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Introduction. Complete denture relines are typically necessary due to ontinuous bone resorption. Because to individual differences in resorption rates, the time between relining procedures varies. As of right now, there are no predictors to help identify people who may need relines frequently or to help advise doctors when they make reline decisions.

Bone mineral and mass are low in limb bones that experience prolonged lack of, or minimal, mechanical stimulation. Cases of ancient human limb paralysis offering an opportunity to examine histological markers of cortical bone modelling and remodelling are rare. To improve our understanding of the spectrum of bone tissue response to its muscular disuse environment in archaeological contexts, we tested whether bone histology in an individual afflicted with long-term loss of muscle function showed unremodelled primary bone due to minimal/absent, mechanical stimulation. We examined cortical bone histology in a 1906–1523 cal BC atrophied post-cranium of a young adult (mid-20s) male who had suffered from Klippel-Feil Syndrome Type III, experiencing minimally paraplegia and potentially complete or intermittent quadriplegia in late childhood/early adolescence. Samples taken from the humeral and femoral midshaft displayed thin cortices and extensive retention of primary bone with only localised Haversian tissue or isolated secondary osteons. The retention of widespread primary bone and thin cortices in this adult individual is evidence for stunted modelling and remodelling due to immobility during early ontogeny. Our bone histology descriptions should be of interest to palaeobiologists investigating the effects of physical inactivity on bone microstructure in fossilised and archaeological human remains. [ABSTRACT FROM AUTHOR]

Aim: Patients with type 2 diabetes (T2DM) have more risk of bone fractures. However, areal bone mineral density (aBMD) by conventional dual-energy xray absorptiometry (DXA) is not useful for identifying this risk. This study aims to evaluate 3D-DXA parameters determining the cortical and trabecular compartments in patients with T2DM compared to non-diabetic subjects and to identify their determinants. Materials and methods: Case-control study in 111 T2DM patients (65.4 ± 7.6 years old) and 134 non-diabetic controls (64.7 ± 8.6-year-old). DXA, 3D-DXA modelling via 3D-Shaper software and trabecular bone score (TBS) were used to obtain aBMD, cortical and trabecular parameters, and lumbar spine microarchitecture, respectively. In addition, biochemical markers as 25- hydroxyvitamin d, type I procollagen N-terminal propeptide (P1NP), Cterminal telopeptide of type I collagen (CTX), and glycated haemoglobin (HbA1c) were analysed. Results: Mean-adjusted values showed higher aBMD (5.4%-7.7%, ES: 0.33- 0.53) and 3D-DXA parameters (4.1%-10.3%, ES: 0.42-0.68) in the T2DM group compared with the control group. However, TBS was lower in the T2DM group compared to the control group (-14.7%, ES: 1.18). In addition, sex (b = 0.272 to 0.316) and body mass index (BMI) (b = 0.236 to 0.455) were the most consistent and positive predictors of aBMD (p ≤ 0.01). BMI and P1NP were negative predictors of TBS (b = -0.530 and -0.254, respectively, p ≤ 0.01), while CTX was a positive one (b = 0.226, p=0.02). Finally, BMI was consistently the strongest positive predictor of 3D-DXA parameters (b = 0.240 to 0.442, p<0.05). Conclusion: Patients with T2DM present higher bone mass measured both by conventional DXA and 3D-DXA, suggesting that 3D-DXA technology is not capable of identifying alterations in bone structure in this population. Moreover, BMI was the most consistent determinant in all bone outcomes. [ABSTRACT FROM AUTHOR]

