Osteoporotic Bone Tissue Research Articles

Optical analysis of the osteoporotic bone tissue and evaluation of its prevention using allogenic hydroxyapatite

The results of the experimental research of the osteoporotic bone tissue and the Raman spectroscopy evaluation of its prevention using allogenic hydroxyapatite during resorption are presented in this work. The Raman spectra were obtained and their deconvolution and comparative analysis was made in this work. The coefficients allowing evaluating the osteoporosis model treatment using hydroxyapatite were implied. The treatment of more intensive osteoporosis model did not show any changes, which indicates that the treatment of this osteoporosis model was not effective in this case.

Pro-osteoporotic miR-320a impairs osteoblast function and induces oxidative stress.

MicroRNAs (miRNAs) are important regulators of many cellular processes, including the differentiation and activity of osteoblasts, and therefore, of bone turnover. MiR-320a is overexpressed in osteoporotic bone tissue but its role in osteoblast function is unknown. In the present study, functional assays were performed with the aim to elucidate the mechanism of miR-320a action in osteoblastic cells. MiR-320a was either overexpressed or inhibited in human primary osteoblasts (hOB) and gene expression changes were evaluated through microarray analysis. In addition, the effect of miR-320a on cell proliferation, viability, and oxidative stress in hOB was evaluated. Finally, matrix mineralization and alkaline phosphatase activity were assessed in order to evaluate osteoblast functionality. Microarray results showed miR-320a regulation of a number of key osteoblast genes and of genes involved in oxidative stress. Regulation of osteoblast differentiation and ossification appeared as the best significant biological processes (PANTHER P value = 3.74E-05; and P value = 3.06E-04, respectively). The other enriched pathway was that of the cellular response to cadmium and zinc ions, mostly by the overexpression of metallothioneins. In hOBs, overexpression of miR-320a increased cell proliferation and oxidative stress levels whereas mineralization capacity was reduced. In conclusion, overexpression of miR-320a increased stress oxidation levels and was associated with reduced osteoblast differentiation and functionality, which could trigger an osteoporotic phenotype.

A novel fracture mechanics model explaining the axial penetration of bone-like porous, compressible solids by various orthopaedic implant tips.

Many features of orthopaedic implants have been previously examined regarding their influence on migration in trabecular bone under axial loading, with screw thread design being one of the most prominent examples. There has been comparatively little investigation, however, of the influence that implant tip design has on migration under axial loads. We present a novel fracture mechanics model that explains how differences in tip design affect the force required for axial penetration of porous, compressible solids similar to trabecular bone. Three tip designs were considered based on typical 5 mm diameter orthopaedic locking screws: flat and conical tip designs, as well as a novel elastomeric tip. Ten axial penetration trials were conducted for each tip design. In order to isolate the effect of tip design on axial migration from that of the threads, smooth steel rods were used. Tip designs were inserted into polyurethane foam commonly used to represent osteoporotic trabecular bone tissue (ASTM Type 10, 0.16 g/cc) to a depth of 10 mm at a rate of 2 mm/min, while force and position were recorded. At maximum depth, elastomeric tips were found to require the greatest force for axial migration (mean of 248.24 N, 95% Confidence Interval [CI]: 238.1-258.4 N), followed by conical tips (mean of 143.46 N, 95% CI: 142.1-144.9 N), and flat tips (mean of 113.88 N, 95% CI: 112.2-115.5 N). This experiment was repeated in cross-section while recording video of material compaction through a transparent window. Strain fields for each tip design were then generated from these videos using digital image correlation (DIC) software. A novel fracture mechanics model, combining the Griffith with porous material compaction, was developed to explain the performance differences observed between the three tip designs. This model predicted that steady-state stress would be roughly the same (~ 4 MPa) across all designs, a finding consistent with the experimental results. The model also suggested that crack formation and friction are negligible mechanisms of energy absorption during axial penetration of porous compressible solids similar to trabecular bone. Material compaction appears to be the dominant mechanism of energy absorption, regardless of tip design. The cross-sectional area of the compacted material formed during migration of the implant tip during axial penetration was shown to be a strong determinant of the force required for migration to occur (Pearson Coefficient = 0.902, p < .001). As such, implant tips designed to maximize the cross-sectional area of compacted material - such as the elastomeric and conical tips in the present study - may be useful in reducing excessive implant migration under axial loads in trabecular bone.

