Head posture and craniofacial morphology

The associations between craniofacial morphology and the posture of the head and the cervical column were examined in a sample of 120 Danish male students aged 22–30 years. Two head positions were recorded on lateral cephalometric radiographs, one determined by the subject's own feeling of a natural head balance (self balance position), and the other by the subject looking straight into a mirror (mirror position). Craniofacial morphology was described by 42 linear and angular variables, and postural relationships by 18 angular variables. A comprehensive set of correlations was found between craniofacial morphology and head posture. The correlations were similar for both head positions investigated. Of the postural variables, the position of the head in relation to the cervical column showed the largest set of correlations with craniofacial morphology. Extension of the head in relation to the cervical column was found in connection with large anterior and small posterior facial heights, small antero-posterior craniofacial dimensions, large inclination of the mandible to the anterior cranial base and to the nasal plane, facial retrognathism, a large cranial base angle, and a small nasopharyngeal space. The possible role of functional factors in mediating the relationship between morphology and posture was discussed.     

Cranial base and jaw relationship

The lateral skull radiographs of 124 boys aged approximately 10 years divided equally between the four angle classes were digitized in an effort to establish the relationship between cranial base size and shape and jaw relationship. Comparison of the means for occlusal groups showed a trend from class II to class III as cranial base dimensions and angle decreased. The condyle was also more distally positioned with respect to nasion, point A and the Pterygomaxillary vertical in the class II groups. Cranial base length correlated strongly with maxillary length but weakly with mandibular length. Nevertheless, the size of the maxilla did not influence its prognathism. The cranial base angle was strongly correlated (-0.7) with angle sella-nasion-point B. It is concluded that cranial base size and shape influence mandibular prognathism by determining the anteroposterior position of the condyle relative to the facial profile.     

Cephalometric analysis of the craniofacial region of the northern Foxe Basin Eskimo

Past investigations of the Eskimo have indicated that there are marked morphological differences in the craniofacial skeleton of this relatively isolated ethnic group compared to other ethnic and racial groups. This study, using cephalometric radiography, attempted to characterize the craniofacial phenotype of the Eskimo living in the northern Foxe Basin, Northwest Territories, Canada. Age changes were examined on a cross-sectional basis with comparisons being made with a Winnipeg Caucasian group. This investigation indicates that the Igloolik Eskimo has a phenotype, established early in life, and is distinct from the Winnipeg group. The overall size of the Eskimo craniofacial complex was significantly larger at three years of age and remained larger through the ages studied. Development of the craniofacial region, however, was fairly similar in rate and direction for both populations. The greatest differences between the Eskimo and Caucasian groups were found in the linear measurements assessing cranial width, facial width, mandibular length, facial height, protrusion of the incisors, chin point development, and nasal morphology. Differences between the two groups in the morphological relationships of the component structures include the angular relationships of the maxilla and nasal bones to the anterior cranial base, the gonial angle of the mandible, and the angle of facial convexity.     

A factor analysis of cranial base and vault dimensions in children

Lengths within the cranial base and vault were measured in cephalometric radiographs of 220 boys and 177 girls ranging in age from 0 to 15 years; all these children are participants in The Fels Longitudinal Growth Study. The present study is based on mixed longitudinal data derived from 1640 radiographs for boys and 1260 radiographs for girls. Factor analysis was applied separately for boys and girls for each age group; i.e., 0–3, 4–6, 7–9, 10–12, and 13–15 years. For the 0–3 year age group, two factors were extracted in each sex, whereas four factors were extracted in the rest of the age groups. The factor structures are similar in the three older age groups of boys (7–9, 10–12, and 13–15 years). The first four factors for these groups are labelled, respectively: cranial vault size, posterior cranial base length, presphenoid length, and basisphenoid length. The order of the third and fourth factors is reversed in the 7–9 year olds. For girls, the factors extracted were also the same in both the 7–9 and 10–12 year age groups, even though the order of factors was different between age groups; i.e., anterior cranial base length, cranial vault size, basisphenoid length, and basioccipital length. Differential growth rates among cranial base dimensions probably cause changes in factor patterns. Obliteration of the spheno-occipital synchondrosis is suggested as the mechanism responsible for the change of factor pattern in the girls. Closure of this synchondrosis would have occurred too late to affect the patterns in boys.     

