Cancellous bone response to strontium-doped hydroxyapatite in osteoporotic rats

In vivo bone regeneration performance of hydroxypropyl methylcellulose hydrogel-based composite bone cements in ovariectomized and ovary-intact rats: a preliminary investigation

The objective of this study is to fabricate and develop hydroxypropyl methylcellulose (HPMC) hydrogel (HG)-based composite bone cements with incorporation of hydroxyapatite (HA), beta-tricalcium phosphate (β-TCP), and with/without polymethylmethacrylate (PMMA) for vertebroplasty. For animal study, twenty female Wister rats (250-300 g, 12 weeks of age) were divided into four groups including a two non-ovariectomy (NOVX) groups and two ovariectomy (OVX)-induced osteoporosis groups. Two prepared biocomposites including HG/β-TCP/HA and HG/β-TCP/HA/PMMA were injected into the tibial defects of both OVX and NOVX rats for evaluating in vivo osteogenesis after 12 weeks. Micro-computed tomography and histological analysis using hematoxylin and eosin (H&E) and Masson's trichrome stains of the two composite cements implanted into the tibial defects of OVX and NOVX rats revealed enhanced bone regeneration potential. However, no statistically significant differences were noted among the groups based on new bone formation, demonstrating that the injected composite cements showed similar osteogenesis effects in both OVX and NOVX rats. These findings suggest that the newly developed composite bone cement composed of HG, β-TCP, HA and/or PMMA may be a promising and professional tool for treating osteoporotic and non-osteoporotic vertebral fractures.

Boron Nano-hydroxyapatite Composite Increases the Bone Regeneration of Ovariectomized Rabbit Femurs

Osteoporosis is a systemic metabolic disease defined by a decreased bone mineral density, microarchitectural deterioration, and an increased incidence of fragility fractures that may lead to morbidity and mortality. Boron may stimulate new bone formation and regeneration, when combined with nano-hydroxyapatite. We questioned whether injecting boron-containing nano-hydroxyapatite composites with hyaluronan increased the bone mineral density and new bone formation in osteoporotic rabbit femurs. The regenerative effects of injectable boron-containing nano-hydroxyapatite composites from 6 to 12 weeks, which may prevent osteoporotic femoral fractures, were assessed. Boron-containing (10 μg/ml) nano-hydroxyapatite composites were injected into the intramedullary femoral cavity with hyaluronan. These significantly increased the histomorphometric new bone surface to the total bone surface ratio at 6 and 9 weeks. The micro-tomographic bone volume to the total volume ratio and bone mineral density in osteoporotic rabbit femurs increased when compared to the hyaluronan (p = 0.004, p = 0.004, p = 0.004, p = 0.01, respectively) and the sham-control (p = 0.01, p = 0.004, p = 0.01, p = 0.037, respectively) groups. The boron-containing group had a higher bone mineralization and new bone formation compared to the nano-hydroxyapatite group, although the difference was not statistically significant. These findings reveal that intramedullary injection of boron-containing nano-hydroxyapatite with hyaluronan increases new bone formation and mineralization in ovariectomized rabbit femurs. Boron-containing nano-hydroxyapatite composites are promising tissue engineering biomaterials that may have regenerative potential in preventing primary and/or secondary femoral fractures in osteoporosis patients.

Comprehensive In Vitro Testing of Calcium Phosphate-Based Bioceramics with Orthopedic and Dentistry Applications

Recently, a large spectrum of biomaterials emerged, with emphasis on various pure, blended, or doped calcium phosphates (CaPs). Although basic cytocompatibility testing protocols are referred by International Organization for Standardization (ISO) 10993 (parts 1-22), rigorous in vitro testing using cutting-edge technologies should be carried out in order to fully understand the behavior of various biomaterials (whether in bulk or low-dimensional object form) and to better gauge their outcome when implanted. In this review, current molecular techniques are assessed for the in-depth characterization of angiogenic potential, osteogenic capability, and the modulation of oxidative stress and inflammation properties of CaPs and their cation- and/or anion-substituted derivatives. Using such techniques, mechanisms of action of these compounds can be deciphered, highlighting the signaling pathway activation, cross-talk, and modulation by microRNA expression, which in turn can safely pave the road toward a better filtering of the truly functional, application-ready innovative therapeutic bioceramic-based solutions.

Ionic Liquid-Assisted Hydrothermal Synthesis of a Biocompatible Filler for Photo-Curable Dental Composite: From Theory to Experiment

Nanostructured hydroxyapatite (HA) is a new class of biocompatible fillers which has been recently utilized in bio hybrid materials by virtue of its excellent tissue bioactivity and biocompatibility. However, the need for higher thermal stability, solubility, surface bioactivity, radiopacity, and remineralization ability suggests a divalent cation substitution of HA for use in light curable dental restorative composites. In this work, structural and optical properties of Sr-doped hydroxyapatite were studied using first-principle calculations based on density functional theory (DFT). Next, Sr-doped hydroxyapatite (HA) was prepared via a new ionic liquid-assisted hydrothermal (ILH) route. Samples were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM)/energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), dynamic light scattering (DLS), Brunauer–Emmett–Teller (BET) surface area analysis, and cell viability. The obtained experimental data showed that the nucleation and crystal growth process controlled by [BMIM]Br molecules results in uniform products with small and regular particles and high specific surface areas. Finally, cytotoxicity tests showed that the as-prepared Sr-doped HA nanoparticles have good biocompatibility (≥91%), confirming their potential for use in photo-curable dental restorative composites.