Influence of DNA methylation on the expression of OPG/RANKL in primary osteoporosis.

Purpose: A key factor in regulating bone absorption is the proportion of RANKL/OPG. Although many reports showing diverse transcription factors or epigenetic modification could be responsible for regulating RANKL&OPG ratio, there is still little exploration on promoter methylation status of both genes in osteoporotic bone tissues. Our aim is to investigate the changes of methylation in CpG island of these genes' promoters in patients with primary osteoporosis.Methods: The diagnosis of osteoporosis was based on the results of dual energy X-ray absorptiometry measurements. All femoral bone tissues were separated in surgeries. After extracting total RNA, we checked the relative expression levels of OPG and RANKL by quantitative real time PCR. The genomic DNA of Non-OPF (Non-osteoporotic fracture bone tissues) & OPF (osteoporotic fracture bone tissues) were treated by bisulfite modification, and methylation status of CpG sites in the CpG island of OPG/RANKL promoters were determined by DNA sequencing.Results: RANKL expression in the OPF group was significantly higher than that in Non-OPF group, and the CpG methylation status in RANKL gene promoter was significantly lower. However, for OPG, lower gene expression level and higher methylation degree were found in the OPF group.Conclusion: Our study demonstrated that DNA methylation influenced the transcriptional expression of OPG and RANKL, which probably take on a “main switch” role in pathogenesis of primary osteoporosis.

Composite Colloidal Gels Made of Bisphosphonate‐Functionalized Gelatin and Bioactive Glass Particles for Regeneration of Osteoporotic Bone Defects

AbstractInjectable composite colloidal gels are developed for regeneration of osteoporotic bone defects through a bottom‐up assembly from bisphosphonate‐functionalized gelatin and bioactive glass particles. Upon bisphosphonate functionalization, gelatin nanoparticles show superior adhesion toward bioactive glass particles, resulting in elastic composite gels. By tuning their composition, these composite colloidal gels combine mechanical robustness with self‐healing ability. The composite colloidal gels support cell proliferation and differentiation in vitro without requiring any osteogenic supplement. In vivo evaluation of the composite colloidal gels reveals their capacity to support the regeneration of osteoporotic bone defects. Furthermore, the bisphosphonate modification of gelatin induces a therapeutic effect on the peri‐implantation region by enhancing the bone density of the osteoporotic bone tissue. Consequently, these composite colloidal gels offer new therapeutic opportunities for treatment of osteoporotic bone defects.

Fixation of distal fibular fractures: A biomechanical study of plate fixation techniques.

Ankle fractures are complex injuries with variable prognoses that depend upon many factors. The aim of the treatment is to restore the ankle joint biomechanical stability with maximum range of motion. Most ankle fractures are fibular fractures, which have a typical oblique fracture line in the distal fibula located in the area of the tibiofibular syndesmosis. The aim of this study was to simulate numerically several fixation techniques of the distal fibular fractures, evaluate their stability, determine their impact on surrounding tissue load, and correlate the results to clinical treatment experience. The following three models of fibular fracture fixation were used: (a) plate fixation with three screws attached above/below and lag screws, (b) plate fixation with two screws attached above/below and lag screws, and (c) three lag screws only. All three fracture fixation models were analyzed according to their use in both healthy physiological bone and osteoporotic bone tissue. Based on the results of Finite Element Analysis for these simulations, we found that the most appropriate fixation method for Weber-B1 fibular fractures was an unlocked plate fixation using six screws and lag screws, both in patients with physiological and osteoporotic bone tissue. Conversely, the least appropriate fixation method was an unlocked plate fixation with four screws and lag screws. Although this fixation method reduces the stress on patients during surgery, it greatly increased loading on the bone and, thus, the risk of fixation failure. The final fixation model with three lag screws only was found to be appropriate only for very limited indications.

