Intraoral vertical ramus osteotomy (IVRO) is a useful surgical procedure for mandibular setback in patients with mandibular prognathism or mandibular asymmetry. IVRO has some intraoperative complications, such as the medial trapping of the proximal segment. Several techniques have been described to overcome this problem, but none can prevent it. This technical report describes a method that prevents the medial trapping of the proximal segment during IVRO.
Intraoral vertical ramus osteotomy (IVRO) is a useful surgical procedure for mandibular setback in patients with mandibular prognathism or mandibular asymmetry. This intraoral approach for VRO was introduced by M oose and W instanley . Additional technical modifications and instrumental refinements have increased intraoperative visibility and reduced operative time , but there are still intraoperative difficulties. The proximal fragment, pulled by the medial pterygoid muscle, is frequently trapped medially when VRO is achieved. Usually, the fragment can be maintained laterally, but this increases the duration of surgery. In approximately 3–8% of patients, the proximal fragment remains medially .
The purpose of this study is to describe a simple technique that prevents medial trapping of the proximal segment.
Technique and patients
A modification of the technique described by E pker & W olford for IVRO was used. A mucosal incision was made along the anterior border of the ramus from the base of the coronoid laterally to the buccal vestibule of the mandible in the first molar area. Dissection exposed the coronoid process, the lateral aspect of the ramus, the antilingula prominence, the sigmoid notch, and the inferior and posterior borders of the ramus. The pterygo-masseteric sling was removed from the inferior border and gonial angle. An oscillating saw, angled at 105°, was used to perform the osteotomy cut of the ramus, posterior to the antilingula prominence, directed superiorly to the sigmoid notch and inferiorly to the mandibular angle. A few millimetres before the osteotomy was completed in the mandibular angle, a freer elevator, bent 100° ( Fig. 1 ), was inserted in the superior part of the osteotomy cut and tilted slightly forwards to prevent medial trapping of the proximal fragment. After osteotomy in the mandibular angle, a periosteal elevator Molt No. 9 (Martin) was inserted in the cut, inferiorly to the freer elevator and tilted forwards ( Fig. 2 ). This permitted the release of the muscular fibres of the medial pterygoid that were still inserted in the proximal fragment and enabled the proximal fragment to be pulled laterally. Wet gauze was placed between the proximal and distal fragments until intermaxillary fixation was performed. The proximal fragment was examined to ensure that it was still placed laterally.