AimPatients with type 2 diabetes (T2DM) have more risk of bone fractures. However, areal bone mineral density (aBMD) by conventional dual-energy x-ray absorptiometry (DXA) is not useful for identifying this risk. This study aims to evaluate 3D-DXA parameters determining the cortical and trabecular compartments in patients with T2DM compared to non-diabetic subjects and to identify their determinants.Materials and methodsCase-control study in 111 T2DM patients (65.4 ± 7.6 years old) and 134 non-diabetic controls (64.7 ± 8.6-year-old). DXA, 3D-DXA modelling via 3D-Shaper software and trabecular bone score (TBS) were used to obtain aBMD, cortical and trabecular parameters, and lumbar spine microarchitecture, respectively. In addition, biochemical markers as 25-hydroxyvitamin d, type I procollagen N-terminal propeptide (P1NP), C-terminal telopeptide of type I collagen (CTX), and glycated haemoglobin (HbA1c) were analysed.ResultsMean-adjusted values showed higher aBMD (5.4%-7.7%, ES: 0.33-0.53) and 3D-DXA parameters (4.1%-10.3%, ES: 0.42-0.68) in the T2DM group compared with the control group. However, TBS was lower in the T2DM group compared to the control group (-14.7%, ES: 1.18). In addition, sex (β = 0.272 to 0.316) and body mass index (BMI) (β = 0.236 to 0.455) were the most consistent and positive predictors of aBMD (p ≤ 0.01). BMI and P1NP were negative predictors of TBS (β = -0.530 and -0.254, respectively, p ≤ 0.01), while CTX was a positive one (β = 0.226, p=0.02). Finally, BMI was consistently the strongest positive predictor of 3D-DXA parameters (β = 0.240 to 0.442, p

INTRODUCTION: A torque-rotation model of the bone-screwing process has been proposed. Identification of model parameters using recorded data could potentially be used to determine the material properties of bone. These properties can then be used to recommend tightening torques to avoid over or under-tightening of bone screws. This paper improves an existing model to formulate it in terms of material properties and remove some assumptions. METHOD: The modelling methodology considers a critical torque, which is required to overcome friction and advance the screw into the bone. Below this torque the screw may rotate with elastic deformation of the bone tissue, and above this the screw moves relative to the bone, and the speed is governed by a speed-torque model of the operator’s hand. The model is formulated in terms of elastic modulus, ultimite tensile strength, and frictional coefficient of the bone and the geometry of the screw and hole. RESULTS: The model output shows the speed decreasing and torque increasing as the screw advances into the bone, due to increasing resistance. The general shape of the torque and speed follow the input effort. Compared with the existing model, this model removes the assumption of viscous friction, models the increase in friction as the screw advances into the bone, and is directly in terms of the bone material properties. CONCLUSION: The model presented makes significant improvements on the existing model. However it is intended for use in parameter identification, which was not evaluated here. Further simulation and experimental validation is required to establish the accuracy and fitness of this model for identifying bone material properties.

• The novel PK/PD model is able to distinguish between bone anabolic and catabolic bone tissue response to PTH administration. • The anabolic effect of PTH is modelled via osteoblast apoptosis reduction, increased osteoblast precursor proliferation and lining cell differentiation. • Intermittent administration of PTH induces bone modelling responses, essential for the substantial bone gain observed in rats. • The model is able to reproduce experimentally observed key features of PTH administration. This paper presents a pharmacokinetic/pharmacodynamic (PK/PD) model of the action of PTH(1-34) on bone modelling and remodelling, developed for quantitatively investigating the dose- and administration pattern-dependency of the bone tissue response to this drug. Firstly, a PK model of PTH(1-34) was developed, accounting for administration via subcutaneous injections. Subsequently, the PK model was coupled to a (mechanistic) bone cell population model of bone modelling and remodelling, taking into account the effects of PTH(1-34) on the differentiation of lining cells into active osteoblasts, on the apoptosis of active osteoblasts, and on proliferation of osteoblast precursors, as well as on the key regulatory pathways of bone cell activities. Numerical simulations show that the coupled PK/PD model is able to distinguish between continuous and intermittent administration patterns of PTH(1-34), in terms of yielding both catabolic bone responses (if drug administration is carried out continuously) and anabolic bone responses (if drug administration is carried out intermittently). The model also features a non-linear relation between bone gain and drug dose (as known from experiments); doubling the dose from 80 μ g/kg/day to 160 μ g/kg/day induced a 1.3-fold increase of the bone volume-to-total volume ratio. Furthermore, the model presented in this paper confirmed that bone modelling represents an essential mechanism of the anabolic response of bone to PTH(1–34) administration in rat models, and that the large amount of bone formation observed in such models cannot be explained via remodelling alone. [ABSTRACT FROM AUTHOR]

