The importance of the anterior nasal spine in predicting soft tissue movement in maxillary orthognathic surgery.

Background: The aim of this study was to compare and analyze the correlation between changes in maxillary hard tissue landmarks and nasolabial soft tissue points in patients with skeletal Class II and Class III malocclusion following Le Fort I osteotomy.

Methods: From 2017 to 2022, patients who underwent Le Fort I osteotomy were recruited in this retrospective study. Three hard tissue landmarks on the maxilla and twelve soft tissue landmarks on the nose and lips were selected for measurement. A Pearson correlation coefficient was used to analyze the coefficient correlations between hard- and soft-tissue changes according to the sagittal and vertical directions. Ratios with significant correlation were calculated.

Results: Totally 219 patients were enrolled. In skeletal Class III malocclusion, there is a widespread and significant correlation between the ANS point and A point in both the sagittal and vertical directions with the nasolabial soft tissue point. However, in skeletal Class II malocclusion, the correlations between hard- and soft-tissue points are relatively weak. Moreover, as one moves further away from the anterior nasal spine, the correlation between hard- and soft-tissue weakens.

Conclusions: In comparison to skeletal Class II malocclusion, skeletal Class III malocclusion exhibits a stronger correlation between the movement of the ANS and A points and changes in nasolabial soft tissue landmarks, particularly in the sagittal direction. This study suggests that changes in the position of the anterior nasal spine may play a potentially significant role in predicting the post-orthognathic surgery nasolabial soft tissue morphology in patients with skeletal Class III malocclusion.