ORIF, two plates

The mandibular symphysis undergoes torsional 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 two plates are applied, they should be separated as much as possible without injuring vital structures.

Illustration shows Champy’s ideal lines of osteosynthesis for symphysis fractures.

Following special considerations may need to be taken into account:

• Multiple fractures
• Edentulous atrophic fractures
• Teeth in the line of fractures
• Involvement of alveolar area
• Infected fracture with or without bone loss
• Complications

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AO Teaching video on two plate fixation

For this procedure the intraoral approach to the symphysis is normally used.

The choice of implant is according to surgeon preference. Simple (linear) fractures with no associated injuries can easily be treated with miniplates. However, there are often associated injuries in the mandible and the surgeon may elect to use more rigid fixation. Locking plates with different profiles offer increased stability and still can be placed using the same surgical approach.

For more information on mandibular plate types, click here.

For further details on compression plate application, click here.

It is necessary to predrill two monocortical holes below the apices of the teeth on either side of the fracture to help place the reduction forceps.

Manipulate the mandible fragments until anatomic reduction is achieved. Apply the reduction forceps and then place the patient into occlusion and secure 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 to prevent fracture displacement when tightening the reduction clamp.

In general, a minimum of two points of fixation should be used to provide stable internal fixation of mandibular symphysis fractures.

Because the mandibular symphysis undergoes twisting during function, two miniplates can prevent such motion from occurring.

Apply the first plate to the inferior border of the mandible.

Contour the plate using bending pliers.

Position the plate a few millimeters superior to the inferior border. 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.

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

Insert a 2.0 mm screw, 6 mm in length. Do not fully tighten it until the final reduction and plate position are confirmed.

For further details on compression plate application, click here.

Insert a second screw on the other side of the fracture in the same way.

Tighten both screws.

Fill the remaining plate holes with screws.

Remove the reduction forceps.

Now place a second miniplate 2.0 below the apices of the tooth roots.

Occasionally, the plate must be positioned higher on the mandible. Great care must be taken when drilling in this area as tooth roots can be just below the cortex and can be damaged using a 6 mm drill bit with stop.

Confirm adequate reduction. There must be no gap at the lingual aspect. Such a gap would lead to occlusal disturbance and mandibular widening.

MMF is released and the occlusion checked.

Because two points of fixation have been applied (two miniplates), it is not essential that the arch bars remain in position.

Routine diagnosis of this type of fracture should include x-rays taken in two planes at 90° to each other; the minimum requirement is a PA view and a panoramic view.

CT scan or digital volume tomography (DVT) imaging may be used as an alternative.

Note that in this symphyseal fracture, the fracture begins between the central incisors and extends posteriorly as it approaches the inferior border.

X-ray shows the completed osteosynthesis.

Clinical view shows fracture fixation with two mandibular miniplates 2.0.

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.