Intraskeletal variability in bone mass

For methodological or other reasons, a variety of skeletal elements are analyzed and subsequently used as a basis for describing general bone loss and mass. However, bone loss and mass may not be uniform within and among skeletal elements of the same individual because of biomechanical factors. We test the hypothesis that a homogeneity in bone mass exists among skeletal elements of the same individual. Measures indicative of bone mass were calculated from the midshafts of six skeletal elements from the same individuals (N = 41). The extent of intraskeletal variability in bone mass (relative cortical area) was then examined for the entire sample, according to age, sex, and pathological status. The results of the analysis showed that all measures reflect a heterogeneity in bone mass (P 相似文献   

Decreased pericellular matrix production and selection for enhanced cell membrane repair may impair osteocyte responses to mechanical loading in the aging skeleton

Transient plasma membrane disruptions (PMD) occur in osteocytes with in vitro and in vivo loading, initiating mechanotransduction. The goal here was to determine whether osteocyte PMD formation or repair is affected by aging. Osteocytes from old (24 months) mice developed fewer PMD (?76% females, ?54% males) from fluid shear than young (3 months) mice, and old mice developed fewer osteocyte PMD (?51%) during treadmill running. This was due at least in part to decreased pericellular matrix production, as studies revealed that pericellular matrix is integral to formation of osteocyte PMD, and aged osteocytes produced less pericellular matrix (?55%). Surprisingly, osteocyte PMD repair rate was faster (+25% females, +26% males) in osteocytes from old mice, and calcium wave propagation to adjacent nonwounded osteocytes was blunted, consistent with impaired mechanotransduction downstream of PMD in osteocytes with fast PMD repair in previous studies. Inducing PMD via fluid flow in young osteocytes in the presence of oxidative stress decreased postwounding cell survival and promoted accelerated PMD repair in surviving cells, suggesting selective loss of slower‐repairing osteocytes. Therefore, as oxidative stress increases during aging, slower‐repairing osteocytes may be unable to successfully repair PMD, leading to slower‐repairing osteocyte death in favor of faster‐repairing osteocyte survival. Since PMD are an important initiator of mechanotransduction, age‐related decreases in pericellular matrix and loss of slower‐repairing osteocytes may impair the ability of bone to properly respond to mechanical loading with bone formation. These data suggest that PMD formation and repair mechanisms represent new targets for improving bone mechanosensitivity with aging.     

F-81 skeleton from Wadi Mataha, Jordan, and its bearing on human variability in the Epipaleolithic of the Levant

The discovery of a Middle Epipaleolithic adult skeleton (F-81) at the site of Wadi Mataha in southern Jordan provides new insights into human variability in the Epipaleolithic of the Levant. This paper analyzes the skeletal morphology of Wadi Mataha F-81 in the context of other Epipaleolithic remains from Jordan and Israel to assess the current evidence for morphological variability throughout this period. The F-81 skeleton shares morphological features with earlier Epipaleolithic skeletons from Ohalo and Nahal Ein Gev, and later Natufian populations. Despite the morphological similarities, F-81 extends the range of known variability prior to the Natufian with its unusually small stature and unique combination of morphological characteristics. High levels of cranial and postcranial robusticity suggest that the F-81 individual was physically active and terrestrially mobile. Pronounced bilateral asymmetry in the upper limb suggests significant lateralization of habitual activity. In the context of Epipaleolithic remains, the F-81 skeleton provides preliminary evidence for greater morphological variability, terrestrial mobility, and lateralized habitual behavior prior to the Natufian, and skeletal gracilization between the Middle and Late Epipaleolithic in the Levant.     

Coexistence of melorheostosis and DISH in a female skeleton from Magna Graecia (Sixth Century BC)

This paper reports on a case of massive hyperostotic alterations observed in the skeleton of an adult woman from the necropolis of Montescaglioso Belvedere (Basilicata, Southern Italy) attributed to the Enotrian culture and dated to the 6th century BC. Hyperostotic changes involve joints, the vertebral column, and the lower limbs. In particular, the large flowing ossification in both the thoracic (T6-T10) and lumbar (L2-L5) tracts, the sacralization of L5, accompanied by sacroiliac fusion on the left side, and the proliferative bone production on both the metaphyseal portion of the left tibia and the left third metatarsal are described. The vertebral antero-lateral ossification and the sacroiliac fusion support a diagnosis of diffuse idiopathic skeletal hyperostosis (DISH), while the flowing bone formation on the lower limbs supports a diagnosis of melorheostosis. The pathological conditions described here were already described in the literature, but this is the first reported case of the coexistence of DISH and the very rare melorheostosis. Furthermore, the skeleton from Montescaglioso Belvedere represents the first case of this disease described for ancient Europe, therefore adding a valuable contribution to the reconstruction of the antiquity and distribution of skeletal dysplasias.     