Dementia and osteoporosis in a geriatric population: Is there a common link?

AIMTo determine the existence of a common pathological link between dementia and osteoporosis through reviewing the current evidence base.METHODSThis paper reviews the current literature on osteoporosis and dementia in order to ascertain evidence of a common predisposing aetiology. A literature search of Ovid MED-LINE (1950 to June 2016) was conducted. The keywords “osteoporosis”, “osteoporotic fracture”, “dementia” and “Alzheimer’s disease” (AD) were used to determine the theoretical links with the most significant evidence base behind them. The key links were found to be vitamins D and K, calcium, thyroid disease, statins, alcohol and sex steroids. These subjects were then searched in combination with the previous terms and the resulting papers manually examined. Theoretical, in vitro and in vivo research were all used to inform this review which focuses on the most well developed theoretical common causes for dementia (predominantly Alzheimer’s type) and osteoporosis.RESULTSDementia and osteoporosis are multifaceted disease processes with similar epidemiology and a marked increase in prevalence in elderly populations. The existence of a common link between the two has been suggested despite a lack of clear pathological overlap in our current understanding. Research to date has tended to be fragmented and relatively weak in nature with multiple confounding factors reflecting the difficulties of in vivo experimentation in the population of interest. Despite exploration of various possible mechanisms in search for a link between the two pathologies, this paper found that it is possible that these associations are coincidental due to the nature of the evidence available. One finding in this review is that prior investigation into common aetiologies has found raised amyloid beta peptide levels in osteoporotic bone tissue, with a hypothesis that amyloid beta disorders are systemic disorders resulting in differing tissue manifestations. However, our findings were that the most compelling evidence of a common yet independent aetiology lies in the APOE4 allele, which is a well-established risk for AD but also carries an independent association with fracture risk. The mechanism behind this is thought to be the reduced plasma vitamin K levels in individuals exhibiting the APOE4 allele which may be amplified by the nutritional deficiencies associated with dementia, which are known to include vitamins K and D. The vitamin theory postulates that malnutrition and reduced exposure to sunlight in patients with AD leads to vitamin deficiencies.CONCLUSIONRobust evidence remains to be produced regarding potential links and regarding the exact aetiology of these diseases and remains relevant given the burden of dementia and osteoporosis in our ageing population. Future research into amyloid beta, APOE4 and vitamins K and D as the most promising aetiological links should be welcomed.

Does Local Application of Strontium Increase Osteogenesis and Biomaterial Osteointegration in Osteoporotic and Other Bone Tissue Conditions: Review of Literature

Summary Osteoporosis and other pathological bone conditions can impair bone regeneration properties, consuming in increased morbidity and decreased quality of life. Changes of bone healing can result in poor osteointegration and surgical failures if implants are used. To overcome and facilitate bone regeneration, more attempts are made to develop an ideal synthetic scaffold with better biocompatibility, osteoconductivity, bioactivity, osteoinductivity and interconnected porosity. It is considered that strontium, being similar to calcium, can be incorporated into the mineral phase of the bone remodeling. This quality had led strontium to be used as an osteoporotic medication to improve quality of bone and to reduce the risk of bone fractures. Also local application of strontium has been widely used within different biomaterials in tissue engineering researches. In this review authors wanted to provide an overview about strontium, its mechanisms of action in bone tissue and initiated changes of bone remodeling within biomaterials.

Improvement on growth of osteoporotic bone tissue around screw and fixation strength of screw induced by stress force from the expanding pedicle screw: dynamic microstructural, histological and biomechanical studies in osteoporotic sheep lumbar vertebrae

Improvement on growth of osteoporotic bone tissue around screw and fixation strength of screw induced by stress force from the expanding pedicle screw: dynamic microstructural, histological and biomechanical studies in osteoporotic sheep lumbar vertebrae

Surgical Treatment of Undisplaced Femur Neck Fractures in Dementia Patients Using Proximal Femoral Nail Antirotation.

