Outer Bone Surface Research Articles

Bone diagenesis at the Florisbad spring site, Free State Province (South Africa): Implications for the taphonomy of the Middle and Late Pleistocene faunal assemblages

The Middle to Late Pleistocene spring site of Florisbad, South Africa, is the name site of the Florisian Land Mammal Age (LMA), and it has produced a large collection of fossil bones from different sedimentary contexts. The largest of these faunal assemblages derives from vertically intrusive dormant spring vents and is taphonomically distinct from specimens associated with a Middle Stone Age occupational horizon. The Florisbad faunal assemblages include several extinct and extant animal species, mainly grazing ungulates that represent a highly productive open grassland environment. The Florisian LMA was characterized by substantially wetter conditions compared to the Holocene. Geological evidence at Florisbad and the characteristic occurrence of water-dependent species, such as lechwe, waterbuck, hippopotamus and a variety of water birds, reflect the presence of a vast intermittent paleolake forming during the wet phases of the Middle and Late Pleistocene. During dry phases, the area of spring activity was not inundated and provided a suitable habitat for both humans and animals. Bones collected from different sedimentary contexts exhibit a number of post-depositional alterations that reflect specific diagenetic processes, which led to fossilization. Two contrasting hypotheses regarding these processes, based on morphological studies of bones and groundwater chemistry, were proposed in the past. The first identified spring water as a major fossilization agent, whereas the second saw it as a medium conducive to bone dissolution. Using Fourier Transform infrared spectrometry (FTIR) and micro-spectrometry (μFTIR), we determined the mineralogical composition of these bones. We show here that specimens from inactive paleo-spring vents are characterized by the formation of carbonate fluorapatite on the outer surface of cortical bone, and locally exhibit authigenic calcite crystals, as opposed to bones collected from non-spring contexts at the site. The nucleation of carbonate fluorapatite is linked to the high fluoride content of the alkaline spring water, thus confirming its key role in the fossilization process of bones recovered from paleo-spring vents. Therefore, our results support the first of the two hypotheses advanced in the past.

Facial bone alterations on maxillary anterior single implants for immediate placement and provisionalization following tooth extraction: a superimposed cone beam computed tomography study.

The purpose of this cone beam computed tomography (CBCT) study was to describe the facial bone changes around single implants for immediate placement and provisionalization following tooth extraction in the maxillary anterior. The data between 2008 and 2013 were collected retrospectively. Superimposed facio-palatal cross-sectional CBCT images for the implants were derived from preoperative and postoperative radiographs via standardized CBCT processes. Horizontal and vertical facial measurements on the implants were identified at preoperative and approximately 1-year postoperative follow-ups. Correlation coefficient for those parameters was evaluated. A total of 12 single implants in 12 patients were included in this study. The mean loading period was 13.3months (range 12-15months). The median data of preoperative bone thickness 0.54mm (A), preoperative vertical bone level 1.46mm (B), postoperative bone thickness 1.77mm (C), postoperative vertical bone level 1.08mm (D), horizontal distance from outer surface of preoperative facial bone to implant surface 2.08mm (E), horizontal gap distance 1.41mm (E-A), horizontal bone resorption -0.26mm (E-C), and vertical bone resorption -0.25mm (B-D) were obtained. The data at the implant platform level (IPL) were selected for the horizontal measurements. Spearman's analysis demonstrated statistically significant correlations between B and D, C and E, E and E-A, and B and E-C (P<0.01). Significant correlations between C and B, D, and E-A were also found, respectively (P<0.05). Immediate placement and provisionalization of single implants procedure in the maxillary anterior showed excellent outcomes with the small facial bone alterations around the implants. Neither preoperative facial bone thickness nor horizontal gap distance influenced the amount of facial bone resorptions.

Periosteal thickness and cellularity in mid‐diaphyseal cross‐sections from human femora and tibiae of aged donors

Due to lack of access in healthy patients, the structural properties underlying the inherent regenerative power and advanced material properties of the human periosteum are not well understood. Periosteum comprises a cellular cambium layer directly apposing the outer surface of bone and an outer fibrous layer encompassed by the surrounding soft tissues. As a first step to elucidating the structural and cellular characteristics of periosteum in human bone, the current study aims to measure cambium and fibrous layer thickness as well as cambium cellularity in human femora and tibiae of aged donors. The major and minor centroidal axes (CA) serve as automated reference points in cross-sections of cadaveric mid-diaphyseal femora and tibiae. Based on the results of this study, within a given individual, the cambium layer of the major CA of the tibia is significantly thicker and more cellular than the respective layer of the femur. These significant intraindividual differences do not translate to significant interindividual differences. Further, mid-diaphyseal periosteal measures including cambium and fibrous layer thickness and cellularity do not correlate significantly with age or body mass. Finally, qualitative observations of periosteum in amputated and contralateral or proximal long bones of the lower extremity show stark changes in layer organization, thickness, and cellularity. In a translational context, these novel data, though inherently limited by availability and accessibility of human mid-diaphyseal periosteum tissue, provide important reference values for the use of periosteum in the context of facilitated healing and regeneration of tissue.

