Differences In Bone Morphology Research Articles

Femoral bone structure and mechanics at the edge and core of an expanding population of the invasive frog Xenopus laevis.

Understanding how living tissues respond to changes in their mechanical environment is a key question in evolutionary biology. Invasive species provide an ideal model for this as they are often transplanted between environments that differ drastically in their ecological and environmental context. Spatial sorting, the name given to the phenomenon driving differences between individuals at the core and edge of an expanding range, has been demonstrated to impact the morphology and physiology of Xenopus laevis from the invasive French population. Here, we combined a structural analysis using micro-CT scanning and a functional analysis by testing the mechanical properties of the femur to test whether the increased dispersal at the range edge drives differences in bone morphology and function. Our results show significant differences in the inner structure of the femur as well as bone material properties, with frogs from the centre of the range having more robust and resistant bones. This is suggestive of an energy allocation trade-off between locomotion and investment in bone formation, or alternatively, may point to selection for fast locomotion at the range edge. Overall, our results provide insights on the growth of the long bones and the formation of trabecular bone in frogs.

Comparison of the three-dimensional bone morphology of the first proximal phalanx and first metatarsal between normal and hallux valgus foot using the homologous model technique

Bone morphology is one of the factors involved in hallux valgus development. However, previous studies have not evaluated the overall bone shape in three dimensions. This study aimed to compare the overall shape of the first proximal phalanx and first metatarsal in hallux valgus with those of normal feet.Homologous models were created from computed tomography data of the first proximal phalanx and first metatarsal of 75 healthy men and 53 women in the control group and 10 men and 71 women in the hallux valgus group. Principal component analysis was performed to examine the differences in bone morphology between the control and hallux valgus groups. In men and women with hallux valgus, the proximal articular surface of the first proximal phalanx was characterized by a more lateral inclination and torsion of the pronated first metatarsal. Additionally, the first metatarsal head was characterized by a more lateral inclination in male hallux valgus. This study is the first to reveal the morphological characteristics of the first metatarsal and first proximal phalanx in hallux valgus as a whole bone using a homologous model technique. These characteristics are considered possible causes of hallux valgus development. The shapes of the first proximal phalanx and first metatarsal in hallux valgus were different from those in normal feet. This finding should be useful when considering the pathogenesis and treatment development for hallux valgus.

Increased Dietary Protein to Energy Ratio in Pre-Weaning Lambs Increases Average Daily Gain and Cortical Bone Thickness in the Tibia

The objective of this study was to examine if diets differing in crude protein (CP) to metabolizable energy (ME) ratio (CP:ME) pre-weaning altered peripheral quantitative computed tomography (pQCT) measures of bone mass and strength in lambs. The left hind leg of lambs were available at the completion of a trial designed to examine the effect that altering the CP:ME ratio in milk replacer had on growth and body composition of pre-weaned lambs reared artificially. Treatments consisted of either normal commercial milk replacer (CMR, n = 10) containing 240 g/kg CP and 21.89 MJ/kg ME, high protein milk replacer (HPM, n = 9) containing CMR with additional milk protein concentrate to reach 478.7 g/kg CP and 19.15 MJ/kg ME or a mix of normal milk replacer and milk protein concentrate adjusted twice-weekly to match optimal CP:ME requirements (MB, n = 8) based on maintenance plus 300 g/d liveweight gain. At 22 kg live weight, lambs were euthanized and the tibia including the surrounding muscle was collected and scanned using pQCT at the mid-diaphysis. Lambs on the HPM and MB diets had a greater average daily gain (p < 0.01). There were limited differences in bone morphology and muscle mass, though notably the higher protein diets (MB and HPM) were associated with greater cortical thickness (p < 0.05) and, therefore, potentially greater peak bone mass at maturity This finding demonstrates that pre-weaning diets, and the protein content in particular, may influence the developmental potential of long bones and attainment of peak bone mass at maturity.

