Authors of section

Authors

Nicolas Homsi, Paulo Rodrigues, Gregorio Sánchez Aniceto, Beat Hammer, Scott Bartlett

Executive Editors

Edward Ellis III, Eduardo Rodriguez

General Editor

Daniel Buchbinder

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Mandible: Etiology

1. Introduction

Despite many advances in maxillofacial surgery, it is still challenging to bring the patient to his previous condition. Most of the unsatisfactory results are due to the following etiological aspects:

2. Diagnostic errors

Failure to recognize the characteristics of the fracture may lead to an inaccurate reduction and/or incorrect choice of osteosynthesis material (eg. improper choice between load sharing and load bearing osteosynthesis techniques). Even if normal occlusion is established, later instability of the fragments can lead to a poor result.
Complete physical examination, imaging and fracture classification may prevent misdiagnosis.

3. Inadequate surgical technique

Inadequate surgical technique can affect the surgical outcomes:

  • Failure to ensure stable MMF may lead to malreduction.
  • When an inappropriate surgical approach is performed, poor visualization of the fracture site may lead to inadequate reduction.
  • Insufficient over-bending of the plate in symphyseal fractures may lead to improper reduction on the lingual aspect of the mandible. This will lead to a transverse deformity such as crossbite or widening of the face.
  • Poor fixation technique may lead to instability and hardware failure (eg. screws inserted in or too close to the fracture line, inadequate number or length of the screws, inadequate plate bending, insufficient irrigation during drilling).

4. Infection

Infections are the most common complications following repair of mandibular fracture and is typically caused by the following:

Tooth in the line of fracture
A tooth in the fracture line that has root fractures or presents with periodontal disease may lead to contamination of the fracture site and should be treated or removed. Devital teeth in the fracture line should either be removed or treated endodontically.

Devitalized tissues in the line of fracture
Devitalized tissues such as fragments of necrotic bone, tooth fragments, or foreign bodies should be removed prior to reduction and fixation

Persistent instability due to inadequate fixation
Persistent instability leads to continuous interruption of the healing process, making the fracture site more susceptible for bacterial proliferation.

The same mechanism applies for the situation where mobility persists in the presence of inadequate osteosynthesis material.

Delayed treatment
If surgical treatment has to be delayed, the fracture should be immobilized until surgical treeatment can be performed.

Systemic pathological disorders
Pathological disorders impair immune system response and will increase the risk of infections. The most common systemic conditions leading to complications in fracture treatment are:

  • Diabetes
  • Human immunodeficiency virus (HIV)
  • Anemia
  • Hypo and hyper thyroidism
  • Osteopathies
  • Chronic renal disease
  • nutritional deficiency

Lack of antimicrobial therapeutics
Systemic antibiotics should be administered as soon as the fracture is diagnosed.

5. Healing Deficiency

The healing process is dependent on both local and systemic factors. The negative effect of systemic pathological conditions and patients' lifestyle on the bones capability to heal should not be underestimated. Factors to be considered are:

  • Diabetes
  • Human immunodeficiency virus (HIV)
  • Anemia
  • Hypo and hyper thyroidism
  • Osteopathies
  • Chronic renal disease
  • Vitamin deficiency
  • Users of bisphosphonates and steroids
  • Alcohol and drug abusers
  • Poor oral hygiene
  • Noncompliant patients

6. Nonunion - Condyle

Introduction:
Some fractures of the condylar process are treated conservatively, due to the small amount and cortical lower quality of bone contact, condyle fractures may heal adequately or lead to a nonunion.

7. Nonunion after conservative treatment

Physiotherapy or MMF with elastic band guidance may be sufficient to lead to proper occlusion, if so, no additional treatment is needed. If slight occlusal discrepancies occur, orthodontic therapy or occlusal adjustments may be needed. If a non-satisfactory occlusion occurs after conservative treatment, we should refer to surgical treatment, if bone healing has not occurred yet, direct reduction of the condyle fracture should be addressed or an orthognatic surgery planned.

8. Nonunion after surgical treatment

Nonunion detected after surgical treatment of the condylar process may be diagnosed by an incorrect occlusion being developed and/or facial asymmetry detected, X-rays or CT scans may show loosening of the screws or even fracture of the plate. For slight malocclusions orthodontic therapy or occlusal adjustments may be needed. In more severe malocclusions a reoperation is needed, in case of loosening and/or fracture of the material it is mandatory we intervene in removing the material and reapplying adequate material.

9. Temporomandibular joint (TMJ)

Injuries to the mandible may result in TMJ disorders, this situation may be presented with TMJ sound, joint stiffness or pain during function. Hypomobility or ankylosis may be developed after trauma. Less invasive treatment should be addressed as possible as we can. Physical therapy is an important aid in this treatment.

10. Surgical treatment of TMJ disorders

Surgical treatment may include arthroplasty, replacement of the joint using autogenous bone graft or prosthesis and distraction osteogenesis. Replacement of the joint may be needed in severe resorption after unsuccessful open reduction and internal fixation.

11. Facial Asymmetry

Facial asymmetry can be found early after inadequate reduction of the fractures or as late complications after malunions or nonunions. Inadequate reduction of symphyseal fracture associated with condylar fractures may lead to widening of the face, either an overbending technique associated with medial pressure of the mandibular rami should be used to prevent this to occur. Loss of posterior height due to malposition or resorption of the condyle may also lead to facial asymmetry.

12. Surgical treatment

In early diagnosis, surgical approach to the original site of the fracture may be effective; hardware removal followed by adequate reduction and fixation should be the treatment.

In late diagnosis, facial asymmetries are treated in a similar way to orthognatic surgery.