The effects of total hip arthroplasty on the structural and biomechanical properties of adult bone

The responsiveness of bone to mechanical stimuli changes throughout life, with adaptive potential generally declining after skeletal maturity is reached. This has led some to question the importance of bone functional adaptation in the determination of the structural and material properties of the adult skeleton. A better understanding of age-specific differences in bone response to mechanical loads is essential to interpretations of long bone adaptation. The purpose of this study is to examine how the altered mechanical loading environment and cortical bone loss associated with total hip arthroplasty affects the structural and biomechanical properties of adult bone at the mid-shaft femur. Femoral cross sections from seven individuals who had undergone unilateral total hip arthroplasty were analyzed, with intact, contralateral femora serving as an approximate internal control. A comparative sample of individuals without hip prostheses was also included in the analysis. Results showed a decrease in cortical area in femora with prostheses, primarily through bone loss at the endosteal envelope; however, an increase in total cross-sectional area and maintenance of the parameters of bone strength, I(x), I(y), and J, were observed. No detectable differences were found between femora of individuals without prostheses. We interpret these findings as an adaptive response to increased strains caused by loading a bone previously diminished in mass due to insertion of femoral prosthesis. These results suggest that bone accrued through periosteal apposition may serve as an important means by which adult bone can functional adapt to changes in mechanical loading despite limitations associated with senescence.     

Obstetric implications of neanderthal robusticity and bone density

Neanderthal pelvic morphology is not well understood, despite the recent find and analysis of the Kebara 2 pelvis. Many of the proposed hypotheses focus on the possible need for a larger birth canal. A previously unexplored aspect involves possible direct obstetric implications of bone robusticity and density. These characteristics ocan affect obstetrics in modern humans, especially the molding of the neonate's head during parturition: engineering studies have shown that denser neonate cranial bones undergo less deformation, and thicker (more robust) cranial bones would also be expected to deform less during the birth process. These bone characteristics may also result in a less flexible birth canal. Thus, more robust or denser bones could result in the need for a larger birth canal or a smaller neonate head, due to decreased flexibility. Examples from modern populations are discussed and the conclusions applied to Neanderthals, who are known to have had high bone robusticity and may have had high bone density, given their heavy musculature. (A positive association between muscle mass and bone density has been observed repeatedly in modern humans.) We conclude that bone robusticity and density may have obstetrical implications for Neanderthals, with particular importance for neonate head molding during birth.     

Articular area responses to mechanical loading: effects of exercise, age, and skeletal location.

How reliable are reconstructions of body mass and joint function based on articular surface areas? While the dynamic relationship between mechanical loading and cross‐sectional geometry in long bones is well‐established, the effect of loading on the subchondral articular surface area of epiphyses (hereafter, articular surface area, or ASA) has not been experimentally tested. The degree to which ASA can change in size and shape is important, because articular dimensions are frequently used to estimate body mass and positional behavior in fossil species. This study tests the hypothesis that mechanical loading influences ASA by comparing epiphyses of exercised and sedentary sheep from three age categories: juvenile, subadult, and adult (n = 44). ASA was measured on latex molds of subchondral articular surfaces of 10 epiphyses from each sheep. Areas were standardized by body mass, and compared to diaphyseal cross‐sectional geometrical data. Nonparametric statistical comparisons of exercised and control individuals found no increases in ASA in response to mechanical loading in any age group. In contrast, significant differences in diaphyseal cross‐sectional geometry were detected between exercised and control groups, but mostly in juveniles. The conservatism of ASA supports the hypothesis that ASA is ontogenetically constrained, and related to locomotor behavior at the species level and to body mass at the individual level, while variations in diaphyseal cross‐sectional geometry are more appropriate proxies for individual variations in activity level. Am J Phys Anthropol 116:266–277, 2001. © 2001 Wiley‐Liss, Inc.     

Segmental bone replacement via patient‐specific,three‐dimensional printed bioresorbable graft substitutes and their use as templates for the culture of mesenchymal stem cells under mechanical stimulation at various frequencies

The treatment of large segmental bone defects remains a challenge as infection, delayed union, and nonunion are common postoperative complications. A three‐dimensional printed bioresorbable and physiologically load‐sustaining graft substitute was developed to mimic native bone tissue for segmental bone repair. Fabricated from polylactic acid, this graft substitute is novel as it is readily customizable to accommodate the particular size and location of the segmental bone of the patient to be replaced. Inspired by the structure of the native bone tissue, the graft substitute exhibits a gradient in porosity and pore size in the radial direction and exhibit mechanical properties similar to those of the native bone tissue. The graft substitute can serve as a template for tissue constructs via seeding with stem cells. The biocompatibility of such templates was tested under in vitro conditions using a dynamic culture of human mesenchymal stem cells. The effects of the mechanical loading of cell‐seeded templates under in vitro conditions were assessed via subjecting the tissue constructs to 28 days of daily mechanical stimulation. The frequency of loading was found to have a significant effect on the rate of mineralization, as the alkaline phosphatase activity and calcium deposition were determined to be particularly high at the typical walking frequency of 2 Hz, suggesting that mechanical stimulation plays a significant role in facilitating the healing process of bone defects. Utilization of such patient‐specific and biocompatible graft substitutes, coupled with patient’s bone marrow cells seeded and exposed to mechanical stimulation of 2 Hz have the potential of reducing significant volumes of cadaveric tissue required, improving long‐term graft stability and incorporation, and alleviating financial burdens associated with delayed or failed fusions of long bone defects.     

