Mandible Anatomy and Fractures

• Mandibular fractures require restoring functional occlusion and facial form.
• Mandible fractures are more frequent than those of any other facial skeleton.
• Treatment involves closed methods or open reduction with plates and screws.

Anatomy

• The mandible is a U-shaped body
• It consists of 2 vertically directed rami plus the Condylar & Coronoid processes
• Includes the Obliqueline and Mental foramen

Internal Anatomy

• Includes the Mandibular foramen, Lingula, Pterygoid fovea & Mylohyoid line
• Mandible also contains Fossae: Submandibular, Sublingual & Digastric
• Includes Mental spines, Genioglossus & Geniohyoid

Jaw Elevators

• Masseter muscle runs from the zygomatic bone to the angle and ramus
• Temporalis muscle runs from the infratemporal fossa to coronoid andramus
• Medial pterygoid muscle originates on the medial surface of the lateral pterygoid plate and pyramidal process, inserting into the lower mandible.

Jaw Depressors

• Lateral pterygoid muscle runs from the lateral pterygoid plate to the condylar neck and TMJ Capsule
• Mylohyoid muscle runs from the mylohyoid line to the body of the hyoid bone
• Digastric muscle runs from the mastoid notch to the bdigastric fossa
• Geniohyoid muscle runs from the genial tubercle to the hyoid bone

Innervation

• CN3 transmits the mandibular nerve, through the foramen ovale
• Inferior alveolar nerve transmits through the mandibular foramen
• Includes Inferior dentalplexus & Mental nerve through the mental foramen.

Classification of Fractures

• Classified based on the Type, Site, Pattern and Cause of fracture

Type of Fracture

• Simple fractures include closed linear fractures of the condyle, coronoid, ramus and edentulous body.
• Compound fractures go through tooth bearing portions of the jaw and into the mouth via the periodontal membrane.
• Comminuted fractures consist of fragmented bone
• Pathological fractures result from a mandible weakened by pre-existing conditions.

Site of Fracture

• Common sites include: Dentoalveolar, Condyle, Coronoid & Ramus
• Common sites also include: Angle, Body, Parasymphysis & Symphysis

Pattern of Fracture

• Can be unilateral, bilateral or multiple

Cause of Fracture

• Causes can include: Direct/Indirect Violence & Excessive muscular contraction
• Excessive Muscular Contraction can cause fractures of the coronoid process

Aetiology

• Common causes are: Road traffic accidents & Interpersonal violence
• Others are Contact sports, industrial trauma & Falls

Epidemiology

• 75% of mandible fractures are caused by motor vehicle accidents and assaults
• 31% of mandibular fractures occur at the angle

Signs & Symptoms

• Common symptoms are Swelling and Lacerations
• Also common are Bleeding from the mouth, Ecchymosis & Pain
• Can also include : Tenderness, Step deformity, Fractured teeth & Limitation in mouth opening

Investigations

• X-rays and Radiographs are key
• Includes extra and intra-oral radiographs and desirable radiographs.

Extra-Oral Radiographs

• Lateral Oblique radiographs(left and right) can show fractures of the body proximal to canine and fractures of the angle or ramus
• Posterior-anterior view can highlight displacement of fractures in the ramus, angle and body

Radiography views

• Reverse Towne's view is ideal for showing lateral or medial condylar displacement

Intra-Oral Radiographs

• Periapical radiographs show the association with a tooth in the line of fracture.
• Can indicate existing pathology related to a tooth in line of fracture
• Can show a fractured tooth in line of mandibular fracture

Desirable Radiographs

• Panoramic tomography provides an overall view of the mandible
• Computed tomography(CT) may be necessary

Management

• Focused on Airway (including dealing with the tongue falling back and blood clots)
• Attention given to: Fractured teeth/segments, Broken fillings & Dentures
• Also includes management of Hemorrhage & Soft tissue lacerations
• Support of bone fragments and Pain control
• Infection control is especially important for compound fractures, Food and Fluids

Definitive Treatment

• Requires Reduction and Restoration of a functional alignment of the bone fragments
• Reduction makes use of occlusion
• Includes Open reduction and Closed reduction too
• Requires Immobilization (Fixation) to allow bone healing

