Intraoperative awakening of the patient during orthognathic surgery: a method to prevent the condylar sag.

PURPOSE: The intraoperative diagnosis, during orthognathic procedures, of an unfavorable condylar position is highly desirable. A simple technique that can reliably identify a malpositioned condyle intraoperatively has obvious advantages. The manual positioning of the condyle is easier, but it requires the utmost care and an experienced operator. Muscle tone is described as maintaining contact across the temporomandibular joint. The anesthetized and curarized patient has a condylar position posterior to that in the same patient when he is awake, with the same seating force applied. Under general anesthesia, the condyle may be inferior and might not feel stable until it moves posteriorly and has adequate compression of the retrodiscal tissues on the posterior wall. Relapse of the occlusion as a result of changes in the condylar position may occur immediately after the removal of the temporary intermaxillary fixation (IMF). The surgeon needs to understand the mechanism of condylar sag and the specific patterns of malocclusion that it may produce. This will enable him to make a diagnosis and to implement the appropriate corrective measures, providing the opportunity for immediate correction of condylar position, thereby obviating the need for a second operation or orthodontic compromise.
MATERIALS AND METHODS: A study group (group A, 76 patients) and a control group (group B, 73 patients) were randomly formed from the dysgnathic patients scheduled for bimaxillary orthognathic surgery (Le Fort I osteotomy and bilateral sagittal split osteotomy). The free mandibular proximal segment was gently and manually positioned in the glenoid fossa. All the mandibles were fixed with bicortical screws. In group A, immediately after the fixation, IMFs were removed and the occlusions were checked with light digital pressure on the chin, then the patients were rapidly awakened (maintaining the intubation) in a state of conscious analgo-sedation and asked to open and close, and to laterally move the mandible. If clinical examination of the passive and active movements of the mandible was suitable, the anesthesia was reinforced and the operation was concluded.
RESULTS: In 11 of the 76 patients of group A, malocclusion was noted, after the rigid fixation, with the method of digital pressure on the chin; the intraoperative awakening of the patients confirmed the clinical appearance and it provided further clinical signs to identify the offending condyle and to favor appropriate corrections. In 8 of the group A patients, malocclusions were not noted with manipulation of the mandible, but they were pointed out during the intraoperative awakening, and then they were appropriately corrected. In 2 of the group B patients, malocclusion was noted, after the rigid fixation, with the method of digital pressure on the chin, and it was immediately corrected. In 7 of the group B patients, malocclusion was not noted during the operation with the method of digital pressure on the chin, but it was noted at the end of the surgical procedure (12-24 hours after).
CONCLUSION: Muscle tone, muscular activity, and proprioception appear to have important roles in the clinical evidence of a postoperative malocclusion during the intraoperative awakening; they can reliably implement the accuracy of the diagnosis of condylar sag, and they can favor its correction.

RCT Entities:   Population Interventions Outcomes