1 Principles topenlarge
Champy’s ideal line of osteosynthesis
For angle fractures the ideal line of osteosynthesis is located along the external oblique ridge (A). If it is not possible to plate this area, a miniplate located along the lateral surface of the mandible can also be used (B).
Be prepared to change the fixation plan to using two miniplates in case of reduction at the basal region or if the stability is not sufficient.
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
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2 Choice of implant topenlarge
The surgeon must choose whether to use a 4- or 6-hole miniplate along the oblique ridge in the angle region. Very often a 4-hole titanium miniplate can be adapted quite nicely to this area. However, if a third molar is present or recently extracted, the bone in this area may be absent. The surgeon may choose to use a longer 6-hole plate to span the defect. Obviously, there may be empty screw holes over the region where bone is missing.
The surgeon has several options when choosing a plate for this region. The minimum size would be a mandible miniplate 2.0. However, some surgeons prefer a more rigid plate such as the locking plate 2.0 which comes in incremental profiles. The small profile and medium profile plates are applicable to the oblique ridge.
3 Reduction topenlarge
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.
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4 Plate adaption topenlarge
Twist the plate approximately 90° to facilitate adaptation to the superior border of mandible in the angle region. Pretwisted mandible plates 2.0 are available at 70°.
Apply the plate to the bone spanning the fracture. Note that the two posterior holes of the plate are located medial to the external oblique ridge and the two anterior holes are placed along the lateral cortex.
5 Fixation topenlarge
Application of first screw
Apply the screw just posterior to the fracture first. Use a 1.5 mm drill to make a monocortical hole.
Insert a 6 mm and tighten it loosely, allowing the anterior portion of the plate to be rotated upwards or downwards as necessary to better adapt it to the bone.
Placement of second screw
Drag the plate anteriorly with a point of a periosteal elevator and move it up or down until it is seated flush with the buccal cortex. Drill the hole just anterior to the fracture.
Insert the second screw and tighten it loosely like the first screw.
Placement of third screw
Drill a hole through the most anterior plate hole. Insert and tighten the screw.
Placement of final screw
In some cases the most posterior hole of the plate is accessible for drilling and screw placement.
If it is not possible to drill and place the most posterior screw because of inadequate access, the mandible can be opened at this point and instrumentation can proceed from underneath the maxillary dentition.
The last screw is inserted.
Release the MMF and check the occlusion for accuracy before proceeding with closure.
X-ray shows the completed osteosynthesis.
Note that the patient is not in MMF in the postoperative phase.
The arch bars are left in place for around two weeks and are only removed if no postoperative complications arise.
Alternative: plate on the lateral surface of the angle
Illustration shows the alternative position of a single plate on the angle.
If it is decided that placement of a bone plate along the external oblique ridge is not possible and instead will be placed on the lateral surface of the bone, a stronger, thicker miniplate is required. In such cases, one should use a miniplate made of grade IV titanium, and one should consider using a thicker plate or one with a broader centerspan, because when a plate is placed on the lateral surface, the plate will be stressed in torsion rather than tension. The plate must be much stronger in such instances. For this technique, transbuccal trocar instrumentation will be necessary to place all screws.