A computed tomography study on two skulls of mistreated dogs from the Roman Age

The study of ancient skeletons is of high interest, as the relationship between men and animals can be reconstructed. In dogs, head injuries frequently result from direct physical traumas. The excavation of a prehistoric well (Genomi, Sardinia) brought to light sixty canine bones of the Age Roman (2nd century AD), although this well was built during the Nuragic Age. (1st millennium BC). Two canine skulls showing three traumatic lesions underwent computed tomography in order to study the endocast of the brain cavity and indirectly locate possible brain lesions. In the first case, a traumatic lesion was found in the left parietal bone with depression of the outer surface. This lesion determined compression of the left frontal cortex and was compatible with life, as can be deduced by the inflammation of the periostenum. In the second case, two different traumatic lesions were found. The former was a wide fracture of the right frontal bone near the orbital cavity. The injured area showed clear signs of bone remodeling which took place many months before death. The latter was a severe comminuted fracture involving both the outer and inner surface of the left frontal bone, which provoked a deep wound in the left frontal cortex. The sharp outline of bone splinters with no signs of bone remodelling indicates that the trauma was not compatible with life. All lesions described were consequent to severe blows from humans and testify mistreatment of dogs in the Roman Age.

Finite element micro-modelling of a human ankle bone reveals the importance of the trabecular network to mechanical performance: New methods for the generation and comparison of 3D models

Most modelling of whole bones does not incorporate trabecular geometry and treats bone as a solid non-porous structure. Some studies have modelled trabecular networks in isolation. One study has modelled the performance of whole human bones incorporating trabeculae, although this required considerable computer resources and purpose-written code. The difference between mechanical behaviour in models that incorporate trabecular geometry and non-porous models has not been explored. The ability to easily model trabecular networks may shed light on the mechanical consequences of bone loss in osteoporosis and remodelling after implant insertion. Here we present a Finite Element Analysis (FEA) of a human ankle bone that includes trabecular network geometry. We compare results from this model with results from non-porous models and introduce protocols achievable on desktop computers using widely available softwares. Our findings show that models including trabecular geometry are considerably stiffer than non-porous whole bone models wherein the non-cortical component has the same mass as the trabecular network, suggesting inclusion of trabecular geometry is desirable. We further present new methods for the construction and analysis of 3D models permitting: (1) construction of multi-property, non-porous models wherein cortical layer thickness can be manipulated; (2) maintenance of the same triangle network for the outer cortical bone surface in both 3D reconstruction and non-porous models allowing exact replication of load and restraint cases; and (3) creation of an internal landmark point grid allowing direct comparison between 3D FE Models (FEMs).

Periosteum, bone's “smart” bounding membrane, exhibits direction-dependent permeability

The periosteum serves as bone's bounding membrane, exhibits hallmarks of semipermeable epithelial barrier membranes, and contains mechanically sensitive progenitor cells capable of generating bone. The current paucity of data regarding the periosteum's permeability and bidirectional transport properties provided the impetus for the current study. In ovine femur and tibia samples, the periosteum's hydraulic permeability coefficient, k, was calculated using Darcy's Law and a custom-designed permeability tester to apply controlled, volumetric flow of phosphate-buffered saline through periosteum samples. Based on these data, ovine periosteum demonstrates mechanically responsive and directionally dependent (anisotropic) permeability properties. At baseline flow rates comparable to interstitial fluid flow (0.5 µL/s), permeability is low and does not exhibit anisotropy. In contrast, at high flow rates comparable to those prevailing during traumatic injury, femoral periosteum exhibits an order of magnitude higher permeability compared to baseline flow rates. In addition, at high flow rates permeability exhibits significant directional dependence, with permeability higher in the bone to muscle direction than vice versa. Furthermore, compared to periosteum in which the intrinsic tension (pre-stress) is maintained, free relaxation of the tibial periosteum after resection significantly increases its permeability in both flow directions. Hence, the structure and mechanical stress state of periosteum influences its role as bone's bounding membrane. During periods of homeostasis, periosteum may serve as a barrier membrane on the outer surface of bone, allowing for equal albeit low quiescent molecular communication between tissue compartments including bone and muscle. In contrast, increases in pressure and baseline flow rates within the periosteum resulting from injury, trauma, and/or disease may result in a significant increase in periosteum permeability and consequently in increased molecular communication between tissue compartments. Elucidation of the periosteum's permeability properties is key to understanding periosteal mechanobiology in bone health and healing, as well as to elucidate periosteum structure and function as a smart biomaterial that allows bidirectional and mechanically responsive fluid transport.

