Improved Fracture Risk Assessment Based on Nonlinear Micro‐Finite Element Simulations From HRpQCT Images at the Distal Radius

More accurate techniques to estimate fracture risk could help reduce the burden of fractures in postmenopausal women. Although micro‐finite element (µFE) simulations allow a direct assessment of bone mechanical performance, in this first clinical study we investigated whether the additional information obtained using geometrically and materially nonlinear µFE simulations allows a better discrimination between fracture cases and controls. We used patient data and high‐resolution peripheral quantitative computed tomography (HRpQCT) measurements from our previous clinical study on fracture risk, which compared 100 postmenopausal women with a distal forearm fracture to 105 controls. Analyzing these data with the nonlinear µFE simulations, the odds ratio (OR) for the factor‐of‐risk (yield load divided by the expected fall load) was marginally higher (1.99; 95% confidence interval [CI], 1.41–2.77) than for the factor‐of‐risk computed from linear µFE (1.89; 95% CI, 1.37–2.69). The yield load and the energy absorbed up to the yield point as computed from nonlinear µFE were highly correlated with the initial stiffness (R² = 0.97 and 0.94, respectively) and could therefore be derived from linear simulations with little loss in precision. However, yield deformation was not related to any other measurement performed and was itself a good predictor of fracture risk (OR, 1.89; 95% CI, 1.39–2.63). Moreover, a combined risk score integrating information on relative bone strength (yield load‐based factor‐of‐risk), bone ductility (yield deformation), and the structural integrity of the bone under critical loads (cortical plastic volume) improved the separation of cases and controls by one‐third (OR, 2.66; 95% CI, 1.84–4.02). We therefore conclude that nonlinear µFE simulations provide important additional information on the risk of distal forearm fractures not accessible from linear µFE nor from other techniques assessing bone microstructure, density, or mass. © 2013 American Society for Bone and Mineral Research.     

Computerized Baropodometry In Obese Patients

Background: Few studies have investigated the influence of obesity on the structural and functional performance of the feet, and its potential implications for the musculoskeletal system. Computerized baropodometric analysis (CPA) is a new investigation for the center of pressure, plantar surface area and plantar pressure while standing on the platform of a specialized apparatus. CPA is relevant to gait and posture, and may be important as well for postoperative musculoskeletal disorders. We investigated the biomechanical dysfunctions of foot pressure by means of CPA in bariatric and non-bariatric subjects. Methods: Subjects (n=67, 71.6% females, age 40.8 ± 13.8 years, BMI 31.4 ± 11.0 kg/m²) included obese (BMI 30.0-60.0 kg/m², n=27), overweight (BMI 25.0-29.9 kg/m², n=12) and normal-weight controls (BMI 20.0-24.9 kg/m², n=28) of equivalent age and gender. Variables included center of pressure location, plantar ground contact area and pressure, and pressure patterns (maximum and average) in different regions of the foot, during quiet standing on the platform of the baropodometer. Results: A significant increase was detected for peak pressure on forefoot and plantar ground contact area in the obese group, compared to control and overweight cases, during quiet standing. Conclusion: Excessive forefoot pressure and enlarged support area were a consequence of obesity, mirroring the efforts of the obese subject to acquire a wider and stronger support base. Although this is originally a physiological change, it may result in maladaptative and degenerative musculoskeletal consequences. Re-education exercises may be advised, in combination with bariatric surgery in the morbidly obese, aiming at restoration of normal gait and posture, as well as at minimization of stress damage to bones and joints in the axial skeleton.     