Objectives: The aim is to highlight a novel three-dimensional (3D) imaging methodology using micro-CT scans to visualize and measure bone modelling in an animal model. In order to validate the new methodology, we compared the 3D imaging method to traditional two-dimensional (2D) histomorphometry to assess growth changes in the jaws of a rodent.Setting and Sample Population: Rodent animal models.Material and Methods: Eleven rats were obtained from a larger previously published study. Sixty undecalcified histological sections from the maxilla and corresponding high-resolution in vivo micro-CT reconstructions were obtained. Bone modelling changes on specific alveolar surfaces were measured using traditional histomorphometry. Measurements of bone growth were also obtained via 3D Slicer software from 3D micro-CT generated models from the same plane containing the histological images. Both qualitative and quantitative 3D methods were compared to traditional histological measurements. Quantitative agreement between methods was categorized as follows: poor (>150 μm), good (150-100 μm) and excellent (<100 μm).Results: Both qualitative (88.3%) and quantitative (86.7%) 3D measurements showed excellent agreement, when compared to histomorphometric measurements. Only 1.7% and 5% of the comparisons exhibited poor agreement (>150 μm) for qualitative and quantitative methods, respectively.Discussion: The new 3D superimposition method compares very favourably with traditional histology. It is likely that in the future, such methods will be used in studies of bone adaptation.Conclusion: The 3D micro-CT qualitative and quantitative methods are reliable for measuring bone modelling changes and compare favourably to histology for the specific application described. [ABSTRACT FROM AUTHOR]

Bone tissue possesses piezoelectric properties, allowing mechanical forces to be converted into electrical potentials. Piezoelectricity has been demonstrated to play a crucial role in bone remodelling and adaptability. Bone remodelling models that consider strain adaptation, both with and without piezoelectric effects, were simulated and validated in this study. This simulation help to better comprehend the interplay between mechanical and electrical stimulations during these processes. This study aimed to optimise the modelling of piezoelectric effects in bone modelling analysis. The connection between mechanical loads applied to bones and the resulting electrical charges generated by the piezoelectric effect was examined. Furthermore, mathematical modelling and simulation techniques were employed to enhance the piezoelectric effect and promote bone tissue growth and repair. The findings from this research have substantial implications for developing novel therapies for bone-related diseases and injuries. It was observed that electrically stimulated bone surfaces increased bone deposition. In some instances of physical disability or osteoporosis, therapeutic electrical stimulation can supplement the mechanical stresses of regular exercise to prevent bone loss. Consequently, the bone remodelling method on the software platform enables easy application and repetition of finite element analysis. This study significantly benefits bone tissue/biomedical engineering, particularly in bone remodelling, healing, and repair. • To optimise the modelling of piezoelectric effects in the bone modelling analysis. • Examined the connection between loads on bones and electrical charges generated by the piezoelectric effect. • To significantly benefits bone biomedical engineering, in remodelling, healing, and repair. • To Observed that electrically stimulated boneb generated charges during activities. [ABSTRACT FROM AUTHOR]

Objectives: To examine the effect of zoledronic acid (ZOL) on cortical bone modelling and healing of extraction sockets in the jaw bones of a rodent model. We hypothesized ZOL suppresses both the bone formation in the modelling mode in the jaw bones and alters the extraction site healing.Material& Methods: Rice rats were administered saline solution and two dose regimens of ZOL: 0.1 mg/kg, twice a week, for 4 weeks (n=17, saline=8 & ZOL=9) and a higher dose of 0.4 mg/kg, weekly, for 9 weeks (n=30, saline=15 & ZOL=15). Two pairs of fluorochrome bone labels were administered. Extraction of maxillary teeth was performed in maxilla. Mineral apposition rate, mineralizing surface and bone formation rate (BFR) were quantified on periodontal (PDL), alveolar and basal bone surfaces, and in the trabecular bone of proximal tibia. Bone volume (BV) was evaluated at extraction sockets. Multivariate Gaussian models were used to account for repeated measurements, and analyzes were conducted in SAS V9.3.Results: ZOL suppressed bone modelling (BFR/BS) at the PDL surfaces in the mandible (P<.05), but its effect was not significant at the periosteal surfaces of both jaws. BV for the healing sockets of ZOL treated animals was not significantly different (P=.07) compared to the saline group. ZOL suppressive effect was higher in the tibia compared to the jaws.Conclusion: ZOL severely suppresses coupled remodelling in the tibia, and the suppression of bone formation in the modelling mode in the jaws demonstrates the site specific effects of ZOL in rice rats. [ABSTRACT FROM AUTHOR]

