Three-dimensional Morphometric Analysis Following Facial Reconstructive Surgery

Soft tissue changes after orthognathic surgery have previously been recorded using 2-dimensional lateral cephalograms. This limits the analysis to landmarks measured in the midline (i.e. subnasale) and involves imaging limitations such as radiographic magnification variations.  However, orthognathic advancement procedures change soft tissue in 3-dimensional areas beyond the midline and dramatically change a person’s appearance in these regions.

Objectives: This study determined the 3-dimensional effects of maxillary advancement through quantification of the changes in the perinasal region and correlation of these morphologic changes to maxillary skeletal change and body-mass-index (BMI).

Methods: Patients undergoing maxillary advancement surgery were enrolled in this CHR-approved study.  We used 3-dimensional cone-beam computed-tomography (CBCT) images in conjunction with InVivo5 software (Anatomage^TM, San Jose, CA) to measure soft tissue changes at the traditional midsagittal landmarks (pronasale, soft tissue A-point, upper and lower lip anterior points) as well as points extending horizontally to the right and left 10-mm, 25-mm, and 35-mm from the three superior midsagittal landmarks. The immediate pre-operative and six-month follow-up CBCTs of 30 patients were analyzed for this study.

Results: Soft tissue change extended up to the infraorbital region from the lower lip, and laterally to the zygomatic region, well beyond the midline structures.  The areas of strongest correlation were at 10-mm left of the soft-tissue A-point, and at the midline and 10-mm left of the upper lip anterior point (Pearson correlation=0.909, 0.897, and 0.848 respectively, p<0.05).  Every point, except vertical movement of the lower lip anterior point, was statistically significant. Patient BMI also showed statistically significant correlations at 10 of the 25 data-points.

Conclusion: This study provides a more comprehensive analysis of the 3D extent of morphologic soft tissue changes after maxillary advancement.  CBCTs for facial reconstructive surgery provide more relevant information than lateral cephalograms.