Local delivery of bisphosphonate from coated orthopedic implants increases implants mechanical stability in osteoporotic rats

Growth factor-functionalized titanium implants for enhanced bone regeneration: A review

Titanium and titanium alloys are widely favored materials for orthopedic implants due to their exceptional mechanical properties and biological inertness. The additional benefit of sustained local release of bioactive substances further promotes bone tissue formation, thereby augmenting the osseointegration capacity of titanium implants and attracting increasing attention in bone tissue engineering. Among these bioactive substances, growth factors have shown remarkable osteogenic and angiogenic induction capabilities. Consequently, researchers have developed various physical, chemical, and biological loading techniques to incorporate growth factors into titanium implants, ensuring controlled release kinetics. In contrast to conventional treatment modalities, the localized release of growth factors from functionalized titanium implants not only enhances osseointegration but also reduces the risk of complications. This review provides a comprehensive examination of the types and mechanisms of growth factors, along with a detailed exploration of the methodologies used to load growth factors onto the surface of titanium implants. Moreover, it highlights recent advancements in the application of growth factors to the surface of titanium implants (Scheme 1). Finally, the review discusses current limitations and future prospects for growth factor-functionalized titanium implants. In summary, this paper presents cutting-edge design strategies aimed at enhancing the bone regenerative capacity of growth factor-functionalized titanium implants-a significant advancement in the field of enhanced bone regeneration.

Bisphosphonate-incorporated coatings for orthopedic implants functionalization

Bisphosphonates (BPs), the stable analogs of pyrophosphate, are well-known inhibitors of osteoclastogenesis to prevent osteoporotic bone loss and improve implant osseointegration in patients suffering from osteoporosis. Compared to systemic administration, BPs-incorporated coatings enable the direct delivery of BPs to the local area, which will precisely enhance osseointegration and bone repair without the systemic side effects. However, an elaborate and comprehensive review of BP coatings of implants is lacking. Herein, the cellular level (e.g., osteoclasts, osteocytes, osteoblasts, osteoclast precursors, and bone mesenchymal stem cells) and molecular biological regulatory mechanism of BPs in regulating bone homeostasis are overviewed systematically. Moreover, the currently available methods (e.g., chemical reaction, porous carriers, and organic material films) of BP coatings construction are outlined and summarized in detail. As one of the key directions, the latest advances of BP-coated implants to enhance bone repair and osseointegration in basic experiments and clinical trials are presented and critically evaluated. Finally, the challenges and prospects of BP coatings are also purposed, and it will open a new chapter in clinical translation for BP-coated implants.

Chemical Bonding of Biomolecules to the Surface of Nano-Hydroxyapatite to Enhance Its Bioactivity

Hydroxyapatite (HA) is a significant constituent of bones or teeth and is widely used as an artificial bone graft. It is often used to replace the lost bones or in reconstructing alveolar bones before dental implantation. HA with biological functions finds its importance in orthopedic surgery and dentistry to increase the local concentration of calcium ions, which activate the growth and differentiation of mesenchymal stem cells (MSC). To make relevant use of HA in bone transplantation, the surfaces of orthopedic and dental implants are frequently coated with nanosized hydroxyapatite (nHA), but its low dispersibility and tendency to form aggregates, the purpose of the surface modification of bone implants is defeated. To overcome these drawbacks and to improve the histocompatibility of bone implants or to use nHA in therapeutic applications of implants in the treatment of bone diseases, various studies suggested the attachment of biomolecules (growth factors) or drugs through chemical bonding at the surface of nHA. The growth factors or drugs bonded physically at the surface of nHA are mostly unstable and burst released immediately. Therefore, reported studies suggested that the surface of nHA needs to be modified through the chemical bonding of biologically active molecules at the surface of bone implants such as proteins, peptides, or naturally occurring polysaccharides to prevent the aggregation of nHA and to get homogenous dispersion of nHA in solution. The role of irradiation in producing bioactive and antibacterial nHA through morphological variations in surfaces of nHA is also summarized by considering internal structures and the formation of reactive oxygen species on irradiation. This mini-review aims to highlight the importance of small molecules such as proteins, peptides, drugs, and photocatalysts in surface property modification of nHA to achieve stable, bioactive, and antibacterial nHA to act as artificial bone implants (scaffolds) in combination with biodegradable polymers.

Nanomaterial reinforced composite for biomedical implants applications: a mini-review

There is heavy demand for suitable implant materials with improved mechanical and biological properties. Classically, the demand was catered by conventional materials like metals, alloys, and polymer-based materials. Recently, nanomaterial reinforced composites have played a significant role in replacing conventional materials due to their excellent properties such as biocompatibility, bioactivity, high strength to weight ratio, long life, corrosion & wear resistance, and tailor-ability. Herein, we composed a systematic focus review on the role of nanoparticles in the form of composite materials for the advancements in orthopedic implants. Several nano materials-based reinforcements have been reviewed with various matrix materials, including metals, alloys, ceramics, composites, and polymers for biomedical implant applications. Moreover, the improved biological properties, mechanical properties, and other functionalities like infection resistance, drug delivery at the target, sensing, and detection of bone diseases, and corrosion & wear resistance are elaborated. At last, a particular focus has been given to the un-resolved challenges in orthopedic implant development.

Drug-Releasing Gelatin Coating Reinforced with Calcium Titanate Formed on Ti–6Al–4V Alloy Designed for Osteoporosis Bone Repair

Ti–6Al–4V alloy has been widely used in the orthopedic and dental fields owing to its high mechanical strength and biocompatibility. However, this alloy has a poor bone-bonding capacity, and its implantation often causes loosening. Osteoporosis increases with the aging of the population, and bisphosphonate drugs such as alendronate and minodronate (MA) are used for the medical treatment. Reliable and multifunctional implants showing both bone bonding and drug releasing functions are desired. In this study, we developed a novel organic-inorganic composite layer consisting of MA-containing gelatin and calcium-deficient calcium titanate (cd–CT) with high bone-bonding and scratch resistance on Ti–6Al–4V alloy. The alloy with the composite layer formed apatite within 7 days in a simulated body fluid and exhibited high scratch resistance of an approximately 50 mN, attributable to interlocking with cd ± CT. Although the gelatin layer almost completely dissolved in phosphate-buffered saline within 6 h, its dissolution rate was significantly suppressed by a subsequent thermal crosslinking treatment. The released MA was estimated at more than 0.10 μmol/L after 7 days. It is expected that the Ti alloy with the MA-containing gelatin and cd–CT composite layer will be useful for the treatment of osteoporosis bone.

Non-linear explicit micro-FE models accurately predict axial pull-out force of cortical screws in human tibial cortical bone

Screws are the most frequently used implants for treatment of bone fractures and play an essential role in determining fixation stability. Robust prediction of the bone-screw interface failure would enable development of improved fixation strategies and implant designs, ultimately reducing failure rates and improving outcomes of bone fracture treatments. This study aimed to compare the accuracy of micro-computed tomography image based bone volume measures, linear micro-finite element (FE) and non-linear micro-FE simulations in predicting pull-out force of 3.5 mm screws in human cadaveric tibial cortical bone. Axial pull-out experiments were performed in forty samples harvested from a single human tibia to measure ultimate force, which was correlated with bone volume around the screw and the predictions by both linear micro-FE and non-linear explicit micro-FE models. Correlation strength was similar for bone volume around the screw (R² = 0.866) and linear micro-FE (R² = 0.861), but the explicit non-linear micro-FE models were able to capture the experimental results more accurately (R² = 0.913) and quantitatively correctly. Therefore, this technique may have potential for future in silico studies aiming at implant design optimization.

Effect of Primary Stabilisation on Osseointegration of Implants With Local and Systemic Zoledronic Acid Application

ABSTRACT

Primary stabilization (PS) is defined as initial tight fit during the surgical placement of an implant. Tight implant placement is quite difficult in cases where bone quality and quantity are insufficient. Zoledronic acid (ZA) is a powerful bisphosphonate that prevents bone resorption. The aim of this study is to investigate the effect of local and systemic ZA application on osseointegration in titanium implants with and without PS. Male Sprague Dawley rats were divided into 2 main groups, with PS, PS + (n = 24), and without primary stabilisation, PS - (n = 24). These main groups were divided into control (n = 8), 2 mg/1 mL local ZA (n = 8) and 0.1 mg/kg systemic ZA (n = 8) groups. All of the subjects were sacrificed after a 4-week recovery period. Bone implant connection (BIC) and thread filling (TF) (%) of the samples was analyzed according to the non-decalcified histological analysis method. In terms of BIC percentages and TF, statistically significant differences were found between the groups with and without PS and between the ZA treatment groups (P < 0.05). The common effect of PS and ZA use on the percentage of BIC was found to be statistically significant (P < 0.05). The common effect of PS and acid type on TF was not statistically significant (P < 0.05). Within the limitations of this study, it may be concluded that systemic and local administration of ZA may increase implant osseointegration.

