A Novel Cephalometric Approach Aiming to Quantify a Normal Range of Bony Chin Protrusion.

[INTRODUCTION] Cephalometric analysis is an essential tool in the diagnostics and planning of orthognathic surgery. No objective criterion exists to facilitate decision making regarding genioplasties. Differing opinions amongst clinicians therefore leads to wide variability amongst treatment options offered to potentially suitable patients. This study has three aims. The first was to quantify the distribution of chin morphology amongst the average population using cephalometric analysis. Secondly, we sought to determine whether cephalometric parameters could be used to predict overlying soft tissue changes. Lastly, we consider the use of a new cephalometric angle, BNPg, for pre- and post-operative assessment of genioplasty patients.

[METHODS] This study retrospectively analysed 231 lateral cephalograms. The angle between the landmarks: B point, Nasion and Pogonion was measured to generate 'BNPg' a novel unit to quantify bony chin protrusion.

[RESULTS] The mean BNPg from all 231 samples was 1.12 degrees with a standard deviation of ± 1.35. Comparison between sexes showed no significant differences between male and females ( = 0.108). Furthermore, bony chin protrusion was found to strongly positively correlate with soft tissue chin appearance ( = 0.731), however, BNPg was found not to correlate with skeletal malocclusion (ANB,  = 0.085).

[CONCLUSION] The novel unit BNPg may serve as a useful tool in contributing to the determination of treatment thresholds in osseous genioplasty for desirable aesthetic outcomes and may be used post-operatively to assess outcomes also. As this is a pilot study, further clinical studies would be required to validate this parameter in genioplasty patients, both pre- and post-operatively.

[SUPPLEMENTARY INFORMATION] The online version contains supplementary material available at 10.1007/s12663-022-01784-5.