Variation, mosaicism and degeneracy in the hominin foot.

The fossil record is scarce and incomplete by nature. Animals and ecological processes devour soft tissue and important bony details over time and, when the dust settles, we are faced with a patchy record full of variation. Fossil taxa are usually defined by craniodental characteristics, so unless postcranial bones are found associated with a skull, assignment to taxon is unstable. Naming a locomotor category based on fossil bone morphology by analogy to living hominoids is not uncommon, and when no single locomotor label fits, postcrania are often described as exhibiting a “mosaic” of traits. Here, we contend that the unavoidable variation that characterises the fossil record can be described far more rigorously based on extensive work in human neurobiology and neuroanatomy, movement sciences and motor control and biomechanics research. In neurobiology, degeneracy is a natural mechanism of adaptation allowing system elements that are structurally different to perform the same function. This concept differs from redundancy as understood in engineering, where the same function is performed by identical elements. Assuming degeneracy, structurally different elements are able to produce different outputs in a range of environmental contexts, favouring ecological robusticity by enabling adaptations. Furthermore, as degeneracy extends to genome level, genetic variation is sustained, so that genes which might benefit an organism in a different environment remain part of the genome, favouring species’ evolvability.

Macrophage-Osteoclast Associations: Origin, Polarization, and Subgroups

Cellular associations in the bone microenvironment are involved in modulating the balance between bone remodeling and resorption, which is necessary for maintaining a normal bone morphology. Macrophages and osteoclasts are both vital components of the bone marrow. Macrophages can interact with osteoclasts and regulate bone metabolism by secreting a variety of cytokines, which make a significant contribution to the associations. Although, recent studies have fully explored either macrophages or osteoclasts, indicating the significance of these two types of cells. However, it is of high importance to report the latest discoveries on the relationships between these two myeloid-derived cells in the field of osteoimmunology. Therefore, this paper reviews this topic from three novel aspects of the origin, polarization, and subgroups based on the previous work, to provide a reference for future research and treatment of bone-related diseases.

Significant Asymmetry of the Bilateral Upper Extremities of a Skeleton Excavated from the Mashiki-Azamabaru Site, Okinawa Island, Japan

The human skeleton of a young adult male with marked asymmetry of the bilateral upper extremities was excavated from the Mashiki-Azamabaru site (3000–2000 BCE) on the main island of Okinawa in the southwestern archipelago of Japan. The skeleton was buried alone in a corner of the cemetery. In this study, morphological and radiographic observations were made on this skeleton, and the pathogenesis of the bone growth disorder observed in the left upper limb was discussed. The maximum diameter of the midshaft of the humerus was 13.8 mm on the left and 21.2 mm on the right. The long bones comprising the left upper extremity lost the structure of the muscle attachments except for the deltoid tubercle of the humerus. The bone morphology of the right upper extremity and the bilateral lower extremities was maintained and was close to the mean value of females from the Ohtomo site in northwestern Kyushu, Japan, during the Yayoi period. It is assumed that the anomalous bone morphology confined to the left upper extremity was secondary to the prolonged loss of function of the muscles attached to left extremity bones. In this case, birth palsy, brachial plexus injury in childhood, and acute grey matter myelitis were diagnosed. It was suggested that this person had survived into young adulthood with severe paralysis of the left upper extremity due to injury or disease at an early age.

Match of the Bimaxillary Basal Bone Arches and Its Variations among Individuals

Introduction. This study is aimed at illustrating the bimaxillary basal bone contours, to clarify the match of the basal bone arches of the upper and lower, especially the posterior segments, including the second molar and retromolar region. Methods. Based on 100 cone-beam computed tomography (CBCT) images (50 males and 50 females), we obtained 100 pairs of basal bone arches, which were the horizontal inner cortex contours passing the furcation of the first molar paralleled to the lower occlusal plane. The Generalized Procrustes Analysis (GPA) was applied to depict average contours and calculate the ratio and difference width of both upper and lower dental arches in different positions. Variations of the basal bone morphology among individuals were revealed using Principal Component Analysis (PCA). Results. The width discrepancy occurred at 7-7 segment (male: upper 65.62 mm and lower 68.81 mm and female: upper 62.98 mm and lower 68.38 mm) and the retromolar region (male: upper 64.67 mm and lower 71.96 mm and female: upper 62.34 mm and lower 71.44 mm). The ratio ( p = 0.006 ) and difference value ( p = 0.009 ) of 7-7 segment and the ratio of retromolar region ( p = 0.044 ) differed in genders. Setting 2 mm overjet, the upper basal bone arch was wider than the lower by approximate 2 mm on both sides, except the second molar and retromolar region. According to PCA, the variation of basal bone arches appeared mainly at terminal segments. Conclusions. For both male and female, the bimaxillary basal bone matched except terminal segments. Mismatch of female bimaxillary posterior basal bone was more pronounced than male. The basal bone arches of male were wider and longer than that of female.