Development of Zoledronic Acid Containing Biomaterials for Enhanced Guided Bone Regeneration

In recent years, biomaterial-based treatments, also called guided bone regeneration (GBR), which aim to establish a bone regeneration site and prevent the migration of gingival connective tissue and / or peripheral epithelium through the defective area during periodontal surgical procedures have come to the fore. In this report, we have developed a nanoparticle bearing thermosensitive in situ gel formulation of Pluronic F127 and poly(D,L-lactic acid) based membrane to reveal their utilization at GBR by in-vivo applications. In addition, the encouragement of the bone formation in defect area via inhibition of osteoclastic activity is intended by fabrication these biodegradable biomaterials at a lowered Zoledronic Acid (ZA) dose. Both of the developed materials remained stable under specified stability conditions (25 °C, 6 months) and provided the extended release profile of ZA. The in-vivo efficacy of nanoparticle bearing in situ gel formulation, membrane formulation and simultaneous application for guided bone regeneration was investigated in New Zealand female rabbits with a critical size defect of 0.5 × 0.5 cm in the tibia bone for eight weeks. Based on the histopathological findings, lamellar bone and primarily woven bone formations were observed after 8 weeks of post-implantation of both formulations, while fibrosis was detected only in the untreated group. Lamellar bone growth was remarkably achieved just four weeks after the simultaneous application of formulations. Consequently, the simultaneous application of ZA-membrane and ZA-nanoparticles loaded in-situ gel formulations offers enhanced and faster GBR therapy alternatives.

On the effect of antiresorptive drugs on the bone remodeling of the mandible after dental implantation: a mathematical model

Bone remodeling identifies the process of permanent bone change with new bone formation and old bone resorption. Understanding this process is essential in many applications, such as optimizing the treatment of diseases like osteoporosis, maintaining bone density in long-term periods of disuse, or assessing the long-term evolution of the bone surrounding prostheses after implantation. A particular case of study is the bone remodeling process after dental implantation. Despite the overall success of this type of implants, the increasing life expectancy in developed countries has boosted the demand for dental implants in patients with osteoporosis. Although several studies demonstrate a high success rate of dental implants in osteoporotic patients, it is also known that the healing time and the failure rate increase, necessitating the adoption of pharmacological measures to improve bone quality in those patients. However, the general efficacy of these antiresorptive drugs for osteoporotic patients is still controversial, requiring more experimental and clinical studies. In this work, we investigate the effect of different doses of several drugs, used nowadays in osteoporotic patients, on the evolution of bone density after dental implantation. With this aim, we use a pharmacokinetic-pharmacodynamic (PK/PD) mathematical model that includes the effect of antiresorptive drugs on the RANK/RANK-L/OPG pathway, as well as the mechano-chemical coupling with external mechanical loads. This mechano-PK/PD model is then used to analyze the evolution of bone in normal and osteoporotic mandibles after dental implantation with different drug dosages. We show that using antiresorptive agents such as bisphosphonates or denosumab increases bone density and the associated mechanical properties, but at the same time, it also increases bone brittleness. We conclude that, despite the many limitations of these very complex models, the one presented here is capable of predicting qualitatively the evolution of some of the main biological and chemical variables associated with the process of bone remodeling in patients receiving drugs for osteoporosis, so it could be used to optimize dental implant design and coating for osteoporotic patients, as well as the drug dosage protocol for patient-specific treatments.

Impact of the antibiotic-cargo from MSNs on Gram-positive and Gram-negative bacterial biofilms

Mesoporous silica nanoparticles (MSNs) are promising drug nanocarriers for infection treatment. Many investigations have focused on evaluating the capacity of MSNs to encapsulate antibiotics and release them in a controlled fashion. However, little attention has been paid to determine the antibiotic doses released from these nanosystems that are effective against biofilm during the entire release time. Herein, we report a systematic and quantitative study of the direct effect of the antibiotic-cargo released from MSNs on Gram-positive and Gram-negative bacterial biofilms. Levofloxacin (LVX), gentamicin (GM) and rifampin (RIF) were separately loaded into pure-silica and amino-modified MSNs. This accounts for the versatility of these nanosystems since they were able to load and release different antibiotic molecules of diverse chemical nature. Biological activity curves of the released antibiotic were determined for both bacterial strains, which allowed to calculate the active doses that are effective against bacterial biofilms. Furthermore, in vitro biocompatibility assays on osteoblast-like cells were carried out at different periods of times. Albeit a slight decrease in cell viability was observed at the very initial stage, due to the initial burst antibiotic release, the biocompatibility of these nanosystems is evidenced since a recovery of cell viability was achieved after 72 h of assay. Biological activity curves for GM released from MSNs exhibited sustained patterns and antibiotic doses in the 2-6 μg/mL range up to 100 h, which were not enough to eradicate biofilm. In the case of LVX and RIF first-order kinetics featuring an initial burst effect followed by a sustained release above the MIC up to 96 h were observed. Such doses reduced by 99.9% bacterial biofilm and remained active up to 72 h with no emergence of bacterial resistance. This pioneering research opens up promising expectations in the design of personalized MSNs-based nanotherapies to treat chronic bone infection.

Bisphosphonates, Old Friends of Bones and New Trends in Clinics

Bisphosphonates, used for a long time in osteoporosis management, are currently the target of intensive research, from pre-formulation studies to more advanced stages of clinical practice. This review presents an overview of the contributions of this family of compounds to human health, starting with the chemistry and clinical uses of bisphosphonates. Following this, their pharmacology is described, highlighting administration-borne handicaps and undesirable effects. The last three sections of the review describe the research efforts that seek to curb delivery-related issues and expand bisphosphonate use. Innovative routes and strategies of administration, such as nano-encapsulation for oral intake or injectable cements for local or in-bone delivery are presented, as well as the latest results of case studies or preclinical studies proposing new therapeutic indications for the clinically approved bisphosphonates. Finally, a selection of anti-infectious bisphosphonate new drug candidates is shown, with focus on the molecules reported in the last two decades.

Nanointeraction: The profound influence of nanostructured and nano-drug delivery biomedical implant surfaces on cell behavior

Nanostructured surfaces feature promising biological properties on biomaterials attracting large interest at basic research, implant industry development, and bioengineering applications. Thou, nanoscale interactions at a molecular and cellular level are not yet completely understood and its biological and clinical implications need to be further elucidated. As follows, the aim of this comprehensive review was to evaluate nanostructured surfaces at biomedical implants focusing on surface development, nanostructuration, and nanoengineered drug delivery systems that can induce specific cell interactions in all relevant aspects of biological, reparative, anti-bacterial, anti-inflammatory and clinical processes. The methods and the physio-chemical properties involved in nanotopography performance, the main cellular characteristics involved at surface/cell interaction, and a summary of results and outlooks reported in studies applying nanostructured surfaces and nano-drug delivery systems is presented. The future prospects and commercial translation of this developing field, particularly concerning multifunctional nanostructured surfaces and its clinical implications are further discussed. At a cellular level, nanostructured biomedical implant surfaces can enhance osteogenesis by targeting osteoblasts, osteocytes, and mesenchymal cells, stimulate fibroblast/epithelial cells proliferation and adherence, inhibit bacterial cell proliferation and biofilm accumulation, and act as immune-modulating surfaces targeting macrophages and reducing pro-inflammatory cytokine expression. Moreover, several methodological options to create drug-delivery systems on metallic implant surfaces are available, however, the clinical translation is yet incomplete. The efficiency of which nanostructured/nano-delivery surfaces may target specific cell interactions and favor clinical outcomes needs to be further elucidated in pre-clinical and clinical studies, along with engineering solutions for commercial translation and approval of controlling agencies.

Total hip arthroplasty in patients with osteoporosis

There is a high prevalence of osteoporosis in patients undergoing total hip arthroplasty. There are several clinically relevant questions related to the management of such cases: the effect of ageing; the initial osseointegration of implants, especially when cementless THA is used; the effect of medical osteoporosis treatment on bone-implant interface; the incidence of intraoperative and late periprosthetic fractures, and the long-term survival of both cemented and cementless total hip arthroplasty performed for proximal femoral fractures and hip osteoarthritis. A critical review of the literature is presented in an attempt to draw practical conclusions.