PurposePeople with dementia have poor mobility and discharge outcomes following hip fractures. The purpose of this study was to evaluate the clinical and radiological results of internal fixation of undisplaced femur neck fractures (Garden types 1 and 2) by proximal femoral nail antirotation (PFNA) in dementia patients.Materials and MethodsWe studied retrospectively 19 patients with undisplaced femur neck fracture. All patients were over 70 years of age, walked independently with a cane or crutches and suffered moderate-to-severe dementia. Patients were treated with PFNA and followed-up for more than 2 years. Revision, loss of fixation, complications, and walking ability outcomes were measured.ResultsIn walking-ability evaluation, patients showed an average decrease of just 0.2 points at the final follow-up. Walking ability was evaluated from before injury to 4 weeks after surgery and decreased by less than 0.5 points. Radiological bone union was achieved in 17 cases; the average time to bone union was 4.14 months (range, 2.5-7 months). Complications included non-union in two cases and femoral head avascular necrosis in one case of non-union.ConclusionWe found that for patients with osteoporotic bone tissues in their femoral heads or patients (e.g., those suffering dementia) for whom cooperating with medical workers for postoperative walking control or rehabilitation exercises is difficult, implanting a mechanically stable spiral blade for fixation of femoral neck fractures could facilitate walking after surgery.

Effect of direct loading of phytoestrogens into the calcium phosphate scaffold on osteoporotic bone tissue regeneration.

3D porous calcium deficient hydroxyapatite (CDHA) scaffolds with phytoestrogens were fabricated for osteoporotic bone tissue regeneration through a combination of 3D printing techniques and cement chemistry as a room temperature process. Quercetin, one of the major phytoestrogens isolated from onions and apples, was directly incorporated into CDHA for local administration in place of bisphosphonates (BPs) (which are recognized as standard treatment in osteoporosis), to avoid drug side effects. The CDHA scaffolds with quercetin (QC-CDHA) showed favorable mechanical properties (compressive strength < 21 MPa) as well as pore morphology. Quercetin was steadily released with the biodegradation of CDHA scaffolds in vitro without any initial burst. The QC-CDHA scaffolds greatly influenced both osteoblast and osteoclast cell activities. The QC-CDHA scaffolds significantly increased pre-osteoblast cell (MC3T3-E1) proliferation, differentiation, and mineralization, whereas osteoclast cell (RANK treated RAW 264.7) proliferation and differentiation were dramatically suppressed. The influence of quercetin on bone tissue regeneration was superior to alendronate, which is one of the most commonly administered BPs. All results indicated that quercetin in CDHA scaffolds plays an important role in both enhancing bone formation and suppressing bone resorption. Consequently, this technology promises great potential in osteoporotic bone tissue regeneration.

Amyloid beta peptide is elevated in osteoporotic bone tissues and enhances osteoclast function