Three-Dimensional Morphometry of Normal Japanese Knees For Designing Total Knee Arthroplasty

Background: To examine racial and sex-related differences in bone morphology and to determine whether it is necessary to take sex-related and ethnic differences into account in designing artificial knee joints.Methods: Hundred Japanese women normal knees, 88 Japanese men normal knees, and 18 Caucasian women normal knees were examined. Knee joints were measured to enable selection and design of artificial knee joints based on assumed bone resection face dimensions in TKA. Results: The dimensional measurements were performed by reading the three-dimensional CT based bone model. F-MAP/F-ML and F-LAP/F-ML relative to F-ML dimensions and T-MAP/T-ML and T-LAP/T-ML relative to T-ML dimensions were determined in both sexes. Results: In both sexes and in both the femur and tibia, the value increased with decreasing size. Therefore, the width narrowed with decreasing size. It was considered that the width may be narrower in women than in men because women have smaller bone sizes than men. The matching ratio was considered to improve as the aspect ratio is adjusted according to the size when an artificial joint is designed. There were no significant differences in the measured sagittal flexion angle between the Japanese and Caucasian women. Conclusion: The individual differences were greater than the racial differences; therefore, we consider that there is no significant need to change the shape of the artificial knee joint according to racial differences in bone morphology.

A way to break bones? The weight of intuitiveness

During the Paleolithic period, bone marrow extraction was an essential source of fat nutrients for hunter-gatherers especially throughout cold and dry seasons. This is attested by the recurrent findings of percussion marks in osteological material from anthropized archaeological levels. Among them some showed indicators that the marrow extraction process was part of a butchery cultural practice, meaning that the inflicted fracturing gestures and techniques were recurrent, standardized and counter-intuitive. In order to assess the weight of the counter-intuitive factor in the percussion mark pattern distribution, we carried out an experiment that by contrast focuses on the intuitive approach of fracturing bones to extract marrow, involving individual without experience in this activity. We wanted to evaluate the influence of bone morphology and the individuals’ behaviour on the distribution of percussion marks. Twelve experimenters broke 120 limb bones, a series of 10 bones per individual. During the experiment, information concerning the fracture of the bones as well as individual behaviour was collected and was subsequently compared to data from the laboratory study of the remains. Then, we applied an innovative GIS (Geographic Information System) method to analyze the distribution of percussion marks to highlight recurrent patterns. Results show that in spite of all the variables there is a high similarity in the distribution of percussion marks which we consider as intuitive patterns. The factor influenced the distribution for the humerus, radius-ulna and tibia series is the bone morphology, while for the femur series individual behaviour seems to have more weight in the distribution. To go further in the subject we need to compare the intuitive models with the distributions of percussion marks registered in fossil assemblages. Thus, it would be possible to propose new hypotheses on butchering practices based on the results presented in this work.

Cartilage Thickness and Bone Shape Variations as a Function of Sex, Height, Body Mass, and Age in Adult Knees.

The functional relationship between bone and cartilage is modulated by mechanical factors. Scarce data exist on the relationship between bone shape and the spatial distribution of cartilage thickness. This study has three aims: first, to characterise the coupled variation in knee bone morphology and cartilage thickness distributions in knees with healthy cartilage. The second aim was to investigate this relationship as a function of sex, height, body mass, and age. The third aim was to characterise the morphological differences between males and females. MR images of 51 adult knees (28.4±4.1 years) were obtained from a previous study and used to train a statistical shape model of the femur, tibia, and patella and their cartilages. Five linear regression models were fitted to characterise morphology as a function of sex, height, body mass, and age. A logistic regression classifier was fitted to characterise morphological differences between males and females, and 10-fold cross-validation was performed to evaluate the models’ performance. Our results showed that cartilage thickness and its distribution was coupled to bone morphology, including both size (mode 1) and shape variations (mode 2 onwards). The first three shape modes captured over 90% of the variance and described the overall size, diaphysis size, femoral shaft angle, and corresponding changes to the spatial distribution of the cartilages. These modes were sex-linked (p < .0001, p < .05, p < .01, for modes 1, 2, and 3 respectively) and could classify sex with an accuracy of 94.1% (95% CI [83.8%, 98.8%]). Height was a predictor of joint size (p <. 0001) and diaphysis size (p < .05). Body mass was a predictor of joint size (p < .1) and femoral shaft angle (p < .1). Age was not correlated with any of the modes. This study demonstrated the coupled relationship between bone and cartilage, showing that cartilage is thicker with increased bone size, diaphysis size, and decreased femoral shaft angle. Our findings show that sexual dimorphism is strong in these first three modes, and that bone shape and cartilage thickness at the joint are strongly correlated with height but weakly correlated with mass.