Effect of the cortex on ultrasonic backscatter measurements of cancellous bone

Ultrasonic backscatter techniques offer a promising new approach for detecting changes in bone caused by osteoporosis. However, several challenges impede clinical implementation of backscatter techniques. This study examines how the dense outer surface of bone (the cortex) affects backscatter measurements of interior regions of porous (cancellous) bone tissue. Fifty-two specimens of bone were prepared from 13 human femoral heads so that the same region of cancellous bone could be ultrasonically interrogated through the cortex or along directions that avoided the cortex. Backscatter signals were analyzed over a frequency range of 0.8–3.0 MHz to determine two ultrasonic parameters: apparent integrated backscatter (AIB) and frequency slope of apparent backscatter (FSAB). The term ‘apparent’ means that the parameters are sensitive to the frequency-dependent effects of diffraction and attenuation. Significant (p < 0.001) changes in AIB and FSAB indicated that measurements through the cortex decreased the apparent backscattered power and increased the frequency dependence of the power. However, the cortex did not affect the correlation of AIB and FSAB with the x-ray bone mineral density of the specimens. This suggests that results from many previous in vitro backscatter studies of specimens of purely cancellous bone may be extrapolated with greater confidence to in vivo conditions.

Periosteal Osteosarcoma of the Mandible: Case Report and Review of the Literature

Osteosarcoma (OS) is the most common primary malignancy of bone, with a reported incidence of 1:100,000 per year.1 These tumors typically originate in the extremities and the pelvis, with only 2.7–6.6% of OSs were located in the jaws.2,3 Although conventional OS arises intramedullary, some OSs occur on the outer surface of bone, this is called surface or juxtacortical OS and exhibits distinct radiographic, histologic features and biological behavior that is obviously different from conventional OS. OSs arising on the surface of bone can be classified into three types according to the nature of the tumor: parosteal, periosteal, and high-grade surface OS.4 Parosteal OS is a low-grade OS, with an incidence of about 4% of all OSs. Periosteal OS is an intermediate-grade chondroblastic OS, accounting for less than 2% of all OSs. High-grade surface OS is the most rare subtype, accounting for less than 1%. Periosteal type tends to have a better prognosis than that of conventional OS or high-grade surface OS, but poorer than that of parosteal OS and it is capable of local recurrence and distant metastasis.5 Periosteal OS occurs extremely rarely in the jaws. To our knowledge, including this report, only ten cases have been reported. We report a case of periosteal OS located at the mental region of the mandible and review the literature with respect to clinical, radiological and histopathological criteria, we also discuss the differential diagnosis.

Medical Fixture Design with CT Images

AbstractIn line with the recent increased use of medical devices designed for individual patients, there is a need to ensure that the surfaces of bone fixtures match the bone surface to which they are fitted. Accordingly, this paper proposes a new process to design such fixtures from CT images using a two-stage process. The first stage involves extracting the outer bone surface of the relevant region from CT images using a level set method with a new speed function to remove the inner surface. In the second stage, a preliminary model designed using commercial CAD software is adopted to trim the extracted outer bone surface obtained in the first stage. The surface of the preliminary model to be attached to the bone is then shaped based on the trimmed outer bone surface to make the desired fixture. The results of experiments performed using the proposed method indicate its suitability for the purpose at hand.

