The assessment of the stability in mandibular setback surgery related to spatial factors under rotational control of the proximal segment.

OBJECTIVE: To evaluate the surgical relapse of mandibular setback, related to the magnitude of setback and LeFort I osteotomy under rotational control of the proximal segment. STUDY DESIGN: Data from 78 patients who had undergone sagittal split ramus osteotomy for mandibular prognathism were reviewed. The stability of the proximal segment was retrospectively confirmed. Serial cephalograms were used to assess relapse over 1 year. The association between relapse and LeFort I osteotomy as well as the magnitude of setback was assessed. RESULTS: Minimal counterclockwise rotation was noted postoperatively, but the proximal segment remained stable for 1 year. Notable forward relapse was shown in the setback of more than 7 mm (P < .01) with resumption of function after 6 weeks, but it was not related with LeFort I osteotomy. CONCLUSIONS: Relapse was related to the amount of setback and occurred on resumption of function despite rotational control of the proximal segment.