osterix (osx; sp7) encodes a zinc-finger transcription factor that controls osteoblast differentiation in mammals. Although identified in all vertebrate lineages, its role in non-mammalian bone formation remains elusive. Here, we show that an osx mutation in medaka results in severe bone defects and larval lethality. Pre-osteoblasts fail to differentiate leading to severe intramembranous and perichondral ossification defects. The notochord sheath mineralizes normally, supporting the idea of an osteoblast-independent mechanism for teleost vertebral centra formation. This study establishes a key role for Osx for bone formation in a non-mammalian species, and reveals conserved and non-conserved features in vertebrate bone formation. [ABSTRACT FROM AUTHOR]

Objective: A third focused workshop explored how to transfer novel findings into clinical orthodontic practice.Setting and Sample Population: Participants met at the Scottsdale Plaza Resort, 12-16 September 2018 for the Consortium for Orthodontic Advances in Science and Technology 2018 Innovators' Workshop. Thirty speakers and four lunch-hour focus group leaders shared and exchanged information with approximately 45 registered attendees.Material and Methods: This Innovators' Workshop was organized according to five themed sessions which covered: (a) The relevance of genetics, biology and environment to therapeutic outcomes; (b) Application of bioinformatics in craniofacial research; (c) Regeneration with and for orthodontic treatment; (d) Technology in precision orthodontics; and (e) Muscle, joint, and airway: Growth, function and pain.Results: The papers that comprise this supplemental issue exemplify the important outcomes of the 2018 COAST Workshop. In addition, matters identified as important needs include improved understanding of neural, skeletal and muscle tissue crosstalk in early craniofacial growth; standardized methods for three-dimensional radiographic and surface landmark and reference plane identification, measurements and serial superimpositioning techniques for use in the clinic; sharing and making available existing data sets (eg, cone beam computed tomography images, genotype-phenotype data); evidence of the usefulness and effectiveness of new devices; guidelines of what to measure to characterize the airway; more information about the influences of the soft tissues on craniofacial morphology; and information about effective digital work flows applied to clinical and educational settings.Conclusions: Progress in bridging the biology-technology gap has identified new needs for improvements in orthodontics and craniofacial care. [ABSTRACT FROM AUTHOR]

Bone׳s mechanostat theory describes the adaptation of bone tissues to their mechanical environment. Many experiments have investigated and observed such structural adaptation. However, there is still much uncertainty about how to define the reference mechanical state at which bone structure is adapted and stable. Clinical and experimental observations show that this reference state varies both in space and in time, over a wide range of timescales. We propose here an osteocyte-based mechanostat theory that encodes the mechanical reference state in osteocyte properties. This theory assumes that osteocytes are initially formed adapted to their current local mechanical environment through modulation of their properties. We distinguish two main types of physiological processes by which osteocytes subsequently modify the reference mechanical state at different timescales. One is cell desensitisation, which occurs rapidly and reversibly during an osteocyte׳s lifetime. The other is the replacement of osteocytes during bone remodelling, which occurs over the long timescales of bone turnover. The novelty of this theory is to propose that long-lasting morphological and genotypic osteocyte properties provide a material basis for a long-term mechanical memory of bone that is gradually reset by bone remodelling. We test this theory by simulating long-term mechanical disuse (modelling spinal cord injury), and short-term mechanical loadings (modelling daily exercises) with a mathematical model. The consideration of osteocyte desensitisation and of osteocyte replacement by remodelling is able to capture a number of phenomena and timescales observed during the mechanical adaptation of bone tissues, lending support to this theory. [ABSTRACT FROM AUTHOR]

