Interrelationship of trabecular mechanical and microstructural properties in sheep trabecular bone

The relationship between primate distal fibula trabecular architecture and arboreality, phylogeny and size

The fibula, despite being traditionally overlooked compared to the femur and the tibia, has recently received attention in primate functional morphology due to its correlation with the degree of arboreality (DOA). Highlighting further fibular features that are associated with arboreal habits would be key to improving palaeobiological inferences in fossil specimens. Here we present the first investigation on the trabecular bone structure of the primate fibula, focusing on the distal epiphysis, across a vast array of species. We collected μCT data on the distal fibula for 21 species of primates, with representatives from most of the orders, and we employed a recently developed approach implemented in the R package 'indianaBones' to isolate the entire trabecular bone underlying an epiphysis or articular facet. After extracting both traditional trabecular parameters and novel topological indices, we tested for the posited relationship between trabecular bone and DOA. To disentangle this effect from others related to body size and phylogenetic relationship, we included a body mass proxy as covariate and employed phylogenetic comparative methods. We ran univariate/multivariate and exploratory/inferential statistical analyses. The trabecular structure of the fibular distal epiphysis in primates does not appear to be associated with the DOA. Instead, it is strongly affected by body mass and phylogenetic relationships. Although we identified some minor trends related to human bipedalism, our findings overall discourage, at this stage, the study of distal fibula trabecular bone to infer arboreal behaviors in extinct primates. We further found that body size distribution is strongly related to phylogeny, an issue preventing us from unravelling the influence of the two factors and that we believe can potentially affect future comparative analyses of primates. Overall, our results add to previous evidence of how trabecular traits show variable correlation with locomotor aspects, size and phylogenetic history across the primate skeleton, thus outlining a complex scenario in which a network of interconnected factors affects the morphological evolution of primates. This work may represent a starting point for future studies, for example, focusing on the effect of human bipedalism on distal fibula trabecular bone, or aiming to better understand the effects of body size and phylogenetic history on primate morphological evolution.

A cellular-meso-macro three-scale approach captures remodelling of cancellous bone in health and disease

Remodelling of cancellous bone due to the combined activity of osteoclasts and osteoblasts at the cellular scale has notable repercussions both at the meso (tissue) as well as the macro (organ) scale. At the meso scale, trabeculae adapt their geometry, typically in terms of their cross section, whereas the nominal bone density evolves at the macro scale, all in response to habitual mechanical loading and its perturbations. To capture this intricate scale coupling, we here propose a novel conceptual three-scale approach to the remodelling of cancellous bone. Therein, we combine a detailed bone cell population model at the cellular scale with an idealised trabecular truss network model with adaptive cross sections, that are driven by the cell population model, at the meso scale, which is eventually upscaled to a continuum bone density adaption model at the macro scale. Algorithmically, we solve the meso and macro problems concurrently within a finite element setting and update the cell activity in a staggered fashion. Our benchmark simulations demonstrate the applicability and effectivity of the three-scale approach to analyse bone remodelling in health and disease (here exemplified for the example of osteoporosis) with rich details, e.g. evolving anisotropy, resolved at each scale.

On the influence of structural and chemical properties on the elastic modulus of woven bone under healing

Introduction

Woven bone, a heterogeneous and temporary tissue in bone regeneration, is remodeled by osteoblastic and osteoclastic activity and shaped by mechanical stress to restore healthy tissue properties. Characterizing this tissue at different length scales is crucial for developing micromechanical models that optimize mechanical parameters, thereby controlling regeneration and preventing non-unions.

Methods

This study examines the temporal evolution of the mechanical properties of bone distraction callus using nanoindentation, ash analysis, micro-CT for trabecular microarchitecture, and Raman spectroscopy for mineral quality. It also establishes single- and two-parameter power laws based on experimental data to predict tissue-level and bulk mechanical properties.

Results

At the macro-scale, the tissue exhibited a considerable increase in bone fraction, controlled by the widening of trabeculae. The Raman mineral-to-matrix ratios increased to cortical levels during regeneration, but the local elastic modulus remained lower. During healing, the tissue underwent changes in ash fraction and in the percentages of Calcium and Phosphorus. Six statistically significant power laws were identified based on the ash fraction, bone fraction, and chemical and Raman parameters.

Discussion

The microarchitecture of woven bone plays a more significant role than its chemical composition in determining the apparent elastic modulus of the tissue. Raman parameters were demonstrated to provide more significant power laws correlations with the micro-scale elastic modulus than mineral content from ash analysis.

Mechanical impact of regional structural deterioration and tissue-level compensation on proximal femur trabecular bone

Introduction

Osteoporosis-induced changes in bone structure and composition significantly reduce bone strength, particularly in the human proximal femur. This study examines how these changes affect the mechanical performance of trabecular bone to enhance diagnosis, prevention, and treatment strategies.

Methods

A proximal femur sample was scanned using micro-CT at 40 μm resolution. Five regions of interest were selected within the femoral head, femoral neck, and greater trochanter. Structural models simulating various stages of osteoporosis were created using image processing software. Micro-finite element analysis evaluated the mechanical properties of trabecular bone under different conditions of structural deterioration and tissue-level elastic modulus variations. The combined effects of structural deterioration and tissue-level mechanical properties on trabecular bone mechanical performance were further analyzed.

Results

The mechanical performance of trabecular bone generally follows a power-law relationship with its microstructural characteristics. However, in any specific region, the apparent mechanical properties linearly decrease with structural deterioration. The femoral neck and greater trochanter are more sensitive to structural deterioration than the femoral head. A 5% bone mass loss in the femoral head led to a 7% reduction in mechanical performance, while the femoral neck experienced a 12% loss. Increasing tissue-level elastic modulus improved mechanical performance, partially offsetting bone mass reduction effects.

Conclusion

Trabecular bone in low bone mass regions is more affected by bone mass loss. Structural deterioration primarily reduces bone strength, but improvements in tissue-level properties can mitigate this effect, especially in early osteoporosis. Targeted assessments and interventions are crucial for effective management. Future research should explore heterogeneous deterioration models to better understand osteoporosis progression.

Hydrogel-chitosan and polylactic acid-polycaprolactone bioengineered scaffolds for reconstruction of mandibular defects: a preclinical in vivo study with assessment of translationally relevant aspects

Background: Reconstruction of mandibular bone defects is a surgical challenge, and microvascular reconstruction is the current gold standard. The field of tissue bioengineering has been providing an increasing number of alternative strategies for bone reconstruction. Methods: In this preclinical study, the performance of two bioengineered scaffolds, a hydrogel made of polyethylene glycol-chitosan (HyCh) and a hybrid core-shell combination of poly (L-lactic acid)/poly ( ε -caprolactone) and HyCh (PLA-PCL-HyCh), seeded with different concentrations of human mesenchymal stromal cells (hMSCs), has been explored in non-critical size mandibular defects in a rabbit model. The bone regenerative properties of the bioengineered scaffolds were analyzed by in vivo radiological examinations and ex vivo radiological, histomorphological, and immunohistochemical analyses. Results: The relative density increase (RDI) was significantly more pronounced in defects where a scaffold was placed, particularly if seeded with hMSCs. The immunohistochemical profile showed significantly higher expression of both VEGF-A and osteopontin in defects reconstructed with scaffolds. Native microarchitectural characteristics were not demonstrated in any experimental group. Conclusion: Herein, we demonstrate that bone regeneration can be boosted by scaffold- and seeded scaffold-reconstruction, achieving, respectively, 50% and 70% restoration of presurgical bone density in 120 days, compared to 40% restoration seen in spontaneous regeneration. Although optimization of the regenerative performance is needed, these results will help to establish a baseline reference for future experiments.

