Proportional Growth of Craniofacial Regions

Abstract

The ratio of the cranium to the face has been traditionally reported in textbooks without any firm evidence base. The present study was undertaken to measure the increase in size with age of the cranium, face, upper and lower face components. Bolton standard mean outlines for ages 1 to 18 years were analysed by the Autoceph computer program. We measured the area of each craniofacial component outline. The ratio of the size of the cranium to the face was less than previously reported at birth, 2 years, and 5 years of age, but more nearly correct in the adult. Growth of the cranium largely ceased by 9-years indicating precocious growth of the brain in relation to the face. The size of the face increased relative to the cranium by 69%. The lower face increased relative to the upper face by 22%. The average percentage increase in area was 78% lower face, 68.9% total face, 58.8% upper face, 26% cranium. The absolute growth rate of the face was greater than that of the cranium, and that of the lower face was greater than that of the upper face. The 95% confidence intervals for the growth rates did not overlap, indicating a statistically significant difference. The relative growth rate (cm2/cm2/yr) was 0.0444 lower face, 0.0391 total face, 0.0328 upper face, 0.0084 cranium. There was a differential gradient of change increasing from the cranium to the upper face to the lower face. This gradient was most clearly expressed by the relative growth rates and average percentage increases in area.