Influence of differences in bone morphology on the distribution patterns of subchondral bone density across the trapeziometacarpal joint

We aimed to clarify the effects of morphological patterns of the trapezium and first metacarpal on the distribution of subchondral bone density across the articular surface of the trapeziometacarpal (TMC) joint using computed tomography osteoabsorptiometry. Thirty-three patients with normal TMC joints were evaluated. The percentages of the high-density areas in the radial-dorsal and ulnar-volar regions of the trapezium were significantly higher than that in the ulnar-dorsal region, and that of the ulnar-dorsal region of the first metacarpal was significantly lower than in the other three regions. The percentage of the high-density area of the radial-dorsal region of the trapezium and trapezial inclination (TI) showed a significant positive correlation, and the percentages of the high-density areas in the ulnar-dorsal and ulnar-volar regions had significant negative correlations with TI at the articular surface of the first metacarpal. These results indicate that bony morphologic differences in the trapezium affect the distribution pattern of subchondral bone density through the TMC joint.

Comparison of Implant Placement Accuracy in Healed and Fresh Extraction Sockets between Static and Dynamic Computer-Assisted Implant Surgery Navigation Systems: A Model-Based Evaluation.

The aim of this model-base study was to compare the accuracy of implant placement between static and dynamic computer-assisted implant surgery (CAIS) systems in a fresh extraction socket and healed ridge. A randomized in vitro study was conducted. Twenty 3D-printed maxillary models and 80 implants were used. One experienced researcher placed the implants using either the static navigation or dynamic navigation system. Accuracy was measured by overlaying the real position in the postoperative CBCT on the virtual presurgical placement of the implant in a CBCT image. Descriptive and bivariate analyses of the data were performed. In the fresh sockets, the mean deviation was 1.24 ± 0.26 mm (entry point), 1.69 ± 0.34 mm (apical point), and 3.44 ± 1.06° (angle discrepancy) in the static CAIS group, and 0.60 ± 0.29 mm, 0.78 ± 0.33 mm, and 2.47 ± 1.09° in the dynamic CIAS group, respectively. In the healed ridge, the mean deviation was 1.09 ± 0.17 mm and 1.40 ± 0.30 mm, and 2.12 ± 1.11° in the static CAIS group, and 0.80 ± 0.29 mm, 0.98 ± 0.37 mm, and 1.69 ± 0.76° in the dynamic CIAS group, respectively. Compared with the static CAIS system, the dynamic CAIS system resulted in significantly lower entry and apical errors in both fresh sockets and healed ridges. Differences in bone morphology therefore seem to have little effect on accuracy in the dynamic CAIS group.

Degenerative Joint Damage Is Not a Risk Factor for Streptococcal Sepsis and Septic Arthritis in Mice.

Septic arthritis (SA) is an aggressive joint disorder causing invalidity and mortality. Although epidemiological studies suggest osteoarthritis (OA) as a risk factor for SA, experimental insights into the relatedness of both diseases are lacking. We therefore sought to investigate whether pre-existing OA indeed promotes SA frequency or severity. We used STR/ort mice that spontaneously develop OA and, in addition, induced OA via anterior cruciate ligament transection (ACLT) in C57BL/6J mice. Mice were infected with Group A Streptococcus (GAS) and then were monitored for clinical signs of sepsis and SA. Sepsis was confirmed via elevated inflammatory cytokines in plasma, while bone morphology was assessed by micro-computed tomography. Cartilage integrity was evaluated histologically. Mice with spontaneous OA developed life-threatening SA, with GAS only moderately affecting the femoral bone structure. Surgically induced OA neither impacted on SA incidence nor on mortality when compared to infected mice without the preceding joint disease. Furthermore, only insignificant differences in bone morphology were detected between both groups. Our data indicate that degenerative joint damage due to ACLT, by itself, does not predispose mice to SA. Hence, we propose that other factors such as prosthetic joint replacement or high age, which frequently coincide with OA, pose a risk for SA development.