Trabecular architecture of the distal femur in extant hominids

Extant great apes are characterized by a wide range of locomotor, postural and manipulative behaviours that each require the limbs to be used in different ways. In addition to external bone morphology, comparative investigation of trabecular bone, which (re-)models to reflect loads incurred during life, can provide novel insights into bone functional adaptation. Here, we use canonical holistic morphometric analysis (cHMA) to analyse the trabecular morphology in the distal femoral epiphysis of Homo sapiens (n = 26), Gorilla gorilla (n = 14), Pan troglodytes (n = 15) and Pongo sp. (n = 9). We test two predictions: (1) that differing locomotor behaviours will be reflected in differing trabecular architecture of the distal femur across Homo, Pan, Gorilla and Pongo; (2) that trabecular architecture will significantly differ between male and female Gorilla due to their different levels of arboreality but not between male and female Pan or Homo based on previous studies of locomotor behaviours. Results indicate that trabecular architecture differs among extant great apes based on their locomotor repertoires. The relative bone volume and degree of anisotropy patterns found reflect habitual use of extended knee postures during bipedalism in Homo, and habitual use of flexed knee posture during terrestrial and arboreal locomotion in Pan and Gorilla. Trabecular architecture in Pongo is consistent with a highly mobile knee joint that may vary in posture from extension to full flexion. Within Gorilla, trabecular architecture suggests a different loading of knee in extension/flexion between females and males, but no sex differences were found in Pan or Homo, supporting our predictions. Inter- and intra-specific variation in trabecular architecture of distal femur provides a comparative context to interpret knee postures and, in turn, locomotor behaviours in fossil hominins.

Osseointegration of photodynamic active biomaterials for bone regeneration in an animal bone model over a period of 12 months

OBJECTIVES

Previous efforts led to the development of two different polymeric biomaterials for periodontal regeneration with antibacterial photodynamic surface activity. The present study aimed to investigate osseointegration and bone formation of both materials in an ovine model.

METHODS

Both biomaterials: 1) urethane dimethacrylate-based Biomaterial 1 (BioM1) and 2) tri-armed oligoester-urethane methacrylate-based Biomaterial 2 (BioM2) are enriched with beta-tri-calcium phosphate and the photosensitizer meso-tetra(hydroxyphenyl)chlorin (mTHPC). These materials were implanted in non-critical size bone defects in the sheep femur (n = 16) and tibia (n = 8). Empty defects served as controls (n = 16). Polyfluorochrome sequential bone labeling was carried out at baseline and after 3, 6, and 12 months. Animals were sacrificed after 12 months. Bone specimens (n = 40) were fixed and subjected to microtomographic analysis (µCT) for the evaluation of the bone-volume-fraction (BV/TV), trabecular number and trabecular thickness. Subsequently, histological sections were arranged and polyfluorochrome sequential bone labeling was analyzed by confocal laser scanning microscopy (cLSM).

RESULTS

cLSM analysis revealed that highest remodeling and bone formation activity occurred during the second half of the study period (6-12 months). Bone formation in the tibia was significantly lower for the control (2.71 ± 1.26%) as compared to BioM1 (6.01 ± 2.99%) and BioM2 (6.45 ± 2.12%); (p = 0.006, p = 0004). Micro-computed tomography revealed a BV/TV volume fraction of 44.72 ± 9.01% in femur defects filled with BioM1 which was significantly higher compared to the control (32.27 ± 7.02%; p = 0.01). Bone architecture (trabecular number, trabecular thickness) did not significantly differ from the self-healed defects.

SIGNIFICANCE

Both biomaterials, especially BioM1 showed good osseointegration and bone formation characteristics and can be recommended for further examination in periodontal regeneration studies.

Challenges and perspectives on functional interpretations of australopith postcrania and the reconstruction of hominin locomotion

In 1994, Hunt published the 'postural feeding hypothesis'-a seminal paper on the origins of hominin bipedalism-founded on the detailed study of chimpanzee positional behavior and the functional inferences derived from the upper and lower limb morphology of the Australopithecus afarensis A.L. 288-1 partial skeleton. Hunt proposed a model for understanding the potential selective pressures on hominins, made robust, testable predictions based on Au. afarensis functional morphology, and presented a hypothesis that aimed to explain the dual functional signals of the Au. afarensis and, more generally, early hominin postcranium. Here we synthesize what we have learned about Au. afarensis functional morphology and the dual functional signals of two new australopith discoveries with relatively complete skeletons (Australopithecus sediba and StW 573 'Australopithecus prometheus'). We follow this with a discussion of three research approaches that have been developed for the purpose of drawing behavioral inferences in early hominins: (1) developments in the study of extant apes as models for understanding hominin origins; (2) novel and continued developments to quantify bipedal gait and locomotor economy in extant primates to infer the locomotor costs from the anatomy of fossil taxa; and (3) novel developments in the study of internal bone structure to extract functional signals from fossil remains. In conclusion of this review, we discuss some of the inherent challenges of the approaches and methodologies adopted to reconstruct the locomotor modes and behavioral repertoires in extinct primate taxa, and notably the assessment of habitual terrestrial bipedalism in early hominins.

Experimentally characterizing the spatially varying anisotropic mechanical property of cancellous bone via a Bayesian calibration method

Traditional experimental tests for characterizing bone's mechanical properties usually hypothesize a uniaxial stress condition without quantitatively evaluating the influence of spatially varying principal material orientations, which cannot accurately predict the mechanical properties distribution of bones in vivo environment. In this study, a Bayesian calibrating procedure was developed using quantified multiaxial stress to investigate cancellous bone's local anisotropic elastic performance around joints as the spatial variation of main bearing orientations. First, the bone cube specimens from the distal femur of sheep are prepared using traditional anatomical axes. The multiaxial stress state of each bone specimen is calibrated using the actual principal material orientations derived from fabric tensor at different anatomical locations. Based on the calibrated multiaxial stress state, the process of identifying mechanical properties is described as an inverse problem. Then, a Bayesian calibration procedure based on a surrogate constitutive model was developed via multiaxial stress correction to identify the anisotropic material parameters. Finally, a comparison between the experiment and simulation results is discussed by applying the optimal model parameters obtained from the Bayesian probability distribution. Compared to traditional uniaxial methods, our results prove that the calibration based on the spatial variation of the main bearing orientations can significantly improve the accuracy of characterizing regional anisotropic mechanical responses. Moreover, we determine that the actual mechanical property distribution is influenced by complicated mechanical stimulation. This study provides a novel method to evaluate the spatially varying mechanical properties of bone tissues enduring complex mechanical loading accurately and effectively. It is expected to provide more realistic mechanical design targets in vivo for a personalized artificial bone prosthesis in clinical treatment.

Enhanced bone formation in locally-optimised, low-stiffness additive manufactured titanium implants: An in silico and in vivo tibial advancement study

A tibial tuberosity advancement (TTA), used to treat lameness in the canine stifle, provides a framework to investigate implant performance within an uneven loading environment due to the dominating patellar tendon. The purpose of this study was to reassess how we design orthopaedic implants in a load-bearing model to investigate potential for improved osseointegration capacity of fully-scaffolded mechanically-matched additive manufactured (AM) implants. While the mechanobiological nature of bone is well known, we have identified a lower limit in the literature where investigation into exceedingly soft scaffolds relative to trabecular bone ceases due to the trade-off in mechanical strength. We developed a finite element model of the sheep stifle to assess the stresses and strains of homogeneous and locally-optimised TTA implant designs. Using additive manufacturing, we printed three different low-stiffness Ti-6Al-4 V TTA implants: 0.8 GPa (Ti1), 0.6 GPa (Ti2) and an optimised design with a 0.3 GPa cortex and 0.1 GPa centre (Ti3), for implantation in a 12-week in vivo ovine pilot study. Static histomorphometry demonstrated uniform bone ingrowth in optimised low-modulus Ti3 samples compared to homogeneous designs (Ti1 and Ti2), and greater bone-implant contact. Mineralising surfaces were apparent in all implants, though mineral apposition rate was only consistent throughout Ti3. The greatest bone formation scores were seen in Ti3, followed by Ti2 and Ti1. Results from our study suggest lower stiffnesses and higher strain ranges improve early bone formation, and that by accounting for loading environments through rational design, implants can be optimised to improve uniform osseointegration. STATEMENT OF SIGNIFICANCE: The effect of different strain ranges on bone healing has been traditionally investigated and characterised through computational models, with much of the literature suggesting higher strain ranges being favourable. However, little has been done to incorporate strain-optimisation into porous orthopaedic implants due to the trade-off in mechanical strength required to induce these microenvironments. In this study, we used finite element analysis to optimise the design of additive manufactured (AM) titanium orthopaedic implants for different strain ranges, using a clinically-relevant surgical model. Our research suggests that there is potential for locally-optimised AM scaffolds in the use of orthopaedic devices to induce higher strains, which in turn encourages de novo bone formation and uniform osseointegration.

