Variation In Trabecular Structure Research Articles

Growth and development of trabecular structure in the calcaneus of Japanese macaques (Macaca fuscata) reflects locomotor behavior, life history, and neuromuscular development.

Bone structure dynamically adapts to its mechanical environment throughout ontogeny by altering the structure of trabecular bone, the three‐dimensional mesh‐like structure found underneath joint surfaces. Trabecular structure, then, can provide a record of variation in loading directions and magnitude; and in ontogenetic samples, it can potentially be used to track developmental shifts in limb posture. We aim to broaden the analysis of trabecular bone ontogeny by incorporating interactions between ontogenetic variation in locomotor repertoire, neuromuscular maturation, and life history. We examine the associations between these variables and age‐related variation in trabecular structure in the calcaneus of Japanese macaques (Macaca fuscata). We used high‐resolution micro‐computed tomography scanning to image the calcaneus in a cross‐sectional sample of 34 juvenile M. fuscata aged between 0 and 7 years old at the Primate Research Institute, Japan. We calculated whole bone averages of standard trabecular properties and generated whole‐bone morphometric maps of bone volume fraction and Young’s modulus. Trabecular structure becomes increasingly heterogeneous in older individuals. Bone volume fraction (BV/total volume [TV]) decreases during the first month of life and increases afterward, coinciding with the onset of independent locomotion in M. fuscata. At birth, primary Young’s modulus is oriented orthogonal to the ossification center, but after locomotor onset bone structure becomes stiffest in the direction of joint surfaces and muscle attachments. Age‐related variation in bone volume fraction is best predicted by an interaction between the estimated percentage of adult brain size, body mass, and locomotor onset. To explain our findings, we propose a model where interactions between age‐related increases in body weight and maturation of the neuromuscular system alter the loading environment of the calcaneus, to which the internal trabecular structure dynamically adapts. This model cannot be directly tested based on our cross‐sectional data. However, confirmation of the model by longitudinal experiments and in multiple species would show that trabecular structure can be used both to infer behavior from fossil morphology and serve as a valuable proxy for neuromuscular maturation and life history events like locomotor onset and the achievement of an adult‐like gait. This approach could significantly expand our knowledge of the biology and behavior of fossil species.

Trabecular bone functional adaptation and sexual dimorphism in the human foot.

Trabecular bone adapts to the strains placed upon the skeleton during life. Anthropological research has largely focused on linking variation in primate trabecular bone to locomotor mode, to provide a context for interpreting fossil morphology. However, intraspecific variation and its underlying mechanisms are still poorly understood. Trabecular bone is influenced by a variety of factors including body mass, age, diet, temperature, genetics, sex, and behavior. Before trabecular structure can be used to infer habitual behavior in the past, the effects of these factors need to be understood. In this article, we examine variation in trabecular structure in the human foot in four archaeological groups in relation to inferred levels of terrestrial mobility and sex. We use high-resolution μCT scanning to examine variation in trabecular structure in the human calcaneus, talus, and first metatarsal in two relatively mobile and two relatively sedentary archaeological groups. The four population samples show similar patterns of trabecular variation throughout the foot, influenced by mechanical loading. Greater inferred terrestrial mobility is associated with greater bone volume fraction and thicker, more widely spaced, and less interconnected trabeculae. However, contrary to diaphyseal rigidity, only limited sexual dimorphism was found in trabecular structure. This work demonstrates that trabecular bone may serve as a useful proxy of habitual behavior in the fossil and archaeological record when other factors are carefully considered. However, the mechanisms underlying sexual dimorphism are not well understood. As such, inferring sex differences in habitual behavior is currently challenging.

Trabecular architecture and joint loading of the proximal humerus in extant hominoids, Ateles, and Australopithecus africanus.

