The goal of this study was to accurately compare the 3D soft tissue changes caused by skeletal transformations after a BSSO advancement one year after surgery.

Methods: 18 consecutive patients with a hypoplastic mandible were treated with a BSSO according to the Hunsuck modification. Preoperative and one year postoperative, a CBCT scan was acquired as well as a 3D photograph (stereophotogrammetry). The pre- and one year postoperative CBCT scan were matched using voxel based registration. After registration, the mandible was segmented automatically and the preoperative mandible was subtracted from the postoperative mandible resulting in the hard tissue difference.

To investigate the soft tissue changes, the preoperative and one year postoperative 3D photographs were registered using surface based registration. The preoperative surface could now be subtracted from the postoperative surface, resulting in the overall volumetric difference.

Furthermore, the soft tissue changes at different anatomical regions as well as the labio-mental fold were investigated.

Results: A mean overall volume increase in bony tissue of 7853 mm ³ was found. For the soft tissues, a mean volume increase of 10,029 mm ³ was found. Looking at the labio-mental fold, a mean preoperative curvature of 3.57 (radius in cm) was found in contrast to a postoperative mean value of 5.24 (radius in cm). In almost all patients, the labio-mental fold stretches significantly after surgery.

Conclusion: Using 3D imaging techniques it is possible to accurately and objectively document surgical changes. This study provides real 3D, volumetric, information about the changes of a patients face after orthognathic surgery.

Conflict of interest: None declared.