PurposeEpidemiological studies show that patients with Alzheimer's disease (AD) have an increased risk of developing osteoporotic hip fracture. However, whether abnormal amyloid beta peptide (Aβ) deposition, one of the pathological hallmarks of AD, also occurs in osteoporosis and the relationship between Aβ and human osteoporosis remain unknown. This study addressed these issues. MethodsForty-five female patients (osteoporosis 21, osteopenia 16 and normal 8) with osteoporotic/traumatic vertebral compression fractures were enrolled and Aβ42 and amyloid precursor protein (APP) levels assessed in the biopsy specimens of vertebral trabecular bone using immunohistochemistry (IHC) staining and semi-quantitative evaluation assays. Spearman rank correlation analysis was applied to explore the association between Aβ42/APP levels and the corresponding bone mineral density (BMD). Moreover, immunofluorescent assays and laser scanning confocal microscopy assays were used to examine the expression patterns of Aβ42/APP in patient bone tissues and osteocytes. Additionally, eight female patients with osteoporotic/traumatic femoral neck fractures, including two control patients were selected and Aβ42 and APP were identified in the femoral necks by RT-PCR and Western blotting (WB) assays. Next, a rat model of ovariectomy-induced osteoporosis was created and we evaluated Aβ42 and APP expression differences in the proximal tibia by IHC and RT-PCR and WB assays in comparison with a sham-operation group. Finally, the RAW264.7 cell line and human bone marrow monocyte (hBMMC) derived osteoclasts and human Aβ42 co-culture assays were performed to investigate the effect of Aβ42 on osteoclasts cell viability, number, differentiation and activation by the Cell Counting Kit-8 assay, tartrate resistant acid phosphatase staining assay, RT-PCR assay measuring the lytic gene expression and hydroxyapatite resorption assay respectively. ResultsThe mRNA and protein expression levels of Aβ42 and APP were elevated remarkably in the osteoporotic bone tissues both from human and ovariectomized rats when compared with the age-/sex-matched controls. Moreover, the expression levels had a negative correlation with corresponding BMD in patients (RAβ42=−0.617, p<0.0001; RAPP=−0.531, p=0.0002). In addition, Aβ42 was located mainly in the membrane and cytoplasm of osteocytes and in the extracellular matrix, while APP was largely located in the membrane of the osteocytes. Finally, Aβ42 can potently enhance osteoclasts differentiation and activation but had no effect on osteoclasts cell viability or number (dose- and time-dependency did not exist and oligomerization of Aβ42 was not a prerequisite in the osteoclastogenesis assay). ConclusionsAβ is relevant to human osteoporosis and may have an important role in the pathogenesis of osteoporosis.

Regeneration of damaged osteoporotic bone tissue with synthetic biomaterials

In some cases in oral and maxillofacial surgery, bone regeneration is required in large quantities. One of these cases is osteoporosis. This paper aims to show the new approach to solving this problem of impaired healing of bone defects in the jaw, as well as in other bones, with the use of synthetic biomaterials whose properties resemble the natural bone. Latest development in this area present an effort to create local drug-delivery systems for BMPs and growth factors, direct delivery of MSCs, as well as scaffolds for osteoconduction and also to utilize nanotechnology to synthesize composite biomaterials, predominantly based on HAp and polymers, that would mimic the natural bone nanocomposite architecture. There is also a tendency to create injectable biomaterials for simplified application.

Micronutrients-incorporated calcium phosphate particles with protective effect on osteoporotic bone tissue.

Supplementation of individual micronutrient is inadequate for maintaining bone function because single micronutrient can not contribute significantly a positive remodeling balance. We developed the highly integrated, stably dietary multi-micronutrients with good bioavailability and low adverse effect on the improvement of bone consolidation in osteoporosis. The trace element-codoped calcium phosphate (teCaP) particles were prepared in the modified body fluid and carefully evaluated. Rats, aged 3 months, were ovariectomized and when 6 month intervened with the conditioned, low, moderate, and high teCaP diets. The teCaP particles showed highly dissolvable in stomach juice-mimicing acidic solutions. Three months after intervention, the body weight increase showed remarkable differences among the low teCaP diet (~52 g), moderate teCaP diet (~34 g) and high teCaP diet (~23 g) group. In particular, the intake of moderate teCaP greatly improved the retention of trace elements in femural bone for better protection against the skeletal weakening, and resulted in a significant increase of bone mineral density (104.06%) in comparison with the conventional high calcium plus vitamin D3 diet (Control group). These investigations improve our understanding of micronutrient retention on bone consolidation in osteoporotic bone tissue, and also provide new mild wet-chemical approach to prepare potent nutritionally effective edible complements to synergistically relieve bone degeneration and prevent osteoporosis.