Several studies have investigated potential functional signals in the trabecular structure of the primate proximal humerus but with varied success. Here, we apply for the first time a "whole-epiphyses" approach to analysing trabecular bone in the humeral head with the aim of providing a more holistic interpretation of trabecular variation in relation to habitual locomotor or manipulative behaviors in several extant primates and Australopithecus africanus. We use a "whole-epiphysis" methodology in comparison to the traditional volume of interest (VOI) approach to investigate variation in trabecular structure and joint loading in the proximal humerus of extant hominoids, Ateles and A. africanus (StW 328). There are important differences in the quantification of trabecular parameters using a "whole-epiphysis" versus a VOI-based approach. Variation in trabecular structure across knuckle-walking African apes, suspensory taxa, and modern humans was generally consistent with predictions of load magnitude and inferred joint posture during habitual behaviors. Higher relative trabecular bone volume and more isotropic trabeculae in StW 328 suggest A. africanus may have still used its forelimbs for arboreal locomotion. A whole-epiphysis approach to analysing trabecular structure of the proximal humerus can help distinguish functional signals of joint loading across extant primates and can provide novel insight into habitual behaviors of fossil hominins.

Trabecular bone patterning across the human hand

Hand bone morphology is regularly used to link particular hominin species with behaviors relevant to cognitive/technological progress. Debates about the functional significance of differing hominin hand bone morphologies tend to rely on establishing phylogenetic relationships and/or inferring behavior from epigenetic variation arising from mechanical loading and adaptive bone modeling. Most research focuses on variation in cortical bone structure, but additional information about hand function may be provided through the analysis of internal trabecular structure. While primate hand bone trabecular structure is known to vary in ways that are consistent with expected joint loading differences during manipulation and locomotion, no study exists that has documented this variation across the numerous bones of the hand. We quantify the trabecular structure in 22 bones of the human hand (early/extant modern Homo sapiens) and compare structural variation between two groups associated with post-agricultural/industrial (post-Neolithic) and foraging/hunter-gatherer (forager) subsistence strategies. We (1) establish trabecular bone volume fraction (BV/TV), modulus (E), degree of anisotropy (DA), mean trabecular thickness (Tb.Th) and spacing (Tb.Sp); (2) visualize the average distribution of site-specific BV/TV for each bone; and (3) examine if the variation in trabecular structure is consistent with expected joint loading differences among the regions of the hand and between the groups. Results indicate similar distributions of trabecular bone in both groups, with those of the forager sample presenting higher BV/TV, E, and lower DA, suggesting greater and more variable loading during manipulation. We find indications of higher loading along the ulnar side of the forager sample hand, with high site-specific BV/TV distributions among the carpals that are suggestive of high loading while the wrist moves through the ‘dart-thrower's’ motion. These results support the use of trabecular structure to infer behavior and have direct implications for refining our understanding of human hand evolution and fossil hominin hand use.

A Novel Morphological Model of Trabecular Bone Based on the Gyroid

Human trabecular bone is known to be structurally very complex. The geometrical distribution of trabecular bone has major effects on its ability to perform its physiological function of load-bearing efficiently. Idealized unit cell models are very helpful in understanding the significance of micro-level properties on macro-level behavior. There is a need for a simple method to model trabecular bone, such that micro-level phenomena (like buckling) can be studied. We investigate a new model for trabecular bone, based on a minimal surface solid called a gyroid. The gyroid-based model is computationally easy to implement, and generates structures that possess strong morphometric and mechanical resemblance to real trabecular bone. We generated gyroid models for a range of volume fractions, representing trabecular bone samples obtained from various anatomic sites and ages. Finite element analysis was performed to obtain the mechanical properties of the gyroid structures. We calculated the small-strain elastic moduli values for each of the gyroid models and plotted these against corresponding apparent density. A power-law relationship was obtained for the gyroid models, in accordance with published studies on real trabecular bone mechanical behavior. The results showed that the gyroid could provide a suitable model for studying the effects of variations in trabecular structure on macro-level bone behavior.

