1 Principles topenlarge
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.
This line is located directly underneath the mucogingival sulcus that can be exposed with ease. The bone thickness of the lateral cortex varies between 6 and 8 mm approximately. To avoid injury of the tooth roots, monocortical screws less than 6 mm long should be used for plate fixation along this section of the ideal osteosynthesis line.
This single plate fixation method is contraindicated in the anterior mandibular body because of the existing rotational forces in that area that have to be neutralized. Two miniplates should be applied to neutralize those forces.
In the posterior transition to the angle and ramus, a second plate just below the oblique ridge may be advantageous in case of reduced bone stock (eg, an impacted wisdom tooth) or significant fracture displacement.
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
Click on any subject for further detail.
2 Reduction topenlarge
In the isolated mandible body fracture, preferably, an arch bar is applied for MMF. The arch bar provides additional stability by tension banding. This equates to a second line of resistance in particular with 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.
MMF bone screws provide temporary fixation only during surgery and do not contribute postoperatively to stabilization.
Reduction is done manually. Since the indication for single miniplate fixation is limited only to minimally displaced fractures, there will be no major discrepancies to be overcome.
The maintenance of the reduction with a conventional clamp becomes more difficult the further posterior the fracture is located. The clamps can be applied into tiny predrilled holes in the outer cortex that do not interfere with later plate placement.
In the midbody and posterior body, the reduction can alternatively be held by the intermaxillary ligatures, or manually by the assistant using an instrument, eg, a periosteal elevator.
3 Fixation topenlarge
Choice of implant
A variety of implants can be used. In the original Champy version a 4-hole miniplate without center space was used.
Today, the same type of plate is still applicable. The following alternatives provide similar or incrementally higher stability:
- 4- or 6-hole mandible plate 2.0 with or without center space
- 4- or 6-hole small profile locking plates 2.0
- 4- or 6-hole medium profile locking plates 2.0
The plate of greater strength is used for additional stability and safety.
Contour the plate according to the surface anatomy adjacent to the fracture line on both sides using bending pliers. Longer adaptation plates should be bent starting at one end and successively proceeding towards the other end. Intermediate steps can be checked on the bony surface for correct seating.
Finally check the plate for precise fitting in-situ.
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 even when using a 6 mm drill bit with stop.
Insert a 2.0 mm screw, 6 mm in length. Do not fully tighten it until the final reduction and plate position are confirmed.
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.
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.
Confirmation of reduction
A splaying of the inferior border of the mandible can be ruled out by further soft-tissue exposure intraoperatively. In minimally displaced fractures this should not be necessary.
Prior to wound closure confirm adequate reduction along the exposed fracture line. The fracture alignment at the lower border can be palpated giving indication of major gapping.
Furthermore, a control of the fracture line in transverse plane is possible only indirectly by checking the occlusion and articulation. Prior to this, the MMF ligatures must be removed.
4 Case example topenlarge
Midbody fracture line at the level between the second premolar and the first molar. Ernst ligatures were applied for temporary immobilization of the lower jaw until surgical treatment.
If arch bars are used, the incision is made more laterally in the vestibule.
However, in this case, since there is an open wound between the second premolar and the first molar, an alternative surgical approach is used. A mucogingival incision in the vestibular sulcus is chosen anteriorly to the wound. In the posterior vestibulum the gingiva of the molars is included in the mucoperiosteal flap after marginal incision.
The longitudinal exposure reaches from the lateral symphysis into the angle region. Two MMF screws are inserted into the maxillary alveolar ridge as anchor points for the wire ligatures. In this case no arch bars are used as they would interfere with surgical access and closure.
MMF screw application in lower jaw
The MMF screws in the lower jaw are applied after exposure of the bony surface.
Note the additional fixation of the fracture using an interdental wire loop.
MMF is applied using MMF screws with wire loops bilaterally.
Choice of implant
A 6-hole medium profile locking plate 2.0 was selected in this case to provide additional stability. The plate exactly contoured to the bone surface is shown in place.
Drilling for the first screw
Drill for the first screw hole next to the fracture line in the anterior fragment using a drill bit with drill stop.
Insertion of first screw
Insert the first screw.
Insertion of second screw
After drilling, insert the second screw next to the fracture line posteriorly.
Screw insertion into the most posterior screw hole
The posterior end of the plate is accessible through lip retraction and does not necessitate an external incision.
Pearl: proper retraction of lips
Retractor tips parallel to instrumentation (not at angles) facilitate exposure with reduced retraction forces on the lips.
Additional screw insertion
Clinical photograph shows all screws inserted.
Checking the occlusion
After checking for correct occlusion, the MMF screws are removed and the wound is closed.
X-rays show the ...
... completed osteosynthesis.
5 Alternative case topenlarge
A nondisplaced vertically running midbody fracture in a fully dentate and compliant patient can be treated straightforwardly using arch bars and a single plate applied on the ideal line of osteosynthesis according to Champy.
In this case, a 6-hole small profile locking plate 2.0 was used for stabilization.