Soft tissue facial angles in Down's syndrome subjects: a three-dimensional non-invasive study.

The aim of the present study was to obtain quantitative information concerning the three-dimensional (3D) arrangement of the facial soft tissues of subjects with Down's syndrome. The 3D co-ordinates of 50 soft tissue facial landmarks were recorded by an electromechanical digitizer in 17 male and 11 female subjects with Down's syndrome aged 12-45 years, and in 429 healthy individuals of the same age, ethnicity and gender. From the landmark co-ordinates, geometric calculations were obtained of several 3D facial angles: facial convexity in the horizontal plane (upper facial convexity, mid facial convexity including the nose, and lower facial convexity), mandibular corpus convexity in the horizontal plane, facial convexity including the nose, facial convexity excluding the nose, interlabial angle, nasolabial angle, angle of nasal convexity, left and right soft tissue gonial angles. Data were compared with that collected for the normal subjects by computing the z-scores. Facial convexity in the horizontal plane (both in the upper and mid facial third), facial convexity in the sagittal plane and the angle of nasal convexity were significantly (P < 0.05) increased (flatter) in subjects with Down's syndrome than in the normal controls. Both left and right soft tissue gonial angles were significantly reduced (more acute) in the Down's syndrome subjects. Subjects with Down's syndrome had a more hypoplastic facial middle third with reduced nasal protrusion, and a reduced lower facial third (mandible) than reference, normal subjects.