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, complex - ORIF

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Glossary

1 Principles top

Complex symphyseal fracture enlarge

Load-bearing fixation

Comminuted fractures should have load-bearing fixation applied across the area of comminution. The bone fragments within the area of comminution will provide no buttressing to help stabilize the fracture. A reconstruction plate with at least three and preferably four screws on each side of the comminuted area is the optimal way load bearing fixation is provided.

Click here for a detailed discussion of load-bearing versus load-sharing 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

Locking versus nonlocking plates

There are several advantages to a locking plate/screw system:

  • Conventional plate/screw systems require precise adaptation of the plate to the underlying bone. Without this intimate contact, tightening of the screws will draw the bone segments toward the plate, resulting in alterations in the position of the osseous segments and the occlusal relationship. Locking plate/screw systems offer certain advantages over other plates in this regard; the most significant being that it becomes unnecessary for the plate to intimately contact the underlying bone in all areas. As the screws are tightened, they "lock" to the plate, thus stabilizing the segments without the need to compress the bone to the plate. This makes it impossible for the screw insertion to alter the reduction.
  • Another potential advantage in locking plate/screw systems is that they do not disrupt the underlying cortical bone perfusion as much as conventional plates, which compress the undersurface of the plate to the cortical bone.
  • A third advantage to the use of locking plate/screw systems is that the screws are unlikely to loosen from the plate. This means that even if a screw is inserted into a fracture gap, loosening of the screw will not occur. Similarly, if a bone graft is screwed to the plate, a locking head screw will not loosen during the phase of graft incorporation and healing. The possible advantage to this property of a locking plate/screw system is a decreased incidence of inflammatory complications due to loosening of the hardware.
  • Locking plate/screw systems have been shown to provide more stable fixation than conventional nonlocking plate/screw systems.

Click here for a description of locking plate principles versus conventional plating.


The reconstruction plate is still considered the most predictable method of treatment. enlarge

Plate selection

For load-bearing fixation, a locking reconstruction plate 2.4 should be used. The plate must be long enough so that there can be a minimum of three or preferably four screws on each side of the fracture. The screws adjacent to the fracture should be at least 7 mm away from the fracture line. Most commonly there will be one or two holes without screws located over the fracture.

3 Reduction top

Reduction enlarge

MMF

Open reduction and stable internal fixation in the dentate patient begins with fixation of the occlusion. Prior to placing the patient into MMF, the fracture should be exposed and any extractions deemed necessary performed. The bones should also be reduced prior to placing the patient into occlusion and securing the MMF.

Click here for further details on methods for applying MMF.


Reduction enlarge

Fracture reduction

Clinical view of a comminuted symphyseal fracture before reduction.


Reduction enlarge

Once the fracture has been exposed, forceps can be used to manipulate the mandibular fragments into proper reduction.
The comminuted fragments can be positioned using bone screws as a handle on them.


Reduction enlarge

Pearl: simplifying the fracture

Temporary/initial fixation of mandibular fragments can be accomplished using small plates and screws applied in locations that do not interfere with the placement of the reconstruction plate.

The small plate(s) may be left in place or may be removed after the placement of the reconstruction plate.

Note that the patient is in MMF and small plates now replace the bone clamps that were initially used to obtain reduction of the fragments. Also note that debridement of some bone was necessary, leaving an area of osseous defect.

4 Fixation top

Fixation enlarge

Plate adaptation

The plate must be contoured to the surface of the mandible flush with the inferior border to avoid injuring the mental and inferior alveolar nerves.

The use of a malleable template is strongly advocated for accurate plate contouring. The risk of mental nerve injury is reduced because the plate will have to be reintroduced multiple times during the bending procedure.

Click here to see a step-by-step description of bending locking reconstruction plates.


Fixation enlarge

Screw insertion

Threaded drill guides should always be used to center the screw within the locking reconstruction plate.
For a step-by-step description click here.

Large fragments (like the triangular one in this photograph) can be secured to the plate to hold them in position.


Fixation enlarge

Removing small plates

The small plates used to simplify the fracture may be removed after the reconstruction plate has been attached to the mandible. They can also be left in position if they will not interfere with future prosthetic appliances.


Fixation enlarge

Management of bone defects

Bone defects may be managed primarily or secondarily, depending on individual circumstances. If there is good soft tissue available for water-tight closure, one may primarily bone graft osseous defects. Otherwise, secondary reconstruction is advisable.

In this instance, adequate soft-tissue was available so the bone defect was filled with allogenic bone putty.


Final check

One should then release the MMF and check the occlusion for accuracy before proceeding with closure.


Outcome enlarge

Outcome

X-ray shows the completed osteosynthesis 12 weeks postoperatively.

v1.0 2008-12-01