Regional variations of gender-specific and age-related differences in trabecular bone structure of the distal radius and tibia

Regional variation in trabecular structure across axial sections is often obscured by the conventional global analysis, which takes an average value for the entire trabecular compartment. The objective of this study is to characterize spatial variability in trabecular structure within a cross-section at the distal radius and tibia, and gender and age effects using in vivo high-resolution peripheral quantitative computed tomography (HR-pQCT). HR-pQCT images of the distal radius and tibia were acquired from 146 healthy individuals aged 20–78 years. Trabecular bone volume fraction (BV/TV), number (Tb.N), thickness (Tb.Th), separation (Tb.Sp), and heterogeneity (Tb.1/N.SD) were obtained in a total of 11 regions—the entire trabecular compartment (the global means), inner, outer, and eight defined subregions. Regional variations were examined with respect to the global means, and compared between women and men, and between young (20–29 years old) and elderly (65–79 years old) adults. Substantial regional variations in trabecular bone structure at the distal radius and tibia were revealed (e.g. BV/TV varied −40% to + 57% and −59% to + 100% of the global means, respectively, for elderly women). The inner-lateral (IL) subregion had low BV/TV, Tb.N, and Tb.Th, and low Tb.Sp and Tb.1/N.SD at both sites; the opposite was true in the outer-anterior (OA) subregion at the distal radius and the outer-medial (OM) and -posterior (OP) subregions at the distal tibia. Gender differences were most pronounced in the inner-anterior (IA) subregion compared to the other regions or the global mean differences at both sites. Trabecular structure associated with age and differed between young and elderly adults predominantly in the inner-posterior (IP) subregion at the distal radius and in the IL and IA subregions at the distal tibia; on the other hand, it remained unchanged in the OA subregion at the distal radius and in the OM subregion at the distal tibia for both women and men. This study demonstrated that not only the conventional global analysis can obscure regional differences, but also assuming bone status from that of smaller subregion may introduce a confounding sampling error. Therefore, a combined approach of investigating the entire region, each subregion, and the cortical compartment may offer more complete information.

Structural and Mechanical Properties of Mandibular Condylar Bone

The trabecular bone of the mandibular condyle is structurally anisotropic and heterogeneous. We hypothesized that its apparent elastic moduli are also anisotropic and heterogeneous, and depend on trabecular density and orientation. Eleven condyles were scanned with a micro-CT system. Volumes of interest were selected for the construction of finite element models. We simulated compressive and shear tests to determine the principal mechanical directions and the apparent elastic moduli. Compressive moduli were relatively large in directions acting in the sagittal plane, and small in the mediolateral direction. The degree of mechanical anisotropy ranged from 4.7 to 10.8. Shear moduli were largest in the sagittal plane and smallest in the transverse plane. The magnitudes of the moduli varied with the condylar region and were proportional to the bone volume fraction. Furthermore, principal mechanical direction correlated significantly with principal structural direction. It was concluded that variation in trabecular structure coincides with variation in apparent mechanical properties.

Jaw trabecular pattern varies with location, gender, age, and weight

Background. Osteoporosis, one of the most common disorders in the elderly, results in over 1.5 million fractures of the hip, spine, and other sites each year in the US. Osteoporosis results in systemic loss of bone mass and microarchitectural deterioration. Dental radiographs potentially offer a means of screening for osteoporosis as they are commonly made on adults and reveal bone structure. Knowledge of anatomic variations in trabecular structure will allow optimal selection of regions to measure for risk analysis.

Quantification of trabecular structure in the distal femur using magnetic resonance phase imaging.

A new approach for quantifying trabecular bone tissue using the phase images of a simple gradient-echo sequence is presented. The proposed method is based on the hypothesis that the differences in susceptibility between bone and bone marrow cause magnetic field (i.e., precession phase) variations between the image voxels. Phase images of the distal femur were obtained in vivo and characterised with the use of the phase variance. Computer simulations and experimental results indicate that the distribution of the phases varies with echo time and image resolution, as expected. Keeping these fixed, however, the phase variance is found to strongly reflect variations in trabecular structure.

Variation in trabecular structure of vertebrae with age.

Radiographs of vertical sections cut through the centre of vertebral bodies and the middle of the remaining left half vertebra were used in a study of the structural changes of cancellous bone with age. The trabeculae were counted in two ways: (a) the number of transverse trabeculae which crossed the mid-line of the vertebra, and (b) all bone spicules in the central area of a specimen. Transverse trabeculae diminished steadily throughout life in the mid-section, but were not affected in the lateral section. The area count in the mid-section showed no change in the trabeculae until 50 years, after which a progressive loss occurred. In the lateral section no change was observed in the area count.