Safety-zone Approach and Facial Nerve Preservation in 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.

• Landmarking Safety-zone (Procedure): A safety-zone triangle for transbuccal incision is encased between three lines: the first is a line 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.

Primary outcomes

• Postoperative Facial Nerve Affection Using Sunnybrook Facial Grading System (in numbers from 0 to 100) [First postoperative week, and third postoperative week.]: Facial nerve function is tested after surgery through subjective facial expressions by the patient and judged by two different investigators grading them on Sunnybrook Facial Grading System

Sex: All, ages: 20 Years to 45 Years, accepts healthy volunteers

Inclusion Criteria:

* Healthy patients (American Society of Anesthesiologists Class I)
* Patients with mandibular fracture that require open reduction and internal fixation with miniplates and screws.
* Mandibular fractures that couldn't be accessed transorally only.
* Non-comminuted fractures

Exclusion Criteria:

* Patients with neurological disorders.
* Patients who take nerve-supporting supplements (such as Vitamin B12 or Vitamin B complex) prior to surgery.
* Presence of facial laceration.
* Infected fractures

• Mohammad Abdelhamid, PhD, Principal investigator, Department of Oral and Maxillofacial Surgery, Faculty of Oral and Dental Medicine, Delta University for Science and Technology