Bone morphological feature extraction for customized bone plate design

Fractures are difficult to treat because of individual differences in bone morphology and fracture types. Compared to serialized bone plates, the use of customized plates significantly improves the fracture healing process. However, designing custom plates often requires the extraction of skeletal morphology, which is a complex and time-consuming procedure. This study proposes a method for extracting bone morphological features to facilitate customized plate designs. The customized plate design involves three major steps: extracting the morphological features of the bone, representing the undersurface features of the plate, and constructing the customized plate. Among these steps, constructing the undersurface feature involves integrating a group of bone features with different anatomical morphologies into a semantic feature parameter set of the plate feature. The undersurface feature encapsulates the plate and bone features into a highly cohesive generic feature and then establishes an internal correlation between the plate and bone features. Using the femoral plate as an example, we further examined the validity and feasibility of the proposed method. The experimental results demonstrate that the proposed method improves the convenience of redesign through the intuitive editing of semantic parameters. In addition, the proposed method significantly improves the design efficiency and reduces the required design time.

Radiographic geometry and clinical glenohumeral range of motion after reverse shoulder athroplasty, a retrospective cohort study

BackgroundThe range of motion (ROM) in reverse shoulder arthroplasty (RSA), is mechanically limited by the surrounding bony obstacles especially in abduction and rotation planes. However, the clinical effect of implant positioning, prosthesis design, and individual differences in bone morphology, on ROM is obscure. The aim of this study was to investigate the correlation between radiographic geometry and clinical glenohumeral (GH) ROM after RSA. MethodsRSA patients operated at Turku University Hospital during 2007–2013 were called for radiological and clinical follow-up. Pre- and postoperative true anteroposterior radiographs were obtained and the positioning of the center of rotation (COR) in relation to the surrounding bony structures was measured. Active and passive shoulder and GH abduction, flexion, internal and external rotation ROM were measured with goniometer. The Constant score (CS) and pain visual analogue scale (VAS) were recorded. The correlation between the radiographically measured parameters and the active and passive ROM and clinical outcome was statistically analyzed. Results91 shoulders were available for analyses with a mean follow-up of 38.7 months ± SD 20 (range 12–83) months. 77% of the patients were female, the mean age was 73 (SD 9) years. The mean angle between the line of supraspinatus fossa, and the line between COR and lateral edge of the acromion (α-angle) was 127° (SD 14) and the mean angle between the lines from lateral edge of the acromion to COR, and from there to the superior edge of the greater tubercle (β-angle) was 54° (SD 11). The mean active shoulder flexion at follow-up was 118° (SD 26), abduction 104° (SD 32), external rotation 41° (SD 22), internal rotation 77° (SD 21). The mean passive GH flexion was 80° (SD 19), abduction 67° (SD 15), external rotation 31° (SD 16) and internal rotation 34° (SD 14). The mean Constant score at follow-up was 53 (SD 18) and pain VAS 2 (SD 3). The positioning of the radiographically measured COR did not statistically significantly correlate with the ROM or clinical outcome scores. ConclusionsPostoperative radiographically measured two-dimensional geometry and positioning of the COR does not significantly correlate with the glenohumeral range of motion or clinical results after RSA. Level of evidenceLevel 3, retrospective cohort study

Bilateral Symmetry, Sex Differences, and Primary Shape Factors in Ankle and Hindfoot Bone Morphology.

Background:Ankle injuries and joint degeneration may be related to ankle bone morphology. Little data exist to characterize healthy hindfoot bone morphology. The purpose of this study was to characterize side-to-side symmetry and sex differences in ankle and hindfoot bone morphology, and to identify the primary shape factors that differentiate ankle and hindfoot bone morphology among individuals.Methods:Computed tomography was used to create 3D surface models of the distal tibia, talus, and calcaneus for 40 ankle and hindfoot bones from 20 healthy individuals. Morphologic differences between left and right bones of the same individual and between males and females were determined. Statistical shape modeling was performed to identify primary shape variations among individuals.Results:Side-to-side differences in bone morphology averaged 0.79 mm or less. The average distal tibia in males was larger overall than in females. No significant sex difference was noted in the tali. The average female calcaneus was longer and thinner than the average male calcaneus. Variability in ankle and hindfoot bone morphology is primarily associated with articulating surface shape, overall length and width, and tendon/ligament attachment points.Conclusion:In general, the contralateral ankle can serve as an accurate guide for operative restoration of native ankle morphology; however, specific regions demonstrate higher asymmetry.Clinical Relevance:Knowledge of regions of high and low bilateral symmetry can improve hindfoot and ankle reconstruction. Design of ankle prostheses can be improved by accounting for differences in bone morphology associated with sex and shape differences among individuals.