Mandibular ramus flexure: A new morphologic indicator of sexual dimorphism in the human skeleton

In the skeleton, male and female characteristics lie along a continuum of morphologic configurations and metric values. Size alone is not the best indicator of sex. In contrast, morphologic differences that arise from genetically sex-linked growth and development allow better separation of the sexes. This study presents a new morphologic indicator of sexual dimorphism in the human mandible. A sample of 300 mandibles from adults of known sex primarily from the Dart collection was analyzed. Of these, 100 were found to have obvious bony pathologies and/or excessive tooth loss (“pathologic” sample). Thus, the normative sample consisted of 200 individuals (116 males, 84 females). Examination of morphologic features led to the discovery of a distinct angulation of the posterior border of the mandibular ramus at the level of the occlusal surface of the molars in adult males. Flexure appears to be a male developmental trait because it is only manifest consistently after adolescence. In most females, the posterior border of the ramus retained the straight juvenile shape. If flexure was noted, it was found to occur either at a higher point near the neck of the condyle or lower in association with gonial prominence or eversion. In the normative sample, overall prediction accuracy from ramus shape was 99%. When the “pathologic” sample was analyzed separately, 91.0% were correctly diagnosed. Because the African samples were overwhelmingly black, this trait was also tested on American samples (N = 247) of whites (N = 85), Amerinds (N = 66), and blacks (N = 96) that included a mix of healthy individuals and those with extensive tooth loss and evidence of pathology. The results were nearly identical to those of the “pathologic” African sample, with accuracies ranging from about 91% in whites and blacks to over 92% in Amerinds. Total accuracy for all African and American samples combined (N = 547) is 94.2%. In conclusion, at 99%, sexing from the shape of the ramus of a healthy mandible is on a par with accuracy attainable from a complete pelvis. Moreover, there is no record that any other single morphologic or metric indicator of sex (that has been quantified from the adult skeleton) surpasses the overall accuracy attained from the more representative mixed sample produced by combining all groups assessed in this study. The usefulness of this trait is enhanced by the survivability of the mandible and the fact that preliminary investigations show that the trait is clearly evident in fossil hominids. © 1996 Wiley-Liss, Inc.     

Development of the skeleton in Japanese quail embryos

In the research fields of experimental embryology, teratological testing, and developmental engineering in avian species, a knowledge of normal embryonic development is necessary so that research may be performed efficiently and precisely. A series of normal stages based on external appearance has been established in both chicken and quail embryos. Those based on skeletal features, however, have not been elucidated. The present study newly established a series of normal stages for the development of the Japanese quail embryo skeleton. This series is composed of 15 stages determined by observing the timing of chondrification and calcification of the skeleton every 24 h, from 3 to 17 days of incubation. Cartilage and ossified bones were stained blue and red with Alcian blue 8GX and alizarin red S, respectively. These skeletogenous stages of the Japanese quail embryo will be useful as a normal control not only in studies of experimental embryology, teratological testing, and developmental engineering, but also in the analysis of mutant embryos with skeletal abnormalities.     

Age estimation of adolescent and young adult male and female skeletons II, epiphyseal union at the upper limb and scapular girdle in a modern Portuguese skeletal sample

This study completes previously reported ages for timing of epiphyseal union in the postcranial skeleton in a recent sample, with data from the scapula, clavicle, humerus, radius, and ulna. A sample of 121 individuals between the ages of 9 and 29 (females = 65, males = 56) was derived from the Lisbon documented skeletal collection. Epiphyseal union was scored at 16 anatomical locations, using a three-stage scheme: 1) no union; 2) partial union; and 3) completed union, all traces of fusion having disappeared. In the upper limb, the epiphyses of the elbow are the first to fuse at around 11 to 15 years of age, followed by those of the shoulder and wrist. In the scapular girdle, the coracoid area is the first to fuse, followed by the glenoid surface and remaining epiphyses, with the medial clavicle fusing last, by the age of 25-27. There is a sex difference in maturation, with females showing an advance relative to males of about 2 years in the upper limb. Sex differences in maturation are less noticeable in the scapular girdle, but data suggest that females are also ahead of males. Results suggest overall similar age ranges for stages of union as previous dry bone observations, but some studies show significant divergences which seem to derive from methodological issues. Although some radiographic reference standards provide comparable age ranges, they should probably be avoided when aging skeletal remains.     