Pediatric CKD-MBD: existing and emerging treatment approaches

The effects of bone and mineral metabolism on skeletal formation, as well as vascular and soft tissue calcifications, define chronic kidney disease-metabolic bone disease (CKD-MBD). Treatment recommendations center on establishing adequate vitamin D status, phosphate control through diet restriction and phosphate binders, and the use of vitamin D analogs for specific indications. Several emerging bone-promoting therapies have now been studied in adults with CKD, including bisphosphonates and denosumab. These approaches are associated with improved bone mass and, in some cases, decreased fracture rates in adults with CKD-MBD and are of potential interest for some children with CKD-MBD. In children with CKD and immobilization and/or muscle weakness, bisphosphonates appear to be an effective treatment to increase bone mass; baseline assessment and careful monitoring of bone density and/or bone biopsy findings are important in consideration of any new bone therapies for children with CKD-MBD.

Three-dimensional radiological anatomy of condyle trabecular bone based on a Volume-of-Interest analysis

OBJECTIVES

Three-dimensional radiological anatomic characteristics of condyle trabeculae was obtained quantitatively based on a volume-of-interest (VOI) analysis.

METHODS

Nine human mandibular condyle specimens were scanned by micro-computed tomography (micro-CT). A total of 34 VOIs were selected from each condyle specimen, which were divided into six layers and four parts to analyze the morphological characteristics of trabeculae based on cylindrical VOIs with a diameter and height of 2 mm. One-way analysis of variance was used to compare the regional differences of morphological parameters among each layer and part.

RESULTS

Values for bone mineral density, bone volume/total volume, trabecular thickness, and trabecular bone number were greater in the anterior part compared with the posterior part; and the lateral part was larger than the medial part in the first, second, and third layers, while the medial part was larger in the fourth and fifth layers; these values in the first and sixth layers were much larger, while those in the third and fourth layers were smaller. Bone surface area/bone volume, trabecular spacing, and trabecular bone pattern factor were larger in the posterior part than in the anterior part; and the lateral part was larger than the medial part in the fourth and fifth layers, while the medial part was larger in the first and second layers.

CONCLUSIONS

The morphological distribution of VOIs was anisotropic within trabecular bone of human mandibular condyles. The upper and lower ends of trabecular bone were much more compact, with higher bone density, trabecular thickness, and trabecular number than in the middle layers.

Antiosteoporosis effect of tanshinol in osteoporosis animal models: A systematic review and meta-analysis

Background: Osteoporosis (OP) is an age-related bone disease that has emerged as a worldwide public health concern due to its increasing incidence and high disability rate. Tanshinol [D (+) β-3,4-dihydroxyphenyl lactic acid, TS], a water-soluble component extracted from Salvia miltiorrhiza, has proven to be effective in attenuating OP in vitro and in vivo. However, there is insufficient evidence to support its clinical application.

Objective: This meta-analysis aimed to investigate available OP animal model studies to demonstrate the antiosteoporosis effects of TS in a systematic manner.

Methods: Electronic searches of related studies were conducted in the following databases: EMBASE, PubMed, Web of Science, Cochrane Library, Chinese National Knowledge Infrastructure, Chinese VIP Database, Chinese Biomedical Literature Database, and Wanfang. The retrieval date was January 2022, and there were no time or language restrictions. The CAMARADES 10-item quality checklist was utilized to test the risk of potential bias for each study, and modifications were performed accordingly. The primary outcome was bone mineral density (BMD, which included the femur and lumbar spine); and secondary outcomes were parameters for trabecular bone such as bone volume over total volume (BV/TV), trabecular number (Tb.N), trabecular thickness (Tb.Th), trabecular separation (Tb.Sp), conditions of the femur (including bone maximum load and bone elastic load), and markers of bone metabolism (serum osteocalcin, S-OCN).

Results: A total of nine studies including 176 rats were chosen for this analysis. Egger’s test revealed the presence of publication bias in various studies regarding the primary outcome. According to this systematic review, TS significantly increased the BMD of the femur (BMD-femur) (SMD = 4.40; 95% CI = 1.61 to 7.19; p = 0.002, I² = 94.6%), BMD of the lumbar spine (BMD-lumbar) (SMD = 6.390; 95% CI = 2.036 to 10.744; p = 0.004, I² = 95.9%), BV/TV (SMD = 0.790; 95% CI = 0.376 to 1.204; p = 0.000, I² = 10.8), Tb.N (SMD = 0.690; 95% CI = 0.309 to 1.071; p = 0.000, I² = 12%), Tb.Th (SMD = 0.772; 95% CI = 0.410 to 1.134; p = 0.000, I² = 32.2%), and S-OCN (SMD = 3.13; 95% CI = 0.617 to 5.65; p = 0.015, I² = 92.3%), while the Tb.Sp level was markedly decreased in OP models in comparison to the controls (SMD = −0.822; 95% CI = −1.207 to −0.437; p = 0.000, I² = 0%). Moreover, TS treatment was associated with a significant improvement of the bone biomechanical indicators, including bone maximum load (SMD = 0.912; 95% CI = 0.370 to 1.455; p = 0.001, I² = 40%) and elasticity load (SMD = 0.821; 95% CI = 0.290 to 1.351; p = 0.002, I² = 0%).

Conclusion: Collectively, our findings suggest that TS can improve BMD, bone microarchitecture, bone biomechanics, and S-OCN expression in rats, implying that it could be used clinically in the future.

Systematic Review Registration:https://inplasy.com/inplasy-2022-3-0053/, identifier [INPLASY202230053].

Ontogenetic Patterning of Human Subchondral Bone Microarchitecture in the Proximal Tibia

High-resolution computed tomography images were acquired for 31 proximal human tibiae, age 8 to 37.5 years, from Norris Farms #36 cemetery site (A.D. 1300). Morphometric analysis of subchondral cortical and trabecular bone architecture was performed between and within the tibial condyles. Kruskal−Wallis and Wilcoxon signed-rank tests were used to examine the association between region, age, body mass, and each morphometric parameter. The findings indicate that age-related changes in mechanical loading have varied effects on subchondral bone morphology. With age, trabecular microstructure increased in bone volume fraction (p = 0.033) and degree of anisotropy (p = 0.012), and decreased in connectivity density (p = 0.001). In the subchondral cortical plate, there was an increase in thickness (p < 0.001). When comparing condylar regions, only degree of anisotropy differed (p = 0.004) between the medial and lateral condyles. Trabeculae in the medial condyle were more anisotropic than in the lateral region. This research represents an innovative approach to quantifying both cortical and trabecular subchondral bone microarchitecture in archaeological remains.

Opportunistic Use of Lumbar Magnetic Resonance Imaging for Osteoporosis Screening

Magnetic resonance imaging (MRI) is a routine assessment before spine surgery. We found that the opportunistic use of MRI with the vertebral bone quality (VBQ) score has good diagnostic ability, with a threshold value of VBQ > 3.0, in recognizing patients who may need further osteoporosis evaluation.