Objective: A second focused workshop explored how to transfer novel findings into clinical orthodontic practice.Setting and Sample Population: Participants met in West Palm Beach (Florida, USA), on 9-11 September 2016 for the Consortium for Orthodontic Advances in Science and Technology 2016 Innovators' Workshop (COAST). Approximately 65 registered attendees considered and discussed information from 27 to 34 speakers, 8 to 15 poster presenters and four lunch-hour focus group leaders.Material and Methods: The innovators' workshops were organized according to five themed sessions. The aims of the discussion sessions were to identify the following: i) the strength and impact of the evidenced-based discoveries, ii) required steps to enable further development and iii) required steps to translate these new discoveries into orthodontic practice.Results: The role of gene-environment interactions that underlie complex craniofacial traits was the focus of several sessions. It was agreed that diverse approaches are called for, such as (i) large-scale collaborative efforts for future genetic studies of complex traits; (ii) deep genome sequencing to address the issues of isolated mutations; (iii) quantifying epigenetic-environmental variables in diverse areas myofascial pain, alveolar remodelling and mandibular growth. Common needs identified from the themed sessions were multiscale/multispecies modelling and experimentation using controlled and quantified mechanics and translation of the findings in bone biology between species. Panel discussions led to the consensus that a consortium approach to establish standards for intra-oral scanning and 3D imaging should be initiated.Conclusions: Current and emerging technologies still require supported research to translate new findings from the laboratory to orthodontic practice. [ABSTRACT FROM AUTHOR]

In the context of patient-specific 3D bone reconstruction, enhancing the surface with cortical thickness (COT) opens a large field of applications for research and medicine. This functionality calls for database analysis for better knowledge of COT. Our study provides a new approach to reconstruct 3D internal and external cortical surfaces from computer tomography (CT) scans and analyses COT distribution and variability on a set of asymptomatic femurs. The reconstruction method relies on a short (∼5 min) initialisation phase based on 3D reconstruction from biplanar CT-based virtual X-rays and an automatic optimisation phase based on intensity-based cortical structure detection in the CT volume, the COT being the distance between internal and external cortical surfaces. Surfaces and COT show root mean square reconstruction errors below 1 and 1.3 mm. Descriptions of the COT distributions by anatomical regions are provided and principal component analysis has been applied. The first mode, 16–50% of the variance, corresponds to the variation of the mean COT around its averaged shape; the second mode, 9–28%, corresponds to a fine variation of its shape. A femur COT model can, therefore, be described as the averaged COT distribution in which the first parameter adjusts its mean value and a second parameter adjusts its shape. [ABSTRACT FROM AUTHOR]

Bone models derived from patient imaging and fabricated using additive manufacturing technology have many potential uses including surgical planning, training, and research. This study evaluated the accuracy of bone surface reconstruction of two diarthrodial joints, the hip and shoulder, from computed tomography. Image segmentation of the tomographic series was used to develop a three-dimensional virtual model, which was fabricated using fused deposition modelling. Laser scanning was used to compare cadaver bones, printed models, and intermediate segmentations. The overall bone reconstruction process had a reproducibility of 0.3 ± 0.4 mm. Production of the model had an accuracy of 0.1 ± 0.1 mm, while the segmentation had an accuracy of 0.3 ± 0.4 mm, indicating that segmentation accuracy was the key factor in reconstruction. Generally, the shape of the articular surfaces was reproduced accurately, with poorer accuracy near the periphery of the articular surfaces, particularly in regions with periosteum covering and where osteophytes were apparent. [ABSTRACT FROM PUBLISHER]

