Forehead Inclination in the Lateral Profile in Koreans

The forehead is the part of the face extending from the line of the hair border to the temples and the eyebrows [1]. It occupies one third of the upper part of the face and plays an important role in facial expressions. The outcome of forehead reconstruction surgery is a significant contributing factor to facial expressions and the quality of life in patients with excavation of the forehead due to an injury or a congenital deformity. The present study aimed to establish the average value of forehead inclination in the modern Korean population, according to sex and age, as a reference for deciding the scope of surgery affecting the contour of the forehead and for evaluating the outcomes of plastic and reconstructive surgery. We selected 200 Koreans, comprising 100 men and 100 women, ranging in age from 20 years, when craniofacial growth is completed, to 50 years. Patients in whom the border line between the hairline and the forehead was behind the vertex were excluded. The reference point for measuring inclination was based on the report of Andrews [2]. The trichion is the point where the center line of the forehead meets the hairline and the uppermost extent of the relatively flat parts of the forehead. The glabella is the lowest part of the forehead and is the point exhibiting the most protrusion between both eyebrows [2,3]. Inclination was measured using a goniometer with the face placed on the Frankfurt horizontal line. The Frankfurt horizontal line is an extension of the imaginary line between the tragus at the height of the external auditory meatus and the lower orbital bone, which is the continuation of the lower lid into the face [4]. When measuring the lateral contour of the forehead, the inclination was measured as the angle between the line from the trichion to the glabella and the line perpendicular to the Frankfurt horizontal line. The line perpendicular to the Frankfurt horizontal line was defined as 0°. Protrusion anterior to the line was considered positive inclination, whereas protrusion posterior to the line was considered negative inclination (Fig. 1). The mean values and 95% confidence intervals (CIs) were calculated for men and women. Comparisons of the forehead inclination by gender were made using the independent t-test. Comparisons of forehead inclination according to age groups after stratification by gender were calculated using analysis of variance. All statistical analyses were carried out using SPSS ver. 21.0 (IBM Co., Armonk, NY, USA). The statistical significance level was set at P < 0.05. The mean values (95% CI) of forehead inclination were -15.90° (-16.81° to -14.92°) for men and -12.47° (-13.34° to -11.63°) for women (Fig. 1B, C). Forehead inclination was found to differ significantly according to gender (P < 0.001) (Table 1).