INTRODUCTION

The purpose of this study was to determine whether the opportunistic use of magnetic resonance imaging (MRI) is useful for identifying spine surgical patients who need further osteoporosis evaluation.

METHODS

This retrospective study evaluated 83 thoracolumbar spine surgery patients age ≥ 50 who received T1-weighted MRI. Opportunistic MRI was evaluated with the vertebral bone quality (VBQ) score, VBQ (fat) score, and signal-to-noise ratio (SNR). Each uses the median L1-L4 vertebral body signal intensities (SI) divided by either the L3 cerebrospinal fluid (CSF) SI, average SI of the L1 and S1 dorsal fat, or standard deviation (SD) of the background SI dorsal to the skin. Single-level VBQ was calculated as the ratio of the L1 vertebral body and L1 CSF SIs. Receiver-operator curve analysis was performed to determine diagnostic ability.

RESULTS

The mean age was 70.10, 80% were female, and 96% were Caucasian. The mean ± SD VBQ, single-level VBQ, VBQ (fat), and SNR were 3.39 ± 0.68, 3.56 ± 0.81, 3.95 ± 1.89, and 113.18 ± 77.26, respectively. Using area under the curve, the diagnostic ability of VBQ, single-level VBQ, VBQ (fat), and SNR for clinical osteoporosis were 0.806, 0.779, 0.608, and 0.586, respectively. Diagnostic threshold values identified with optimal sensitivity and specificity were VBQ of 2.95 and single-level VBQ of 3.06.

CONCLUSION

Opportunistic use of MRI is a simple, effective tool that may help recognize patients who are at risk for complications related to bone disease. A VBQ > 3.0 can identify patients who need additional diagnostic evaluation.

The effect of Staphylococcus aureus exposure on white-tailed deer trabecular bone stiffness and yield

With a growing number of osteomyelitis diagnoses, many of which are linked to Staphylococcus aureus (S. aureus), it is imperative to understand the pathology of S. aureus in relation to bone to provide better diagnostics and patient care. While the cellular mechanisms of S. aureus and osteomyelitis have been studied, little information exists on the biomechanical effects of such infections. The aim of this study was to determine the effect of S. aureus exposure on the stiffness and yield of trabecular bone tissue. S. aureus-ATCC-12600, a confirmed biofilm producer, along with one hundred and three trabecular cubes (5 × 5 × 5 mm) from the proximal tibiae of Odocoileus virginianus (white-tailed deer) were used in this experiment. Bone cubes were disinfected and then swabbed to confirm no residual living microbes or endospore contamination before inoculation with S. aureus (test group) or sterile nutrient broth (control group) for 72 h. All cubes were then tested in compression until yield using an Instron 5942 Single-Column machine. Structural stiffness (N/mm) and yield (MPa) were calculated and compared between the two groups. Our results revealed that acute exposure to S. aureus, within the context of our deer tibia model, does not significantly decrease trabecular bone stiffness or yield. The results of this study may be of value clinically when assessing fracture risks for osteomyelitis or other patients whose cultures test positive for S. aureus.

Determination of an Initial Stage of the Bone Tissue Ingrowth Into Titanium Matrix by Cell Adhesion Model

For achieving early intervention treatment to help patients delay or avoid joint replacement surgery, a personalized scaffold should be designed coupling the effects of mechanical, fluid mechanical, chemical, and biological factors on tissue regeneration, which results in time- and cost-consuming trial-and-error analyses to investigate the in vivo test and related experimental tests. To optimize the fluid mechanical and material properties to predict osteogenesis and cartilage regeneration for the in vivo and clinical trial, a simulation approach is developed for scaffold design, which is composed of a volume of a fluid model for simulating the bone marrow filling process of the bone marrow and air, as well as a discrete phase model and a cell impingement model for tracking cell movement during bone marrow fillings. The bone marrow is treated as a non-Newtonian fluid, rather than a Newtonian fluid, because of its viscoelastic property. The simulation results indicated that the biofunctional bionic scaffold with a dense layer to prevent the bone marrow flow to the cartilage layer and synovia to flow into the trabecular bone area guarantee good osteogenesis and cartilage regeneration, which leads to high-accuracy in vivo tests in sheep . This approach not only predicts the final bioperformance of the scaffold but also could optimize the scaffold structure and materials by their biochemical, biological, and biomechanical properties.

Trabecular organization of the proximal femur in Paranthropus robustus: Implications for the assessment of its hip joint loading conditions

Reconstruction of the locomotor repertoire of the australopiths (Australopithecus and Paranthropus) has progressively integrated information from the mechanosensitive internal structure of the appendicular skeleton. Recent investigations showed that the arrangement of the trabecular network at the femoral head center is biomechanically compatible with the pattern of cortical bone distribution across the neck, both suggesting a full commitment to bipedalism in australopiths, but associated with a slightly altered gait kinematics compared to Homo involving more lateral deviation of the body center of mass over the stance limb. To provide a global picture in Paranthropus robustus of the trabecular architecture of the proximal femur across the head, neck and greater trochanter compartments, we applied techniques of virtual imaging to the variably preserved Early Pleistocene specimens SK 82, SK 97, SK 3121, SKW 19 and SWT1/LB-2 from the cave site of Swartkrans, South Africa. We also assessed the coherence between the structural signals from the center of the head and those from the trabecular network of the inferolateral portion of the head and the inferior margin of the neck, sampling the so-called vertical bundle, which in humans represents the principal compressive system of the joint. Our analyses show a functionally related trabecular organization in Pa. robustus that closely resembles the extant human condition, but which also includes some specificities in local textural arrangement. The network of the inferolateral portion of the head shows a humanlike degree of anisotropy and a bone volume fraction intermediate between the extant human and the African ape patterns. These results suggest slight differences in gait kinematics between Pa. robustus and extant humans. The neck portion of the vertical bundle revealed a less biomechanically sensitive signal. Future investigations on the australopith hip joint loading environment should more carefully investigate the trabecular structure of the trochanteric region and possible structural covariation between cortical bone distribution across the neck and site-specific trabecular properties of the arcuate bundle.

Microarchitecture of cetacean vertebral trabecular bone among swimming modes and diving behaviors

Cetaceans (dolphins, whales, and porpoises) are fully aquatic mammals that are supported by water's buoyancy and swim through axial body bending. Swimming is partially mediated by variations in vertebral morphology that creates trade-offs in body flexibility and rigidity between axial regions that either enhance or reduce displacement between adjacent vertebrae. Swimming behavior is linked to foraging ecology, where deep-diving cetaceans glide a greater proportion of the time compared to their shallow-diving counterparts. In this study, we categorized 10 species of cetaceans (Families Delphinidae and Kogiidae) into functional groups determined by swimming patterns (rigid vs. flexible torso) and diving behavior (shallow vs. deep). Here, we quantify vertebral trabecular microarchitecture (a) among functional groups (rigid-torso shallow diver (RS), rigid-torso deep diver (RD), and flexible-torso deep diver (FD)), and (b) among vertebral column regions (posterior thoracic, lumbar, caudal peduncle, and fluke insertion). We microCT scanned vertebral bodies, from which 1-5 volumes of interest were selected to quantify bone volume fraction (BV/TV), specific bone surface (BS/BV), trabecular thickness (TbTh), trabecular number (TbN), trabecular separation (TbSp), and degree of anisotropy (DA). We found that BV/TV was greatest in the rigid-torso shallow-diving functional group, smallest in flexible-torso deep-diving species, and intermediate in the rigid-torso deep-diving group. DA was significantly greater in rigid-torso caudal oscillators than in their flexible-torso counterparts. We found no variation among vertebral regions for any microarchitectural variables. Despite having osteoporotic skeletons, cetacean vertebrae had greater BV/TV, TbTh, and DA than previously documented in terrestrial mammalian bone. Cetacean species are an ideal model to investigate the long-term adaptations, over an animal's lifetime and over evolutionary time, of trabecular bone in non-weight-bearing conditions.