Ontogenic growth changes of the skull base in four genera of nonhuman primates.

Cross-sectional studies of the degree of the cranial base flexion were carried out in infant, juvenile and adult skulls in four genera of nonhuman primates (P. paniscus, H. lar, P. urinus, and M. mullatta). The cephalometric observations of the cranial base included linear and angular measurements of each specimen. The data obtained in this study showed that the anterior portion of the cranial base exhibits a significant shortening trend as the mammalian evolutionary scale ascends. Moreover, the growth pattern of the anterior portion of the skull base follows that of the facial bony structures. The ontogenic growth changes of the posterior portion of the skull base follows the growth pattern of the endocranial cavity. The significant trend of elongation in this area directly contributes to the posterior migration of the foramen magnum. The magnitude of these growth changes decreases as the evolutionary scale ascends. The angular measurements of the cranial flexion showed a less obtuse cranial base angle in young specimens and the ones higher on the mammalian scale. The skull kyphosis was less pronounced in these specimens and the anatomical features of the cranial base were more humanlike, including the balance of the head expressed by the position of the foramen magnum.     

Cranial base angulation and prognathism related to cranial and general skeletal maturation in human fetuses.

The purpose of the present study was to describe normal midsagittal craniofacial morphology in second trimester human fetuses. Measurements of the cranial base angle and the prognathism of the maxilla and the mandible were performed on radiographs of cranial midsagittal tissue blocks of 52 fetuses with a gestational age from 13 to 27 weeks. Special procedures were developed for the definitions of the nasion and sella reference points on the radiographs in the early stages of fetal development. Mean data were reported for stages of crown rump length (CRL) and maturation of the fetal cranial base (MSS), usable as reference in assessment of pathological fetal crania in reports and autopsy procedures. Regression equations were determined for the regression of the angular values on CRL, MSS, and general skeletal maturation (TNO). The cranial base angle was found to decrease significantly, and the angles of prognathism to increase significantly with increasing CRL, TNO, and MSS values. It was suggested that these simultaneous and similar changes in the three angles could be accounted for by the upwards movement of the sella point produced by a cranial displacement of the pituitary fossa caused by local cartilagenous growth and bony remodelling during the period of study. The study thus reflects the influence of cranial skeletal maturation on the early development in shape of the craniofacial complex.     

A craniometric study of bicoronal craniosynostosis (BCC).

We compared 20 cases of bicoronal craniosyntosis (BCC) using the linear and angular values of the normal statistical material for the same age and sex. The skull in BCC is significantly shortened and flattened but with normal width. The height of the frontal arch (FNBR) is significantly decreased. The base of the skull is depressed with angle AB2 significantly increased, and angle NTNO significantly decreased and, even in some cases, with negative angular values. This is inducing a sinking of LEA (length from N to T), and in some cases LEA is lower than the line LNO (distance from N to O). The cephalic index (CI) was significantly increased, and the calculated cranial capacity (CC) was significantly decreased. Bregma (BR) is moving anteriorly in BCC, inducing an anterior movement of the calvaria with a bulge around BR. In this anterior movement we designate lack of positive occipital rotation. In BCC there is an evident lack of positive occipital rotation. Superimposing our drawings on the reference line NBA, we found for the first time a movement of anatomical landmarks similar to that observed in the negative occipital rotation in vestibular orientation.     

A craniometric study of sagittal craniosynostosis (SC).

Twenty cases of sagittal craniosynostosis (SC) were compared with the linear and angular values of the normal statistical material for the same age and sex. There were significantly increased values of the length of the skull (LI) and the height of the frontal arch (FNBR) and significantly decreased width (WI) and height of the skull (HI) as well as the depth of the cerebellar fossa (PEP). The length of the anterior cerebral fossa (LEA) remained within normal limits and the distance BRPI between bregma (BR) and the internal protuberance (PI) was within normal limits or increased. The angular value of the basal angle (angle NT-BA, AB2) decreased significantly and the angle NTNO (angle between the lines NT and NO) and the angle BRTPI (the angle between the lines TBR and TPI) were significantly increased. The cephalic index (CI) was significantly decreased. The cranial capacity (CC) is normal or decreased. There is demonstrated an occipital over-rotation of the skull.     