Enhancement of local bone formation on titanium implants in osteoporotic rats by biomimetic multilayered structures containing parathyroid hormone (PTH)-related protein

Osteoporosis is a severe health problem causing bone fragility and consequent fracture. Titanium (Ti) implants, used in patients with osteoporotic fractures, are prone to failure because of the decreased bone mass and strength. Therefore, it is of utmost importance to fabricate implants possessing osteogenic properties to improve implant osseointegration. To improve the long-term survival rate of Ti implants in osteoporotic patients, hyaluronic acid/ϵ-polylysine multilayers containing the parathyroid hormone (PTH)-related protein (PTHrP) were deposited on Ti implants by a layer-by-layer (LBL) electro assembly technique. The murine pre-osteoblast cell line MC3T3-E1, possessing a high potential of osteoblast differentiation, was used to evaluate the osteo-inductive effects of Ti-LBL-PTHrP in vitro. In addition, the performance of the Ti (Ti-LBL-PTHrP) implant was evaluated in vivo in a femoral intramedullary implantation in Sprague Dawley rats. The Ti-LBL-PTHrP implant regulated the release of the loaded PTHrP to increase bone formation in the early stage of implantation. The in vitro results revealed that cells on Ti-LBL-PTHrP did not show any evident proliferation, but a high level of alkaline phosphatase activity and osteoblast-related protein expression was found, compared to the uncoated Ti group (p < 0.05). In addition, in vivo micro-CT and histological analysis demonstrated that the Ti-LBL-PTHrP implants could significantly promote the formation and remodeling of new bone in osteoporotic rats at 14 d after implantation. Overall, this study established a profound and straightforward methodology for the manufacture of biofunctional Ti implants for the treatment of osteoporosis.

Adjuvant Drug-Assisted Bone Healing: Advances and Challenges in Drug Delivery Approaches

Bone defects of critical size after compound fractures, infections, or tumor resections are a challenge in treatment. Particularly, this applies to bone defects in patients with impaired bone healing due to frequently occurring metabolic diseases (above all diabetes mellitus and osteoporosis), chronic inflammation, and cancer. Adjuvant therapeutic agents such as recombinant growth factors, lipid mediators, antibiotics, antiphlogistics, and proangiogenics as well as other promising anti-resorptive and anabolic molecules contribute to improving bone healing in these disorders, especially when they are released in a targeted and controlled manner during crucial bone healing phases. In this regard, the development of smart biocompatible and biostable polymers such as implant coatings, scaffolds, or particle-based materials for drug release is crucial. Innovative chemical, physico- and biochemical approaches for controlled tailor-made degradation or the stimulus-responsive release of substances from these materials, and more, are advantageous. In this review, we discuss current developments, progress, but also pitfalls and setbacks of such approaches in supporting or controlling bone healing. The focus is on the critical evaluation of recent preclinical studies investigating different carrier systems, dual- or co-delivery systems as well as triggered- or targeted delivery systems for release of a panoply of drugs.

Bisphosphonate-Functionalized Scaffolds for Enhanced Bone Regeneration

The local sustained release of bioactive substances are attracting increasing attention in bone tissue engineering, which is beneficial to bone tissue formation and helps to improve the bone ingrowth ability of a scaffold. Bisphosphonates (BPs), as a representative kind of osteoclast inhibitors, are proven to possess excellent osteogenic induction capability. Accordingly, various physical and chemical strategies are developed to functionalize bone tissue scaffolds with BPs to achieve controlled release profiles. Compared with traditional treatment modalities, local release of BPs from these composite scaffolds will contribute to continuous bone integration without the risk of many complications. This review explores the molecular mechanisms of BPs on bone metabolism and analyzes the appropriate concentrations of BPs that promote bone regeneration. The advanced BP loading strategies, implant modification technologies, and BP-loaded composite scaffolds based on different matrices are summarized. Finally, the latest advances and the future development of BP-modified scaffolds for enhanced bone regeneration are discussed. This article provides leading-edge design strategies of the BP-functionalized bone engineering scaffolds for improved bone repairability.

Immobilization of BMP-2, BMP-7 and alendronic acid on titanium surfaces: Adhesion, proliferation and differentiation of bone marrow-derived stem cells

This study analyzed the influence of titanium (TiO₂ ) surface modifications with two osteogenic proteins (BMP-2, BMP-7) and an anti-osteoclastic drug (alendronic acid [AA]) on sandblasted/acid-etched (SLA) and plain TiO₂ (PT) on cell adhesion, proliferation and differentiation (alkaline phosphatase [AP] and osteocalcin [OC]) of bone-marrow derived stem cells (BMSCs) after 1, 3 and 7 days in-vitro. Initially, AA surfaces showed the highest cell number and surface coverage. At day 3 and 7, BMP and AA-modified surfaces exhibited a significantly enhanced cell growth. For proliferation, at days 3 and 7, an enhancement on BMP-2, BMP-7 and AA-surfaces was seen. At day 7, SLA also showed a higher proliferation when compared to PT. Initially, AP expression was elevated on SLA and AA surfaces. At days 3 and 7, a significant increased AP expression was seen for SLA, BMP-2, BMP-7 and AA discs. For OC, SLA and AA surfaces had the highest expression after 1 day whereas after 3 and 7 days a significant difference was recorded for SLA, BMP-2, BMP-7 and AA. In conclusion, a beneficial biological effect of a chemical immobilization method of BMP-2, BMP-7 and alendronate onto titanium surfaces on BMSCs was proven.

Recent advances in musculoskeletal local drug delivery

Musculoskeletal disorders are a significant burden on the global economy and public health. Advanced drug delivery plays a key role in the musculoskeletal field and holds the promise of enhancing the repair of degenerated and injured musculoskeletal tissues. Ideally, drug delivery should have the ability to directly deliver therapeutic agents to the diseased/injured sites with a desirable drug level over a period of time. Here, we present a mini-review of the current state-of-the-art research associated with local drug delivery and its use for the treatment of musculoskeletal disorders. First, an overview of drug delivery strategies, with a focus on issues related to musculoskeletal pathology, potential therapeutic strategies, conventional and non-conventional drugs, and various delivery systems, is introduced. Then, we highlight recent advances in the emerging fields of musculoskeletal local drug delivery, involving therapeutic drugs (e.g., genes, small molecule therapeutics, and stem cells), novel delivery vehicles (e.g., 3D printing and tissue engineering techniques), and innovative delivery approaches (e.g., multi-drug delivery and smart stimuli-responsive delivery). The review concludes with future perspectives and associated challenges for developing local drug delivery for musculoskeletal applications. STATEMENT OF SIGNIFICANCE: Three important aspects are highlighted in this manuscript: 1) The advanced musculoskeletal drug delivery is introduced from the aspects ranging from musculoskeletal disorders, potential therapeutic solutions, and various drug delivery systems. 2) The recent advances in the emerging fields of musculoskeletal local drug delivery, involving therapeutic drugs (e.g., genes, small molecule therapeutics, and stem cells), novel delivery vehicles (e.g., 3D printing and tissue engineering technique), and innovative delivery approaches (e.g., multi-drug delivery and smart stimuli-responsive delivery), are highlighted. 3) The challenges and perspectives of future research directions in the development of musculoskeletal local drug delivery are presented.

50 years of scanning electron microscopy of bone-a comprehensive overview of the important discoveries made and insights gained into bone material properties in health, disease, and taphonomy

Bone is an architecturally complex system that constantly undergoes structural and functional optimisation through renewal and repair. The scanning electron microscope (SEM) is among the most frequently used instruments for examining bone. It offers the key advantage of very high spatial resolution coupled with a large depth of field and wide field of view. Interactions between incident electrons and atoms on the sample surface generate backscattered electrons, secondary electrons, and various other signals including X-rays that relay compositional and topographical information. Through selective removal or preservation of specific tissue components (organic, inorganic, cellular, vascular), their individual contribution(s) to the overall functional competence can be elucidated. With few restrictions on sample geometry and a variety of applicable sample-processing routes, a given sample may be conveniently adapted for multiple analytical methods. While a conventional SEM operates at high vacuum conditions that demand clean, dry, and electrically conductive samples, non-conductive materials (e.g., bone) can be imaged without significant modification from the natural state using an environmental scanning electron microscope. This review highlights important insights gained into bone microstructure and pathophysiology, bone response to implanted biomaterials, elemental analysis, SEM in paleoarchaeology, 3D imaging using focused ion beam techniques, correlative microscopy and in situ experiments. The capacity to image seamlessly across multiple length scales within the meso-micro-nano-continuum, the SEM lends itself to many unique and diverse applications, which attest to the versatility and user-friendly nature of this instrument for studying bone. Significant technological developments are anticipated for analysing bone using the SEM.