Bone is a remarkable living material that comes in two forms with different porosities and different macrostructure, but with the same highly organised microstructure and nanostructure. As bone accumulates damage, it is removed and replaced. When the mechanical demands on bone increase the bone mass increases, while reductions in the loading leads to the removal of bone, thus bone can be considered a 'smart material'. The ongoing replacement of old bone tissue by new bone tissue is called remodelling. Bone formation, repair and remodelling is controlled and produced by four types of cell, namely osteoblasts, osteoclasts, osteocytes and bone lining cells. Bone remodelling is regulated by signals to these cells generated by mechanical loading. Exactly how loads are transferred into bone, how the bone cells sense these loads and how the signals are translated into bone formation or removal is unknown. In this review, the structure of bone and the cells responsible for maintaining bone are described. The mechanisms that cause bone to adapt to mechanical loading have been investigated. The methods that have been employed in attempts to determine this mechanism are considered. [ABSTRACT FROM AUTHOR]

The article presents a study which determines the bone volume and central tarsal bone (CTB) density in a cross-sectional study of racing greyhounds using computed tomography (CT). It describes the methodology and results of asymmetry in terms of average bone volume to determine the significant covariates in tarsal bone injury. The study implies that CT is an effective imaging system for CTB in live racing dogs.

Abstract: We have developed a mathematical approach for modelling the piezoelectric behaviour of bone tissue in order to evaluate the electrical surface charges in bone under different mechanical conditions. This model is able to explain how bones change their curvature, where osteoblasts or osteoclasts could detect in the periosteal/endosteal surfaces the different electrical charges promoting bone formation or resorption. This mechanism also allows to understand the BMU progression in function of the electro-mechanical bone behaviour. [Copyright &y& Elsevier]

Abstract: Osteoimmunological interactions are central to maintaining bone homeostasis and are key mechanisms in bone pathology. Macrophages are highly adaptable cells with pleiotropic actions. They have important roles in development, homeostasis and both innate and adaptive immunity. Macrophages can have broad ranging effects on bone, particularly in pathologic situations, but they are most commonly considered for their in vitro potential as an osteoclast precursor. We have recently shown that, like most tissues, the endosteum and periosteum contain a population of resident tissue macrophages (OsteoMacs) that impact on the bone formation process and are likely to play important roles in the bone niche. This review discusses the wider impact of macrophages in bone homeostasis and disease and proposes novel roles for OsteoMacs in bone modelling and remodelling. [Copyright &y& Elsevier]

Abstract: Background: At present the interest in medical field about the generation of three-dimensional digital models of anatomical structures increases due to the widespread diffusion of CAS – computer assisted surgery – systems. Most of them are based on CT – computer tomography – or MR – magnetic resonance – data volumes but sometimes this information is not available; there are only few X-ray, ultrasound or fluoroscopic images. Methods: This paper describes the study and the development of a script for a commercial software package (3ds Max) able to reconfigure the template model of a femur starting from two orthogonal images representing the specific patient''s anatomy. Results: The script was used in several tests as summarized in this paper and the results appear to be interesting and acceptable, even for the medical experts that evaluated them. Conclusions: The script developed in this work allows the generation of the 3D model of a femur in a very simple way (the user interface has been developed obeying to the main usability guidelines) and using a widespread commercial package. The quality of the results can be compared to the quality of more expensive and specialized systems. [Copyright &y& Elsevier]

Abstract: Intermittent administration of parathyroid hormone peptides has anabolic skeletal effects and reduces fracture risk in postmenopausal women with osteoporosis but the cellular and structural mechanisms by which these effects are mediated have not been fully established. In cancellous and endocortical bone, there is evidence that both modelling and remodelling-based formation contribute to the increase in bone mass although the contribution of these at different time points in the response to PTH has not been established. Despite the large increase in spine bone mineral density, however, significant increases in iliac crest cancellous bone volume and trabecular thickness have not been consistently demonstrated, possibly reflecting site-specific differences in PTH-induced skeletal effects and/or the large sampling and measurement variance associated with assessment of iliac crest cancellous bone volume and structure. In iliac crest cortical bone, increased cortical thickness has been demonstrated, due at least in part to increased endosteal bone formation; there is also some evidence for increased formation on periosteal surfaces. At some sites an increase in cortical porosity may also occur and the overall effects on cortical bone strength, particularly at the hip, remain to be established. Studies in iliac crest bone indicate a trend towards a lower mineralisation density of bone matrix and increased heterogeneity of mineralisation, consistent with new bone formation. In addition, there is a reduction in mineral crystallinity and a shift towards more divalent collagen cross-links, indicating a change towards a younger bone profile. The potential clinical implications of these effects on bone are currently unknown. The stimulatory effect of PTH peptides on bone formation may favour their use in low turnover bone disease and in states of advanced bone loss. Furthermore, if beneficial effects on cortical bone strength are confirmed, efficacy at non-vertebral sites might be superior to those observed with antiresorptive drugs. Better definition of the effects of intermittent PTH administration on cancellous and cortical bone remodelling and structure at different skeletal sites may inform these speculations and is an important area for future research. [Copyright &y& Elsevier]

