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

Plate is placed as close as possible to the inferior border of the mandible. enlarge

Biomechanics of the symphysis

The mandibular symphysis undergoes rotational 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 one plate is applied along with a stable arch bar, the plate should be placed as close as possible to the inferior border of the mandible.

This technique requires a stable arch bar be placed across the fracture line. For those cases where there is a tooth missing in the line of fracture or the teeth are loose, an arch bar is not recommended to provide the second point of fixation. Thus, a second point of fixation on the bone must be provided.


Special considerations

Following special considerations may need to be taken into account:

Click on any subject for further detail.

2 Reduction top

How to predrill two monocortical holes below the apices of the teeth enlarge

Drilling monocortical holes

It is necessary to pre-drill two monocortical holes below the apices of the teeth on either side of the fracture to help when placing the reduction forceps.

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

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


The 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.

3 Fixation top

Shows the different plate types. enlarge

Choice of implant

An ideal choice is a large, thick and wide plate type such as the large profile locking plate 2.0, dynamic compression plates (DCP) or universal fracture plates (UFP).

The minimum size for the plate at the lower border of the mandible is a mandible plate 2.0 or a small profile locking plate 2.0.


Contouring a 4-hole plate by using bending pliers. enlarge

Plate contouring

Contour the plate using bending pliers.


Plate is positioned to the desired location. enlarge

Plate positioning

Position the plate in the desired location. 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.
Because miniplates do not compress the fracture, the fracture must be perfectly reduced prior to application of plates because the plates will not facilitate better reduction as might a compression technique do.


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.


Screws placed from opposite sides 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 a 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 osteosynthesis. enlarge

Additional screw placement

Fill the remaining plate holes with screws.


Final osteosynthesis using a 6-hole locking plate 2.0 enlarge

Alternative: 6-hole locking plate 2.0

Illustration showing the final osteosynthesis using a 6-hole locking plate 2.0.
Screws inserted bicortically could provide additional stability when using a medium or large profile 2.0 locking plate.


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 may be released and the occlusion checked.
The arch bar must be maintained for 5-6 weeks to provide a second point of fixation.

4 Case example top

Example of a simple symphyseal fracture. enlarge

Simple symphyseal fracture

Example of a simple symphyseal fracture.


A stable arch bar has been applied enlarge

Exposure of fracture

Note that a stable arch bar has been applied.


Completed osteosynthesis enlarge

Completed osteosynthesis

Clinical photographs shows the completed osteosynthesis.


X-ray of the completed osteosynthesis. enlarge

X-ray of the completed osteosynthesis

X-ray shows the completed osteosynthesis

v1.0 2008-12-01