Mesoporous bioactive glass/ɛ-polycaprolactone scaffolds promote bone regeneration in osteoporotic sheep

Macroporous scaffolds made of a SiO2-CaO-P2O5 mesoporous bioactive glass (MBG) and ɛ-polycaprolactone (PCL) have been prepared by robocasting. These scaffolds showed an excellent in vitro biocompatibility in contact with osteoblast like cells (Saos 2) and osteoclasts derived from RAW 264.7 macrophages. In vivo studies were carried out by implantation into cavitary defects drilled in osteoporotic sheep. The scaffolds evidenced excellent bone regeneration properties, promoting new bone formation at both the peripheral and the inner parts of the scaffolds, thick trabeculae, high vascularization and high presence of osteoblasts and osteoclasts. In order to evaluate the effects of the local release of an antiosteoporotic drug, 1% (%wt) of zoledronic acid was incorporated to the scaffolds. The scaffolds loaded with zoledronic acid induced apoptosis in Saos 2 cells, impeded osteoclast differentiation in a time dependent manner and inhibited bone healing, promoting an intense inflammatory response in osteoporotic sheep. STATEMENT OF SIGNIFICANCE: In addition to an increase in bone fragility and susceptibility to fracture, osteoporosis also hinders the clinical success of endosseous implants and grafting materials for the treatment of bone defects. For the first time, macroporous scaffolds made of mesoporous bioactive glass and ε-caprolactone have been evaluated in a sheep model that mimics the osteoporosis conditions in humans. These implants fostered bone regeneration, promoting new bone formation at both the peripheral and the inner parts of the scaffolds, showing thick trabeculae and a high vascularization degree. Our results indicate that macroporous structures containing highly bioactive mesoporous glasses could be excellent candidates for the regenerative treatment of bone defects in osteoporotic patients.

Bioinspired polydopamine and polyphenol tannic acid functionalized titanium suppress osteoclast differentiation: a facile and efficient strategy to regulate osteoclast activity at bone-implant interface

Osseointegration of metallic implants in porous osteoporotic bone remains a challenge. Surface modification of implants to reduce peri-implant osteoclastic bone resorption was explored in the study. Bioinspired polydopamine (pDOP) and polyphenol tannic acid (pTAN) are nature-derived universal coating systems that have emerged either as a sole coating or ad-layer for biomolecular conjugation on different biomaterials. The effects pDOP and pTAN on osteoclast development have not been reported before. In this study, osteoclast development was investigated on titanium (Ti) substrates coated with pDOP (Ti-pDOP) and pTAN (Ti-pTAN). The results showed that Ti-pDOP and Ti-pTAN coating reduced tartrate-resistant acid phosphatase activity and osteoclast cell number as compared with pristine Ti. Intriguingly, the reduction was higher on Ti-pTAN than on Ti-pDOP. Economical and biocompatible tannic acid serves as a superior coating in decreasing osteoclast activity when compared with that of pDOP coating and could be used to modulate osteoclast activity at bone-implant interfaces.

The effect of zoledronic acid on middle ear osteoporosis: An animal study

Hearing function in older patients may be related to bone structure. We conducted an experiment to evaluate the effect of zoledronic acid on osteoporotic middle ear ossicles in an animal model. Our subjects were 19 female New Zealand white rabbits (38 ears) weighing 2 to 4 kg. We divided the rabbits into three groups: one group consisted of 6 rabbits with osteoporotic ears that were treated with zoledronic acid; the second group was made up of 8 rabbits with osteoporotic ears that were not treated; a control group included 5 rabbits with normal ears that were untreated. After an oophorectomy, the 6 study rabbits were administered 0.1 ml/kg of zoledronic acid intravenously. All rabbits were sacrificed 16 weeks later, and the middle ear ossicles were removed for investigation under light microscopy. Although osteoporosis enhanced the osteoclastic bone resorption of the ossicles, zoledronic acid enhanced osteoblastic activity on osteoporotic middle ear ossicles. The incidence of osteoporosis was 93.8% in the untreated osteoporosis group and 33.3% in zoledronic acid group-a statistically significant difference (OR: 0.24; 95% CI: 0.09 to 0.58; p < 0.001). Osteoporosis appears to increase the resorption of the middle ear ossicles, a process that can be avoided with zoledronic acid administration. Prevention of the effects of osteoporosis in humans may help decrease the irreversible changes in the middle ear ossicles.

Non-setting, injectable biomaterials containing particulate hydroxyapatite can increase primary stability of bone screws in cancellous bone

BACKGROUND

Fracture fixation in weak bone is still a clinical challenge. Screw augmentation was shown to successfully increase their primary stability. The currently used calcium phosphate or polymeric bone cements, however, present important drawbacks such as induced toxicity and/or impaired bone neo-formation. A new approach to enhance bone screw primary stability without affecting bone formation is the use of non-setting, calcium phosphate loaded soft materials as the augmentation material.

METHODS

Two types of biomaterials (non-crosslinked hyaluronic acid as viscous fluid and agar as hydrogel) were loaded with 40 wt/vol% of hydroxyapatite particles and characterized. The screw augmentation effect of all materials was evaluated through pull-out tests in bovine cancellous bone and compared to the non-augmented situation (control). The bone mineral density of each test sample was measured with μCT scans and was used to normalize the pull-out strength.

FINDINGS

Both materials loaded with hydroxyapatite increased the normalized pull-out strength of the screws compared to control samples and particle-free materials. This counter-intuitive augmentation effect increased with decreasing bone mineral density and was independent from the type of the soft materials used.

INTERPRETATION

We were able to demonstrate that non-setting, injectable biomaterials loaded with ceramic particles can significantly enhance the primary stability of bone screws. This material combination opens the unique possibility to achieve a screw augmentation effect without impairing or even potentially favoring the bone formation in proximity to the screw. This effect would be particularly advantageous for the treatment of osteoporotic bone fractures requiring a stabilization with bone screws.

Alendronate release from calcium phosphate cement for bone regeneration in osteoporotic conditions

Osteoporosis represents a major health problem in terms of compromising bone strength and increasing the risk of bone fractures. It can be medically treated with bisphosphonates, which act systemically upon oral or venous administration. Further, bone regenerative treatments in osteoporotic conditions present a challenge. Here, we focused on the development of a synthetic bone substitute material with local diminishing effects on osteoporosis. Composites were created using calcium phosphate cement (CPC; 60 wt%) and polylactic-co-glycolic acid (PLGA; 40 wt%), which were loaded with alendronate (ALN). In vitro results showed that ALN-loaded CPC/PLGA composites presented clinically suitable properties, including setting times, appropriate compressive strength, and controlled release of ALN, the latter being dependent on composite degradation. Using a rat femoral condyle bone defect model in osteoporotic animals, ALN-loaded CPC/PLGA composites demonstrated stimulatory effects on bone formation both within and outside the defect region.

Pain Management After Bone Reconstruction Surgery Using an Analgesic Bone Cement: A Functional Noninvasive In Vivo Study Using Gait Analysis

Postoperative pain after bone reconstruction is a serious complication that could jeopardize the global success of a surgery. This pain must be controlled and minimized during the first 3 to 4 postoperative days to prevent it from becoming chronic. In this study, a critical-size bone defect was created at the femoral distal end of rats and filled by an injectable calcium phosphate cement (CPC) loaded or not with local anesthetics (bupivacaine or ropivacaine). A functional evaluation of the gait was performed using the CatWalk system to compare the postoperative pain relief enhanced by the different CPCs after such a bone filling surgery. The results demonstrated significant pain relief during the short-term postoperative period, as shown by the print area and intensity parameters of the operated paw. At 24hours, the print area decreased by 65%, 42%, and 24%, and the intensity decreased by 25%, 9%, and 1% for unloaded, ropivacaine-loaded, and bupivacaine-loaded CPCs, respectively, compared with the preoperative values. Bupivacaine-loaded CPC provided an earlier return to full functional recovery than ropivacaine-loaded CPC. Moreover, the CPCs retained their biologic and mechanical properties. For all these reasons, anesthetic-loaded CPCs could be part of the global pain management protocol after bone reconstruction surgery such as iliac crest bone grafting procedures.