BMP9 Reduces Bone Loss in Ovariectomized Mice by Dual Regulation of Bone Remodeling

Bone remodeling is dynamic and is tightly regulated through bone resorption dominated by osteoclasts and bone formation dominated by osteoblasts. Imbalances in this process can cause various pathological conditions, such as osteoporosis. Bone morphogenetic protein 9 (BMP9), a biomolecule produced and secreted by the liver, has many pharmacological effects, including anti-liver fibrosis, antitumor, anti-heart failure, and antidiabetic activities. However, the effects of BMP9 on the regulation of osteoblast and osteoclast functions and the underlying molecular mechanism(s) have not yet been investigated. In this study, BMP9 increased the expression of osteoblastogenic gene markers, such as ALP, Cola1, OCN, RUNX2, and OSX, and ALP activity in MC3T3-E1 cells by upregulating LGR6 and activating the Wnt/β-catenin pathway. BMP9 also suppressed receptor activator of nuclear factor-κB (NF-κB) ligand (RANKL)-induced osteoclast differentiation of bone marrow macrophages (BMMs) by inhibiting the Akt-NF-κB-NFATc1 pathway. More importantly, in an ovariectomy (OVX) mouse model, BMP9 attenuated bone loss and improved bone biomechanical properties in vivo by increasing bone-forming activity and suppressing bone resorption activity. Accordingly, our current work highlights the dual regulatory effects that BMP9 exerts on bone remodeling by promoting bone anabolic activity and inhibiting osteoclast differentiation in OVX mice. © 2020 American Society for Bone and Mineral Research.     

Bone Mass,Bone Microstructure and Biomechanics in Patients with Hand Osteoarthritis

The impact of primary hand osteoarthritis (HOA) on bone mass, microstructure, and biomechanics in the affected skeletal regions is largely unknown. HOA patients and healthy controls (HCs) underwent high-resolution peripheral quantitative computed tomography (HR-pQCT). We measured total, trabecular, and cortical volumetric bone mineral densities (vBMDs), microstructural attributes, and performed micro–finite element analysis for bone strength. Failure load and scaled multivariate outcome matrices from distal radius and second metacarpal (MCP2) head measurements were analyzed using multiple linear regression adjusting for age, sex, and functional status and reported as adjusted Z-score differences for total and direct effects. A total of 105 subjects were included (76 HC: 46 women, 30 men; 29 HOA: 23 women, six men). After adjustment, HOA was associated with significant changes in the multivariate outcome matrix from the MCP2 head (p < .001) (explained by an increase in cortical vBMD (Δz = 1.07, p = .02) and reduction in the trabecular vBMD (Δz = −0.07, p = .09). Distal radius analysis did not show an overall effect of HOA; however, there was a gender-study group interaction (p = .044) explained by reduced trabecular vBMD in males (Δz = −1.23, p = .02). HOA was associated with lower failure load (−514 N; 95%CI, −1018 to −9; p = 0.05) apparent in males after adjustment for functional status. HOA is associated with reduced trabecular and increased cortical vBMD in the MCP2 head and a reduction in radial trabecular vBMD and bone strength in males. Further investigations of gender-specific changes of bone architecture in HOA are warranted. © 2020 The Authors. Journal of Bone and Mineral Research published by American Society for Bone and Mineral Research.     

Effect of Osteoclast Co-culture on the Differentiation of Human Mesenchymal Stem Cells Grown on Bone Graft Granules

Traditional approaches to bone repair are currently being integrated with innovative tissue-engineering techniques, as researchers and clinicians shift their treatment focus toward regenerating functional tissue rather than just filling a defect to provide structural support. Cells are expanded and incorporated into implantable systems in hopes of enhancing the bone-forming capabilities of traditional bone graft substitutes. The present study examined how osteoclasts might be used to stimulate the differentiation of human mesenchymal stem cells (hMSCs) into bone forming cells. The two cell types were co-cultured on a resorbable, three-dimensional bone graft substitute. Osteoclasts were seeded prior to the addition of hMSCs, as well as simultaneously, to determine if resorption of the scaffold would have any bearing on observed response by hMSCs. When seeded directly with hMSCs on the 3-D substrates, the osteoclasts had an increase in TRAP expression over time if seeded simultaneously. The co-culture setup had a positive influence on the proliferation of hMSCs. Late stage osteoblast differentiation markers (bone sialoprotein) were positively affected by direct co-culture with osteoclasts. The addition of RANKL to the culture medium for osteoclastogenesis appears to be a factor in the observed responses by hMSCS, but is not the only factor influencing the MSCs. Osteoclasts were shown to have an influence on the development of mesenchymal stem cells into osteoblasts when cultured in vitro. Findings from this study, coupled with the knowledge obtained from our previous work, will aid in the development of a clinically viable mesenchymal stem cell based bone graft system.     

