3D vector analysis of mandibular condyle stability in mandibular setback surgery with bicortical bioabsorbable screw fixation.

INTRODUCTION: Bioabsorbable screws became widely used for stable fixation in orthognathic surgery as biomechanical technology advanced. Recently, 3D image analyses begin to be used to evaluate surgical changes. The purpose of this study was to evaluate, using 3D vector analysis, the stability of bicortical bioabsorbable screw fixation in mandibular setback using a sagittal split ramus osteotomy. Spatial change of the mandibular condyle was determined by 3D coordinates containing directional information.

MATERIALS AND METHODS: Bicortical screw fixation was performed using either a bioabsorbable screw (25 patients) or a titanium screw (5 patients) in orthognathic surgery. Pre- and post-operative CT images (6 months after surgery) were superimposed digitally. A 3D coordinate (X, Y, Z) and vectors were employed to quantify spatial changes of the condyle and analysed statistically.

RESULTS: Measuring on 3D image showed stable error about 0.16 mm. There were no significant differences in the total spatial changes of the condyle between titanium and bioabsorbable screws with the exception of the lateral-medial direction of the condylar centre (P = 0.042). The directional vector components were stable, regardless of mandibular setback.

CONCLUSION: In 3D vector analysis, bioabsorbable screw fixation in SSRO with distal segment osteotomy shows clinically acceptable postoperative condylar position stability.