Osteotomy length and postoperative stability in vertical subcondylar ramus osteotomy

The osteotomy sites in 80 patients treated for mandibular prognathism by intraoral (IVSO) or extraoral (EVSO) vertical subcondylar ramus osteotomy and their relationships to postoperative mandibular stability were studied. A model study demonstrated that metric orthopantomographic measurements of the ramus showed insignificant variability of magnification and distortion. The relative osteotomy length and the bony overlapping area of the osteotomized fragments were evaluated on 6-week postoperative orthopantomograms. High correlation was found between the clinical estimate of osteotomy length and metric registrations. Bony overlapping area of the IVSO and the EVSO group did not reveal differences. The mandibular positional changes during the fixation/postfixation periods were analyzed on 6-week and 6-month postoperative lateral cephalograms. Significant correlations could not be demonstrated between postoperative stability and osteotomy length or overlapping bony area. Thus the osteotomy length appears to be factor of minor importance for postoperative stability.