Assessing patterns of variation in BV/TV in the calcaneus and C2 vertebra of Gorilla gorilla, Pan troglodytes, and populations of Homo sapiens from the Pleistocene and Holocene that differ in physical activity levels

OBJECTIVES

Because trabecular bone volume fraction (BV/TV) is influenced by variations in physical activity recent declines in BV/TV in humans are often attributed to modern sedentary lifestyles. This study tests the hypothesis that presumed variations in mechanical loading between groups can predict the observed BV/TV patterns in humans, chimpanzees and gorillas in two bones: the calcaneus which experiences high and well characterized impact forces, and the C2 vertebrae which experiences reduced locomotor forces.

MATERIALS AND METHODS

BV/TV and other structural variables were quantified from high-resolution microCT scans in gorillas, chimpanzees, and four Homo sapiens populations: Pleistocene, semi-sedentary Natufians; Holocene hunter-gatherers from Point Hope, Alaska; Holocene nomadic pastoralists from medieval Europe; and modern, sedentary Americans.

RESULTS

In the calcaneal tuberosity, Natufian BV/TV was 36, 46, and 46% greater than Alaskans (p = .02), Europeans (p = .005) and modern Americans (p = .002), respectively, but not significantly different from apes. BV/TV was not significantly different between modern Americans and Alaskans or Europeans. In the C2, Natufian BV/TV was 53 and 25% greater than in the Alaskan (p = .0001) and European (p = .048) populations.

DISCUSSION

These results suggest that phenomena other than or in addition to variations in physical activity are needed to explain BV/TV patterns observed in H. sapiens, and point to a systemic decline in H. sapiens BV/TV after the Pleistocene.

Bioinspired material architectures from bighorn sheep horncore velar bone for impact loading applications

Rocky Mountain bighorn sheep rams (Ovis canadensis canadensis) routinely conduct intraspecific combat where high energy cranial impacts are experienced. Previous studies have estimated cranial impact forces to be up to 3400 N during ramming, and prior finite element modeling studies showed the bony horncore stores 3 × more strain energy than the horn during impact. In the current study, the architecture of the porous bone within the horncore was quantified, mimicked, analyzed by finite element modeling, fabricated via additive manufacturing, and mechanically tested to determine the suitability of the novel bioinspired material architecture for use in running shoe midsoles. The iterative biomimicking design approach was able to tailor the mechanical behavior of the porous bone mimics. The approach produced 3D printed mimics that performed similarly to ethylene–vinyl acetate shoe materials in quasi-static loading. Furthermore, a quadratic relationship was discovered between impact force and stiffness in the porous bone mimics, which indicates a range of stiffness values that prevents impact force from becoming excessively high. These findings have implications for the design of novel bioinspired material architectures for minimizing impact force.

Routine serum biomarkers, but not dual-energy X-ray absorptiometry, correlate with cortical bone mineral density in children and young adults with chronic kidney disease

Background. Biomarkers and dual-energy X-ray absorptiometry (DXA) are thought to be poor predictors of bone mineral density (BMD). The Kidney Disease: Improving Global Outcomes guidelines suggest using DXA if the results will affect patient management, but this has not been studied in children or young adults in whom bone mineral accretion continues to 30 years of age. We studied the clinical utility of DXA and serum biomarkers against tibial cortical BMD (CortBMD) measured by peripheral quantitative computed tomography, expressed as Z-score CortBMD, which predicts fracture risk.

Methods. This was a cross-sectional multicentre study in 26 patients with CKD4 and 5 and 77 on dialysis.

Results. Significant bone pain that hindered activities of daily living was present in 58%, and 10% had at least one low-trauma fracture. CortBMD and cortical mineral content Z-scores were lower in dialysis compared with CKD patients (P = 0.004 and P = 0.02). DXA BMD hip and lumbar spine Z-scores did not correlate with CortBMD or biomarkers. CortBMD was negatively associated with parathyroid hormone (PTH; r = −0.44, P &lt; 0.0001) and alkaline phosphatase (ALP; r = −0.22, P = 0.03) and positively with calcium (Ca; r = 0.33, P = 0.001). At PTH &lt;3 times upper limit of normal, none of the patients had a CortBMD below −2 SD (odds ratio 95% confidence interval 7.331 to infinity). On multivariable linear regression PTH (β = −0.43 , P &lt; 0.0001), ALP (β = −0.36, P &lt; 0.0001) and Ca (β = 0.21, P = 0.005) together predicted 57% of variability in CortBMD. DXA measures did not improve this model.

Conclusions. Taken together, routinely used biomarkers, PTH, ALP and Ca, but not DXA, are moderate predictors of cortical BMD. DXA is not clinically useful and should not be routinely performed in children and young adults with CKD 4–5D.

Deciphering an extreme morphology: bone microarchitecture of the hero shrew backbone (Soricidae: Scutisorex)

Biological structures with extreme morphologies are puzzling because they often lack obvious functions and stymie comparisons to homologous or analogous features with more typical shapes. An example of such an extreme morphotype is the uniquely modified vertebral column of the hero shrew Scutisorex, which features numerous accessory intervertebral articulations and massively expanded transverse processes. The function of these vertebral structures is unknown, and it is difficult to meaningfully compare them to vertebrae from animals with known behavioural patterns and spinal adaptations. Here, we use trabecular bone architecture of vertebral centra and quantitative external vertebral morphology to elucidate the forces that may act on the spine of Scutisorex and that of another large shrew with unmodified vertebrae (Crocidura goliath). X-ray micro-computed tomography (µCT) scans of thoracolumbar columns show that Scutisorex thori is structurally intermediate between C. goliath and S. somereni internally and externally, and both Scutisorex species exhibit trabecular bone characteristics indicative of higher in vivo axial compressive loads than C. goliath. Under compressive load, Scutisorex vertebral morphology is adapted to largely restrict bending to the sagittal plane (flexion). Although these findings do not solve the mystery of how Scutisorex uses its byzantine spine in vivo, our work suggests potentially fruitful new avenues of investigation for learning more about the function of this perplexing structure.

Differential effects of jump versus running exercise on trabecular bone architecture and strength in rats

PURPOSE

This study compared differences in trabecular bone architecture and strength caused by jump and running exercises in rats.

METHODS

Ten-week-old male Wistar rats (n=45) were randomly assigned to three body weight-matched groups: a sedentary control group (CON, n=15); a treadmill running group (RUN, n=15); and a jump exercise group (JUM, n=15). Treadmill running was performed at 25 m/min without inclination, 1 h/day, 5 days/week for 8 weeks. The jump exercise protocol comprised 10 jumps/day, 5 days/week for 8 weeks, with a jump height of 40 cm. We used microcomputed tomography to assess microarchitecture, mineralization density, and fracture load as predicted by finite element analysis (FEA) at the distal femoral metaphysis.

RESULTS

Both jump and running exercises produced significantly higher trabecular bone mass, thickness, number, and fracture load compared to the sedentary control group. The jump and running exercises, however, showed different results in terms of the structural characteristics of trabecular bone. Jump exercises enhanced trabecular bone mass by thickening the trabeculae, while running exercises did so by increasing the trabecular number. FEA-estimated fracture load did not differ significantly between the exercise groups.

CONCLUSION

This study elucidated the differential effects of jump and running exercise on trabecular bone architecture in rats. The different structural changes in the trabecular bone, however, had no significant impact on trabecular bone strength.