Accelerated bone loss, but not low periosteal expansion, is associated with higher all-cause mortality in older men – prospective MINOS study

Background Low bone mineral density (BMD), high bone resorption, fragility fractures and, possibly, accelerated bone loss are associated with higher mortality. However, it is not known if the higher mortality is related to lower volumetric BMD or lower bone width, to faster bone loss on endosteal surfaces (inside bone) or to slower periosteal apposition (formation of bone on the outer bone surface). Methods We assessed the association of 10-year mortality with bone width and bone loss in 782 men aged 50–85 years. Results Low bone width and slow periosteal apposition at the femoral neck, distal radius and distal ulna were not associated with higher mortality. Accelerated apparent bone loss (decrease in BMD), net bone loss (decrease in bone mineral content) and estimated endosteal bone loss were associated with a higher 10-year all-cause mortality after adjustment for age and other confounders. Accelerated apparent bone loss at the total hip (lowest quartile) was associated with a two-fold higher mortality (Hazard Ratio (HR)=1.96, 95% Confidence interval (CI): 1.33, 2.89, p<0.001). Conclusion Lack of association between bone size and mortality shows that periosteal expansion is not an artifact induced by the selective mortality of men with narrow bones. We confirmed that poor bone status reflects poor health. These data should be interpreted with caution because of the study limitations, especially the lack of representativity of the cohort and dropout of older and sick men. However, they suggest that older men with low BMD or accelerated bone loss should obtain detailed diagnostic assessment to establish general factors that can contribute to their poor bone status.

The Relationship Between Cephalic Scales and Bones in Lizards: A Preliminary Microtomographic Survey on Three Lacertid Species

In the last two decades, there has been a great deal of interest in the morphology and anatomy of the lizard skull in an ecological and evolutionary perspective. However, the relationship between variations in many key anatomical features remains largely unknown. Using microtomography and geometric morphometrics, we examined the relationship between bones and scales associated with the parietal foramen in the three lizards species most common in the Italian peninsula: Podarcis muralis, P. sicula, and Lacerta bilineata. The imprints of the scales are clearly recognizable on the outer bone surface, and this may suggest a structural interaction between these elements. The temporal osteoderms are visible in the larger males and in the larger females of L. bilineata, but they are absent in the smaller specimens of L. bilineata and in all Podarcis specimens. Two parallel rows of pterygoid teeth are present in all the specimens of L. bilineata and are absent in the smaller male of L. bilineata and in both Podarcis species. Cheek osteoderms occurred only in the largest specimens of our sample (i.e., large L. bilineata), being possibly related to hyperostotic processes and densitometric thresholds more than to phylogeny. Minor differences may be also associated with the form of the parietal foramen. In absolute terms the parietal foramen tends to be largest in L. bilineata but in relation to skull length the foramen tends to be larger in P. muralis. In this latter species the foramen is also more elongated. In all three species the fronto-parietal suture occupies a similar location relatively to the scale spatial organization. A shared allometric pattern shows that the main vault enlargement can be localised at the areas anterior to the fronto-parietal suture, providing further information on the possible morphogenetic dynamics associated with the interaction between scales and bones around this structure.

MODELLING SUBJECT-SPECIFIC HIP GEOMETRY AFFECTS HIP CONTACT FORCES IN GAIT

Craniofacial malformations implicate a risk of medical complications and a negative psychological impact on the patient. In order to correct functional and aesthetic aspects of these malformations, skull reconstruction is required. Because of the complexity of the surgery, pre-operative planning is unavoidable. Current and previously developed planning environments often lack the opportunity to transfer the simulated surgery to the operation room on a cheap but accurate, and easy to handle basis.This study applies an automated filter procedure, implemented in Matlab®, to generate a set of adapted contours from which a surface mesh can be directly deduced. Skull reconstruction planning is performed on the generated outer bone surface model. For each resected/osteotomized bone part, the presented semi-automatic Matlab® procedure generates surface based bone cutting guides, also denoted bone segment templates. Autoclaved aluminium templates transfer the surgical plan to the operation room.The clinical feasibility is demonstrated by the successful pre-operative planning and surgical correction of three skull reconstruction cases in which the proposed procedure leads to considerable reduction in surgery time and good results.A cost-efficient and planning-environment-independent solution is generated for an accurate and fast transfer of a complex cranial surgery plan to the operation room.

Skull reconstruction planning transfer to the operation room by thin metallic templates: Clinical results

Craniofacial malformations implicate a risk of medical complications and a negative psychological impact on the patient. In order to correct functional and aesthetic aspects of these malformations, skull reconstruction is required. Because of the complexity of the surgery, pre-operative planning is unavoidable. Current and previously developed planning environments often lack the opportunity to transfer the simulated surgery to the operation room on a cheap but accurate, and easy to handle basis. This study applies an automated filter procedure, implemented in Matlab, to generate a set of adapted contours from which a surface mesh can be directly deduced. Skull reconstruction planning is performed on the generated outer bone surface model. For each resected/osteotomized bone part, the presented semi-automatic Matlab procedure generates surface based bone cutting guides, also denoted bone segment templates. Autoclaved aluminium templates transfer the surgical plan to the operation room. The clinical feasibility is demonstrated by the successful pre-operative planning and surgical correction of three skull reconstruction cases in which the proposed procedure leads to considerable reduction in surgery time and good results. A cost-efficient and planning-environment-independent solution is generated for an accurate and fast transfer of a complex cranial surgery plan to the operation room.