Osteocytes in the American Alligator (Alligator mississippiensis)

American alligators (Alligator mississippiensis) are a large crocodilian living in the southeastern United States of America. Compared to mammals, they have an extended growth period after reaching adulthood. Evolutionarily, they are also one of few vertebrates that have survived long geological periods with conservative morphology. Thus among many aspects related to the growth, development, and physiological adaptions of this long surviving species, the bone biology is interesting in terms of extended bone growth and maintenance, and especially the morphology and behavior of the osteons, the fundamental functional unit in the cortical bone. In this study, alligator bones were analyzed to visualize reptilian osteocytes and compare them to those of mice, the most commonly used mammalian model in bone biology and pharmaceutical studies. In the femora of a one‐year‐old alligator, the osteon structure of the cortical bone was studied to reveal the density and structure of osteons, as well as the morphology of osteocytes, using confocal imaging by Fluorescein Iso‐Thio‐Cyanate sample preparation and staining, and osteocyte morphology was visualized using acid‐etch SEM. Results demonstrated that in this relatively fast growing individual, there were few osteon‐like structures lined along the periosteum and endosteum, indicating a slow rate of bone remodeling. Compared to osteocytes in mice, osteocytes in the alligator specimen were irregular in shape and less evenly distributed, and had fewer dendrites. This study demonstrated the morphology of alligator osteocytes for the first time. The findings indicate that there are significant differences in bone morphology and physiology at the microstructural level between reptiles and mammals; the implications in our understanding of bone biology is yet to be fully understood. This study also suggests that American alligators will be an idea model for studying bone development, adaptation, and evolution at the pre‐mammalian stage.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Hind- and midfoot bone morphology varies with foot type and sex.

Foot type has been associated with pain, injury, and altered gait mechanics. Morphological variations in foot bones due to foot type variation may impact surgical and therapeutic treatments. The purpose of this study was to utilize principal component analysis (PCA) to determine how morphology of the hind- and midfoot bones differs among foot types and sex. The calcaneus, talus, navicular, and cuboid were segmented using previously obtained computed tomography (CT) scans and converted to surface models. The CTs were sorted into four foot types-cavus, neutrally aligned, asymptomatic planus, and symptomatic planus. Morphometric shape analysis software (Geomorph) was used to perform a PCA to determine which components varied between foot types and between sexes. The calcaneus showed planus feet of both types to have calcanei that have decreased height and increased length compared to neutrally aligned feet. The talus demonstrated increased posterior mass for cavus feet compared to neutrally aligned feet. For the navicular, symptomatic planus had a more posteriorly positioned tuberosity and were wider than asymptomatic planus feet. The cuboid did not exhibit any differences between foot types. Sex differences, found only at the talus and navicular, were subtle. PCA is an objective technique that helped elucidate differences in bone morphology between foot types and sex without needing to determine the features of interest before comparing groups. Understanding these variations can help inform diagnosis of foot pathologies and surgical protocols as well as improve computer models of the foot. Published 2018. This article is a U.S. Government work and is in the public domain in the USA. J Orthop Res 9999:1-16, 2019.

Alterations to the Gut Microbiome Impair Bone Strength and Tissue Material Properties.