Postnatal growth of the cranial base in Macaca nemestrina.

Postnatal growth of the cranial base was longitudinally studied in 21 male and 11 female Macaca nemestrina. The basicranium of each animal was marked with tantulum implants in order that the tracings of each serial roentgenogram could be superimposed. Between the ages of 3.0 and 5.0 years the degree of sexual demorphism in both angular and linear dimensions increased. The cranial base flattened as a result of the upward and forward migration of nasion and the upward and backward relocation of basion. The movement of basion was primarily due to differential growth recorded at the spheno-occipital synchondrosis. Sexual difference in the relative growth of this synchondrosis resulted in a longer and somewhat flatter male cranial base. Male and female velocity curves showed accelerations that coincide with their estimated age for the onset of puberty.     

Cephalometric and anthropomorphic observations of Binder's syndrome: a study of 19 patients

Binder's syndrome (maxillonasal dysplasia) is a disorder characterized by nasomaxillary hypoplasia. To ascertain the extent of underdevelopment of the midfacial skeleton and soft tissues, 19 of 29 patients with Binder's syndrome were retrospectively evaluated, both with cephalometry and anthropometry. Ten females and nine males were placed collectively into three age groups: 6 years, 10 years, and 16 to 17 years. Cephalometric measurements disclosed a short anterior cranial base (S-N), a normal length of the vertical maxilla (SE-PNS), a decreased horizontal maxilla (PNS-A, Co-A), a recessed orbitale (SNO), and a high-normal mandibular length (Co-Gn). Anthropometry revealed a large nasofrontal angle, acute nasal inclination and nasolabial angle, decreased nasal prominence (Sn-Prn), a decreased columellar length (C-Sn), and a normal vertical nose (N-Sn) and upper lip (Sn-Sto) length.     

Asymmetric vault modification in Hopi crania

Cradleboarding was practiced by numerous prehistoric and historic populations, including the Hopi. In this group, one result of cra-dleboarding was bilateral or asymmetric flattening of the posterior occipital. We test whether cradleboarding had significant effects on the morphology of the cranial vault, cranial base, and face. Additionally, we examine associations between direction of flattening and asymmetric craniofacial growth. A skeletal sample of Hopi from the Old Walpi site includes both nonmodified (N = 43) and modified individuals (N = 39). Three-dimensional coordinates of 53 landmarks were obtained using a diagraph. Thirty-six landmarks were used to define nine finite elements in the cranial vault, cranial base, and face. Finite element scaling was used to compare average nonmodified individuals, with averages of bilaterally, right, and left modified individuals. The significance of variation among “treatment” groups was evaluated using a bootstrap test. Pearson product-moment correlations test the association of asymmetry with direction of modification. Hopi cradleboarding has a significant effect on growth of the cranial vault, but does not affect morphology of the cranial base or face. Bilateral flattening of the cranial vault leads to decreased length and increased width of the cranial vault. Flattening of the right or left cranial vault results in ipsilaterally decreased length and width coupled with a corresponding increased length and width on the contralateral side of the cranial vault. There is a significant correlation of size asymmetry with direction of modification in the cranial vault, but not with size or shape change in the cranial base or face. © 1995 Wiley-Liss, Inc.     

Craniocervical morphology and posture in Australian aboriginals

The length of the spinal column as a percentage of stature is smaller in the Australian aboriginal than in most other ethnic groups (Abbie, 1957). It is conceivable that relative lengths of the cervical column might influence population differences in craniocervical posture and craniofacial morphology. The present study aimed to elucidate this relationship by comparing head posture and craniofacial morphology in Australian aboriginals to the same features in a previously studied sample of 120 Danish students (Solow and Tallgren, 1976). The aboriginal sample consisted of 42 young male adults from the Yuendumu settlement, Northern Territory, Australia. Cephalometric films of the natural head position were taken during a field trip to the settlement. The comparison comprised 18 postural and 61 morphological variables. In the aboriginals, the cervical column was shorter and had a less pronounced lordosis. The head was held about 3° lower, and the upper cervical column was 81/2° more forward inclined. As a consequence, the craniocervical angle was about 6° larger. Comparison of the craniofacial morphology in the two groups showed in the aboriginals a shorter upper facial height, a larger anterior lower facial height, and a larger vertical jaw relationship (NL/ML). The length of the posterior cranial base, s-ba, was 4 mm shorter (P <0.001) in the aboriginals, possibly developmentally related to the generally shorter spinal column in Australian aboriginals.     