Mimicking high strength lightweight novel structures inspired from the trabecular bone microarchitecture

Nature's evolution of a billion years has advanced flawless functionality in limitless optimized structures like bone structural adaptation in various physiological behaviours. In this study, porous structures are designed and fabricated from the nature-inspired trabecular bone microarchitecture. A three-dimensional (3D) model of the porous trabecular architecture from the compressive proximal zone of the femoral head was constructed using the micro-computed tomography scanning tool. The model was modified to get porous structures of different volume fractions varying from 20 to 40% with an increment of 10%. The obtained porous structures were 3D printed and analysed for deformation-resistant behaviour. Quasi-static compressive loading was performed at different strain rates (0.001-1 s^-1) to get an insight into lightweight, high strength structural behaviour. Mechanical parameters, such as specific modulus, specific strength and specific energy absorption, were analysed for the optimal volume fraction. The original volume fraction (30%) of the trabecular bone shows the highest value of mechanical parameters. This study can help engineers to select and design lightweight porous structures with high energy-absorbing capacity, mimicking the desired architecture and porosity available in nature. This article is part of the theme issue 'Bioinspired materials and surfaces for green science and technology (part 3)'.

Are we crying Wolff? 3D printed replicas of trabecular bone structure demonstrate higher stiffness and strength during off-axis loading

Roux's principle of bone functional adaptation postulates that bone tissue, and particularly trabecular bone tissue, responds to mechanical stimuli by adjusting (modeling) its architecture accordingly. Hence, it predicts that the new modeled trabecular structure is mechanically improved (stiffer and stronger) in line with the habitual in vivo loading direction. While previous studies found indirect evidence to support this theory, direct support was so far unattainable. This is attributed to the fact that each trabecular bone is unique, and that trabecular bone tissue tends to be damaged during mechanical testing. Consequently, a unique modeled trabecular structure can be mechanically tested only along one direction and a comparison to other directions for that specific structure is impossible. To address this issue, we have 3D printed 10 replicas of a trabecular structure from a sheep talus cropped along the 3 principal axes of the bone and in line with the principal direction of loading (denoted on-axis model). Next, we have rotated the same cropped trabecular structure in increments of 10° up to 90° to the bone principal direction of loading (denoted off-axis models) and printed 10 replicas of each off-axis model. Finally, all on-axis and off-axis 3D printed replicas were loaded in compression until failure and trabecular structure stiffness and strength were calculated. Contrary to our prediction, and conflicting with Roux's principle of bone functional adaptation, we found that a trabecular structure loaded off-axis tended to have higher stiffness and strength values when compared to the same trabecular structure loaded on-axis. These unexpected results may not disprove Roux's principle of bone functional adaptation, but they do imply that trabecular bone adaptation may serve additional purposes than simply optimizing bone structure to one principal loading scenario and this suggests that we still don't fully understand bone modeling in its entirety.

Trabecular bone architecture in the stylopod epiphyses of mustelids (Mammalia, Carnivora)

Mustelidae, a carnivoran clade that includes for instance weasels, badgers, otters and martens, has undergone several evolutionary transitions of lifestyle, resulting in specializations for fossorial, natatorial and scansorial locomotion, in addition to more generalized species. The family is therefore regarded as offering an adequate framework for morpho-functional analyses. However, the architecture of the epiphyseal trabecular bone, which is argued to be particularly responsive to the biomechanical environment, has never been studied. Here, we quantify trabecular bone parameters of the proximal and distal epiphyses of the humerus and femur in 29 species of mustelids and assess the differences of these parameters among groups defined a priori based on the aforementioned locomotor types. The parameters are assessed in a phylogenetic framework, taking into account the potential effect on an individual's body mass. The range of variation described by the acquired parameters is relatively restricted when compared to that of other clades. Generalists, however, are featuring a wider range of variation than the other types. While clear discrimination of locomotor types is difficult, some differences were highlighted by our analysis, such as a greater bone fraction associated with the natatorial taxa, which we discuss in a functional context.

An Investigation on the Correlation between the Mechanical Properties of Human Skull Bone, Its Geometry, Microarchitectural Properties, and Water Content

With increasingly detailed imaging and mechanical analysis, modalities need arises to update methodology and assessment criteria for skull bone analysis to understand how bone microarchitecture and the presence of attached tissues may affect the response to mechanical load. The main aim was to analyze the effect of macroscopic and microstructural features, as well as periosteal attachment, on the mechanical properties of human skull bone. Fifty-six skull specimens from ethanol-phenoxyethanol-embalmed cadavers were prepared from two human cadavers. Assuming symmetry of the skull, all samples from one-half each were stripped of periosteum and dura mater, while the soft tissues were kept intact on the remaining samples on the contralateral side. The specimens were analyzed using microcomputed tomography to assess trabecular connectivity density, total surface area, and volume ratio. The specimens were loaded under three-point bend tests until fracture with optical co-registration. The bone fragments were then lyophilized to measure their water content. With increasingly detailed imaging and mechanical analysis modalities, there is a need to update methodology and assessment criteria for skull bone analysis to understand how the bone microarchitecture and the presence of attached tissues may affect the response to mechanical load. The mechanical properties were negatively correlated to bone thickness and water content. Conversely, most microarchitectural features did not influence either mechanical parameter. The correlation between mechanical response data and morphologic properties remains similar between the results of embalmed tissues presented here and fresh osseous tissue from literature data. The findings presented here add to the existing methodology to assess human skull for research purposes. The interaction between most microarchitectural features in ethanol-phenoxyethanol-embalmed embalmed skull samples and bending stress appear to be minute.

Trabecular architecture in the humeral metaphyses of non-avian reptiles (Crocodylia, Squamata and Testudines): Lifestyle, allometry and phylogeny

The lifestyle of extinct tetrapods is often difficult to assess when clear morphological adaptations such as swimming paddles are absent. According to the hypothesis of bone functional adaptation, the architecture of trabecular bone adapts sensitively to physiological loadings. Previous studies have already shown a clear relation between trabecular architecture and locomotor behavior, mainly in mammals and birds. However, a link between trabecular architecture and lifestyle has rarely been examined. Here, we analyzed trabecular architecture of different clades of reptiles characterized by a wide range of lifestyles (aquatic, amphibious, generalist terrestrial, fossorial, and climbing). Humeri of squamates, turtles, and crocodylians have been scanned with microcomputed tomography. We selected spherical volumes of interest centered in the proximal metaphyses and measured trabecular spacing, thickness and number, degree of anisotropy, average branch length, bone volume fraction, bone surface density, and connectivity density. Only bone volume fraction showed a significant phylogenetic signal and its significant difference between squamates and other reptiles could be linked to their physiologies. We found negative allometric relationships for trabecular thickness and spacing, positive allometries for connectivity density and trabecular number and no dependence with size for degree of anisotropy and bone volume fraction. The different lifestyles are well separated in the morphological space using linear discriminant analyses, but a cross-validation procedure indicated a limited predictive ability of the model. The trabecular bone anisotropy has shown a gradient in turtles and in squamates: higher values in amphibious than terrestrial taxa. These allometric scalings, previously emphasized in mammals and birds, seem to be valid for all amniotes. Discriminant analysis has offered, to some extent, a distinction of lifestyles, which however remains difficult to strictly discriminate. Trabecular architecture seems to be a promising tool to infer lifestyle of extinct tetrapods, especially those involved in the terrestrialization.

