Development and validation of a photonumeric scale for assessment of chin retrusion

Background: A validated scale is needed for objective and reproducible comparisons of chin appearance before and after chin augmentation in practice and clinical studies. Objective: To describe the development and validation of the 5-point photonumeric Allergan Chin Retrusion Scale. Methods: The Allergan Chin Retrusion Scale was developed to include an assessment guide, verbal descriptors, morphed images, and real subject images for each scale grade. The clinical significance of a 1-point score difference was evaluated in a review of multiple image pairs representing varying differences in severity. Interrater and intrarater reliability was evaluated in a live-subject validation study (N = 298) completed during 2 sessions occurring 3 weeks apart. Results: A difference of ≥1 point on the scale was shown to reflect a clinically meaningful difference (mean [95% confidence interval] absolute score difference, 1.07 [0.94-1.20] for clinically different image pairs and 0.51 [0.39-0.63] for not clinically different pairs). Intrarater agreement between the 2 live-subject validation sessions was substantial (mean weighted kappa = 0.79). Interrater agreement was substantial during the second rating session (0.68, primary end point). Conclusion: The Allergan Chin Retrusion Scale is a validated and reliable scale for physician rating of severity of chin retrusion.