Cephalometric Growth Analyses of the Human

This study was designed to demonstrate quantitative growth trends in the human upper face region before birth. Photographs of 68 sagittally sectioned fetal heads were measured using a series of linear and angular measurements for changing height, length and shape. Cross-sectional types of data were treated with a statistical model which tested for linearity of the data, correlation between growth changes and increasing fetal age, significance of the differences between rates of change in related upper face regions and the general significance of the trends shown in the study. Pooled data for the second and third trimesters suggested three distinct growth trends. Linear measurements of the cranial base, nasal area, and palate correlated significantly with increasing crown-rump length. Finally, a composite upper face profile for the sample suggested a relative migration of the region downward and forward away from the anterior cranial base and the hypophyseal fossa. These three trends collectively demonstrated that the pattern of upper facial growth before birth involves progressive enlargement of a relatively static profile. I t should be understood that this pattern is a group trend as shown by cross-sectional sampling of many individuals over a period of time with no individual being measured more than once, Conversely, variabilities in a specific individual's growth are most appropriately demonstrated by measuring that individual several times throughout some time span, i.e., by longitudinal sampling. Studies of the human fetus are restricted generally to the cross-sectional sampling technique. The close similarity of these prenatal trends with those reported for postnatal craniofacial growth suggests that certain patterns of facial growth in childhood can be seen as early as the beginning of the fetal period and emphasizes the continuum of human development. Growth of the human face is a dynamic developmental continuum which begins in the embryo and continues throughout postnatal life. This continuum involves a timerelated interplay between differentiation at cellular, tissue and organ levels, the development of function, and morphogenic changes in size and shape. The present study is specifically concerned with changes in size and shape of the human upper face before birth. Postnatal changes in size and shape of the face have received considerable attention from many workers representing a broad spectrum of scientific disciplines and techniques, as well as clinical interests. However, apart from the classic work of Scammon and Calkins ('29), few studies have been concerned AM. J. ANAT., 125: 113-122. specifically with human prenatal cephalometrics and general patterns of growth before birth. The reported studies of the human face before birth have been concerned more with descriptive, non-metric accounts of regional morphogenesis, the development of specific systems or structures and with providing embryological explanations for congenital defects and abnormal growth patterns of the postnatal face. Recently, greater emphasis has been directed toward filling the existing void of cephalometric data on size, form and directional growth in statistically representative 'This investigation was supported, in part, by research grant HD 00178 from the National Institute of Child Health and Human Development, National Institutes of Health, USPHS. 113 114 ALPHONSE R. BURDI populations of human fetuses. In other words, “How fast and in what direction is the human face growing before birth?” The purpose of this study is to demonstrate trends in changing height, length and shape of the human upper face before birth. Possible differences between second and third trimester growth patterns are also emphasized. Finally, to emphasize the continuum of human development, the observed prenatal patterns are related to growth trends reported for the upper face during the first years of postnatal life. MATERIALS AND METHODS Sixty-eight human fetuses representing ages 12 weeks through term or 70 through 420 mm crown-rump length (CRL) wei-e selected for this study. This selection was made on the basis that all specimens were fixed in 1096 neutral formalin and were free from gross craniofacial defects. The procedures of specimen preparation, the definition of basic cephalometric landmarks, and the detailed descriptions of linear and angular measurements have been reported (Burdi, ’65) . In general, cephalometric analyses consisted of both linear and angular measurements based on such landmarks as nasion ( N ) , sella (S) , basion (Ba) , crista galli ( C G ) , septa1 point (SP), anterior nasal spine (ANS) , posterior nasal spine (PNS) and uvular point (UP) . Linear measurements reflected changes in height and length of the cranial base, nasal septum, and palate. Changes in shape of these regions were analyzed by a series of angular measurements. Cross-sectional type data derived from the study sample of 68 fetuses were analyzed using a statistical model designed and implemented in consultation with the staff of The University of Michigan Statistical Research Laboratory. Initially, an IBM ANTERIOR CRANIAL BASE LENGTH Y = 39.100 + ,513 X CRL ~ ‘ r & ANS BASE LENGTH POSTERIOR CRANIAL BASE LENGTH Y = 38.626 + ,295 X CRL