Influence of long-term hypodynamy on spongy bone tissue in Japanese quails

Weightlessness can cause various damages especially on the musculoskeletal system both in animals and humans. The aim of our study was to observe the influence of simulated, long-term microgravity on the spongy bone tissue of the femur in Japanese quails. A total of 80 cockerels at the age of 2 days were exposed to simulated microgravity – hypodynamy. After days 56, 63, 90 and 180, six birds from the experimental group and six birds from the control group were euthanised. Samples for histological examination were collected from femur epiphysis. The whole femur of the other limb was used for the analysis of the calcium content. Microscopic examination showed differences between experimental and control animals in the spongy bone tissue after every day of the experiment. In the experimental animals, there were numerous, big, multinucleated cells osteoclasts, lying on the bone trabeculae surface, which were damaged. The highest difference in the calcium content in femurs between the control and experimental animals was found after 90 days of hypodynamy. This study builds on short-term hypodynamy experiments; such long periods had never been studied before in birds. Because our findings are similar to those found in osteoporotic bone tissue, it could by useful in the development of countermeasures against the negative influence of microgravity and immobilization.

Related Biological Research in the Interface between Bone Cement and Bone after Percutaneous Vertebroplasty

Percutaneous vertebroplasty (PVP) is widely used in the treatment of painful osteoporotic vertebral compression fractures with the injection of PMMA cement, and the controversy for PMMA damage to the osteoporotic bone tissue and to affect the fractures repairing never stops. 72 old female rabbits, each age 3.0~3.5 y, rabbits were assigned randomly to two groups of thirty-six each; PMMA cement were injected into vertebral body in rabbits via mimic PVP, sacrificed at 1 h, 24 h, 3 d, 7 d, 4 w, and 12 w. The expression VEGF and collagen type I, the tissue response, and repair reaction in the interface between PMMA and bone tissue were observed dynamically with RT-PCR and western blot technique; the osteocalcin expression were studied by immunohistochemistry. Compared with the control group, the expression of collagen I increased at 1 hour and was higher from 24 h to 3 d. From 4 weeks to 12 weeks after injection of PMMA. The expression of VEGF decreased at 1 hour and 24 hours, significantly increased at 3 days, decreased once again at 7 days, then increased significantly at 4–12 weeks. The osteocalcin expression continued to increase during 4 to 12 week. PMMA would not cause local bone permanent necrosis, and interface injury repairing cycle could be prolonged in a vertebroplasty.

Bone Regeneration Associated with Nontherapeutic and Therapeutic Surface Coatings for Dental Implants in Osteoporosis

Oral implantology is considered as the treatment of choice for replacing missing teeth in elderly people. However, implant complications may occur in patients with osteoporosis. The pathogenesis underlying osteoporosis is due to an alteration in bone cell response to hormonal, nutritional, and aging factors. For such challenging situations, improved bone regeneration has been shown around dental implants for certain surface modifications. These modifications include coatings of titanium implants with calcium phosphate (CaP) ceramics. Surface coating developments also allow for the addition of organic biomolecules, like growth factors, into the inorganic coatings that increase the bone formation process at the bone-implant interface. The application of therapeutic-based coatings is becoming a rapidly growing research field of interest. CaP-coated implants have the ability to incorporate anti-osteoporotic drugs, which then can be locally released over time from an implant surface in a controlled manner. Thus, it can be anticipated that nontherapeutic and/or therapeutic coated implants can significantly increase low bone density as well as improve impaired bone regeneration in osteoporosis. This review aims to provide a thorough understanding of the underlying mechanisms for impaired bone regeneration around dental implants in osteoporosis. Secondly, the review will focus on biological interactions and beneficial role of the surface-coated (i.e., nontherapeutics and therapeutics) bone implants in osteoporotic bone tissue.

Chlamydia pneumoniae and osteoporosis-associated bone loss: a new risk factor?