Correlation Between Cryogenic Parameters and Physico-Chemical Properties of Porous Gelatin Cryogels

In the present work, we have performed an in-depth physico-chemical and bio-physical evaluation of a series of previously described porous gelatin scaffolds (S. VanVlierberghe, V. Cnudde, P. Dubruel, B. Masschaele, A. Cosijns, I. DePaepe, P.J.S. Jacobs, L. VanHoorebeke, J.P. Remon and E. Schacht, Biomacromolecules 8, 331 (2007)). All scaffolds were prepared by a cryogenic treatment and subsequent freeze-drying. Three types of scaffolds were prepared by using different gelatin concentrations and cooling protocols. Type-I hydrogels were composed of cone-like pores with decreasing diameter from top (330 μm) to bottom (20–30 μm). Type-II and type-III scaffolds contained spherical pores with an average diameter of 135 (type II) and 65 μm (type III), respectively. The physico-chemical and bio-physical properties studied include the water uptake capacity and kinetics, the mechanical properties and the enzyme-mediated degradation. We can conclude that the pore geometry affects the water uptake capacity, the mechanical properties and the degradation profile of the hydrogels. Type-I hydrogels possess the highest water uptake, the lowest compression modulus and the fastest enzyme mediated degradation, indicating a clear effect of the pore morphology (elongated channels for type I versus spherical pores for types II and III) on the physico-chemical and bio-physical properties of the materials. In contrast to the effect of the pore geometry (channel-like versus spherical), the pore size does not significantly affect the water uptake, the mechanical properties and the enzyme mediated degradation in the investigated pore size range (65–135 μm). To the best of our knowledge, this is the first report in which the effects of a cryogenic treatment on the hydrogel network properties are investigated in such detail.     

Fabrication of Injectable Calcium Sulfate Bone Graft Material

Calcium sulfate (CaSO₄), as a commonly used implanting material, shows good biocompatibility, biodegradability, osteoconductivity and mechanical properties. Studies about using CaSO₄ as bone filler for the treatment of bone defects are reported now and then, but the fabrication of injectable implant was hardly studied. In this study, calcium sulfate hemihydrate (CSH), as the basic material, was incorporated with a cellulose derivative, poly(ethylene glycol) (PEG), calcium sulfate dehydrate (CSD) crystal coated with PEG (P-CSD), and a certain amount of water to form injectable CaSO₄ bone fillers. The structure of the bone fillers with different compositions was analyzed with scanning electron microscopy (SEM), infrared spectroscopy (IR) and X-ray diffraction (XRD). The effects of additives such as P-CSD, CSD, PEG and cellulose derivative on setting time, water absorption ability, mechanical properties and structure of the injectable bone fillers were studied. The in vitro degradation test showed that the injectable bone fillers have appropriate degradation time in phosphate-buffered solution (PBS), and they can maintain integrity throughout the degradation process. In vitro cell culture and preliminary animal model experiments demonstrated that the bone fillers do not exhibit a deleterious effect on cell viability and can hasten bone growth in bone defect model.     

The Effects of One-Step Self-Etch Adhesives on the Induction of Oxidative Stress and Production of TGF-β1 and BMP-2 by Human Gingival Fibroblasts