Alterations in the gut microbiome have been associated with changes in bone mass and microstructure, but the effects of the microbiome on bone biomechanical properties are not known. Here we examined bone strength under two conditions of altered microbiota: (1) an inbred mouse strain known to develop an altered gut microbiome due to deficits in the immune system (the Toll-like receptor 5-deficient mouse [TLR5KO]); and (2) disruption of the gut microbiota (ΔMicrobiota) through chronic treatment with selected antibiotics (ampicillin and neomycin). The bone phenotypes of TLR5KO and WT (C57Bl/6) mice were examined after disruption of the microbiota from 4 weeks to 16 weeks of age as well as without treatment (n = 7 to 16/group, 39 animals total). Femur bending strength was less in ΔMicrobiota mice than in untreated animals and the reduction in strength was not fully explained by differences in bone cross-sectional geometry, implicating impaired bone tissue material properties. Small differences in whole-bone bending strength were observed between WT and TLR5KO mice after accounting for differences in bone morphology. No differences in trabecular bone volume fraction were associated with genotype or disruption of gut microbiota. Treatment altered the gut microbiota by depleting organisms from the phyla Bacteroidetes and enriching for Proteobacteria, as determined from sequencing of fecal 16S rRNA genes. Differences in splenic immune cell populations were also observed; B and T cell populations were depleted in TLR5KO mice and in ΔMicrobiota mice (p < 0.001), suggesting an association between alterations in bone tissue material properties and immune cell populations. We conclude that alterations in the gut microbiota for extended periods during growth may lead to impaired whole-bone mechanical properties in ways that are not explained by bone geometry. © 2017 American Society for Bone and Mineral Research.

A parametric approach to construct femur models and their fixation plates

ABSTRACTAlthough anatomic plates reflect an important breakthrough in the treatment of distal femur fractures, there are still some patients experiencing healing complications. For individual differences in bone morphology and fractures, the development of patient specific plates is very complex and needs a long cycle. In this study, a parametric approach was proposed to conveniently construct femur models and design their fixation plates. First, the typical femur anatomy was described with the average femur model. Second, five surface features were defined to represent the femur surface model by setting up parameterization and parameter constraints. Third, according to the fracture information of a specific patient, customized plate surface with a suitable contour was created from the reconstructed femur model. Finally, the femur plate was represented by feature parameterization, and the hierarchical constraints between femur parameters and plate parameters were built to construct a plate model. The experimental results showed that the proposed method could effectively represent femur surface shape features and intuitively construct and edit individualized plates with high-level parameters. The method is competitive in time saving and design convenience and may provide a basic tool for digital restoration of incomplete femurs and the design of patient specific femur plates.

Jagged1 is essential and sufficient for osteoblast development during maxillary ossification (921.2)

Maxillary hypoplasia occurs due to insufficient maxillary intramembranous ossification, leading to poor dental occlusion, respiratory obstruction and cosmetic deformities. Conditional deletion of Jagged1 (Jag1) in cranial neural crest (CNC) cells using Wnt1‐cre (Jag1CKO) led to maxillary hypoplasia characterized by intrinsic differences in bone morphology and density using μCT evaluation. Jag1CKO maxillas had altered collagen deposition, delayed ossification, and reduced expression of early and late determinants of osteoblast development during maxillary ossification. In vitro bone cultures on Jag1CKO mouse embryonic maxillary mesenchymal (MEMM) cells demonstrated decreased mineralization that was also associated with diminished induction of osteoblast determinants. BMP receptor expression was reduced in the Jag1CKO MEMM cells suggesting that these cells were unable to respond to BMP‐induced differentiation. Jag1‐Fc rescued in vitro mineralization and osteoblast gene expression changes. These data suggest that Jag1 signaling in CNC‐derived MEMM cells is required for osteoblast development and differentiation during maxillary ossification.Grant Funding Source: 5K08DE17953‐5