Direct electromagnetic coupling for non-invasive measurements of stability in simulated fracture healing

Diagnostic monitoring and prediction of bone fracture healing is critical for the detection of delayed union or non-union and provides the requisite information as to whether therapeutic intervention or timely revision are warranted. A promising approach to monitor fracture healing is to measure the mechanical load-sharing between the healing callus and the implanted hardware used for internal fixation. The objectives of this study were to evaluate a non-invasive measurement system in which an antenna electromagnetically couples with the implanted hardware to sense deflections of the hardware due to an applied load and to investigate the efficacy of the system to detect changes in mechanical load-sharing in an ex vivo fracture healing model. The measurement system was applied to ovine metatarsal bones treated with osteotomies, resulting in four different levels of bone stability which simulated various degrees of fracture healing. Computational finite element simulations supplemented these ex vivo experiments to compare the osteotomy model of fracture healing to a more clinically applicable callus stiffening model of healing. In the ex vivo experiments, the electromagnetic coupling system detected significant differences between the four simulated degrees of healing with good repeatability. Computational simulations indicated that the experimental model of fracture healing provided a good surrogate for studying healing during the early time period as the callus stiffness is increasing as well as when diagnostic monitoring of the healing process is most critical. Based upon the data reported herein, the direct electromagnetic coupling method holds strong potential for clinical assessments and predictions of fracture healing. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

Trabecular architecture of the great ape and human femoral head

Studies of femoral trabecular structure have shown that the orientation and volume of bone are associated with variation in loading and could be informative about individual joint positioning during locomotion. In this study, we analyse for the first time trabecular bone patterns throughout the femoral head using a whole-epiphysis approach to investigate how potential trabecular variation in humans and great apes relates to differences in locomotor modes. Trabecular architecture was analysed using microCT scans of Pan troglodytes (n = 20), Gorilla gorilla (n = 14), Pongo sp. (n = 5) and Homo sapiens (n = 12) in medtool 4.1. Our results revealed differences in bone volume fraction (BV/TV) distribution patterns, as well as overall trabecular parameters of the femoral head between great apes and humans. Pan and Gorilla showed two regions of high BV/TV in the femoral head, consistent with hip posture and loading during two discrete locomotor modes: knuckle-walking and climbing. Most Pongo specimens also displayed two regions of high BV/TV, but these regions were less discrete and there was more variability across the sample. In contrast, Homo showed only one main region of high BV/TV in the femoral head and had the lowest BV/TV, as well as the most anisotropic trabeculae. The Homo trabecular structure is consistent with stereotypical loading with a more extended hip compared with great apes, which is characteristic of modern human bipedalism. Our results suggest that holistic evaluations of femoral head trabecular architecture can reveal previously undetected patterns linked to locomotor behaviour in extant apes and can provide further insight into hip joint loading in fossil hominins and other primates.

First metatarsal trabecular bone structure in extant hominoids and Swartkrans hominins

Changes in first metatarsal (MT1) morphology within the hominin clade are crucial for reconstructing the evolution of a forefoot adapted for human-like gait. Studies of the external morphology of the MT1 in humans, non-human apes, and fossil hominins have documented changes in its robusticity, epiphyseal shape and its articulation with the medial cuneiform. Here, we test whether trabecular structure in the MT1 reflects different loading patterns in the forefoot across extant large apes and humans, and within this comparative context, infer locomotor behavior in two fossil hominins from Swartkrans, South Africa. Microtomographic scans were collected from the MT1 of Pongo sp. (n = 6), Gorilla gorilla (n = 10), Pan troglodytes (n = 10), Homo sapiens (n = 11), as well as SKX 5017 (Paranthropus robustus), and SK 1813 (Hominin gen. sp. indet.). Trabecular structure was quantified within the head and base using a 'whole-epiphysis' approach with medtool 4.2. We found that modern humans displayed relatively higher bone volume fraction (BV/TV) in the dorsal region of each epiphysis and a higher overall degree of anisotropy (DA), whereas great apes showed higher BV/TV in the plantar regions, reflecting dorsiflexion at the metatarsophalangeal (MTP) joint in the former and plantarflexion in the latter. Both fossils displayed low DA, with SKX 5017 showing a hyper-dorsal concentration of trabecular bone in the head (similar to humans), while SK 1813 showed a more central trabecular distribution not seen in either humans or non-human apes. Additionally, we found differences between non-human apes, modern humans, and the fossil taxa in trabecular spacing (Tb.Sp.), number (Tb.N.), and thickness (Tb.th.). While low DA in both fossils suggests increased mobility of the MT1, differences in their trabecular distributions could indicate variable locomotion in these Pleistocene hominins (recognizing that the juvenile status of SK 1813 is a potential confounding factor). In particular, evidence for consistent loading in hyper-dorsiflexion in SKX 5017 would suggest locomotor behaviors beyond human-like toe off during terrestrial locomotion.

Biomaterials-aided mandibular reconstruction using in vivo bioreactors

Large mandibular defects are clinically challenging to reconstruct due to the complex anatomy of the jaw and the limited availability of appropriate tissue for repair. We envision leveraging current advances in fabrication and biomaterials to create implantable devices that generate bone within the patients themselves suitable for their own specific anatomical pathology. The in vivo bioreactor strategy facilitates the generation of large autologous vascularized bony tissue of customized geometry without the addition of exogenous growth factors or cells. To translate this technology, we investigated its success in reconstructing a mandibular defect of physiologically relevant size in sheep. We fabricated and implanted 3D-printed in vivo bioreactors against rib periosteum and utilized biomaterial-based space maintenance to preserve the native anatomical mandibular structure in the defect site before reconstruction. Nine weeks after bioreactor implantation, the ovine mandibles were repaired with the autologous bony tissue generated from the in vivo bioreactors. We evaluated tissues generated in bioreactors by radiographic, histological, mechanical, and biomolecular assays and repaired mandibles by radiographic and histological assays. Biomaterial-aided mandibular reconstruction was successful in a large superior marginal defect in five of six (83%) sheep. Given that these studies utilized clinically available biomaterials, such as bone cement and ceramic particles, this strategy is designed for rapid human translation to improve outcomes in patients with large mandibular defects.

Intensive terrestrial or marine locomotor strategies are associated with inter- and intra-limb bone functional adaptation in living female athletes

OBJECTIVES

To systematically characterize intra-limb patterns of skeletal plasticity to loading among living women, in order to better understand regional complexity in structural adaptation within the lower limb and more accurately infer behavior in the past.

MATERIALS AND METHODS

We used peripheral quantitative computed tomography imaging of the femur, tibia, first and second metatarsals to quantify bone morphology among female controls and athletes representative of either terrestrial or marine mobility, grouped by loading category (odd-impact, repetitive low-impact, and high-magnitude). Parameters included midshaft bone density, areas, rigidity, and shape, epiphyseal bone densities and areas. We assessed between-group differences and the influence of training history on significant variation among the loading groups.

RESULTS

Terrestrial mobility strategies were best distinguished by significant midshaft periosteal hypertrophy across the lower limb/foot relative to controls, and by particularly high midshaft femoral and tibial cortical bone areas relative to rowers. Enhanced midshaft bone area was typically paired with decreased bone density among athlete groups. Sport-specific variation in training duration/timing was significantly correlated with multiple midshaft parameters.

DISCUSSION

Results demonstrate characteristic patterns of intra-limb adaptation to terrestrial and marine mobility strategies among active women relative to controls, and highlight components of these patterns that may be shaped in part by differences in loading duration/timing. Additionally, our findings support constraints on skeletal variation in the distal tibia and foot relative to more proximal locations about the knee among living women. For example, metatarsal variation was constrained, but where present reflected sport-specific variation in force distribution in the foot.

Cancellous bone and theropod dinosaur locomotion. Part I-an examination of cancellous bone architecture in the hindlimb bones of theropods

This paper is the first of a three-part series that investigates the architecture of cancellous ('spongy') bone in the main hindlimb bones of theropod dinosaurs, and uses cancellous bone architectural patterns to infer locomotor biomechanics in extinct non-avian species. Cancellous bone is widely known to be highly sensitive to its mechanical environment, and has previously been used to infer locomotor biomechanics in extinct tetrapod vertebrates, especially primates. Despite great promise, cancellous bone architecture has remained little utilized for investigating locomotion in many other extinct vertebrate groups, such as dinosaurs. Documentation and quantification of architectural patterns across a whole bone, and across multiple bones, can provide much information on cancellous bone architectural patterns and variation across species. Additionally, this also lends itself to analysis of the musculoskeletal biomechanical factors involved in a direct, mechanistic fashion. On this premise, computed tomographic and image analysis techniques were used to describe and analyse the three-dimensional architecture of cancellous bone in the main hindlimb bones of theropod dinosaurs for the first time. A comprehensive survey across many extant and extinct species is produced, identifying several patterns of similarity and contrast between groups. For instance, more stemward non-avian theropods (e.g. ceratosaurs and tyrannosaurids) exhibit cancellous bone architectures more comparable to that present in humans, whereas species more closely related to birds (e.g. paravians) exhibit architectural patterns bearing greater similarity to those of extant birds. Many of the observed patterns may be linked to particular aspects of locomotor biomechanics, such as the degree of hip or knee flexion during stance and gait. A further important observation is the abundance of markedly oblique trabeculae in the diaphyses of the femur and tibia of birds, which in large species produces spiralling patterns along the endosteal surface. Not only do these observations provide new insight into theropod anatomy and behaviour, they also provide the foundation for mechanistic testing of locomotor hypotheses via musculoskeletal biomechanical modelling.