Articular structure and function in Hylobates,Colobus, and Papio

It has been demonstrated in clinical and experimental studies that subarticular trabecular bone responds to mechanical loads transmitted across joints through changes in mass and structural organization. We investigated differences in mass, volume, and density of subarticular trabecular bone of the humeral and femoral head in Hylobates syndactylus, Colobus guereza, and Papio cynocephalus. Our hypothesis was that variations in trabecular properties between taxa may reflect differences in mechanical loading associated with different locomotor repertoires. A nondestructive method for measuring trabecular properties using optical luminance data measured from radiographs was developed. We also examined the relationship between internal trabecular properties and the external size and surface area of the humeral and femoral heads in these taxa. Our results suggest that internal and external articular structure are relatively independent of each other and may be adapted to different aspects of the mechanical environment. Differences in trabecular mass between taxa appear to correspond to differences in the magnitudes of mechanical loads borne by the joint, whereas aritcular volume and surface area are related primarily to differences in joint mobility. Because of the apparent physiological “de-coupling” of articular mass and volume, variations in articular density (mass/volume) are difficult to interpret in isolation. Comparisons of internal and external articular structure may provide new ways to reconstruct the locomotor/positional behavior of extinct taxa. © 1994 Wiley-Liss, Inc.     

Features of mono- and multinucleated bone resorbing cells of the zebrafish Danio rerio and their contribution to skeletal development, remodeling, and growth.

To provide basic data about bone resorbing cells in the skeleton during the life cycle of Danio rerio, larvae, juveniles, and adults (divided into six age groups) were studied by histological procedures and by demonstration of the osteoclast marker enzyme tartrate-resistant acid phosphatase (TRAP). Special attention was paid to the lower jaw, which is a standard element for fish bone studies. The presence of osteoclasts at endosteal surfaces of growing bones of all animals older than 20 days reveals that resorption is an important part of zebrafish skeletal development. The first bone-resorbing cells to form are mononucleated. They appear in 20-day-old animals concurrently in the craniofacial skeleton and vertebral column. Mononucleated osteoclasts are predominant in juveniles. Regional differences characterize the appearance of osteoclasts; at thin skeletal elements (neural arches, nasal) mononucleated osteoclasts are predominant even in adults. Multinucleated bone-resorbing cells were first observed in 40-day-old animals and are the predominant osteoclast type of adults. Both mono- and multinucleated osteoclasts contribute to allometric bone growth but multinucleated osteoclasts are also involved in lacunar bone resorption and repeated bone remodeling. Resorption of the dentary follows the pattern described above (mononucleated osteoclasts precede multinucleated cells) and includes the partial removal of Meckel's cartilage. Bone marrow spaces created by resorption are usually filled with adipose tissue. In conclusion, bone resorption is primarily subjected to the demands of growth, the appearance of mono- and multinucleated osteoclasts is site- and age-related, and bone remodeling occurs. The results are discussed in relation to findings in other teleosts and in mammals.     

The role of nervous system in adaptive response of bone to mechanical loading

Bone tissue is remodeled through the catabolic function of the osteoclasts and the anabolic function of the osteoblasts. The process of bone homeostasis and metabolism has been identified to be co-ordinated with several local and systemic factors, of which mechanical stimulation acts as an important regulator. Very recent studies have shown a mutual effect between bone and other organs, which means bone influences the activity of other organs and is also influenced by other organs and systems of the body, especially the nervous system. With the discovery of neuropeptide (calcitonin gene-related peptide, vasoactive intestinal peptide, substance P, and neuropeptide Y) and neurotransmitter in bone and the adrenergic receptor observed in osteoclasts and osteoblasts, the function of peripheral nervous system including sympathetic and sensor nerves in bone resorption and its reaction to on osteoclasts and osteoblasts under mechanical stimulus cannot be ignored. Taken together, bone tissue is not only the mechanical transmitter, but as well the receptor of neural system under mechanical loading. This review aims to summarize the relationship among bone, nervous system, and mechanotransduction.     

3D strain map of axially loaded mouse tibia: a numerical analysis validated by experimental measurements

A combined experimental/numerical study was performed to calculate the 3D octahedral shear strain map in a mouse tibia loaded axially. This study is motivated by the fact that the bone remodelling analysis, in this in vivo mouse model should be performed at the zone of highest mechanical stimulus to maximise the measured effects. Accordingly, it is proposed that quantification of bone remodelling should be performed at the tibial crest and at the distal diaphysis. The numerical model could also be used to furnish a more subtle analysis as a precise correlation between local strain and local biological response can be obtained with the experimentally validated numerical model.