Executive Editor: Marcelo Figari, Gregorio Sánchez Aniceto General Editor: Daniel Buchbinder

Authors: Ricardo Cienfuegos, Carl-Peter Cornelius, Edward Ellis III, George Kushner

Mandible - Symphysis and parasymphysis, simple - ORIF

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Glossary

1 Principles top

Illustration shows Champy’s ideal lines of osteosynthesis for symphysis fractures. enlarge

Biomechanics of the symphysis

The mandibular symphysis undergoes torsional forces (twisting) during function. Therefore, fixation strategies must take this into account. When using anything less stable than a reconstruction plate, two points of fixation should be applied.

In general, the further apart the points of fixation, the more stable the construct. For symphysis fractures, when two plates are applied, they should be separated as much as possible without injuring vital structures.

Illustration shows Champy’s ideal lines of osteosynthesis for symphysis fractures.


Special considerations

Following special considerations may need to be taken into account:

Click on any subject for further detail.

2 Choice of implant top

Different plate types. enlarge

The choice of implant is according to surgeon preference. Simple (linear) fractures with no associated injuries can easily be treated with miniplates. However, there are often associated injuries in the mandible and the surgeon may elect to use more rigid fixation. Locking plates with different profiles offer increased rigidity and still can be placed using the same surgical approach.

3 Reduction top

How to predrill two monocortical holes. enlarge

Predrilling monocortical holes

It is necessary to predrill two monocortical holes below the apices of the teeth on either side of the fracture to help place the reduction forceps.

Manipulate the mandible fragments until anatomic reduction is achieved. Apply the reduction forceps and then place the patient into occlusion and secure with MMF.

Some surgeons prefer to place the patient into occlusion and apply MMF before using the reduction forceps.


Clamp has to be placed perpendicular to the line of fracture. enlarge

Clamp application

The clamp has to be placed perpendicular to the line of fracture to prevent fracture displacement when tightening the reduction clamp.

4 Fixation top

Illustration shows Champy’s ideal lines of osteosynthesis for symphysis fractures. enlarge

General consideration

In general, a minimum of two points of fixation should be used to provide stable internal fixation of mandibular symphysis fractures.

Because the mandibular symphysis undergoes twisting during function, two miniplates can prevent such motion from occurring.


Contour the plate using bending pliers. enlarge

Plate contouring

Apply the first plate to the inferior border of the mandible.

Contour the plate using bending pliers.


Plate is positioned a few millimeters superior to the inferior border. enlarge

Plate positioning

Position the plate a few millimeters superior to the inferior border. Because miniplate fixation is adaptation osteosynthesis and does not compress the fracture, the plate can be placed in a direction other than perpendicular to the fracture line.


Usage of a 1.5 mm drill bit with 6 mm stop enlarge

Drill first screw hole

Use a 1.5 mm drill bit with 6 mm stop to drill monocortically through the plate hole next to the fracture.


Insertion of a 2.0 mm screw, 6 mm in length. enlarge

Insert screw

Insert a 2.0 mm screw, 6 mm in length. Do not fully tighten it until the final reduction and plate position are confirmed.


Insertion of the second screw on the other side of the fracture enlarge

Insert second screw

Insert a second screw on the other side of the fracture in the same way.

Tighten both screws.


Completed first plate application. enlarge

Additional screw placement

Fill the remaining plate holes with screws.


Second plate is positioned higher on the mandible. enlarge

Application of second plate

Remove the reduction forceps.

Now place a second miniplate 2.0 below the apices of the tooth roots.

Occasionally, the plate must be positioned higher on the mandible. Great care must be taken when drilling in this area as tooth roots can be just below the cortex and can be damaged using a 6 mm drill bit with stop.


Completed two miniplate fixation of simple symphyseal fractures. enlarge

Confirmation of reduction

Confirm adequate reduction. There must be no gap at the lingual aspect. Such a gap would lead to occlusal disturbance and mandibular widening.

MMF is released and the occlusion checked.

Because two points of fixation have been applied (two miniplates), it is not essential that the arch bars remain in position.

5 Case example top

Fracture begins between the central incisors and extends posteriorly as it approaches the inferior border. enlarge

Diagnosis

Routine diagnosis of this type of fracture should include x-rays taken in two planes at 90° to each other; the minimum requirement is a PA view and a panoramic view.

CT scan or digital volume tomography (DVT) imaging may be used as an alternative.


Fracture begins between the central incisors and extends posteriorly as it approaches the inferior border. enlarge

Fracture begins between the central incisors and extends posteriorly as it approaches the inferior border. enlarge

Note that in this symphyseal fracture, the fracture begins between the central incisors and extends posteriorly as it approaches the inferior border.


Completed osteosynthesis. enlarge

Completed osteosynthesis

X-ray shows the completed osteosynthesis.


Fracture fixation with two mandibular miniplates 2.0. enlarge

Clinical view shows fracture fixation with two mandibular miniplates 2.0.

v1.0 2008-12-01