This study examines the osteological changes in the hands and fingers of rock climbers that result from intense, long-term mechanical stress placed on these bones. Specifically, it examines whether rock climbing leads to metacarpal and phalange modelling in the form of increased cortical thickness as well as joint changes associated with osteoarthritis. This study also attempts to identify specific climbing-related factors that may influence these changes, including climbing intensity and frequency of different styles of climbing. Radiographs of both hands were taken for each participant and were scored for radiographic signs of osteoarthritis using an atlas method. Total width and medullary width were measured directly on radiographs using digital calipers and used to calculate cross-sectional area and second moment of area based on a ring model. We compared 27 recreational rock climbers and 35 non-climbers for four measures of bone strength and dimensions (cross-sectional area, second moment of area, total width and medullary width) and osteoarthritis. A chi-squared test for independence was used to compare climber and non-climber osteoarthritis scores. For each measure of bone strength climbers and non-climbers were compared using amanova test. Significantmanova tests were followed by principal components analysis (PCA) and individualanova tests performed on principal components with eigenvalues greater than one. A second PCA was performed on the climber subsample and the first principal component was then used as the dependent variable in linear regression variable selection procedures to determine which climbing-related variables affect bone thickness. The results suggest that climbers are not at an increased risk of developing osteoarthritis compared with non-climbers. Climbers, however, do have greater cross-sectional area as well as second moment of area. Greater total width, but not meduallary width, indicates that additional bone is deposited subperiosteally. The strength of the finger and hand bones are correlated with styles of climbing that emphasize athletic difficulty. Significant predictors include the highest levels achieved in bouldering and sport climbing. [ABSTRACT FROM AUTHOR]

The use of a rapid prototyping method was utilised to produce a pre-operative solid model of the proximal tibia in a patient with a massive defect of the medial tibial plateau. The solid model was reconstructed from aligned sequential CT images of the knee. This was then used to determine the level of bone resection of the proximal tibia for the optimum placement of the tibial component of a total knee replacement. This technique gives the surgeon both the three-dimensional anatomical information needed to ascertain whether there is adequate bony support after cutting for the prosthesis, as well as a solid model on which to carry out the proposed surgery, before undertaking the procedure on the patient. [Copyright &y& Elsevier]

Forward mandibular displacement in animal models is associated with faster and/or redirected condylar growth. Here the effect of forward displacement induced with an intraoral appliance on modelling/remodelling of the mandibular condyle was investigated in eight, 4-month-old, castrated male Merino sheep, randomly allocated to experimental and control groups (n=4 in each group). The study period was 15 weeks, during that time, (1) calcein, (2) tetracycline, and (3) alizarin red S fluorochromes were given to all animals from day 1. Midsagittal sections of the temporomandibular joints were selected for analysis. Dynamic variables of bone formation, static indices of bone-forming and -resorbing activity, and structural indices of trabecular bone were estimated histomorphometrically. The sampling site was divided into two regions for analysis: (a) a ‘subchondral region’ (2 and 3 labels only), believed to be the bone newly formed during the experimental period; (b) a ‘central region’ (labelled by all three fluorochromes), believed to be the bone that existed before the experiment. Regional differences in adaptive response were found. In the experimental group, the bone-volume fraction (BV/TV) of the subchondral regions had decreased, although the specific bone-surface and bone-formation rates had increased. This low BV/TV was associated with decreased trabecular thickness and increased trabecular separation. In the central condylar region of the experimental group, BV/TV was unchanged, but an increased osteoid surface was apparent when the eroded surface was taken into consideration. These adaptive condylar responses to forward mandibular displacement appeared to be the result of increased osteoblastic activity. Further studies are recommended to examine why the subchondral and central regions responded differently. [Copyright &y& Elsevier]