Functionalization of Ceramic Coatings for Enhancing Integration in Osteoporotic Bone: A Systematic Review

Background: The success of reconstructive orthopaedic surgery strongly depends on the mechanical and biological integration between the prosthesis and the host bone tissue. Progressive population ageing with increased frequency of altered bone metabolism conditions requires new strategies for ensuring an early implant fixation and long-term stability. Ceramic materials and ceramic-based coatings, owing to the release of calcium phosphate and to the precipitation of a biological apatite at the bone-implant interface, are able to promote a strong bonding between the host bone and the implant. Methods: The aim of the present systematic review is the analysis of the existing literature on the functionalization strategies for improving the implant osteointegration in osteoporotic bone and their relative translation into the clinical practice. The review process, conducted on two electronic databases, identified 47 eligible preclinical studies and 5 clinical trials. Results: Preclinical data analysis showed that functionalization with both organic and inorganic molecules usually improves osseointegration in the osteoporotic condition, assessed mainly in rodent models. Clinical studies, mainly retrospective, have tested no functionalization strategies. Registered trademarks materials have been investigated and there is lack of information about the micro- or nano- topography of ceramics. Conclusions: Ceramic materials/coatings functionalization obtained promising results in improving implant osseointegration even in osteoporotic conditions but preclinical evidence has not been fully translated to clinical applications.

Bioceramics and bone healing

Calcium phosphates have long been used as synthetic bone grafts. Recent studies have shown that the modulation of composition and textural properties, such as nano-, micro- and macro-porosity, is a powerful strategy to control and synchronize material resorption and bone formation.Biomimetic calcium phosphates, which closely mimic the composition and structure of bone mineral, can be produced using low-temperature processing routes, and offer the possibility to modulate the material properties to a larger extent than conventional high temperature sintering processes.Advanced technologies open up new possibilities in the design of bioceramics for bone regeneration; 3D-printing technologies, in combination with the development of hybrid materials with enhanced mechanical properties, supported by finite element modelling tools, are expected to enable the design and fabrication of mechanically competent patient-specific bone grafts.The association of ions, drugs and cells allows leveraging of the osteogenic potential of bioceramic scaffolds in compromised clinical situations, where the intrinsic bone regeneration potential is impaired. Cite this article: EFORT Open Rev 2018;3 DOI: 10.1302/2058-5241.3.170056.

Percutaneous Injection of Strontium Containing Hydroxyapatite versus Polymethacrylate Plus Short-Segment Pedicle Screw Fixation for Traumatic A2- and A3/AO-Type Fractures in Adults

Introduction

Polymethacrylate (PMMA) is commonly used in vertebroplasty and balloon kyphoplasty, but its use has been associated with complications. This study tests three hypotheses: (1) whether strontium hydroxyapatite (Sr-HA) is equivalent to PMMA for restoring thoracolumbar vertebral body fractures, (2) whether the incidence of PMMA leakage is similar to that of Sr-HA leakage, and (3) whether Sr-HAis is resorbed and substituted by new vertebral bone.

Materials and Methods

Two age- and sex-matched groups received short percutaneous pedicle screw fixation plus PEEK implant (Kiva, VCF Treatment System, Benvenue Medical, Santa Clara, CA, USA) filled with either Sr-HA (Group A) or PMMA (Group B) after A2- and A3/AO-type thoracolumbar vertebral body fractures. The Visual Analog Scale (VAS) score and imaging parameters, which included segmental kyphosis angle (SKA), vertebral body height ratios (VBHr), spinal canal encroachment (SCE), bone cement leakage, and Sr-HA resorption, were compared between the two groups.

Results

The average follow-up was 28 months. No differences in VAS scores between Groups A and B were observed at baseline. Baseline back pain in both groups improved significantly three months postoperatively. Anterior, middle, and posterior VBHr did not differ between the two groups at any time point. SKA was improved insignificantly in both groups. SCE decreased insignificantly in both groups on 12-month follow-up using computed tomography (CT). PMMA leakage was observed in one patient, while no Sr-HA paste leakages occurred. Sr-HA resorption and replacement with vertebral bone were observed, and no new fractures were observed.

Conclusions

As all hypotheses were confirmed, the authors recommend the use of Sr-HA instead of PMMA in traumatic spine fractures, although more patients and longer follow-up will be needed to strengthen these results. This trial is registered with NCT03431519.

Strontium-doped hydroxyapatite polysaccharide materials effect on ectopic bone formation

Previous studies performed using polysaccharide-based matrices supplemented with hydroxyapatite (HA) particles showed their ability to form in subcutaneous and intramuscular sites a mineralized and osteoid tissue. Our objectives are to optimize the HA content in the matrix and to test the combination of HA with strontium (Sr-HA) to increase the matrix bioactivity. First, non-doped Sr-HA powders were combined to the matrix at three different ratios and were implanted subcutaneously for 2 and 4 weeks. Interestingly, matrices showed radiolucent properties before implantation. Quantitative analysis of micro-CT data evidenced a significant increase of mineralized tissue formed ectopically with time of implantation and allowed us to select the best ratio of HA to polysaccharides of 30% (w/w). Then, two Sr-substitution of 8% and 50% were incorporated in the HA powders (8Sr-HA and 50Sr-HA). Both Sr-HA were chemically characterized and dispersed in matrices. In vitro studies performed with human mesenchymal stem cells (MSCs) demonstrated the absence of cytotoxicity of the Sr-doped matrices whatever the amount of incorporated Sr. They also supported osteoblastic differentiation and activated the expression of one late osteoblastic marker involved in the mineralization process i.e. osteopontin. In vivo, subcutaneous implantation of these Sr-doped matrices induced osteoid tissue and blood vessels formation.