Right-angled drilling and screw driving instruments are an alternative to transbuccal systems.
In comparison to the transbuccal system, any transcutaneous incisions can be avoided. Thus, using a rectangular or 90° drill/screwdriver system via a strictly transoral approach is considered a less invasive procedure.
An endoscope or minicamera equipment (alternatively, a small mirror) can be used to monitor the use of a drill/screwdriver in anatomical sites that are difficult to visualize.
In principle, the 90° drill/screwdriver allows drilling and insertion of screws perpendicular to the bony surface through a transoral approach.
The drill/screwdriver is construed of several main components:
The handle's back has a quick coupling connection to attach an electric motor or a handgrip for manual screw insertion.
The most commonly used screw dimensions with 90° screwdrivers are 1.5, 2.0, and 2.4.
The screwdriver shafts and drill bits are inserted into the head of the shaft.
The indications for using the 90° drill/screwdriver are fractures extending into the lower border of the mandibular angle and the ascending ramus, including the caudal and low parts (subcondylar division) of the condylar process.
A note of caution: A bicortical screw insertion is usually challenging to perform.
The 90° drill/screwdriver can also be used for plate fixation of sagittal split osteotomies.
A typical application of the angled drill/screwdriver for plate fixation of a condylar fragment.
6. Pitfalls and backup strategies
Endoscopically assisted procedures, and the use of 90° drills and screwdrivers require a team effort and sufficient training before clinical use.
Limited space in the superior ramus region and relatively high torque requirements for screw insertion in the mandible are challenges for predrilling, plating, and screw insertion in these regions. Endoscopically assisted subcondylar fracture repair can be very complex and technically demanding.
If the planned procedure cannot be successfully performed, a backup strategy is mandatory and must be agreed upon with the patient in the informed consent form.