Accuracy assessment of CT-based outer surface femur meshes

Objectives: Computer-aided bone surgery planning and implant design applications require accurate and compact representations of the patient's bone. The accuracy of bone segmentation from medical images has been studied extensively, with each study using a specific ground truth and a specific type and number of accuracy measurements. However, for convenience and practical reasons these three specifications have always been limited. The goal of this study is to thoroughly assess the absolute 3D accuracy of CT-based bone outer surface meshes, using femora as the examples.Materials and Methods: Using dense and very accurate optical surface scans of 15 dried femora as an absolute ground truth, this paper reports on the absolute 3D geometric accuracy of triangulated bone outer surface meshes, which were segmented from the CT scans of the corresponding formalin-fixed intact cadaver specimens using the author's previously presented contour-based segmentation algorithm on the one hand, and the commercially available Mimics® software (Materialise N.V., Leuven, Belgium) on the other. The study incorporates the effect of soft tissue presence on hard tissue segmentation and simultaneously reveals the accuracy shift introduced as a result of boiling the cadaver bones by processing extra CT scans of the dried bones.Results: The presented study demonstrates that, when using the optimal parameter settings for the respective segmentation procedures, sub-voxel mesh accuracies can be attained. Compact surface representations of femora can be generated with mean absolute accuracies of up to one fifth of the voxel size and Root Mean Square (RMS) error of half the voxel size.Conclusions: The 3D accuracy of the contour-based segmentation previously presented by the author makes it most suitable for generating outer bone surface meshes for use in the aforementioned applications. The optimal parameter settings for this segmentation procedure have been identified. For the Mimics® bone surface meshes, a single, but excellent, pre-defined set of parameters was identified.

Organization of a unique net-like meshwork of CGRP+ sensory fibers in the mouse periosteum: Implications for the generation and maintenance of bone fracture pain

Although bone fracture frequently results in significant pain and can lead to increased morbidity and mortality, it is still not clearly understood how sensory neurons are organized to detect fracture pain. In the present report we focused on the periosteum, as this thin tissue is highly innervated and tightly adherent to the outer surface of bone. To define the organization and distribution of the sensory and sympathetic fibers in the mouse femoral periosteum, we used whole-mount preparations, transverse sections, immunofluoresence and laser scanning confocal microscopy. While both the outer fibrous layer and the inner more cellular cambium layer of the periosteum receive an extensive innervation by calcitonin gene-related peptide (CGRP) and 200-kDa neurofilament (NF200) positive sensory fibers as well as tyrosine hydroxylase (TH) positive sympathetic fibers, there is a differential organization of sensory vs. sympathetic fibers within the periosteum. In both layers, the great majority of TH+ fibers are closely associated with CD31+ blood vessels and wind around the larger vessels in a corkscrew pattern. In contrast, the majority of CGRP+ and NF200+ sensory fibers in both layers lack a clear association with CD31+ blood vessels and appear to be organized in a dense net-like meshwork to detect mechanical distortion of periosteum and bone. This organization would explain why stabilization/fixation causes a marked attenuation of movement-evoked fracture pain. Understanding the organization, plasticity and molecular characteristics of sensory and sympathetic nerve fibers innervating the skeleton may permit the development of novel mechanism-based therapies for treating non-malignant skeletal pain.

Biomineralization and adaptive plasticity of the temporomandibular joint in myostatin knockout mice

