General considerations Transbuccal instrumentation extends the versatility of transoral approaches. In addition to the transoral exposure the soft tissues overlaying the posterior divisions of the mandible are pierced from externally. Via this transbuccal route a special instrumentation is inserted: the so-called transbuccal handle with cannula. Through the cannula, drilling and screw insertion becomes possible at a right angle to the lateral mandibular surface. Control and guidance of the procedure is done simultaneously from the external side and the internal approach. In the clinical situation (contrasting in contrast to this illustration) the soft tissues are less retracted.
AO Teaching Video "The Transbuccal System"
Resiliency The soft-tissue resiliency of the cheek is the key for shifting the transbuccal cannula to the intended screw insertion site. As a principle the cannula is best movable if it is inserted at the maximal transverse extension of the wound cavity. Movements are limited approaching the borders of the cavity being reduced along concentric lines around the soft-tissue channel. The dissection cavity along the lateral surface of the mandible is reduced in its transverse spacing towards the posterior border of the ramus and towards the mental foramen.
Be aware that if the cannula is inserted in the vicinity of the mental foramen, the neurovascular bundle can easily be stretched or damaged by brisk movements of the transbuccal handle. Usually, the zone next to the neurovascular mental bundle is preferably reached transorally. In case of placing several screws at a time, eg, for application of a longer osteosynthesis plate, it may be advantageous to use several transbuccal channels. This provides a perpendicular insertion of the drill bit and screw driver.
To use the full space of the dissection cavity the retractor should be mounted at a short distance to the tip of the cannula.
2. Transbuccal system
Transbuccal guide The main component of the transbuccal system is the handle, equipped with either an attached (as illustrated) or fixed cannula. The trocar (also known as obturator) is used to penetrate the soft tissues with a pointed tip.
Mountable retractors Through the transoral route the cannula is mounted with a self-holding retractor for the buccal soft tissues. There are several retractor types available used depending on the preference of the surgeon.
Ring shaped retractor (fixed with a screw to the cannula shaft)
Blade retractor (fixed with a screw to the cannula shaft)
Forceps retractor (fixed to the cannula shaft)
U-shaped retractor (fixed externally to the handle)
Drill sleeves For an exact drilling procedure, a set of exchangeable drill sleeves is available according to the different diameters of the drill bits.
Some drill sleeves offer the possibility to connect a plate to its tip, thus facilitating plate positioning.
The side windows in some of the drill sleeves allow for depth control during drilling or screw insertion and for direct irrigation
3. Insertion of transbuccal instrument
Make stab incision Make a small stab incision to prepare for the insertion of the cannula. The location is predetermined by palpation. The index finger is placed over the desired osteosynthesis site and matched with the thumb on the cheek surface and marked.
The orientation of the scalpel blade must be parallel to the relaxed skin tension lines (RSTL).
Insert the cannula with trocar through the facial tissue down to the bone.
Remove the trocar to open the cannula as a channel for the screw insertion procedure.
4. Cheek retractor options
Ring Choose the cheek retractor ring and place it intraorally over the cannula tip. For facilitation the tip of the cannula is angulated forward to improve the accessibility.
Using the screwdriver 2.0 or 2.4, tighten the screw until the ring is secure on the cannula.
The cheek soft tissues can now be retracted using the outside handle.
Straight cheek retractor Place the blade-shaped cheek retractor over the forward-tilted cannula tip.
Tighten the blade fixation screw.
The cheek soft tissues can now be retracted.
U-shaped Start the application of the U-shaped cheek retractor by placing the forked inner end of the retractor around the cannula intraorally.
Place the outer end over the cannula disk at the handle.
The handle and the U-shaped retractor can be hinged around a clickable joint on the outer cannula end. The handle is brought into a comfortable working position.
Clamp Place the forceps cheek retractor next to the cannula tip, which is tilted forward. Then open the beak-shaped forceps mouth and grip the cannula tip. Adjust it to the appropriate height and close the forceps along its ratcheting mechanism.
The cheek soft tissues can now be retracted with the handle of the forceps. This allows for viewing and handling the cannula tip inside the transoral surgical cavity simultaneously. The cheek soft tissues can also be retracted using the external handle. Viewing and handling is separated by the cheek tissues and requires switching the view from inside to outside and vice versa.
5. Screw insertion
Insert drill guide Next an appropriate drill guide is chosen and inserted into the cannula. The screw insertion is demonstrated using the ring cheek retractor.
Drill hole The tip of the cannula containing the drill guide is placed exactly at the intended screw position directly on the bony surface or onto the hole of an osteosynthesis plate.
Drill a hole using the appropriate drill guide and drill bit. The advancement of the drill bit into the bone cannot be directly observed unless a drill sleeve with window is used or the cannula is retracted slightly showing the exiting drill bit.
Determine screw length The appropriate screw length is determined with a depth gauge and the screw is inserted using a self-holding screwdriver.
Note: the drill guide must be removed before the depth gauge is inserted.
Screw insertion The self-retaining screw driver with the screw mounted on the tip of its blade is introduced into the cannula strictly in the axis of the cannula hole. If it is slanted the screw can easily be lost from the screw driver blade.
After the first turns to tighten the screw, the cannula can be slightly retracted to observe the further progress of screw insertion.
The transbuccal system is dismantled after all screws have been placed.