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Life expectancies have increased dramatically over the last 100 years, affording greater opportunities to study the impact of age on adult craniofacial morphology. This article employs a novel application of established geometric morphometric methods to examine shape differences in adult regional facial bone curvature with age. Three-dimensional semilandmarks representing the curvature of the orbits, zygomatic arches, nasal aperture, and maxillary alveolar process were collected from a cross-sectional cranial sample of mixed sex and ancestry (male and female; African- and European-American), partitioned into three age groups (young adult = 18-39; middle-aged = 40-59 years; and elderly = 60+ years). Each facial region's semilandmarks were aligned into a common coordinate system via generalized Procrustes superimposition. Regional variation in shape was then explored via a battery of multivariate statistical techniques. Age-related shape differences were detected in the orbits, zygomatic arches, and maxillary alveolar process. Interactions between age, sex, and ancestry were also identified. Vector plots revealed patterns of superoinferior compression, lateral expansion, and posterior recession depending on the population/subpopulation, location, and age groups examined. These findings indicate that adult craniofacial curvature shape is not static throughout human life. Instead, age-related spatial modifications occur in various regions of the craniofacial skeleton. Moreover, these regional alterations vary not only through time, but across human populations and the sexes., (© 2010 Wiley-Liss, Inc.)

Background: The clinical observation has been made that the shape of the mandible changes with age in certain individuals. Because the shape and size of the mandible are so important to the human perception of youth, this observation was subjected to a pilot study., Methods: Longitudinal data available at the Bolton Brush Growth Study were evaluated. Only dentate individuals were included in the study. Serial frontal radiographs were analyzed from the same individual taken during youth and maturity for 16 individuals, eight female subjects and eight male subjects (n = 16). The mean age for youth was 16.2 years for female and male subjects. The mean age at maturity was 56.1 years for female subjects and 56.4 years for male subjects. Tracings were made of the mandibular border for each individual, at youth and at maturity. The only reliable way to analyze shape is the modern technique of geometric morphometric analysis, which was therefore used in this study. Other techniques, such as angular values and two-dimensional linear measurements, were dismissed because they have been shown to be unreliable for evaluating shape., Results: There was a statistically significant difference in shape for both male subjects and female subjects that occurred with age (p = 0.02 for female subjects and p = 0.001 for male subjects). The mandible continued to grow: the shape changed because some areas continued to grow faster than other areas. This is in accordance with the principle of differential growth of the facial skeleton., Conclusions: It is important for the cosmetic surgeon to evaluate the lower face before surgery and to understand that both bone and soft tissue can play a role in the appearance of the lower face in older individuals. A small lower face is highly attractive and conveys the impression of youth, and any soft-tissue procedure that can create the illusion of a diminutive lower face will improve the cosmetic result of the face lift procedure.

The aim of this study is to quantify patterns of age-related shape change in the human thorax using Procrustes superimposition. Landmarks (n=106) selected from anonymized computed tomography (CT) scans of 63 adult males free of skeletal pathology were used to describe the form of the rib cage. Multivariate linear regression was used to determine a relationship between landmark location and age. Linear and quadratic models were also investigated. A permutation test employing 1 x 10(5) random trials was used to assess the model significance for both model formulations. Linear relationships between the centroid size (CS) of a landmark set and the corresponding individual's height, weight, and BMI were conducted to enable scaling of the dimensionless results from the Procrustes analysis. A significance level of alpha=0.05 was used for all tests. The average age of the study subjects was 57.0+/-17.3 years. Complete landmark sets were obtained from most of the scans (44 of 63). The quadratic relationship between the age and landmark location was found to be significant (p=0.037), thereby establishing a relationship between the age and thoracic shape change. The linear relationship was mildly significant as well (p=0.073). Significant relationships between the centroid size of the dataset and subject weight, height and BMI were determined, with the best-correlated value being weight (p=0.002, R(2)=0.22). Landmark datasets calculated using the quadratic model exhibited shape change consistent with the clinical observations (increasing kyphosis and rounding of the thoracic cage). Procrustes superimposition represents a potential improvement in the approach used to generate computational models for injury biomechanics studies. The coefficients from the quadratic model are provided and can be used to generate the complete set of model landmark data points at a given age.

Motor vehicle accidents are the leading cause of death of people between one and thirty-four years of age in the U.S., and head trauma is a significant lethal injury in such cases. During a motor vehicle crash, the head often experiences blunt force trauma from impacts with seat backs, steering wheels, windows, and dashes. The resulting injuries can cause skull fractures, concussions, bleeding and swelling of the brain. Crash test dummies and finite element models are often used to study the nature and likelihood of injury during a crash, but these are currently based on scaled versions of a standard, 50th percentile male. This approach fails to accurately capture the size and shape variation in even the adult population, but may be especially inappropriate for modeling pediatric head injuries where, for instance, infants have fontanelles and reduced bone structure. In this presentation, an approach for modification of a finite element model of the human head based on 50th percentile male dimensions and representing the skull, brain, dura/CSF layer, and Falx Celebri, that will incorporate the anatomical and nonlinear morphological changes observed in pediatric skulls during ontogeny. Using 96 CT scans of normal pediatric skulls, landmark coordinate points are identified to map the changes in skull shape and size as aging occurs. The pediatric skull changes rapidly in size and shape during the first two years of age. Using this information, a pediatric finite element head model will be created, using parametric mesh generation software, to measure head injury in children in a motor vehicle crash.

To fully understand the effects of aging on the integrity of the normal skeleton, detailed geometric models are needed to complement material property data. The purpose of this research is to develop a predictive model for age-related changes in rib-cage geometry using the generalized Procrustes approach, an advanced method of shape analysis. This predictive model is coupled with the finite element method to isolate the effects age-related size and shape change have on the structural response of the rib cage. Using a relatively small sample set (n = 12), trends in the age-related size and shape change of the human thorax consistent with clinical observations are identified. Finite element models constructed from landmark datasets generated via the generalized Procrustes approach demonstrate a decrease with age in the energy absorbing capacity of the thorax during a blunt impact.