Jagged1 is essential for osteoblast development during maxillary ossification

Maxillary hypoplasia occurs due to insufficient maxillary intramembranous ossification, leading to poor dental occlusion, respiratory obstruction and cosmetic deformities. Conditional deletion of Jagged1 (Jag1) in cranial neural crest (CNC) cells using Wnt1-cre; Jagged1f/f (Jag1CKO) led to maxillary hypoplasia characterized by intrinsic differences in bone morphology and density using μCT evaluation. Jag1CKO maxillas revealed altered collagen deposition, delayed ossification, and reduced expression of early and late determinants of osteoblast development during maxillary ossification. In vitro bone cultures on Jag1CKO mouse embryonic maxillary mesenchymal (MEMM) cells demonstrated decreased mineralization that was also associated with diminished induction of osteoblast determinants. BMP receptor expression was dysregulated in the Jag1CKO MEMM cells suggesting that these cells were unable to respond to BMP-induced differentiation. JAG1-Fc rescued in vitro mineralization and osteoblast gene expression changes. These data suggest that JAG1 signaling in CNC-derived MEMM cells is required for osteoblast development and differentiation during maxillary ossification.

Bone Microarchitecture and Estimated Strength in 499 Adult Danish Women and Men: A Cross-Sectional, Population-Based High-Resolution Peripheral Quantitative Computed Tomographic Study on Peak Bone Structure

High-resolution peripheral quantitative computed tomography (HR-pQCT) allows in vivo assessment of cortical and trabecular bone mineral density (BMD), geometry, and microarchitecture at the distal radius and tibia in unprecedented detail. In this cross-sectional study, we provide normative and descriptive HR-pQCT data from a large population-based sample of Danish Caucasian women and men (n = 499) aged 20-80 years. In young adults (<35 years), women (n = 100) compared to men (n = 64) had smaller total and cortical areas, inferior metric trabecular indices, higher network inhomogeneity, lower cortical porosity, and lower finite element estimated bone strength. The changes in parameters with age were estimated from multiple regression analyses. In men, with age the greatest changes (from parameter minimum or maximum) until 80 years were found for cortical porosity (1.91 IQR), BV/TV (-1.09 IQR), and trabecular thickness (-0.87 IQR) in the radius and BV/TV (-1.55 IQR), cortical BMD (-1.25 IQR), and cortical porosity (1.25 IQR) in the tibia. In women changes were most pronounced for cortical porosity (4.76 IQR), trabecular inhomogeneity (3.84 IQR), and cortical BMD (-2.86 IQR) in the radius and cortical BMD (-5.06 IQR), cortical porosity (3.86 IQR), and cortical area (-1.64 IQR) in the tibia. These findings emphasize the age- and sex-related differences in bone morphology, with men having a structural advantage over women from early adult life translating into superior indices of bone strength. With age women are further disadvantaged compared to men by greater decrements in cortical and trabecular architecture in the radius and cortical architecture in the tibia.

Galea and periosteum flap filled with bone fragments in rabbits

To study the bone viability of a vascularized galea and periosteum flap filled with bone fragments, as a substitute of the bone graft in facial reconstructive surgery. Forty rabbits were studied, and divided in two groups. One had a simple galea and periosteum flap done and the other had the same flap done and filled with bone fragments of the calvaria. The bone formation was evaluated by radiographies, macroscopic and microscopic analysis. The bone neoformation in both groups with differences in bone morphology and structure especially at histological analysis. This study demonstrated osseous formation in both groups of galea and periosteum flaps, with and without bone fragments.

Periprosthetic infections after total shoulder arthroplasty: a 33-year perspective

To examine the rates and predictors of deep periprosthetic infections after primary total shoulder arthroplasty (TSA). We used prospectively collected data on all primary TSA patients from 1976-2008 at Mayo Clinic Medical Center. We estimated survival free of deep periprosthetic infections after primary TSA using Kaplan-Meier survival. Univariate and multivariable Cox regression was used to assess the association of patient-related factors (age, gender, body mass index), comorbidity (Deyo-Charlson index), American Society of Anesthesiologists class, implant fixation, and underlying diagnosis with risk of infection. A total of 2,207 patients, with a mean age of 65 years (SD, 12 years), 53% of whom were women, underwent 2,588 primary TSAs. Mean follow-up was 7 years (SD, 6 years), and the mean body mass index was 30 kg/m(2) (SD, 6 kg/m(2)). The American Society of Anesthesiologists class was 1 or 2 in 61% of cases. Thirty-two confirmed deep periprosthetic infections occurred during follow-up. In earlier years, Staphylococcus predominated; in recent years, Propionibacterium acnes was almost as common. The 5-, 10-, and 20-year prosthetic infection-free rates were 99.3% (95% confidence interval [CI], 98.9-99.6), 98.5% (95% CI, 97.8-99.1), and 97.2% (95% CI, 96.0-98.4), respectively. On multivariable analysis, a male patient had a significantly higher risk of deep periprosthetic infection (hazard ratio, 2.67 [95% CI, 1.22-5.87]; P = .01) and older age was associated with lower risk (hazard ratio, 0.97 [95% CI, 0.95-1.00] per year; P = .05). The periprosthetic infection rate was low at 20-year follow-up. Male gender and younger age were significant risk factors for deep periprosthetic infections after TSA. Future studies should investigate whether differences in bone morphology, medical comorbidity, or other factors are underlying these associations.

