Validity of Safety-zone Approach on Facial Nerve Preservation During Transbuccal-accessed Fixation of Mandibular Fractures

Mandibular fractures, in particular mandibular angle fractures, can be fixed with various techniques. Of all, open reduction and internal fixation (with titanium plates and screws) stands as one of the most commonly used techniques for mandibular angle fracture management.

Different approaches could be followed to access the mandibular angle. Transbuccal approach is considered one of the most conservative approaches for such goal. Conjoined with a transoral access for fracture reduction and plates adaptation, a small incision is made extraorally on the cheek opposite to the fracture line to facilitate application of a transbuccal trocar, through which drilling and screws fixation can be done into the plates.

A reported risk of facial nerve injury raises fears towards this extraoral cheek incision, even being considerably small. That's why a safety-zone was proposed as a triangle between three lines drawn cross each other. The first is drawn from the ear tragus to the facial notch. The second is drawn from the outer eye canthus to the mandibular angle. The third is on the lower mandibular border. This safety-zone triangle was suggested beforehand in a cadeveric study to be a safe land for cheek incisions without endangering the facial nerve branches, in particular buccal and marginal mandibular branches.

This study aims at testing whether the implementation of this safety-zone may decrease the risk of facial nerve affection among patients in whom these landmarks were followed, or there may not be such difference between these patients and other patients who underwent same fracture pattern management with the same approach but without implementing these safety-zone landmarks.