PERSPECTIVE

Bupivacaine-loaded CPC provided an earlier return to full gait function than ropivacaine-loaded CPC, with preserved bone filling properties. Such analgesic CPCs deserve further in vivo investigation and may be part of the global pain management protocol after bone reconstruction or bone augmentation surgery such as iliac crest bone grafting.

Modulation of Osteoclast Interactions with Orthopaedic Biomaterials

Biomaterial integration in bone depends on bone remodelling at the bone-implant interface. Optimal balance of bone resorption by osteoclasts and bone deposition by osteoblasts is crucial for successful implantation, especially in orthopaedic surgery. Most studies examined osteoblast differentiation on biomaterials, yet few research has been conducted to explore the effect of different orthopaedic implants on osteoclast development. This review covers, in detail, the biology of osteoclasts, in vitro models of osteoclasts, and modulation of osteoclast activity by different implant surfaces, bio-ceramics, and polymers. Studies show that surface topography influence osteoclastogenesis. For instance, metal implants with rough surfaces enhanced osteoclast activity, while smooth surfaces resulted in poor osteoclast differentiation. In addition, surface modification of implants with anti-osteoporotic drug further decreased osteoclast activity. In bioceramics, osteoclast development depended on different chemical compositions. Strontium-incorporated bioceramics decreased osteoclast development, whereas higher concentrations of silica enhanced osteoclast activity. Differences between natural and synthetic polymers also modulated osteoclastogenesis. Physiochemical properties of implants affect osteoclast activity. Hence, understanding osteoclast biology and its response to the natural microarchitecture of bone are indispensable to design suitable implant interfaces and scaffolds, which will stimulate osteoclasts in ways similar to that of native bone.

Dual modulation of bone formation and resorption with zoledronic acid-loaded biodegradable magnesium alloy implants improves osteoporotic fracture healing: An in vitro and in vivo study

Osteoporotic fracture (OPF) remains a major clinical challenge for skeletal regeneration. Impaired osteogenesis and excessive remodeling result in prolonged and poor quality of fracture healing. To augment bone formation and inhibit excessive resorption simultaneously, we constructed a biodegradable magnesium-based implant integrated with the anti-catabolic drug zoledronic acid (ZA); this implant exhibits controllable, sustained release of magnesium degradation products and ZA in vitro. The extracts greatly stimulate the osteogenic differentiation of rat-bone marrow-derived mesenchymal stem cells (rBMSCs), while osteoclastogenesis is inhibited by ZA. Implantation of intramedullary nails to fix femur fracture in ovariectomy-induced osteoporotic rats for up to 12 weeks demonstrates magnesium implants alone can enhance OPF repair through promoting callus formation compared to conventional stainless steel, while the combinatory treatment with local ZA release from implant coating further increases bone regeneration rate and callus size, remarkably improves bone quality and mechanical strength and suppresses osteoclasts and bone remodeling, due to the synergistic effect of both agents. The slow and uniform degradation of the implant ensures a steady decrease in bending force, which meets clinical requirements. In summary, biodegradable magnesium-based implants can locally co-deliver magnesium degradation products and zoledronic acid in a controlled manner, and can be superior alternatives for the reconstruction of osteoporosis-related fracture.

STATEMENT OF SIGNIFICANCE

Management of osteoporotic fracture has posed a major challenge in orthopedics, as the imbalance between diminished osteogenesis and excessive bone remodeling often leads to delayed and compromised fracture repair. Among various efforts expended on augmenting osteoporotic fracture healing, herein we reported a new strategy by engineering and utilizing a biodegradable magnesium-based implant integrated with local drug delivery, specifically, zoledronic acid (ZA)-loaded polylactic acid/brushite bilayer coating on a biodegradable Mg-Nd-Zn-Zr alloy (denoted as Mg/ZA/CaP), aiming to combine the favorable properties of Mg and zoledronic acid for simultaneous modulation of bone formation and bone resorption. In vitro and in vivo studies demonstrated its superior treatment efficacy along with adequate degradation. It stimulated new bone formation while suppressing remodeling, ascribed to the local release of magnesium degradation products and zoledronic acid. To our knowledge, the enhanced fracture repair capability of Mg-based implants was for the first time demonstrated in an osteoporotic fracture animal model. This innovative biodegradable Mg-based orthopedic implant presents great potential as a superior alternative to current internal fixation devices for treating osteoporotic fracture.

A randomized controlled clinical trial evaluating the efficacy of zoledronate gel as a local drug delivery system in the treatment of chronic periodontitis: A clinical and radiological correlation

Background

This study aimed to evaluate the efficacy of local drug delivery system of zoledronate (ZLN) gel as an adjunct to scaling and root planing (SRP) for the treatment of human periodontal intrabony defects clinically and radiographically.

Materials and Methods

Forty intrabony defects (three walled and combined defects without involving furcation) in moderate to severely affected forty chronic periodontitis patients (range, 30-50 years) were randomly divided into two groups and treated either with 0.05% ZLN gel (ZLN n = 20; 1 dropout) or placebo gel (control group [CG] n = 20) after SRP. Clinical parameters such as plaque index (PI), gingival index (GI), tooth-specific pocket probing depth (T_s PPD), and clinical attachment levels (TsCAL) were assessed at baseline and at 3 and 6 months using occlusal acrylic stent. Radiographic parameters were assessed at baseline and 6 months, utilizing "ONIS 2.5 PROFESSIONAL" and "SYNGO" software compatible with DentaScan to measure the volumetric bone changes in intrabony defects.

Results

In intragroup comparisons, both groups showed significant PI and GI reduction (P < 0.001) after treatment at 3 and 6 months. In intergroup comparisons, T_s PPD reduction and T_s CAL gain were significant only in ZLN at 6 months from both baseline and 3 months. Radiographically, significant reduction in defect depth and buccolingual width with volumetric defect gain of 40.24% ± 7.44% in ZLN compared to insignificant gain of 1.60% ± 4.06% in CG was observed at 6 months.

Conclusion

ZLN gel applied subgingivally in intrabony defects resulted in significant improvements both clinically and radiographically.

Simple 3,4-Dihydroxy-L-Phenylalanine Surface Modification Enhances Titanium Implant Osseointegration in Ovariectomized Rats

Osteoporosis presents a challenge to the long-term success of osseointegration of endosseous implants. The bio-inspired 3,4-dihydroxy-L-phenylalanine (Dopa) coating is widely used as a basic layer to bind osteogenetic molecules that may improve osseointegration. To date, little attention has focused on application of Dopa alone or binding inhibitors of bone resorption in osteoporosis. Local use of a bisphosphonate such as zoledronic acid (ZA), an inhibitor of osteoclast-mediated bone resorption, has been proven to improve implant osseointegration. In this study, ovariectomized rats were divided into four groups and implanted with implants with different surface modifications: sandblasted and acid-etched (SLA), SLA modified with Dopa (SLA-Dopa), SLA modified with ZA (SLA-ZA), and SLA modified with Dopa and ZA (SLA-Dopa + ZA). Measurement of removal torque, micro-computed tomography and histology revealed a greater extent of bone formation around the three surface-modified implants than SLA-controls. No synergistic effect was observed for combined Dopa + ZA coating. Microarray analysis showed the Dopa coating inhibited expression of genes associated with osteoclast differentiation, similarly to the mechanism of action of ZA. Simple Dopa modification resulted in a similar improvement in osseointegration compared to ZA. Thus, our data suggest simple Dopa coating is promising strategy to promote osseointegration of implants in patients with osteoporosis.

Local application of an ibandronate/collagen sponge improves femoral fracture healing in ovariectomized rats

Non-union is a major clinical problem in the healing of fractures, especially in patients with osteoporosis. The systemic administration of drugs is time consuming and large doses are demanding and act slowly, whereas local release acts rapidly, increases the quality and quantity of the bone tissue. We hypothesize that local delivery demonstrates better therapeutic effects on an osteoporotic fracture. The aim of this paper is to investigate the effect of the local application of ibandronate loaded with a collagen sponge on regulating bone formation and remodeling in an osteoporotic rat model of fracture healing. We found that the local delivery of ibandronate exhibited excellent effects on improving the bone microarchitecture and suppressed effects on bone remodeling. At 4 weeks, more callus formation and improvement of mechanical character and microstructure were observed in a local delivery via μCT, mechanical test, histological research and serum analysis. The suppression of bone remodeling was compared with a systemic treatment at 12 weeks, and the structural mechanical properties and microarchitecture were also improved with local delivery. This research identifies an earlier, safer and integrated approach for local delivery of ibandronate with collagen and provides a better strategy for the treatment of osteoporotic fracture in rats.

