An ontogenetic framework linking locomotion and trabecular bone architecture with applications for reconstructing hominin life history.

The ontogeny of bipedal walking is considered uniquely challenging, due in part to the balance requirements of single limb support. Thus, locomotor development in humans and our bipedal ancestors may track developmental milestones including the maturation of the neuromuscular control system. Here, we examined the ontogeny of locomotor mechanics in children aged 1-8, and bone growth and development in an age-matched skeletal sample to identify bony markers of locomotor development. We show that step-to-step variation in mediolateral tibia angle relative to the vertical decreases with age, an indication that older children increase stability. Analyses of trabecular bone architecture in the distal tibia of an age-matched skeletal sample (the Norris Farms #36 archaeological skeletal collection) show a bony signal of this shift in locomotor stability. Using a grid of eleven cubic volumes of interest (VOI) in the distal metaphysis of each tibia, we show that the degree of anisotropy (DA) of trabecular struts changes with age. Intra-individual variation in DA across these VOIs is generally high at young ages, likely reflecting variation in loading due to kinematic instability. With increasing age, mean DA converges on higher values and becomes less variable across the distal tibia. We believe the ontogeny of distal tibia trabecular architecture reflects the development of locomotor stability in bipeds. We suggest this novel bony marker of development may be used to assess the relationship between locomotor development and other life history milestones in fossil hominins.

Ontogenetic Patterning of Human Subchondral Bone Microarchitecture in the Proximal Tibia.

High-resolution computed tomography images were acquired for 31 proximal human tibiae, age 8 to 37.5 years, from Norris Farms #36 cemetery site (A.D. 1300). Morphometric analysis of subchondral cortical and trabecular bone architecture was performed between and within the tibial condyles. Kruskal−Wallis and Wilcoxon signed-rank tests were used to examine the association between region, age, body mass, and each morphometric parameter. The findings indicate that age-related changes in mechanical loading have varied effects on subchondral bone morphology. With age, trabecular microstructure increased in bone volume fraction (p = 0.033) and degree of anisotropy (p = 0.012), and decreased in connectivity density (p = 0.001). In the subchondral cortical plate, there was an increase in thickness (p < 0.001). When comparing condylar regions, only degree of anisotropy differed (p = 0.004) between the medial and lateral condyles. Trabeculae in the medial condyle were more anisotropic than in the lateral region. This research represents an innovative approach to quantifying both cortical and trabecular subchondral bone microarchitecture in archaeological remains.

Skeletal biology over the life span: a view from the surfaces.

The biocultural interpretation of skeletal remains is based upon the foundation of skeletal biology. In this review we examine the current state of skeletal biology research outside of the mainstream anthropology literature. The focus is on the structural changes of bone development and growth, and modeling and repair in the four bone surfaces: periosteal, Haversian, endosteal, and trabecular. The pattern of skeletal changes is placed within the framework of the human life span. New perspectives and direction of research on the environmental, biological, and genetic influences on modeling and remodeling processes are discussed chronologically at each bone surface. Implications for biological anthropologists are considered. This approach emphasizes variation in skeletal biology as a dynamic record of development, maturity, and aging.

Patterns in ontogeny of human trabecular bone from SunWatch Village in the Prehistoric Ohio Valley: general features of microarchitectural change.

Although adult skeletal morphological variation is best understood within the framework of age-related processes, relatively little research has been directed towards the structure of and variation in trabecular bone during ontogeny. We report here new quantitative and structural data on trabecular bone microarchitecture in the proximal tibia during growth and development, as demonstrated in a subadult archaeological skeletal sample from the Late Prehistoric Ohio Valley. These data characterize the temporal sequence and variation in trabecular bone structure and structural parameters during ontogeny as related to the acquisition of normal functional activities and changing body mass. The skeletal sample from the Fort Ancient Period site of SunWatch Village is composed of 33 subadult and three young adult proximal tibiae. Nondestructive microCT scanning of the proximal metaphyseal and epiphyseal tibia captures the microarchitectural trabecular structure, allowing quantitative structural analyses measuring bone volume fraction, degree of anisotropy, trabecular thickness, and trabecular number. The microCT resolution effects on structural parameters were analyzed. Bone volume fraction and degree of anisotropy are highest at birth, decreasing to low values at 1 year of age, and then gradually increasing to the adult range around 6-8 years of age. Trabecular number is highest at birth and lowest at skeletal maturity; trabecular thickness is lowest at birth and highest at skeletal maturity. The results of this study highlight the dynamic sequential relationships between growth/development, general functional activities, and trabecular distribution and architecture, providing a reference for comparative studies.

Asymmetry in the Cortical and Trabecular Bone of the Human Humerus During Development.

Many studies have noted that the bones of the human upper limb display bilateral asymmetry, commonly linking this asymmetry in external and internal morphology to handedness and lateralization. Few studies, however, have attempted to track asymmetry throughout ontogeny. This study assesses the ontogenetic development of cortical and trabecular bone asymmetry in the humerus. We predict that directional asymmetry in structural properties will emerge in concert with hand preference and increased activity levels during the juvenile period. Paired humeri from 57 individuals from the Norris Farms #36 archaeological skeletal collection ranging in age from neonate to adult were used in the current study. Cortical bone cross-sectional properties and three-dimensional trabecular bone structure were quantified from microcomputed tomography data. The results indicate significant absolute asymmetry in all measured cortical and trabecular bone variables across all ages. Trabecular bone displays significantly higher absolute asymmetry than cortical bone. Contrary to expectations, however, this study found very little evidence for significant directional asymmetry in humeral length and cortical or trabecular bone variables, except in adults. The presence of significant absolute asymmetry in all age groups, and the lack of significant directional asymmetry in almost all variables at all ages, suggests that structural differences due to higher levels of habitual loading in the dominant arm are overlain on a template of potentially significant existing asymmetry. Anat Rec, 301:1012-1025, 2018. © 2017 Wiley Periodicals, Inc.

Development of cortical bone geometry in the human femoral and tibial diaphysis.

Ontogenetic growth processes in human long bones are key elements, determining the variability of adult bone structure. This study seeks to identify and describe the interaction between ontogenetic growth periods and changes in femoral and tibial diaphyseal shape. Femora and tibiae (n = 46) ranging developmentally from neonate to skeletally mature were obtained from the Norris Farms No. 36 archeological skeletal series. High-resolution X-ray computed tomography scans were collected. Whole-diaphysis cortical bone drift patterns and relative bone envelope modeling activity across ages were assessed in five cross-sections per bone (total bone length: 20%, 35%, 50%, 65%, and 80%) by measuring the distance from the section centroid to the endosteal and periosteal margins in eight sectors using ImageJ. Pearson correlations were performed to document and interpret the relationship between the cross-sectional shape (Imax /Imin ), total subperiosteal area, cortical area, and medullary cavity area for each slice location and age for both the femur and the tibia. Differences in cross-sectional shape between age groups at each cross-sectional position were assessed using nonparametric Mann-Whitney U tests. The data reveal that the femoral and tibial midshaft shape are relatively conserved throughout growth; yet, conversely, the proximal and distal femoral diaphysis and proximal tibial diaphysis appear more sensitive to developmentally induced changes in mechanical loading. Two time periods of accelerated change are identified: early childhood and prepuberty/adolescence.