Evaluation of postoperative stability after BSSRO to correct facial asymmetry depending on the amount of bone contact between the proximal and distal segment.

Sagittal split ramus osteotomy (SSRO) benefits patients through the wide bone contact between the proximal and distal segment, which contributes to postoperative stability. Recently, a posterior bending osteotomy (PBO), an additional vertical osteotomy performed posterior to the second molar after SSRO, has been introduced to avoid positional changes of the condyle from bony interference in patients with facial asymmetry, which leads to decreases in bone contact. The aim of this study was to investigate postoperative stability after SSRO with PBO. Forty patients with facial asymmetry were enrolled and divided into two groups according to the surgical method used on the deviated side: PBO (n = 18) and grinding method (n = 22). Cephalometric analysis was performed. In addition, adaptation and bone healing of the PBO segments were assessed with 3-month postoperative three-dimensional computed tomography depending on the fixation of the PBO segment. The two groups showed no significant difference in postoperative relapse. Most PBO segments were well-adapted to the proximal segment. Twelve segments with fixation exhibited good bone healing. Two of three segments without fixation, however, had poor bone healing. In summary, PBO did not cause postoperative instability, and the PBO segments were well-healed with rigid fixation.