Effect of local zoledronate delivery on osseointegration: a systematic review of preclinical studies

PURPOSE

The aim of the present systematic review was to assess the effect of local zoledronate (ZOL) delivery (topical or as implant surface coatings) on osseointegration.

MATERIALS AND METHODS

In this systematic review, the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were followed. To address the focused question, 'Does local zoledronate delivery enhance osseointegration?' indexed databases were searched without time or language restrictions up to and including April 2017 using various combination of the following keywords: 'zoledronate', 'bisphosphonates', 'osseointegration' and 'topical administration'. Letters to the Editor, historic reviews, commentaries, case-series and case-reports were excluded.

RESULTS

Initially, 383 articles were identified out of which, 23 experimental studies fulfilled the inclusion criteria. In 18 studies, ZOL was incorporated into implants surfaces as a coating and in five studies ZOL was applied topically (bone graft or irrigation) into the bone cavities. Results from 87% studies reported that local delivery of ZOL (coating or topical) is effective in enhancing osseointegration or new bone formation around implants.

CONCLUSIONS

Local ZOL delivery (coating or topical) seems to enhance osseointegration in animals; however, from a clinical perspective, further randomized control trials with long-term follow-up are needed in this regard.

Effect of Collagen-Polycaprolactone Nanofibers Matrix Coating on the In Vitro Cytocompatibility and In Vivo Bone Responses of Titanium

The objective of this study was to improve the biomechanical performance of titanium (Ti) using a biocompatible electrospun nanofiber matrix. The study is based on the hypothesis that coating a Ti surface with a nanofiber matrix (NFM) made of collagen (CG) and polycaprolactone (PCL) electrospun nanofibers could increase the mechanical fixation of Ti/bone by improving the surface and cytocompatibility properties of Ti. This study prepared Ti samples with and without CG-PCL NFM coatings. This study determined the in vitro effects of each group of Ti samples on the surface topography and cytocompatibility (osteoblast cell adhesion, proliferation, mineralization and protein adsorption) properties. This study also determined in vivo interface shear strength and bone volume fraction of each group of Ti samples with bone using a rabbit model. This study found that the CG-PCL NFM coating on Ti improved the surface roughness, osteoblast cell adhesion, proliferation, mineralization and protein adsorption properties of Ti. In vivo studies found that interface shear strength of CG-PCL NFM-coated Ti/bone samples was significantly higher compared to those values of control Ti/bone samples (p value < 0.05) due to an increase in the amount of growth of the connective tissue joining the Ti implant. Therefore, the developed CG-PCL NFM coating technique should further be investigated for its potential in clinical applications.

Microgroove and Collagen-poly(ε-caprolactone) Nanofiber Mesh Coating Improves the Mechanical Stability and Osseointegration of Titanium Implants

The effect of depositing a collagen (CG)-poly-ε-caprolactone (PCL) nanofiber mesh (NFM) at the microgrooves of titanium (Ti) on the mechanical stability and osseointegration of the implant with bone was investigated using a rabbit model. Three groups of Ti samples were produced: control Ti samples where there were no microgrooves or CG-PCL NFM, groove Ti samples where microgrooves were machined on the circumference of Ti, and groove-NFM Ti samples where CG-PCL NFM was deposited on the machined microgrooves. Each group of Ti samples was implanted in the rabbit femurs for eight weeks. The mechanical stability of the Ti/bone samples were quantified by shear strength from a pullout tension test. Implant osseointegration was evaluated by a histomorphometric analysis of the percentage of bone and connective tissue contact with the implant surface. The bone density around the Ti was measured by micro–computed tomography (μCT) analysis. This study found that the shear strength of groove-NFM Ti/bone samples was significantly higher compared to control and groove Ti/bone samples (p < 0.05) and NFM coating influenced the bone density around Ti samples. In vivo histomorphometric analyses show that bone growth into the Ti surface increased by filling the microgrooves with CG-PCL NFM. The study concludes that a microgroove assisted CG-PCL NFM coating may benefit orthopedic implants.

Randomised trial of bisphosphonate-coated dental implants: Radiographic follow-up after five years of loading

The results of a randomised trial with bisphosphonate-coated dental implants have been reported previously. Each patient received one coated and one uncoated implant in a double-blind split-mouth design study. After 6 months of osseointegration, resonance frequency analysis indicated better fixation of the coated implants. Reduced marginal bone resorption was also shown. However, it was not known whether the advantage of the bisphosphonate coating would persist over time. The radiographic results at 5 years after implant installation are reported herein. A blinded investigator measured marginal resorption on fresh radiographs obtained for 14 of the 16 patients (two had died) and compared these with the post-implantation images. Non-parametric statistics were used. All implants functioned well. The median marginal bone loss for control implants was found to be 0.70mm, which is less than usually reported in the literature. The bisphosphonate-coated implants showed even less resorption (median 0.20mm). The median difference within each pair of implants after 5 years of use was 0.34mm (95% confidence interval 0.00-0.75mm; P=0.04). The present data suggest that bisphosphonate-coated implants enable prolonged preservation of the marginal bone.

The effect of alendronate soaking and ultraviolet treatment on bone-implant interface

OBJECTIVE

Rapid and stable fixation of dental implants is crucial for successful treatment. Herein, we examined whether the simultaneous treatment of titanium implants with ultraviolet (UV) and alendronate (ALN) synergistically improved the bone-to-implant contact.

MATERIALS AND METHODS

We assessed the in vitro effects of UV radiation-treated (UV+/ALN-), ALN-soaked (UV-/ALN+), and UV radiation/ALN-treated (UV+/ALN+) titanium implants on cell proliferation, cytotoxicity, cell adhesion, and osteoblast differentiation using MG-63 osteoblast-like cells by the assays of MTS, live/dead, scanning electron microscopy (SEM), alkaline phosphatase (ALP) activity, and alizarin red S (AR-S) staining, respectively. Furthermore, in vivo bone formation at the bone-implant interface efficiency determined using a rabbit tibia implantation. Implants were divided into 3 experimental groups (UV+/ALN-, UV-/ALN+, UV+/ALN+) and the non-treated control (UV-/ALN-) group and transplanted into the proximal tibia of rabbits. At 1, 2, 4, and 8 weeks post-operation, bone formation at the bone-implant interface was evaluated by micro-computed tomography and histological analysis.

RESULTS

MG-63 cells cultured on UV+/ALN+ implants showed significantly higher cell proliferation, ALP activity, and calcium mineralization than those cultured on other implants (P < 0.05). Furthermore, SEM observation showed the highest increase in cell attachment and growth on the UV+/ALN+ implants. In vivo, experimental groups at all time points showed greater peri-implant bone formation than the control group. At 8 weeks post-implantation, in the UV+/ALN+ group, significantly higher bone formation was observed than the UV+/ALN- or UV-/ALN+ group, respectively (P < 0.05).

CONCLUSIONS

Treatment of titanium surfaces with UV and ALN may synergistically enhance osteoblastic differentiation and mineralization in vitro and enhance bone formation at the bone-implant interface in vivo. These data suggest that UV and ALN treatment may improve the osseointegration of titanium implants.

Effects of local delivery of BMP2, zoledronate and their combination on bone microarchitecture, biomechanics and bone turnover in osteoporotic rabbits

The hip fracture is one major clinical challenge associated with osteoporosis, resulting in heavy socioeconomic burdens and high mortality. Systemic therapies of anti-osteoporosis drugs are expensive, time-consuming and also evoke substantial side effects, which fails to provide early protection from fractures. Accumulating evidence demonstrates the high bioavailability and therapeutic efficacy of local drug delivery in accelerating facture healing and bone defect repair. This study aims at investigating the effects of local delivery of BMP2 and zoledronate (two promising anabolic/anti-catobolic reagents) encapsulated by fibrin sealants into femoral necks on regulating bone quality and remodeling in osteoporotic rabbits subjected to combined ovariectomy and glucocorticoid injection. We show that 6-week BMP2 delivery exhibited more prominent effect on mitigating trabecular bone microarchitecture deterioration and mechanical strength reduction of femoral necks than local zoledronate treatment. BMP2 plus zoledronate showed more significant improvement of bone microstructure, mechanical strength and bone formation rate at 12 weeks post injection than single BMP2 or zoledronate delivery via μCT, biomechanical, histomorphometric and serum biochemical analyses. This study enriches our knowledge for understanding the availability of local drug delivery for improving bone quantity and quality, which may lead to earlier, safer and more efficient protection from osteoporosis-induced fractures in clinics.

