Intraoral vertical ramus osteotomy(IVRO) is one of the most common procedures for surgically correcting mandibular prognathism. It has many advantages such as a safe and easily performed surgical technique, less temporomandibular joint
dysfunction
and
less damage to the inferior alveolar nerve, etc. Its good clinical results and relative stability are also well-documented. In IVRO, bony healing undergoes in a stage of cortex-to-cortex contact, i.e. the proximal segments placed lateral to the
distal
segment without any fixations. This was different from the traditional bony healing of fractures. Although many studies on the displacement of the mandibular condyle have been reported, long-term evaluations on skeletal remodeling and its amount
of
the
osteotomized segments after IVRO are lacking.
The aim of this investigation was to study the radiographic time of a long-term morphologic change and its amount of the osteotomized segments after IVRO in mandibular prognathism, evaluated by panoramic, posterior-anterior cephalometric and
lateral
cephalometric recordings. Radiographs were taken immediately after surgery, 1 month, 3 months, 6 months and 1 year postoperatively.
To study this, radioraphic analysis was done on 21 patients(male 8, female 13) who were diagnosed as having mandibular prognathism and treated with IVRO from October 1992 to September 1993 and followed up over 1 year.
@ES the following results were obtained:
@EN 1. Between 3 months and 6 months postoperatively, continuity of sigmoid notch and mandibular angle and disappearance of osteotomy line were most frequently observed.
2. There were continuous decrease in vertical length of the proximal segments and horizontal length between proximal segments, Continuous increase of mandibular angle and also disappearance of osteotomy line in overlapping area in all case were
observed.
3. There were no significant difference of linear and angular changes according to the timetable between the vertical length of proximal segment and the gap of the proximal and distal segment, horizontal length of proximal segment and mandibular
angle.
4. According to results of correlation analysis between corresponding parameters, the vertical change of the proximal segment showed a high positive correlation(r>0.8) until 1year postoperatively and the gap change between the proximal and the
distal
segments showed a moderated change(0.6>r>0.5) until 3 months postoperatively(p<0.01) and a low positive change(r<0.3) from 3 months to 1 year after surgery.
5. In all 21 cases, there were no complications such as bone necrosis of proximal segments or nonurion between proximal and distal segments
From the above results, the following conclusion was obtined. Radiographic skeletal remodeling was mostly observed between 3 months and 6 months after IVRO and this may be due to the positional change of the proximal segment and due to broad
dissection
of the proximal and distal segment. And also broad dissection of the proximal segment resulted in promoting skeletal remodeling but there was no evidence of complications such as nonunion or necrosis of osteotomized segments. Under the
circumstances of
early mandibular movement and broad periosteal dissection more detailed study on long-term skeletal remodeling may be needed in the future.
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