We found an association between the presence of Chlamydia pneumoniae DNA both in osteoporotic bone tissue and peripheral blood mononuclear cells (PBMCs) and the increase in circulating resorptive cytokines. Our study was designed to determine whether C. pneumoniae infection may be involved in osteoporosis-associated bone loss. The study included 59 women undergoing hip joint replacement surgery for femoral neck fracture: 32 with osteoporosis and 27 with osteoarthritis. A total of 118 tissue specimens (59 bone tissues, 59 PBMCs) were examined for C. pneumoniae DNA by real-time polymerase chain reaction (PCR). Serum levels of soluble receptor activator of nuclear factor kappa B ligand (sRANKL), osteoprotegerin (OPG), interleukin (IL)-1β, tumor necrosis factor-α, and IL-6 were also measured. C. pneumoniae DNA was detected in osteoporotic bone tissue whereas it was not found in non-osteoporotic bone tissue (p < 0.05). A significantly higher rate of C. pneumoniae DNA (p < 0.05) was found in PBMCs of osteoporotic patients than in those of osteoarthritis patients. Among osteoporotic patients, serum sRANKL, IL-1, and IL-6 concentrations as well as sRANKL/OPG ratio significantly differ between patients with bone tissue and PBMCs positive to C. pneumoniae and C. pneumoniae-negative patients. The association between the presence of C. pneumoniae DNA, both in bone tissue and PBMCs, and the increase in sRANKL/OPG ratio as well as in IL-1β and IL-6 levels observed in osteoporotic patients suggests C. pneumoniae infection as a new risk factor for osteoporosis.

Nanoparticles of cobalt-substituted hydroxyapatite in regeneration of mandibular osteoporotic bones

Indications exist that paramagnetic calcium phosphates may be able to promote regeneration of bone faster than their regular, diamagnetic counterparts. In this study, analyzed was the influence of paramagnetic cobalt-substituted hydroxyapatite nanoparticles on osteoporotic alveolar bone regeneration in rats. Simultaneously, biocompatibility of the material was tested in vitro, on osteoblastic MC3T3-E1 and epithelial Caco-2 cells in culture. The material was shown to be biocompatible and nontoxic when added to epithelial monolayers in vitro, while it caused a substantial decrease in the cell viability as well as deformation of the cytoskeleton and cell morphology when incubated with the osteoblastic cells. In the course of 6 months after the implantation of the material containing different amounts of cobalt, ranging from 5 to 12 wt%, in the osteoporotic alveolar bone of the lower jaw, the following parameters were investigated: histopathological parameters, alkaline phosphatase and alveolar bone density. The best result in terms of osteoporotic bone tissue regeneration was observed for hydroxyapatite nanoparticles with the largest content of cobalt ions. The histological analysis showed a high level of reparatory ability of the nanoparticulate material implanted in the bone defect, paralleled by a corresponding increase in the alveolar bone density. The combined effect of growth factors from autologous plasma admixed to cobalt-substituted hydroxyapatite was furthermore shown to have a crucial effect on the augmented osteoporotic bone regeneration upon the implantation of the biomaterial investigated in this study.

Work conjugacy error in commercial finite-element codes: its magnitude and how to compensate for it

Most commercial finite-element programs use the Jaumann (or co-rotational) rate of Cauchy stress in their incremental (Riks) updated Lagrangian loading procedure. This rate was shown long ago not to be work-conjugate with the Hencky (logarithmic) finite strain tensor used in these programs, nor with any other finite strain tensor. The lack of work-conjugacy has been either overlooked or believed to cause only negligible errors. Presented are examples of indentation of a naval-type sandwich plate with a polymeric foam core, in which the error can reach 28.8 per cent in the load and 15.3 per cent in the work of load (relative to uncorrected results). Generally, similar errors must be expected for all highly compressible materials, such as metallic and ceramic foams, honeycomb, loess, silt, organic soils, pumice, tuff, osteoporotic bone, light wood, carton and various biological tissues. It is shown that a previously derived equation relating the tangential moduli tensors associated with the Jaumann rates of Cauchy and Kirchhoff stresses can be used in the user’s material subroutine of a black-box commercial program to cancel the error due to the lack of work-conjugacy and make the program perform exactly as if the Jaumann rate of Kirchhoff stress, which is work-conjugate, were used.