Bone structure and fracture risk: Do they go arm in arm?

increased cortical and trabecular thickness and greater cortical density at both the distal radius and the distal tibia. (12,13) In the current study, 29 Chinese-American and 68 white postmenopausal women were evaluated. Areal bone mineral density (aBMD) at the spine, hip, and radius was measured using dualenergy X-ray absorptiometry (DXA), and bone microstructure at the distal radius and tibia was assessed using HR-pQCT. As expected, the Chinese-American women were shorter and weighed less than the white women. Surprisingly, however, aBMD was similar between the two groups at all skeletal sites. Postmenopausal Chinese-American women had approximately 10% smaller bone cross-sectional area but 5% to 6% higher cortical density and 16% to 18% higher cortical thickness than whites. Chinese-American women also had fewer trabeculae at the distal radius and fewer but thicker trabeculae at the distal tibia compared with whites. Differences in bone cross-sectional area were attenuated somewhat after adjusting for the shorter stature and lower weight of the Chinese-American women, whereas differences in cortical and trabecular thickness were largely unaffected. The net result of these differences in bone morphology, evaluated by finite-element analysis (FEA), showed similar compressive stiffness in the two groups, suggesting that the smaller cross-sectional area in Chinese-American women was compensated for by their increased cortical and trabecular thicknesses. The study provides novel insights into differences in bone structure by ethnicity, yet several issues should be considered when interpreting the results, including (1) the modest sample size, (2) the limitations of HR-pQCT measurements and assumptions used for derivation of some microarchitecture features, and (3) lack of information on tissue material properties. The authors examined a relatively small convenience sample of only 29 Chinese-American subjects who were, on average, 2 years younger and tended to be closer to the menopause than the white women. After adjusting the analyses for age and body mass index (BMI), the strength of some of the ethnicity-related differences was attenuated, although most of the differences

The Age of Puberty Determines Sexual Dimorphism in Bone Structure: A Male/Female Co-Twin Control Study

Taller stature and larger bone size in males are attributed to more rapid growth than in females. However, comparing sexes of the same age mismatches by pubertal stage, so males will be less mature than females. Comparing sexes of the same pubertal stage mismatches by age, so males will be older than females. We hypothesized that sex differences in stature and bone structure are the result of sex differences in the duration but not the rate of prepubertal and pubertal growth. We measured bone dimensions in 90 male/female co-twin pairs aged 7-18 yr using anthropometry and dual x-ray absorptiometry. Forty-two pairs had follow-up assessments. Within-pair differences were expressed as a percentage of the pair mean. Thirty percent of the 1-1.5 sd sex difference in bone widths and midfemur bending strength observed in 11 postpubertal pairs was present in 43 prepubertal pairs. In prepubertal pairs, annual growth in leg length was about 1.5 times truncal growth, but neither rate differed by sex. During puberty, truncal growth in both sexes was higher than before puberty but did not differ by sex. The longer period of pre- and intrapubertal growth in males produced most of the sex difference in bone morphology observed in postpubertal twins. Sex differences in bone morphology are the result of the later onset of puberty in males, not more rapid growth. Differences in bone widths are partly established before puberty.