Authors of section

Authors

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

Executive Editors

Marcelo Figari, Gregorio Sánchez Aniceto

General Editor

Daniel Buchbinder

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ORIF, two plates (basal triangle)

1. Principles

Biomechanics

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

Symphyseal basal triangular fractures therefore should be considered comminuted fractures requiring load-bearing fixation across the basal triangle via an extraoral approach. This can be provided one of two ways:

Using one reconstruction plate or ...

Using a reconstruction plate.

... using two plates , but the one along the inferior border being a heavy locking plate 2.0 of large or extra-large profile.

Sequence of plate insertion

The superior plate is inserted first. This will prevent inadvertent displacement of the fragments during the subsequent contouring and insertion of the inferior border plate.

Using two plates.

Special considerations

2. Selection of approach

These fractures can often be approached and treated through the intraoral approach.

orif one plate and arch bar

However, depending on the difficulty or severity of the fracture, and/or the presence of a laceration suitable, an extraoral approach via the submental route may be indicated.

revision orif

3. Choice of implant for two plate fixation

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

Superior border plate

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

Screw application is commonly bicortical.

Inferior border plate

4. Reduction

MMF

In symphyseal fractures with basal triangular fragments, an arch bar is preferred for MMF.
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.
Click here for a description of MMF application.

Symphyseal fracture with basal triangular fragment.

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 main fragments are reduced as a first step. Ensure that the basal triangle is loose enough be reduced secondarily into the remaining bone gap.
From evaluating the preoperative 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 the reduction more difficult. The inner fragment will not usually be accessible using an intraoral approach that only exposes the anterior surface of the mandible.

Reduction of the basal triangle

The basal triangle itself must be repositioned by pushing and dragging with an appropriate instrument. Bone screws inserted into the basal triangle function well as a handle on the fragment and are useful for reduction. Using a transoral approach the lingual cortex of the mandible can be accessed only with addition of a percutaneous hook.
To keep the basal triangle in position it can be compressed between the greater fragments. An alternative is the preliminary fixation with a miniplate that does not interfere with the planned position of the inferior border plate.

How to reposition the basal triangle.

The maintenance of the reduction of the alveolar portion of the fracture with a conventional clamp becomes more difficult the higher the basal triangle is located. If the basal triangle segment is large and extends superiorly, the reduction clamp can actually “squeeze out” the fragment. If possible, a clamp is applied into tiny predrilled holes in the outer cortex in an area that will not interfere with the later plate placement.

How to reposition the basal triangle.

5. Fixation of superior border plate

Plate contouring

The plate is contoured to the outer surface of the superior aspect of the mandible in a position avoiding tooth roots.

Plate is contoured to the outer surface of the superior aspect of the mandible.

Drill first screw hole

Hold the plate with an appropriate instrument in place (eg, periosteal elevator or forceps).
Use a 1.5 mm drill bit with 6 mm stop to drill monocortically through the plate hole on one side of the fracture.
Note: the cortical bone in this region may be very thin and tooth roots can be damaged even when using a 6mm drill bit with stop.

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

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 2.0 mm screw, 6 mm in length.

Insert second screw

Insert a second screw in the hole next to the fracture line on the opposite side of the fracture. 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.

Insertion of a second screw in the hole next to the fracture line on the opposite side of the fracture.

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.

Additional screw placement.

6. Fixation of lower border plate

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 one intends to place a screw into the basal triangle, the plate is positioned with at least one hole of the plate overlying the triangle.
The use of a malleable template may be helpful.
The correct plate position and adaptation must be checked either by direct vision or probing with a blunt instrument.
Ensure that the plate is located on bone over its full length so that all screws will engage the bone.
Click here for further details on plate bending.

Pearl: plate insertion in parasymphyseal fractures

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.
A medium profile locking plate 2.0 is used, in this case at the lower border.
Note that a screw is placed into the basal triangle.
The fixation of the lower border will be illustrated using a 7-hole large profile locking plate with bicortical screw fixation. The basal triangle is prefixed with a miniplate at the apex.

Plate insertion in parasymphyseal fracture.

Drill first screw hole

Hold the plate with an appropriate instrument (eg, periosteal elevator, forceps).
Use a 1.5 mm drill bit to drill bicortically through the plate hole next to the fracture line in one fragment.

How to drill the first screw hole.

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.

Insertion of the first screw

Insert second screw

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

Insertion of the second screw.

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 additional screws as necessary. 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 whether the triangle is separated or not.
Removal of miniplate
If an additional miniplate was used for fracture simplification, it can be removed.
Final check
Release the MMF and check the occlusion for accuracy and the bony surfaces for precise anatomic reduction.

Additional screw placement.

Final osteosynthesis

Clinical photograph showing the final osteosynthesis.

Final osteosynthesis

7. Aftercare following ORIF of mandibular symphysis, body, angle and ramus fractures

If arch bars or MMF screws are used intraoperatively, they are usually removed at the conclusion of surgery if proper fracture reduction and fixation have been achieved. Arch bars may be maintained postoperatively if functional therapy is required or if required as part of the fixation.

Postoperative x-rays are taken within the first days after surgery. In an uneventful course, follow-up x-rays are taken after 4–6 weeks.

The patient is examined approximately 1 week postoperatively and periodically thereafter to assess the stability of the occlusion and to check for infection of the surgical wound. During each visit, the surgeon must evaluate the patients ability to perform adequate oral hygiene and wound care, and provide additional instructions if necessary.

Adequate dental care is required in most patients having suffered a mandibular fracture.

If a malocclusion is detected, the surgeon must ascertain its etiology (with appropriate imaging technique). If the malocclusion is secondary to surgical edema or muscle splinting, training elastics may be beneficial. The lightest elastics as possible are used for guidance, because active motion of the mandible is desirable. Patients should be shown how to place and remove the elastics using a hand mirror.

If the malocclusion is secondary to a bony problem due to inadequate reduction or hardware failure or displacement, elastic training will be of no benefit. The patient must return to the operating room for revision surgery.

Follow-up appointments are at the discretion of the surgeon, and depend on the stability of the occlusion on the first visit. If a malocclusion is noted and treatable with training elastics, weekly appointments are recommended.

Postoperatively, patients will have to follow three basic instructions:

1. Diet
Depending upon the stability of the internal fixation, the diet can vary between liquid and semi-liquid to “as tolerated”, at the discretion of the surgeon. Any elastics are removed during eating.

2. Oral hygiene
Patients having only extraoral approaches are not compromised in their routine oral hygiene measures and should continue with their daily schedule.
Patients with intraoral wounds must be instructed in appropriate oral hygiene procedures. The presence of the arch-bars and any elastics makes this a more difficult procedure than normal. A soft toothbrush (dipping in warm water makes it softer) should be used to clean the surfaces of the teeth and arch-bars. Any elastics are removed for oral hygiene procedures. Chlorhexidine oral rinses should be prescribed and used at least three times each day to help sanitize the mouth. For larger debris, a 1:1 mixture of hydrogen peroxide/chlorhexidine can be used. The bubbling action of the hydrogen peroxide helps remove debris. A Waterpik® is a very useful tool to help remove debris from the wires. If a Waterpik is used, care should be taken not to direct the jet stream directly over intraoral incisions as this may lead to wound dehiscence.

3. Physiotherapy
Physiotherapy can be prescribed at the first visit and opening and excursive exercises begun as soon as possible. Goals should be set, and, typically, 40 mm of maximum interincisal jaw opening should be attained by 4 weeks postoperatively. If the patient cannot fully open his mouth, additional passive physical therapy may be required such as Therabite or tongue-blade training.