The craniofacial pattern of the Lengua Indians of Paraguay

Lateral cephalometric headfilms of 30 male and 30 female Lengua Indians taken in the Chaco area of Paraguay were compared with a sample of 23 male and 25 female South African Caucasoids with excellent occlusion. The most obvious difference noted between the two population groups was the degree of prognathism evident in the Lengua. This was attributed to the generally shorter anterior cranial base in the latter group rather than to the size or forward positioning of their jaws. The significantly larger ANB (Subspinale, Nasion, Supramentale) angle observed in the Lengua was attributed to one or both of two factors, namely, the short anterior cranial base or the clockwise rotation (forward tipping) of the jaws relative to the anterior cranial base. Chinpoint position relative to the anterior cranial base in the Lengua is not much different from that of our Caucasoid sample. The lower incisor teeth in the Lengua, but not the upper ones, are more labially inclined than those of the Caucasoids.     

Soft-tissue facial morphometry from 6 years to adulthood: a three-dimensional growth study using a new modeling

A recently introduced three-dimensional computerized system with landmark representation of the soft-tissue facial surface allows noninvasive and fast quantitative study of facial growth. The aims of the present investigation were (1) to quantify growth changes in soft-tissue facial morphology, (2) to evaluate sex differences in growth patterns, and (3) to provide reference data for selected angular and linear measurements that could be of interest for the objective analysis of maxillofacial surgery or orthodontic patients. The three-dimensional coordinates of 22 standardized facial landmarks were automatically collected by automated infrared photogrammetry using the three-dimensional facial morphometry method in a mixed longitudinal and cross-sectional study, in which 2023 examinations were obtained in 1348 healthy nonpatient subjects between 6 years of age and young adulthood. Selected parameters (angles, linear distances, and ratios) were calculated and averaged for age and sex. Male values were compared with female values by means of Student's t test. Within each age group, linear distances were significantly larger in boys than in girls (p < 0.05) with some exceptions coinciding with the earlier female growth spurt, whereas angular measurements did not show a corresponding sexual dimorphism. Linear distances in girls had almost reached adult dimensions in the 12-to-13-year-old age group, whereas in boys a large increase was still to occur. This was most evident in the middle third of the face, where both sexes showed almost the same dimension and amount of growth up to the age of 13, with significant differences afterward, boys being larger than girls. On the contrary, in the lower third of the face, significant differences occurred throughout the whole investigated period, boys being always larger than girls. The male versus female angular comparison reflected the differential timing in attainment of adult proportions. The three-dimensional facial morphometry method allowed the noninvasive evaluation of a large sample of nonpatient subjects, leading to the definition of three-dimensional normative data about facial soft tissues. The method could supplement more invasive radiographic evaluations, allowing frequent examinations of children and adolescents before and during treatment, as well as in the follow-up.     

Sexual size dimorphism and allometric growth of Morelet's crocodiles in captivity

Few studies have conducted morphological analyses of crocodilians, and little information exists on differences between size-classes and sexes in Neotropical crocodilians. In this study, we measured nine morphological traits in 121 captive Morelet's crocodiles Crocodylus moreletii (81 females and 40 males). Our results revealed that individuals < 2 m total length do not exhibit sexual dimorphism in morphometric characteristics. However, for crocodiles over 2 m in length, males were significantly larger than females in terms of dorsal-cranial length, cranial width, snout width and snout-ventral length. In general, morphological traits demonstrated a strongly significant relationship with total length at the smaller size class of 150-200 cm length. However, in the highest size class of 250-300 cm length (large adult males), morphological traits were no longer significantly related with total length. Male crocodiles demonstrated allometric growth of cranial morphology with significantly greater increase in cranial width, snout width, and mid-snout width relative to total length at higher size classes. Morphological dimorphism and allometric growth may be associated with adaptive strategies for reproductive success.     