Trabecular bone patterning in the hominoid distal femur

BACKGROUND

In addition to external bone shape and cortical bone thickness and distribution, the distribution and orientation of internal trabecular bone across individuals and species has yielded important functional information on how bone adapts in response to load. In particular, trabecular bone analysis has played a key role in studies of human and nonhuman primate locomotion and has shown that species with different locomotor repertoires display distinct trabecular architecture in various regions of the skeleton. In this study, we analyse trabecular structure throughout the distal femur of extant hominoids and test for differences due to locomotor loading regime.

METHODS

Micro-computed tomography scans of Homo sapiens (n = 11), Pan troglodytes (n = 18), Gorilla gorilla (n = 14) and Pongo sp. (n = 7) were used to investigate trabecular structure throughout the distal epiphysis of the femur. We predicted that bone volume fraction (BV/TV) in the medial and lateral condyles in Homo would be distally concentrated and more anisotropic due to a habitual extended knee posture at the point of peak ground reaction force during bipedal locomotion, whereas great apes would show more posteriorly concentrated BV/TV and greater isotropy due to a flexed knee posture and more variable hindlimb use during locomotion.

RESULTS

Results indicate some significant differences between taxa, with the most prominent being higher BV/TV in the posterosuperior region of the condyles in Pan and higher BV/TV and anisotropy in the posteroinferior region in Homo. Furthermore, trabecular number, spacing and thickness differ significantly, mainly separating Gorilla from the other apes.

DISCUSSION

The trabecular architecture of the distal femur holds a functional signal linked to habitual behaviour; however, there was more similarity across taxa and greater intraspecific variability than expected. Specifically, there was a large degree of overlap in trabecular structure across the sample, and Homo was not as distinct as predicted. Nonetheless, this study offers a comparative sample of trabecular structure in the hominoid distal femur and can contribute to future studies of locomotion in extinct taxa.

Midfemoral Bone Volume of Walking Subjects with Chronic Hemiparesis Post Stroke

BACKGROUND AND PURPOSE

Muscle and bone form a functional unit. Residual physical poststroke impairments such as muscle weakness, spasticity, and decrease in function can promote metabolic bone changes. Moreover, muscle strength can influence this process. Thus, the purpose of the present study was to investigate bone volume and mobility performance in subjects with chronic hemiparesis post stroke.

METHODS

A cross-sectional study was performed on 14 subjects post stroke who were paired with healthy controls. Bone volume, isometric muscle performance, and mobility levels were measured. Midfemoral bone volumes were determined using magnetic resonance imaging, and muscular performance was measured by dynamometry. Mobility was measured using the Timed Up and Go Test and the 10-Meter Walk Test.

RESULTS

Regarding bone volume total, there was no difference in the medullary and cortical groups (P ≥ .05). During torque peak isometric flexion, the paretic group was significantly different compared with the other groups (P = .001). However, the control presented no difference compared with the nonparetic limb (P = .40). With regard to the extension isometric torque peak, the paretic limb was significantly different compared with the nonparetic (P = .033) and the control (P = .001) limbs, and the control was different from the nonparetic limb (P = .045). Bone volume variables correlated with the isometric torque peak.

CONCLUSIONS

Chronic hemiparetic subjects maintain bone geometry compared with healthy volunteers matched by age, body mass index, and gender. The correlation between bone volume midfemoral structures and knee isometric torque was possible.

Multiscale investigation on the effects of additional weight bearing in combination with low-magnitude high-frequency vibration on bone quality of growing female rats

This study aimed to explore the effects of additional weight bearing in combination with low-magnitude high-frequency vibration (LMHFV; 45 Hz, 0.3 g) on bone quality. One hundred twenty rats were randomly divided into ten groups; namely, sedentary (SED), additional weight bearing in which the rat wears a backpack whose weight is x% of the body weight (WBx; x = 5, 12, 19, 26), basic vibration (V), and additional weight bearing in combination with LMHFV in which the rat wears a backpack whose weight is x% of the body weight (Vx; x = 5, 12, 19, 26). The experiment was conducted for 12 weeks, 7 days per week, and 15 min per day. A three-point bending mechanical test, micro computed tomography, and a nanoindentation test were used. Serum samples were analyzed chemically. Failure load in V19 rats was significantly lower than that in SED rats (P < 0.05). Vx (x = 5, 12, 19, 26) rats showed poor microarchitectures. The content of tartrate-resistant acid phosphatase 5b was significantly higher in Vx (x = 5, 12, 19, 26) rats than that in SED rats (P < 0.05). V26 rats demonstrated comparatively better nanomechanical properties of materials than the other vibrational groups. Additional weight bearing in combination with LMHFV negatively affected the macromechanical properties and microarchitecture of bone. Heavy additional weight bearing, such as 26% of body weight, in combination with LMHFV was able to improve the nanomechanical properties of growing bone material compared with LMHFV. A combined mechanical stimulation was used, which may provide useful information to understand the mechanism of this mechanical stimulation on bone.

Trabecular architecture in the forelimb epiphyses of extant xenarthrans (Mammalia)

Background

Bone structure has a crucial role in the functional adaptations that allow vertebrates to conduct their diverse lifestyles. Much has been documented regarding the diaphyseal structure of long bones of tetrapods. However, the architecture of trabecular bone, which is for instance found within the epiphyses of long bones, and which has been shown experimentally to be extremely plastic, has received little attention in the context of lifestyle adaptations (virtually only in primates). We therefore investigated the forelimb epiphyses of extant xenarthrans, the placental mammals including the sloths, anteaters, and armadillos. They are characterised by several lifestyles and degrees of fossoriality involving distinct uses of their forelimb. We used micro computed tomography data to acquire 3D trabecular parameters at regions of interest (ROIs) for all extant genera of xenarthrans (with replicates). Traditional, spherical, and phylogenetically informed statistics (including the consideration of size effects) were used to characterise the functional signal of these parameters.

Results

Several trabecular parameters yielded functional distinctions. The main direction of the trabeculae distinguished lifestyle categories for one ROI (the radial trochlea). Among the other trabecular parameters, it is the degree of anisotropy (i.e., a preferential alignment of the trabeculae) that yielded the clearest functional signal. For all ROIs, the armadillos, which represent the fully terrestrial and fossorial category, were found as characterised by a greater degree of anisotropy (i.e., more aligned trabeculae). Furthermore, the trabeculae of the humeral head of the most fossorial armadillos were also found to be more anisotropic than in the less fossorial species.

Conclusions

Most parameters were marked by an important intraspecific variability and by a size effect, which could, at least partly, be masking the functional signal. But for some parameters, the degree of anisotropy in particular, a clear functional distinction was recovered. Along with data on primates, our findings suggest that a trabecular architecture characterised by a greater degree of anisotropy is to be expected in species in which the relevant epiphyses withstand a restricted range of load directions. Trabecular architecture therefore is a promising research avenue for the reconstruction of lifestyles in extinct or cryptic species.

Electronic supplementary material

The online version of this article (10.1186/s12983-017-0241-x) contains supplementary material, which is available to authorized users.