1 Principles top
A load-bearing fixation is indicated for the open surgical treatment in all types of comminuted fractures in the mandibular body.
Historically, many surgeons have been reluctant to open comminuted fractures, fearing that the small bony fragments will become devascularized and result in subsequent infection and sequestration. Although this complication is still a possibility, surgeons have demonstrated a distinct advantage in ORIF of comminuted fractures.
The load-bearing fixation bridges the area of comminution. The bone fragments within the area of comminution do not provide buttressing for load transmission between the adjacent intact portions of the mandible. The reconstruction plate is fixed with at least three and preferably four screws on each side of the comminuted area.
Stepwise repair: simplification prior to load-bearing reconstruction
When treating comminuted mandibular body fractures, the surgeon should proceed in a stepwise fashion.
After placing the patient in occlusion and securing MMF, the comminuted fractures are simplified using miniplates.
The load-bearing fixation is performed as a second step.
To simplify the fracture pattern within a comminuted area the small fragments are reduced and fixed to each other, in order to build up larger bone compounds that will fit into the gap. These bone components are used for realignment of the overall bone shape and will help the contouring of the reconstruction plate along the realigned lower mandibular border.
Choice of implant
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.
Reduction/fixation - general considerations
Reduce the main fragments adjacent to the comminuted area and fix them using
occlusion and MMF. Now, the size and dimension of the comminuted area are
defined. Start with realignment of the comminuted fragments. It is convenient
to regroup the larger fragments into subunits. These subunits are connected
with monocortical miniplate fixation and used as building blocks for
simplification and reestablishing the bony continuity across the comminution
gap. Shattered bone pieces are either reduced and left loose, or can be fixed
If tiny pieces have lost their mucosal attachments and are devascularized, it is sometimes advisable to remove them.
Note: For the simplification of the fragments inside the comminuted zone, reduction and fixation can alternate to achieve bone continuity in a stepwise fashion.
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 MMF topenlarge
In the isolated mandible body fracture, an arch bar is preferred for MMF. This equates to a second line of resistance in particular with biting load anterior to the fracture line.
MMF bone screws provide temporary fixation only during surgery and do not contribute to stabilization postoperatively.
Click here for further details on methods for applying MMF.
3 Simplification topenlarge
Realignment and fixation of fragments at the superior border
The intact portions adjacent to the comminuted area are reduced as a first step.
The comminuted zone can then be simplified to reduce the smaller fragments into one large fragment by using miniplates.
This is best done by starting at the superior border (alveolar process).
Reduction of the fragments is done manually or with the use of elevators or bone hooks.
One long plate can be selected to span and adapt all alveolar process fragments at once. This can be more difficult than using several short plates since these allow for fine tuning the reduction of each individual fragment before inserting the load-bearing (basal) plate. Miniplates are cut and contoured and fixed monocortically. Sometimes lag screws can also be useful.
Realignment and fixation of fragments at the inferior border
After a framework has been created at the superior border, the
simplification process is continued at the inferior border.
Reduction of the fragments is done manually or with the use of elevators, bone clamps, or bone hooks.
The fragments are reduced and fixed either one by one or fixed all simultaneously.
Pearl: manipulating fragments
Insert a monocortical screw into the center of larger bone pieces. The fragment can then be moved (dragged) with the help of a ligature forceps attached to the screw head.
4 Fixation of lower border reconstruction plate topenlarge
Choice of implant
A locking reconstruction plate 2.4 is the implant of choice with an adequate length (at least three holes on either side of the fracture zone are required) straight or prebent for use in the angle.
Contouring of reconstruction plates is demanding. A straight plate can be inserted at the lower border of the mandibular body bridging the comminution zone if this is confined to the anterior and midbody region. If the comminution zone extends towards the angle a prebent plate is advantageous.
The use of a malleable template is strongly advocated for accurate plate contouring. The risk of mental nerve injury is low since the nerve is reflected out of the field due to the upward soft-tissue retraction (submandibular approach).
The correct plate contour and adaptation is checked visually. Ensure that the plate is located on bone over its full length so that all screws will engage in the bone. A screw fixation of the realigned fragments along the inferior mandibular border should be possible with ease. Therefore, the plate must be contoured accordingly.
Click here for further details on plate bending.
Temporary fixation of the reconstruction plate by holding forceps
Fix the plate to the intact bone portions using the holding forceps.
Drill first screw hole
Use a 1.8 mm drill bit to drill bicortically through the plate hole. The first screw can be placed in any plate hole over either the anterior or posterior bone portion.
Insert first screw
Prior to screw insertion determine the appropriate screw length using a depth gauge.
Insert a 2.4 mm locking head screw of appropriate length.
Insert second screw
The second 2.4 locking head screw is inserted into a plate hole over the opposite intact bone portion.
Additional screw placement
Fill the remaining plate holes over the intact bone portions with 2.4 mm locking head screws.
Finally the basal fragments are secured centrally with additional 2.4 mm locking head screws. A locking head screw is preferred over a conventional screw to avoid secondary displacement. The screws can be inserted either mono- or bicortically depending if the fragments are split sagittally or not.
Conventional screws placed at an angle can be used to stabilize large fragments.
Removal of basal adaptation plate
The surgeon has the option of removing the basal adaptation plate according to personal preference.
Release the MMF and check the occlusion for accuracy and the bony surfaces for precise anatomic reduction.
Intraoral wound closure
The intraoral wound closure has to take into account mucosal lacerations and tooth and bone loss. Appropriate flaps and mucoperiosteal undermining have to be chosen to achieve a water-tight wound closure.
Extraoral wound closure
Extraoral wound closure is done in a standard manner.
The use of a suction drain may be considered.
5 Case example I topenlarge
Intraoperative series of a reduction and fixation of a comminuted fracture in the mandibular body.
Submandibular surgical access for exposure of a displaced complex fracture of the mandibular body
Preliminary reduction of the major fragments.
Realignment of all fragments and simplification of the fracture using miniplates on the superior border and on the basal border. The position of the anatomically reduced fragments is maintained and facilitates the bending and contouring of a reconstruction plate.
The contoured reconstruction plate fixed with holding clamps.
Screw fixation of the reconstruction plate with several screws (at least three) on either side of the comminuted area to achieve load-bearing fixation.
6 Case example II topenlarge
Comminution zone extending from the anterior mandible into the mandibular body on the left.
Anterior 3-D CT view.
Lateral 3-D CT view.
Note the anteromedially displaced condylar head fracture.
Posterior 3-D CT view shows that the width of the mandible is slightly broadened.
Exposure of the fracture site with bilateral submandibular incisions combined with a submental incision.
Fracture is reduced and simplified with miniplates. The miniplates are located at the superior border on the lateral bony surface and below the basal border of the mandible to achieve an exact three-dimensional reconstruction.
Contouring of a template for subsequent bending of a long spanning reconstruction plate.
Locking head screw fixation of the reconstruction plate in intact bony regions adjacent to the fractured area.
Postoperative imaging control: Lateral 3-D CT view.
Postoperative imaging control: anterior 3-D CT view.
Posterior 3-D CT view shows the restored width of the mandibular arch. Note the screw tips after bicortical fixation of the reconstruction plate (five screws in right angle, four screws in left anterior and midbody region).