest incidence of nonunion of all mandibular sites

· Causes

1. incomplete reduction

2. soft tissue interposition

3. teeth in line of fracture

4. infection

5. poor blood supply

6. nutritional/metabolic alterations

· treatment of nonunion generally consists of removing any infected teeth, debridement of fracture, and reapplication of rigid internal fixation with or without bone grafting.

Malocclusion

· Postoperative malocclusion secondary to internal fixation requires repeat operation in the vast majority of cases. Should not rely on elastics.

Nerve injury

· 19% permanent infraalveolar nerve injury

Others

· Plate exposure

· Tooth loss

· Trismus

· Ankylosis