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

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

Mandible - Body, simple - ORIF

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Glossary

1 Principles top

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Plate location

The superior border plate is positioned on the ideal line of osteosynthesis.

The inferior border plate is located at the base of the mandibular body in a longitudinal field below the course of the mandibular canal.

Ideal line of osteosynthesis
The ideal line of osteosynthesis in the body region runs at the vertical height of the tooth apices from the canine region to the oblique line. This carries into the oblique ridge which turns into the anterior outer rim of the ramus.

According to Champy, in the transition to the symphysis (anterior mandibular body) the insertion of two plates along the upper and lower border of the mandible is mandatory because there may be rotational forces that have to be neutralized. In the posterior transition to the angle and ramus a second plate just below the oblique ridge may be advantageous in a reduced bone stock due to an impacted wisdom tooth or in major dislocation.


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Biomechanics

All biomechanical models developed to date have shown that two points of fixation (ie, two plates) provide much more stability than a single plate. Therefore, when more stability is deemed necessary the addition of a second plate provides more rigidity.


Sequence of plate insertion

The superior plate is inserted first in order to achieve preliminary fixation. This will prevent inadvertent displacement of the fragments during subsequent contouring and the insertion of the inferior border plate.


Surgical approach

The accessibility of the inferior border of the mandible via an intraoral approach decreases from the anterior to the posterior body region. In the posterior area a transbuccal approach will be necessary at least for screw insertion into the posterior plate holes.

Click here for a detailed description of the transbuccal system and its risks for mental nerve injury.


Special considerations

Following special considerations may need to be taken into account:

Click on any subject for further detail.

2 Choice of implant top

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Superior border plate

The superior border is treated with a tension band plate with monocortical screw fixation. The profile of this plate can be minimal.

The plate selection can be as follows:

  • 4- or 6-hole mandible plate 2.0 with or without center space
  • 4- or 6-hole small profile locking plate 2.0 with or without center space

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Inferior border plate

The profile and type of the inferior border plate can range from a conventional miniplate to locking plates of incremental size, large sized fracture plates to reconstruction plates.

For simple fractures, the following varieties will yield sufficient stability:

  • 4- or 6-hole mandible plate 2.0 with or without center space
  • 4- or 6-hole small profile locking plate 2.0
  • 4- or 6-hole medium profile locking plate 2.0
  • 4- or 6-hole large profile locking plate 2.0 (straight or curved)

3 Reduction top

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MMF

Rigid fixation of a mandibular fracture in the dentate patients begins with fixation of the occlusion. The surgeon has the choice of using arch bars, MMF screws, or local wiring techniques.

Considerations of which MMF technique to be used will depend on fracture morphology, associated injuries, and personal preference.

Click here for further details on methods for applying MMF.


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Manual reduction

Reduction of the fragments is done manually or with the use of elevators or bone hooks. A gross reduction is done prior to the MMF application. Fine tuning for precise anatomical reduction is done with MMF in place.
The maintenance of the reduction with a conventional clamp becomes more difficult the further posterior the fracture is located. The clamps can be applied into tiny predrilled holes in the outer cortex not interfering with later plate placement.


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Maintaining reduction

In the midbody and posterior body the reduction can alternatively be held by the intermaxillary ligatures or manually by the assistant using an instrument, eg, periosteal elevator.

4 Fixation of superior border plate top

Plate contouring

The bony surface of the alveolar process in the major portion of the mandibular body is almost flat. Therefore, plate contouring is generally necessary only in the transition zones to the angle and anterior mandible.


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Drill first screw hole

Hold the plate with an appropriate instrument (eg, periosteal elevator or forceps).

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

The surgeon must be aware that a cortical plate may be very thin in this region and damage to the tooth roots is still possible using a 6 mm drill bit with stop.


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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.


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Insert second screw

Insert a second screw in the hole next to the fracture line in the posterior fragment. The elevator is used now to keep the far end of the plate at the correct vertical level.
Tighten both screws.

The clamp can be removed afterwards.


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Additional screw placement

Fill the remaining plate holes with screws in an orderly fashion continuing from the plate holes next to the fracture to the outer plate holes.

5 Fixation of lower border plate top

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Plate contouring

According to the profile of the selected plate, the contouring may be more or less technically demanding. Usually a straight plate can be inserted at the lower border of the mandibular body. Adjustments to the bony surface must be made by out-of-plane bending.

For larger plate profiles the use of a malleable template is helpful. This minimizes the risk of mental nerve injury as repeated plate insertion is avoided.

Correct plate contour and adaptation must be checked either by direct vision or by probing with a blunt instrument.

Ensure that the plate is located on bone over its full length so that all screws will engage in the bone. Improved vision can be obtained using appropriate retractors with fiberoptic lighting. Alternatively, some surgeons advocate the use of an endoscope.

Click here for further details on plate bending.


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Plate insertion

An obstacle to plate placement are the exiting branches of the mental nerve. This area represents a danger zone for nerve damage. The bone region below the branches must be dissected carefully. The plate is positioned in the area below the mental foramen. The nerve branches must be mobilized out of the field during the introduction of the plate. During screw placement in the mental nerve area, the nerve branches must be protected.

Transbuccal instrumentation may be needed for proper posterior screw insertion.

The fixation of the lower border plate is achieved using a 6-hole conventional miniplate with bicortical screw fixation.


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Drill first screw hole

Hold the plate with an appropriate instrument (eg, periosteal elevator or forceps)

Use a 1.5 mm drill bit to drill through the plate hole next to the fracture line in the anterior fragment.


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Insert first screw

Prior to screw insertion, determine the appropriate screw length using a depth gauge.

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


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Insert second screw

Insert a second screw in the hole next to the fracture line in the posterior fragment. The elevator is used now to keep the far end of the plate at the correct vertical level.

Tighten both screws.

The clamp can be removed afterwards.


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Additional screw placement

Fill the remaining plate holes with screws in an orderly fashion continuing from the plate holes next to the fracture to the outer plate holes.

Final check
Release the MMF and check the occlusion for accuracy and the bony surfaces for precise anatomic reduction.

6 Completed osteosynthesis top

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General remarks

The following X-rays show several completed osteosyntheses in the mandibular body region. In all cases, additional fractures involve other sites.
Note: If no arch bars are visible, MMF screws were used temporarily intraoperatively.

Case 1:
Anterior body fracture on the right-hand side repaired with two conventional miniplates 2.0.

Posterior body fracture on the left-hand side repaired with a single monocortical superior border plate.


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Case 2:

Two small profile locking plates 2.0 were used in this simple left mandibular body fracture.

Note the additional fracture in the contralateral condylar process.


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Perfect consolidation after 1 year.


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Case 3:

X-ray shows fixation of a right mandibular body fracture by two locking plates 2.0. A small profile plate subapical and a larger one at the inferior border.


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Case 4:

In this case the indication for the use of a larger plate at the inferior border (locking plate 2.0 large profile) was the patient’s general condition due to a cervical spine injury. He was placed in a halo-frame pin fixation.

Note: Additional fracture in contralateral angle.


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3-D CT reconstruction of the anterior body fracture shows the bicortical screws exiting from the bony lingual surface.

v1.0 2008-12-01