A biphasic calcium phosphate coating for potential drug delivery affects early osseointegration of titanium implants

BACKGROUND

Calcium phosphate (CaP) surface coatings may accelerate osseointegration and serve as a drug delivery system for mineral-binding biomolecules. In a pilot study, the impact of a commercially available, thin CaP coating on early osseous bone remodeling was compared with a modern, subtractive-treated rough surface (SLA-like) in an animal trial.

METHODS

In 16 rabbits, 32 endosseous implants (CaP; n = 16, SLA-like; n = 16) were bilaterally inserted in the proximal tibia after randomization. After 2 and 4 weeks, bone-implant contact (BIC;%) in the cortical (cBIC) and the trabecular bone (sBIC) as well as volume of bone within the screw thread with the highest amount of new-formed bone (area;%) were analyzed.

RESULTS

After 2 weeks, cBIC was significantly higher for CaP when compared with SLA-like (58 ± 7% versus 40.4 ± 18%; P = 0.021). sBIC for CaP was 14.7 ± 8% and for SLA-like 7.2 ± 7.8% (P = 0.081). For area, the mean volumes were 82.8 ± 10.8% for CaP and 73.6 ± 22% for SLA-like (P = 0.311). After 4 weeks, cBIC was 42.9 ± 13% for the CaP and 46.5 ± 29.1% for the SLA-like group (P = 0.775). An sBIC of 6.9 ± 9.3% was calculated for CaP and of 12.3 ± 4.8% for SLA-like (P = 0.202). The values for area were 62.3 ± 24.1% for CaP and 50.1 ± 25.9% for SLA-like (P = 0.379).

CONCLUSIONS

The CaP coating has putative additional advantages in the early osseoconduction phases. It seems suitable for a feasible and clinical applicable bioactivation.

Implant-delivered Alendronate Causes a Dose-dependent Response on Net Bone Formation Around Porous Titanium Implants in Canines

BACKGROUND

Bony fixation of cementless orthopaedic implants is not always achieved, particularly in challenging scenarios such as revision surgery, trauma, and tumor reconstruction. An adjunct therapy for improving porous implant fixation could improve the reliability and durability of these reconstructive procedures.

QUESTIONS/PURPOSES

In this study, we asked whether there is a positive and dose-dependent effect of the local release of the bisphosphonate alendronate from (1) alendronate/hydroxyapatite (HA) porous-coated titanium implants compared with bare metal porous controls; and (2) alendronate/HA on porous-coated titanium implants compared with HA-coated porous controls with respect to extent of bone ingrowth, bone apposition, and periimplant bone formation in a canine model?

METHODS

Three-dimensional printed porous-coated cylindrical implants coated with three different doses (0.02, 0.06, and 0.18 mg/cm(2)) of alendronate were inserted bilaterally in the intramedullary canal of the proximal femora of 15 adult mongrel dogs (age range, 3-9 years; mean, 5 years) weighing between 36 kg and 60 kg (mean, 43 kg). In each dog, an implant coated with HA and one of three different doses of alendronate was inserted on one side while the contralateral femur had a bare metal porous control implant and an identical control implant with a coating of HA. The dose effect of locally released alendronate on the extent of bone ingrowth, bone apposition, and periimplant bone was assessed by backscattered electron microscopy of three pairs of cross-sections taken from each implant at 12 weeks after surgery. A linear mixed model was used to perform the statistical analyses to account for the correlation in the data resulting from the multiple measures performed on each dog.

RESULTS

Compared with paired bare metal controls, periimplant bone increased by 92% (p = 0.007), and 114% (p < 0.001) in the femora with the alendronate implants with a dose of 0.06 mg/cm(2), or 0.18 mg/cm(2), respectively. At a dose of 0.02 mg/cm(2), there was no difference (46% change; p = 0.184, with the numbers available). The comparison of the alendronate-dosed implants with their HA-coated controls showed that the intermediate dose of 0.06 mg/cm(2) alendronate had the greatest effect on net bone formation. Bone apposition was enhanced with the 0.06-mg/cm(2) alendronate femoral implants (82%; p = 0.008), although there was no change in bone ingrowth (37% change; p = 0.902, with the numbers available). When compared with the HA-coated control implants, the greatest effect of the alendronate-dosed implants was the increased amount of periimplant bone at the intermediate dose of 0.06-mg/cm(2) (108%, p = 0.009). There was no effect of the low (0.02-mg/cm(2)) and high (0.18-mg/cm(2)) alendronate-dosed implants (4%, and 6%, respectively; p = 0.321, p = 0.502). Overall, all three alendronate-dosed implants revealed little to no effect on bone ingrowth compared with the HA-coated control implants.

CONCLUSIONS

The local release of alendronate from a three-dimensional printed porous-coated implant from the three doses studied showed an overall improvement in bone apposition and periimplant bone at the intermediate dose compared with bare metal or with HA-coated controls, although the effect was more pronounced compared with bare metal. Long-term studies to show the effects of localized alendronate delivery and mechanical fixation would be the next step for future studies.

CLINICAL RELEVANCE

Local release of alendronate from a three-dimensional printed porous-coated implant may improve the reliability of cementless fixation of currently available porous-coated bare metal implants.

Effect of osteoporosis medications on fracture healing

Antiosteoporotic medications are often used to concurrently treat a patient's fragility fractures and underlying osteoporosis. This review evaluates the existing literature from animal and clinical models to determine these drugs' effects on fracture healing. The data suggest that these medications may enhance bone healing, yet more thorough prospective studies are warranted. Pharmacologic agents that influence bone remodeling are an essential component of osteoporosis management. Because many patients are first diagnosed with osteoporosis when presenting with a fragility fracture, it is critical to understand how osteoporotic medications influence fracture healing. Vitamin D and its analogs are essential for the mineralization of the callus and may also play a role in callus formation and remodeling that enhances biomechanical strength. In animal models, antiresorptive medications, including bisphosphonates, denosumab, calcitonin, estrogen, and raloxifene, do not impede endochondral fracture healing but may delay repair due to impaired remodeling. Although bisphosphonates and denosumab delay callus remodeling, they increase callus volume and result in unaltered biomechanical properties. Calcitonin increases cartilage formation and callus maturation, resulting in improved biomechanical properties. Parathyroid hormone, an anabolic agent, has demonstrated promise in animal models, resulting in accelerated healing with increased callus volume and density, more rapid remodeling to mature bone, and improved biomechanical properties. Clinical data with parathyroid hormone have demonstrated enhanced healing in distal radius and pelvic fractures as well as postoperatively following spine surgery. Strontium ranelate, which may have both antiresorptive and anabolic properties, affects fracture healing differently in normal and osteoporotic bone. While there is no effect in normal bone, in osteoporotic bone, strontium ranelate increases callus bone formation, maturity, and mineralization; forms greater and denser trabeculae; and improves biomechanical properties. Further clinical studies with these medications are needed to fully understand their effects on fracture healing in order to simultaneously treat fragility fractures and underlying osteoporosis.

Guided bone regeneration in osteoporotic conditions following treatment with zoledronic acid

OBJECTIVES

To evaluate new bone formation in calvarial critical size defects (CSD) under dense polytetrafluoroethylene (d-PTFE), microporous membranes for guided bone regeneration (GBR) in healthy, osteoporotic and osteoporotic treated with zoledronic acid (ZA) rats.

METHODS

Forty-eight, female, 6-month old Wistar rats were included in the study. Osteoporosis was induced by ovariectomy (OVX) and calcium-deficient diet in 32 rats. Sixteen OVX rats were treated with a single dose of Zolendronic Acid (ZA) (OZ), while 16 OVX rats received no treatment (O). The remaining 16 rats were sham-operated and used as healthy controls (C). At 6 weeks following osteoporosis induction, two 5 mm CSD were created in the parietal bones and one of them was treated with a double d-PTFE membrane. The healing periods were 30 and 60 days. New bone formation (NB) was assessed by qualitative and quantitative histological analysis.

