Methods: Twenty-eight patients were included in this study, after meeting strict inclusion criteria. Thirteen underwent a BSSO with an MC to address transverse discrepancy, while the other fifteen patients only had a BSSO. Twenty-four BSSO procedures were advancements and the rest were setbacks. Images of the patients’ faces were obtained using the 3DMD photo imager before and 5 months after surgery, which allowed for the superimposition and manipulation of the 3D data with an accuracy of 0.5 mm. The pre and post surgical images were overlaid, anatomical landmarks identified, and the soft tissue measured for changes.
Results: Statistically significant changes in the transverse direction at the mandibular body and gonial angle were measured when a BSSO was combined with MC. In MC patients, the transverse skeletal to soft tissue ratio in the posterior mandible was 1:0.6. Soft tissue changes induced by mandibular advancement and setback were most prominent in the facial midline in 38% of the cases. The skeletal to soft tissue ratio in the anterior and posterior (A-P) direction ranged from 1:0.43 to 1:0.75. In BSSO advancement, the vertical height of the mandible remained relatively constant while the mentolabial fold moved downward following the clockwise rotation associated with mandibular advancement.
Conclusions: This study demonstrated that the soft tissue changes occur at a higher degree outside the facial midline. This may represent a limitation of 2D lateral cephalometric soft tissue analysis. 3D analysis of soft tissue changes, using the 3dMD imager allows accurate facial analysis of the A-P, vertical, and transverse changes induced by orthognathic surgery. Supported by the NIH Grant No. T35 DE07150.