Long-term skeletal stability after maxillary advancement with distraction osteogenesis using a rigid external distraction device in cleft maxillary deformities

Rigid external distraction is a highly effective technique for correction of maxillary hypoplasia in patients with orofacial clefts. The clinical results after correction of sagittal maxillary deformities in both the adult and pediatric age groups have been stable. The purpose of this retrospective longitudinal cephalometric study was to review the long-term stability of the repositioned maxilla in cleft patients who underwent maxillary advancement with rigid external distraction. Between April 1, 1995, and April 1, 1999, 17 consecutive patients with cleft maxillary hypoplasia underwent maxillary advancement using rigid external distraction. There were 13 male patients and four female patients, with ages ranging from 5.2 to 23.6 years (mean, 12.6 years). After a modified complete high Le Fort I osteotomy and a latency period of 3 to 5 days, patients underwent maxillary advancement with rigid external distraction until proper facial convexity and dental overjet and overbite were obtained. After active distraction, a 3- to 4-week period of rigid retention was undertaken; this was followed by removable elastic retention for 6 to 8 weeks using, during sleep time, an orthodontic protraction face mask. Cephalometric radiographs were obtained preoperatively, after distraction, at 1 year after distraction, and 2 or more years after distraction. The mean follow-up was 3.3 years (minimum, 2.1 years; maximum, 5.3 years). The following measurements were obtained in each cephalogram: three linear horizontal and two linear vertical maxillary measurements, two angular craniomaxillary measurements, and one craniomandibular measurement. Differences between the preoperative and postoperative cephalometric values were analyzed by paired t tests (p < 0.05). The cephalometric analysis demonstrated postoperatively significant advancement of the maxilla. In addition, the mandibular plane angle opened 1.2 degrees after surgery. After the 1- to 3-year follow-up period, the maxilla was stable in the sagittal plane. Minimal anteroposterior growth was observed in the maxilla compared with that exhibited in the anterior cranial base. However, there was significant vertical maxillary growth over the 3-year observation period. The mandibular plane angle tended to decrease during the follow-up period. The cephalometric data from this study support the clinical impression of maxillary stability after maxillary advancement with rigid external distraction in cleft patients. This effective and stable technique is now considered for all pediatric patients with severe cleft maxillary hypoplasia and for adolescent and adult patients with moderate to severe deformities.     

Craniofacial dimensions in children in rural Oaxaca, southern Mexico: secular change, 1968-2000

The objective of this investigation was to analyze the underlying cause(s) of secular changes in craniofacial dimensions among indigenous children in an isolated community in Oaxaca, southern Mexico, between 1968-2000. Subjects were schoolchildren resident in a rural, agrarian, Zapotec-speaking community in the Valley of Oaxaca, previously characterized as mildly-to-moderately undernourished with growth-stunting in 1968 and 1978. In 2000, children had experienced a secular increase in height compared with two prior growth surveys. Four craniofacial dimensions (head length, head breadth, and bizygomatic and bigonial breadths) were measured during anthropometric surveys of schoolchildren aged 6-13 years in 1968, 1978, and 2000. Cephalic and zygomandibular indices were calculated. Samples by survey were: 1968, 151 males and 157 females; 1978, 179 males and 184 females; and 2000, 180 males and 186 females. The analysis was based on a total of 1,037 children. Multivariate analysis of covariance was used to assess secular trend effects, with height, age, and age2 as covariates by sex. Over the interval of 32 years, significant secular changes occurred in craniofacial dimensions and one index: 1) head length was shorter in boys and girls; 2) bizygomatic breadth was narrower in boys and girls; 3) head breadth increased over time only among girls; 4) brachycephalization increased significantly in a linear manner among both sexes; and 5) the zygomandibular index decreased significantly only in boys. Thus, the cranial complex remodeled to a shorter head length, both relatively (brachycephalization) and absolutely. Remodeling over time also resulted in a narrower face, with the midface changing at about the same rate as the lower face (i.e., mandible). Secular changes are generally recognized as multifactorial. Changes in the cephalic index and cranium over time in schoolchildren in an isolated rural agrarian Zapotec-speaking community in the Valley of Oaxaca suggest that the underlying forces for the secular change are associated: 1) decreased food (maize) coarseness or grit content (masticatory stress), and 2) relaxed natural selection, resulting in 3) a greater role for developmental plasticity.     