RESULTS

After 30 days of healing, NB (mean% (95% CI)) was 78.9% (21), 93.1% (9.3) and 84.2% (26.9) in the membrane treated defects and 18.8% (24.1), 27.1% (7.9) and 31% (38.8) in the untreated defects of group O, OZ and C, respectively. After 60 days of healing, NB was 78.3% (14.4), 95.8% (9) and 90.1% (26.1) in the membrane treated defects and 10.8% (17.4), 51.6% (39.4) and 15.7% (12.1) in the untreated defects of group O, OZ and C, respectively. Hierarchical analysis of variance showed that treatment with ZA (P = 0.001) and the use of membrane (P = 0.000) significantly increased new bone formation while presence of osteoporosis may have reduced new bone formation (P = 0.028).

CONCLUSION

d-PTFE membranes for GBR promote bone healing in osteoporotic and healthy rats. Treatment with ZA may improve new bone formation in osteoporotic rats.

Synergistic effects of elastic modulus and surface topology of Ti-based implants on early osseointegration

Elastic modulus and surface micro-scale topographical structure of Ti alloy implants have a synergistic effect on cell attachment, osteogenic differentiation of rBMSCs in vitro and early osseointegration in vivo.

In vitro and in vivo investigation of bisphosphonate-loaded hydroxyapatite particles for peri-implant bone augmentation

Locally applied bisphosphonates, such as zoledronate, have been shown in several studies to inhibit peri-implant bone resorption and recently to enhance peri-implant bone formation. Studies have also demonstrated positive effects of hydroxyapatite (HA) particles on peri-implant bone regeneration and an enhancement of the anti-resorptive effect of bisphosphonates in the presence of calcium. In the present study, both hydroxyapatite nanoparticles (nHA) and zoledronate were combined to achieve a strong reinforcing effect on peri-implant bone. The nHA-zoledronate combination was first investigated in vitro with a pre-osteoclastic cell assay (RAW 264.7) and then in vivo in a rat model of postmenopausal osteoporosis. The in vitro study confirmed that the inhibitory effect of zoledronate on murine osteoclast precursor cells was enhanced by loading the drug on nHA. For the in vivo investigation, either zoledronate-loaded or pure nHA were integrated in hyaluronic acid hydrogel. The gels were injected in screw holes that had been predrilled in rat femoral condyles before the insertion of miniature screws. Micro-CT-based dynamic histomorphometry and histology revealed an unexpected rapid mineralization of the hydrogel in vivo through formation of granules, which served as scaffold for new bone formation. The delivery of zoledronate-loaded nHA further inhibited a degradation of the mineralized hydrogel as well as a resorption of the peri-implant bone as effectively as unbound zoledronate. Hyaluronic acid with zoledronate-loaded nHA, thanks to its dual effect on inducing a rapid mineralization and preventing resorption, is a promising versatile material for bone repair and augmentation. Copyright © 2015 John Wiley & Sons, Ltd.

Bone augmentation using a new injectable bone graft substitute by combining calcium phosphate and bisphosphonate as composite--an animal model

Objective

The aim of this study was to create a new injectable bone graft substitute by combining the features of calcium phosphate and bisphosphonate as a composite bone graft to support bone healing and to evaluate the effect of alendronate to the bone healing process in an animal model.

Material and method

In this study, 24 New Zealand white rabbits were randomly divided into two groups: a calcium phosphate alendronate group and a calcium phosphate control group. A defect was created at the proximal medial tibia and filled with the new created injectable bone graft substitute calcium phosphate alendronate or with calcium phosphate. Healing process was documented by fluoroscopy. To evaluate the potential of the bone graft substitute, the proximal tibia was harvested 2, 4, and 12 weeks after operation. Histomorphological analysis was focused on the evaluation of the dynamic bone parameters using the Osteomeasure system.

Results

Radiologically, the bone graft materials were equally absorbed. No fracture was documented. The bones healed normally. After 2 weeks, the histological analysis showed an increased new bone formation for both materials. The osteoid volume per bone volume (OV/BV) was significantly higher for the calcium phosphate group. After 4 weeks, the results were almost equal. The trabecular thickness (Tb.Th) increased in comparison to week 2 in both groups with a slight advantage for the calcium phosphate group. The total mass of the bone graft (KEM.Ar) and the bone graft substitute surface density (KEM.Pm) were consistently decreasing. After 12 weeks, the new bone volume per tissue volume (BV/TV) was still constantly growing. Both bone grafts show a good integration. New bone was formed on the surface of both bone grafts. The calcium phosphate as well as the calcium phosphate alendronate paste had been enclosed by the bone. The trabecular thickness was higher in both groups compared to the first time point.

Conclusion

Calcium phosphate proved its good potential as a bone graft substitute. Initially, the diagrams seem to show a tendency that alendronate improves the known properties of calcium phosphate as a bone graft substitute. The composite graft induced a good and constant new bone formation. Not only the graft was incorporated into the bone but also a new bone was formed on its surface. But we could not prove a significant difference between the grafts. Both implants proved their function as a bone graft substitute, but the bisphosphonate alendronate does not support the bone healing process sufficiently that the known properties of calcium phosphate as a bone graft substitute were improved in the sense of a composite graft. In this study, alendronate used as a bone graft in a healthy bony environment did not influence the bone healing process in a positive or negative way.

Single-dose local simvastatin injection improves implant fixation via increased angiogenesis and bone formation in an ovariectomized rat model

Background

Statins have been reported to promote bone formation. However, taken orally, their bioavailability is low to the bones. Implant therapies require a local repair response, topical application of osteoinductive agents, or biomaterials that promote implant fixation.

Material/Methods

The present study evaluated the effect of a single local injection of simvastatin on screw fixation in an ovariectomized rat model of osteoporosis.

Results

Dual-energy X-ray absorptiometry, micro-computed tomography, histology, and biomechanical tests revealed that 5 and 10 mg simvastatin significantly improved bone mineral density by 18.2% and 22.4%, respectively (P<0.05); increased bone volume fraction by 51.0% and 57.9%, trabecular thickness by 16.4% and 18.9%, trabeculae number by 112.0% and 107.1%, and percentage of osseointegration by 115.7% and 126.3%; and decreased trabeculae separation by 34.1% and 36.6%, respectively (all P<0.01). Bone mineral apposition rate was significantly increased (P<0.01). Furthermore, implant fixation was significantly increased (P<0.05), and bone morphogenetic protein 2 (BMP2) expression was markedly increased. Local injection of a single dose of simvastatin also promoted angiogenesis. Vessel number, volume, thickness, surface area, and vascular volume per tissue volume were significantly increased (all P<0.01). Vascular endothelial growth factor (VEGF), VEGF receptor-2, von Willebrand factor, and platelet endothelial cell adhesion molecule-1 expression were enhanced.

Conclusions

A single local injection of simvastatin significantly increased bone formation, promoted osseointegration, and enhanced implant fixation in ovariectomized rats. The underlying mechanism appears to involve enhanced BMP2 expression and angiogenesis in the target bone.

Time course of bone screw fixation following a local delivery of Zoledronate in a rat femoral model - a micro-finite element analysis

A good fixation of osteosynthesis implants is crucial for a successful bone healing but often difficult to achieve in osteoporotic patients. One possible solution to this issue is the local delivery of bisphosphonates in direct proximity to the implants, A critical aspect of this method, that has not yet been well investigated, is the time course of the implant fixation following the drug release. Usual destructive mechanical tests require large numbers of animals to produce meaningful results. Therefore, a micro-finite element (microFE) approach was chosen to analyze implant fixation. In vivo micro computed tomography (microCT) scans were obtained, first weekly and later bi-weekly, after implantation of polymeric screws in the femoral condyles of ovariectomized rats. In one half of the animals, Zoledronate was released from a hydrogel matrix directly in the peri-implant bone stock, the other animals were implanted only with screws as control. The time course of the implant fixation was investigated with linear elastic microFE models that were created based on in vivo microCT scans. The numerical models were validated against experimental pullout-tests measurements in an additional cadaver study. The microFE analysis revealed a significant increase in force at yield of the Zoledronate treated group compared to the control group. The force of the treated group was 28% higher after 17 days of screw implantation, 42% higher after 31 days. The significant difference persisted until the end of the in vivo study at day 58 (p<0.01). The early onset and prolonged duration of the implant anchorage improvement that was found in this study indicates the great potential of Zoledronate-loaded hydrogel for an enhancement of osteosynthesis implant fixation in impaired bone.