Mice lacking myostatin (GDF-8), a negative regulator of skeletal muscle growth, show a significant increase in muscle mass versus normal mice. We compared wild-type and myostatin deficient mice to assess the postnatal effect of elevated masticatory loads due to increased jaw-adductor muscle activity and greater bite forces on mandibular condyle morphology. Microcomputed tomography (microCT) was used to provide details of internal condylar morphology and quantify bone density in three condylar regions. Biomineralization levels, as well as external mandibular dimensions, were used to characterize within-slice, within-joint, within-group and between-group variation. Dimensions of the mandible and mandibular condyle were similar between the myostatin knockout and normal mice. Knockout mice exhibited significantly more biomineralization on the outer surface of the condylar subchondral bone and along the condylar neck, most notably on the buccal side of the condylar neck. The buccal side of the inner aspect of the condyle was significantly less biomineralized in knockout mice, both for the pooled data and for the posterior and anterior condylar slices. Whilst normal mice had symmetric subchondral bone surfaces, those of knockout mice were asymmetric, with a lower, less convex surface on the buccal side versus the lingual side. This appears related to the ontogenetic effects of increased masticatory stress in the mandibles of knockout mice as compared to normal mice. Significant differences in biomineralization between normal and myostatin knockout mice, coupled with the lack of significant differences in certain external dimensions, underscores a need for information on the external and internal morphology of mineralized tissues vis-à-vis altered or excessive mechanical loads.

Influence of Occlusal Stimuli on the Remodelling of Alveolar Bone in a Rat Hypofunction-Recovery Model

Remodelling of alveolar bone is a crucial factor determining tooth movement against orthodontic forces. Occlusion is the most influential stimulus causing physiological remodelling of alveolar bone. A removable metal appliance was devised, which can sequentially induce hypofunctional occlusion at molar teeth and reestablish normal occlusion. Using this appliance, remodelling of the alveolar bone was examined by histological morphometric analyses, with particular attention to localized regions of bone resorption by identifying the receptor activator of NF-κB ligand (RANKL), a growth factor inducing osteoclastogenesis, and osteoclasts. In the occlusal hypofunction period, the number of TRAP-positive cells increased at the margin of marrow spaces, and the marrow space enlarged. RANKL-positive osteoblasts also increased, especially around the blood vessels. In bone morphometric parameters, BV/TV, Tb. Th and Tb. N decreased, and Tb. Sp and Oc. N increased. These results are consistent with active bone remodelling consisting of active resorption at the inner alveolar bone and bone formation on the outer alveolar bone surface. In the 3 days recovery group, many TRAP-positive cells were observed at the inner alveolar bone and around the bone surface. RANKL-positive osteoblasts were observed at the margin of the marrow space in alveolar bone. However, BV/TV, Tb. Th, and Tb. Sp returned to the control level in the 7 days recovery group, with decreased TRAP-positive cells and RANKL-positive osteoblasts. These findings suggest that occlusal stimuli play important roles in the maintenance of functional alveolar structure and the regulation of alveolar bone in rats.

Invited Review: Pathogenesis of osteoporosis.

Patients with fragility fractures may have abnormalities in bone structural and material properties such as larger or smaller bone size, fewer and thinner trabeculae, thinned and porous cortices, and tissue mineral content that is either too high or too low. Bone models and remodels throughout life; however, with advancing age, less bone is replaced than was resorbed within each remodeling site. Estrogen deficiency at menopause increases remodeling intensity: a greater proportion of bone is remodeled on its endosteal (inner) surface, and within each of the many sites even more bone is lost as more bone is resorbed while less is replaced, accelerating architectural decay. In men, there is no midlife increase in remodeling. Bone loss within each remodeling site proceeds by reduced bone formation, producing trabecular and cortical thinning. Hypogonadism in 20-30% of elderly men contributes to bone loss. In both sexes, calcium malabsorption and secondary hyperparathyroidism increase remodeling: more bone is removed from an ever-diminishing bone mass. As bone is removed from the endosteal envelope, concurrent bone formation on the periosteal (outer) bone surface during aging partly offsets bone loss and increases bone's cross-sectional area. Periosteal apposition is less in women than in men; therefore, women have more net bone loss because they gain less on the periosteal surface, not because they resorb more on the endosteal surface. More women than men experience fractures because their smaller skeleton incurs greater architectural damage and adapts less by periosteal apposition.

Toward an expanded understanding of the role of the periosteum in skeletal health.

Toward an expanded understanding of the role of the periosteum in skeletal health.

Post-mortem intake of lead in 11th century human bones and teeth studied by milli- and microbeam PIXE and RBS

Pb concentrations in human bone and tooth samples from a 11th century mining community were analysed to study the influence of long-term burial in polluted soils. PIXE and RBS analysis with 20–300 μm proton beams and 300 μm 4He+ beams at the University of Freiburg Van de Graaff laboratory and less than 5 μm at the University of Melbourne Microanalytical Research Centre was performed and strongly increased Pb levels at outer and inner bone and tooth surfaces were found, reaching more than 1000 ppm in some of the bone samples, and decreasing to equilibrium levels in the order of 5–10 ppm in some non-porous inner sections of the analysed bones and teeth.