The aim of this study was to evaluate and compare the effects of two self-etch adhesive materials on the induction of oxidative stress and production of transforming growth factor-β1 (TGF-β1) and bone morphogenetic protein-2 (BMP-2) by cultured human gingival fibroblasts (HGF). Inflammation-free attached gingiva was obtained from healthy donors under informed consent. Following 24- and 72-h exposure of HGF to two different elutes of the test materials, cell viability was determined using the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl tetrazolium bromide (MTT) assay. Lipid peroxidation, a major indicator of oxidative stress, was measured by the thiobarbituric acid reactive substance (TBARS) assay. TGF-β1 and BMP-2 levels in cell-free culture media were determined by enzyme-linked immunosorbent assay (ELISA). Cell viability of the test groups was significantly lower than those of control at 24 and 72 h (P < 0.001), but showed an increase at 72 h (P < 0.001). The TBARS levels of both test groups were significantly greater than that of control (P < 0.05), and displayed similar values at 72 h (P > 0.05). For both materials, the levels of TGF-β1 and BMP-2 were significantly greater than that of control (P < 0.05). Both test groups showed increased TGF-β1 levels. These results indicate that the tested self-etch adhesives might be capable of inducing production of TGF-β1 and BMP-2 in cultured HGF, despite their cytotoxic and oxidative stress-producing potential.     

Development and Characterization of Biodegradable Nanocomposite Injectables for Orthopaedic Applications Based on Polyphosphazenes

Self-setting hydroxyapatite–biodegradable injectable composites are excellent candidates for applications in orthopaedics. We have previously demonstrated the feasibility of development of self-setting calcium-deficient nanocrystalline hydroxyapatite–polymer composites using different calcium phosphate precursors and biodegradable polyphosphazenes. This study aimed to evaluate these novel injectable composites as suitable materials for orthopaedic applications through evaluating their biomechanical properties, osteoblast cellular attachment and gene expression over time.Our studies demonstrated that the morphology of the composite groups (PNEA–CDHA, PNEA–CDSHA, PNEA₅₀mPh₅₀–CDHA, PNEA₅₀mPh₅₀–CDSHA, PNEA₅₀PhPh₅₀–CDHA, and PNEA₅₀PhPh₅₀–CDSHA) formed was similar and found to have micro- and nanoporous structures resembling trabecular bone. The osteoblast phenotypic marker of bone, alkaline phosphatase, was expressed by the cells on the surface of the composites throughout the study and was comparable to tissue-culture polystyrene (control). Furthermore, the cells seeded on the composites expressed the characteristic osteoblastic genes, such as type-I collagen, alkaline phosphatase, osteocalcin, osteopontin and bone sialoprotein, indicating osteoblast differentiation, maturation and mineralization. Within our injectable composite groups, significant gene expression levels were displayed (P < 0.05). These novel injectable biodegradable polyphosphazenes–calcium-deficient hydroxyapatites materials are promising candidates for orthopaedic applications.     

Developing porosity of poly(propylene glycol-co-fumaric acid) bone graft substitutes and the effect on osteointegration: A preliminary histology study in rats

Abstract -Bioresorbable bone graft substitutes could eliminate disadvantages associated with the use of autografts, allografts and other synthetic materials. We investigated a bioresorbable bone graft substitute made from the unsaturated polyester poly(propylene fumarate) which is crosslinked in the presence of soluble and insoluble calcium filler salts. This compact bone graft substitute material develops porosity in vivo by leaching of the soluble filler salts. In attempt to develop materials whose in vivo porosity can be designed such that implant degradation would occur at a rate that remains supportive of the overall structural integrity of the repairing defect site, we studied the early tissue response upon implantation in a bony defect. Three grout formulations of varying solubilities using slightly soluble hydroxyapatite (HA) and soluble calcium acetate (CA) were evaluated in 3 mm holes made in the anteromedial tibial metaphysis of 200 g Sprague Dawley rats (n = 16 per formulation for a total of 48 animals). Grout formulations cured in situ. Animals from each formulation were sacrificed in groups of 8 at 4 days and 3 weeks postoperatively. Histologic analysis of the healing process revealed improved in vivo osteointegration of bone graft substitutes when a higher loading of calcium acetate was employed. All formulations maintained implant integrity and did not provoke sustained inflammatory responses. This study suggested that the presence of a soluble salt permits in vivo development of porosity of a poly(propylene fumarate) based bone graft substitute material.