Horizontal rotation of the condyle after sagittal split osteotomy of the mandible.

Displacement of the proximal segment of the condyle such that the condyle is no longer in its correct position has been cited as a major factor in postsurgical skeletal relapse after mandibular, sagittal split osteotomy. This study examined the effects of sagittal split osteotomy on the horizontal rotation of the condyle in 16 dissected mandibles for which clamp, screw, and wire fixations were used to advance the mandible or set it back. The results showed that, after sagittal split osteotomy, horizontal rotation usually occurred, regardless of the position of the distal segment or the type of fixation used. Our finding that 82% of the condylar angles increased after surgery indicates that the lateral pole of the condyle had rotated anteriorly, while the medial pole had rotated posteriorly. There were no consistent differences in horizontal rotation between the condyles on the side where the proximal segment had been fixed first and those on the side where it had been fixed second; nor did the sizes of the original intercondylar angles affect the magnitudes of change in the postoperative intercondylar angles. The only statistically significant difference (p = 0.005) between the angles after fixation by the three different methods was between screw and wire osteosyntheses when the distal segments were in the forward position. The reason for this difference is unclear.