Analysis, evolution and layout in bone mechanics are described as seen from an optimal design and solid mechanics perspective. Anisotropic behaviour and three-dimensional modelling are necessary and focus is therefore put on the aspects of dealing with a large number of material parameters. The tools of homogenization, inverse homogenization and some basic results from optimal structural design are described. [ABSTRACT FROM AUTHOR]

In femoral bone of 10 adult patients without bone disease and of 15 patients with secondary hyperparathyroidism, the endosteal surface of the diaphysis was studied by scanning electron microscopy after non-mineralised organic material had been removed from the endosteal surface by sodium hypochlorite. This technique permits one to analyse the effects of past osteoblastic and osteoclastic activities. In normal bone, the endosteal envelope shows a highly ordered texture: The main part of the inner surface is represented by fully mineralised smooth surfaces without evidence of apposition or resorption (so called neutral surfaces). In apposition areas, collagen fibers are still incompletely mineralised. Ordered mineral deposits are observed, consisting of spindleshaped calcospherites of uniform size. The resorption areas are sharply delimited. The resorption layer shows a small difference of level with respect to the surrounding neutral surface. Resorption areas consist of numerous lacunae with a smooth bottom. Individual lacunae are encircled by shallow ridges which run almost perpendicularly to the main direction of collagen fibers that have been exposed by resorption. These findings suggest that in normal bone osteoclasts act as a coordinated group of cells. The direction of advance of the resorption area is to some extent influenced by the collagen pattern of bone. In patients with secondary hyperparathyroidism, domain formation of the endosteal surface can no longer be recognized. The size and shape of calcospherites are extremely heterogeneous, a finding interpreted as evidence of formation of woven bone. Resorption areas are irregularly determined and often resemble worm-eaten wood. The planes of resorption vary in direction and depth and in general resorption cavities penetrate deeper than in normal bone. These findings point to loss of coordinated cell action under the influence of hyperparathyroidism. The observations suggest that in hyperparathyroidism endosteal cells do not respond to local factors which influence endosteal cell activities in modelling processes of normal bone. Such local factors consist of the pattern of collagen and lamellar organisation on one hand and mechanical forces presumably via pizo-electrical potentials, on the other. In hyperpara-thyroidism the interdependence between bone matrix texture and spatial orientation of bone surface lining cell activities is lost. [ABSTRACT FROM AUTHOR]

To better understand the intra-uterine bone modelling and remodelling process in small-for-gestational-age (SGA) newborn infants, long bone growth was studied using postmortem X-ray films in a group of such infants (n = 34). Bone length, diaphyseal diameter, medullary diameter, cortical thickness, cortical area, the Barnett-Nordin index, and the percentage of cortical area were determined in femur, tibia, and humerus. A separate group of appropriate-for-gestational-age (AGA) newborn infants (n = 146) was used as controls. Length and cortical bone mass in all three bones were significantly lower in SGA infants than in AGA infants. Decreased cortical bone mass in SGA infants was the result of decreased diaphyseal diameters and increased medullary diameters. Similar results were obtained when SGA infants were subclassified as preterm and term and compared with the control group of AGA infants. Bone lengths and diaphyseal diameters in SGA infants did not differ from those observed in a weight-matched control group of AGA infants although the latter were younger by 4 weeks' gestation. However, the cortical bone mass was lower than in the control group because of the relative greater medullary diameters in all three long bones in the SGA infants. Our present results indicate that reduced cortical bone mass in SGA infants is a mixed growth modelling and remodelling dependent process. [ABSTRACT FROM AUTHOR]