Sexual dimorphism in the growth of the cranium

The major sexual dimorphisms in body size appear at puberty but, by then, 95% of the growth of the cranium is completed. As sexual dimorphism in the cranium is as great as for other parts of the body, this suggests that it must appear at an earlier age, and that cranium/body size ratios for the two sexes will vary during growth. Results from a longitudinal study of Montreal children are used to investigate this phenomenon. The effect is expressed quantitatively by proportional growth and growth velocity curves, based on the final size of boys, which show that the dimorphism indeed makes an early appearance. The data are also analyzed on an age scale relative to the ages of peak growth velocity in stature, derived from the individual growth curves. This shows that although there is a minor pubertal spurt in growth for the external cranial dimensions of boys, it contributes relatively little to the final dimorphism in cranial size. To summarize this aspect of growth, an index of cephalization is calculated: head length × head width/stature. Cross-sectional standards for the change of the mean index with age show a linear decline for boys and girls until puberty, with a constant difference between them. After puberty, the index becomes equal in the two sexes. Individual development curves for the index are however not linear.     

The ontogeny of cranial base angulation in humans and chimpanzees and its implications for reconstructing pharyngeal dimensions

This paper examines differences in the processes by which the cranial base flexes in humans and extends in chimpanzees. In addition, we test the extent to which one can use comparisons of cranial base angles in humans and non-human primates to predict vocal tract dimensions. Four internal cranial base angles and one external cranial base angle were measured in a longitudinal sample of Homo sapiens and a cross-sectional sample of Pan troglodytes. These data show that the processes of cranial base angulation differ substantially in these species. While the human cranial base flexes postnatally in a rapid growth trajectory that is complete by two years, the cranial base in P. troglodytes extends postnatally in a more prolonged skeletal growth trajectory. These comparisons also demonstrate that the rate of cranial base angulation is comparable for different measures, but that angles which incorporate different anterior cranial base measurements correlate poorly. We also examined ontogenetic relationships between internal and external cranial base angles and vocal tract growth in humans to test the hypothesis that cranial base angulation influences pharyngeal dimensions and can, therefore, be used to estimate vocal tract proportions in fossil hominids. Our results indicate that internal and external cranial base angles are independent of the horizontal and vertical dimensions of the vocal tract. Instead, a combination of mandibular and palatal landmarks can be used to predict dimensions of the vocal tract in H. sapiens. The developmental contrasts in cranial base angulation between humans and non-human primates may have important implications for testing hypotheses about the relationship between cranial base flexion and other craniofacial dimensions in hominid evolution.     

Brain expansion and comparative prenatal ontogeny of the non-hominoid primate cranial base

The basicranium is the keystone of the primate skull, and understanding its morphological interdependence on surrounding soft-tissue structures, such as the brain, can reveal important mechanisms of skull development and evolution. In particular, several extensive investigations have shown that, across extant adult primates, the degree of basicranial flexion and petrous orientation are closely linked to increases in brain size relative to cranial base length. The aim of this study was to determine if an equivalent link exists during prenatal life. Specific hypotheses tested included the idea that increases in relative endocranial size (IRE5), relative infratentorial size (RIE), and differential encephalization (IDE) determine the degree of basicranial flexion and coronal petrous reorientation during non-hominoid primate fetal development. Cross-sectional fetal samples of Alouatta caraya (n=17) and Macaca nemestrina (n=24) were imaged using high-resolution magnetic resonance imaging (hrMRI). Cranial base angles (CBA), petrous orientations (IPA), base lengths, and endocranial volumes were measured from the images. Findings for both samples showed retroflexion, or flattening, of the cranial base and coronal petrous reorientation as well as considerable increases in absolute and relative brain sizes. Although significant correlations of both IRE5 and RIE were observed against CBA and IPA, the correlation with CBA was in the opposite direction to that predicted by the hypotheses. Variations of IDE were not significantly correlated with either angle. Correlations of IPA with IRE5 and RIE appeared to support the hypotheses. However, partial coefficients computed for all significant correlations indicated that changes to the fetal non-hominoid primate cranial base were more closely related to increases in body size than the hypothesized influence of relative brain enlargement. These findings were discussed together with those from a previous study of modern human fetuses.