Immobilization

• Achieved through fixation of the fracture line
• Can be Rigid or Semi-rigid

Management of Teeth in Fracture Line

• Requires Appropriate antibiotic therapy and Splinting of the tooth if mobile
• Endodontic therapy is important if pulp is exposed
• Immediate extraction occurs if a fracture becomes infected or the existence of a root fracture

Immobilization Considerations

• Stable fixation varies according to the Site of fracture and Presence of teeth in the fracture line
• Depends on the Age of the patient & presence or absence of infection

Time of Immobilization

• For a young adult with a fracture of the angle and early treatment, with a tooth removed from fractureline - immobilization is around 3 weeks

Time of Immobilization - Ifs

• Add 1 week if a tooth is retained in fracture line
• Add 1 week if the Fracture is at Symphysis
• Add 1 or 2 weeks if the Age is 40yrs and above
• Subtract 1 week if the patient is a Child or adolescent

Methods of Immobilization

• Intermaxillary fixation using Bonded brackets & Dental wiring
• Includes Eyelet(ivy loop wiring) & Arch bars + Cap splints
• Or Osteosynthesis without intermaxillary fixation

Osteosynthesis

• Osteosynthesis without intermaxillary fixation includes use of Non-compression small plates and Compression plates
• Alternatives are Mini plates & Lag screws

Closed Reduction

• Fracture reduction is achieved without opening the skin or mucosa
• Fracture site heals with secondary bone healing, therefore this is also a form of non-rigid fixation
• It is considered the simplest method to achieve optimal results for mandibular fractures

Indications for Closed Reduction

• Nondisplaced favorable fractures & Mandibular fractures in children with developing dentition
• Condylar fractures

Contra-Indications for Closed Reduction

• Unfavorable fractures & certain Medical conditions

Medical conditions that prevent closed reduction

• Alcoholics , Seizure disorder, Mental retardation & Nutritional concerns
• Respiratory diseases like Chronic Obstructive Pulmonary Disease (COPD)

Advantages of Closed Reduction

• Low cost and fast
• Can be performed in clinical setting with local anesthesia or sedation
• Its and easy procedure

Disadvantages of Closed Reduction

• No absolute stability, therefore secondary bone healing is less ideal
• Oral hygiene is difficult to maintain & Possible TMJ sequelae can occur

Possible TMJ Sequelae

• Muscular atrophy/stiffness and Decreased range of motion

Techniques for Closed Reduction

• Arch bars (using Erich arch bars) & Ivy loops
• Alternatives are Splints & Intermaxillary fixation screws

Open Reduction

• Requires opening of skin or mucosa to visualize the fracture and reduction
• Can be used for manipulating any fracture
• Can be used for non-rigid and rigid fixation of the fracture

Indications for Open Reduction

• Unfavorable/unstable mandibular fractures
• Fractures of the edentulous mandible with severe displacement
• Delayed treatment with interposition of soft tissue that prevents adequate closed reduction.

Special Considerations

• Edentulous mandible
• Mandible in children

Mandibular Fractures are different in Children

• Mandible is more resilient during childhood
• Green stick fractures & High ratio of bone to teeth substance are more likely
• Must consider interference with growth, fixation issues in deciduous/mixed dentition & unerupted teeth

Fracture of Edentulous Mandible

• Influenced by Decreased inferior alveolar artery
• Dependent on periosteal blood flow
• Affected by Medical conditions that delay healing
• Reduction in ability to heal with age & Altered physical characteristics with tooth loss

Immobilization for Edentulous Mandibles

• Involves Direct Osteosynthesis with Bone plates, Transosseous wiring & Circumferential wiring
• Can include Indirect skeletal fixation via External Pin fixation & Bone clamps
• Can include Intermaxillary fixation using a gunning type splint

Complications after any treatment

• Misapplied fixation , Infection & TMJ ankylosis
• Nerve damage & Displaced teeth with Gingival and periodontal complications

Malunion may also occur

• Or Delayed union and Non union as a result of : Inadequate immobilization, fracturealignment
• May involve Interposition of soft tissue or foreign body & Incorrect technique.
• May result in Limitation in mouth opening & Scar formation

Conclusion

• Adequate knowledge of the diagnosis and management of mandibular fractures is needed to provide treatment to prevent complications.