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

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

Mandible - Body, complex - 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.


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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 one.
The basal triangle decreases the bone buttressing and interfragmentary support. This condition demands a degree of stability beyond pure load sharing.

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

Accessibility to the inferior border of the mandible via an intraoral approach decreases from the anterior to the posterior body region. Under favorable circumstances the basal triangular fractures in the anterior body region can be treated transorally. In the midbody or posterior body region the reduction of the triangle may be so difficult to achieve transorally that a transbuccal instrumentation may not be helpful. An external submandibular approach is often necessary for an accurate reduction and fixation.


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

Only large profile plates meet the biomechanical requirements of basal triangular fractures.

One of the following plates should be considered for fixation at the inferior border. The chosen plate should allow for a fixation of the triangle to the plate. This precludes the use of plates with a center space.

  • 6- to 8-hole large profile locking plates 2.0
  • 6- to 8-hole extra large profile locking plates 2.0

Screw application is commonly bicortical.

3 Reduction top

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MMF

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

In the mandible body fractures with basal triangular fragments, an arch bar is preferably applied for MMF. This equates to another line of resistance in particular with the biting load anterior to the fracture line. The arch bar should include at least all teeth in the affected quadrant of the jaw. It is not necessary to encompass the whole dental arch.

The application of the arch bar is unproblematic because only one fracture line runs through the alveolar process and is not affected by the triangular fragmentation.

MMF bone screws only provide temporary fixation during surgery and do not contribute postoperatively to stabilization.

Click here for further details on methods for applying MMF.


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Reduction of the main fragments

Reduction of the fragments is done manually with the use of elevators, bone hooks, or bone screws inserted as handles. Gross reduction is done prior to the MMF application. Fine tuning for precise anatomical reduction is best done with MMF in place.

The maintenance of the reduction of the alveolar portion of the fracture with a conventional clamp becomes more difficult the further posterior the fracture is located. If possible, a clamp is applied into tiny predrilled holes in the outer cortex in an area that will not interfere with later plate placement.

The main fragments are reduced as a first step. Ensure that the basal triangle is loose enough to be reduced secondarily into the remaining bone gap.

From evaluating the preoperative conventional x-rays it is assumed that the basal triangle is a single and solid bony triangle. It becomes apparent from CT scanning that basal triangles are often divided into an outer and inner table fragment which makes reduction more difficult. The inner fragment will not usually be accessible using an intraoral approach only exposing the lateral surface of the mandible.

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 periosteal 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 Reduction of the basal triangle top

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The basal triangle itself must be repositioned by pushing and dragging with an appropriate instrument. Using a transoral approach, the lingual cortex of the mandible can only be accessed with the addition of a percutaneous hook. If a separation of the basal triangle into an inner or outer piece has been assessed radiographically the reduction should be performed via a submandibular approach.

To keep the basal triangle in place it can be compressed between the greater fragments. One alternative is a temporary fixation using a miniplate (as illustrated) that will not interfere with the planned position of the inferior border plate.

In a transoral approach, temporary plate fixation is to be located in the upper angle of the triangle allowing it to be pulled upwards into the gap between the large fragments.


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In a submandibular approach the temporary fixation can be achieved with a horizontally oriented plate along the basal aspect of the mandibular border. Via a submandibular approach, the position of the basal triangle and the adjacent major fragment can be controlled three dimensionally. Nonetheless, separate fragments of the inner cortex will not be amenable to subsequent fixation.

6 Fixation of lower border plate top

Plate contouring

Contouring of large profile plates is demanding. Usually a straight plate can be inserted at the lower border of the mandibular body overlying the reduced basal triangle. Adjustments to the bony surface must be made by out-of-plane bending.

If screw placement into the basal triangle is intended, the plate is positioned with at least one hole of the plate overlying the triangle.

The use of a malleable template may be helpful. This minimizes the risk of mental nerve injury as repeated plate insertion is avoided.

Correct plate position 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 engage the bone. Improved vision can be achieved by 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 space below the mental foramen, if necessary. 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.

Note that the screw fixing the basal segment is locked to the plate.

The fixation of the lower border is achieved using a 7-hole large profile locking plate with bicortical screw fixation. The basal triangle is prefixed with a miniplate at the apex.


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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 bicortically 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.


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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.

Finally the basal triangle is secured with an additional screw. A locking head screw is preferred over a conventional screw to avoid secondary displacement of the basal triangle. The screw can be inserted either monocortically or bicortically depending on whether the triangle is separated.


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Removal of miniplate

If the basal triangle is fixed to the large plate at the lower border of the mandible, the miniplate used for its temporary fixation can be removed.


Final check

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

7 Completed osteosynthesis top

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Case example

Anterior body fracture on the left side repaired at the superior border with a 1.5 mm MatrixMandible plate and a MatrixMandible adaptation plate 2.0 at the inferior border.

Note: there are two other mandibular fractures:

  1. Ipsilateral condylar process on the left fixed with a mandible plate 2.0 in combination with a 5-hole dynamic compression plate (DCP) 2.0
  2. Contralateral angle fracture with a basal triangle treated with the same type of MatrixMandible plates as used for the anterior body fracture. A third plate has been left in place to secure the apex of the triangular fragment.

Two plate fixation of basal triangle body fractures enlarge

v1.0 2008-12-01