The bisphosphonate pamidronate on the surface of titanium stimulates bone formation around tibial implants in rats

Effects of TiO2 nanotubes with different diameters on gene expression and osseointegration of implants in minipigs

Titanium dioxide (TiO(2)) nanotubes can accelerate the adhesion and differentiation of osteoblasts, yet little is known how this nano-modified implant surface affects osseointegration at molecular level in vivo. The aim of this study was to investigate the effects of TiO(2) nanotubes with different diameters (30 nm, 70 nm and 100 nm) on biological attachment mechanism of implants to bone in vivo by studying the gene expression and bone formation around the implants. The histological features and fluorochrome labeling changes of bone around implants on the non-decalcified sections (at 3, 5 and 8 weeks after implantation) were investigated by using traditional light- and fluorescent microscopy, and the gene expression of alkaline phosphatase (ALP), osterix (Osx), collagen-I (Col-I) and tartrate-resistant acid phosphatase (TRAP) was examined by using real-time PCR at 1, 2, 3, 4 and 5 weeks after implantation. Comparing with machined titanium implants, a significant increase in bone-implant contact (BIC) and gene expression levels was found in the bone attached to implants with TiO(2) nanotubes, especially with 70 nm diameter nanotubes. At the same time, the sequential fluorescent labeling images illustrated dynamic bone deposition. In conclusion, TiO(2) nanotubes can modulate bone formation events at the bone-implant interface as to reach favorable molecular response and osseointegration; in addition, the diameters of nanotubes can be precisely controlled in order to obtain better bone formation.

Evaluation of Neridronate on the Osseointegration Process of Endeous Titanium Implants in Animal Models

Bisphosphonates are compounds that inhibit bone reabsorption mediated by osteoclasts. The use of bisphosphonates in oral implantology is still in the experimental stage. The aim of this study is to evaluate the efficacy of an aminobisphosphonate to increase the ability of the drug to act on the implant and bone surfaces in the development of the osseointegration in sheep. Forty SLA titanium implants were used on sheep iliac crests. Neridronate added to connective gel (test 1) or to physiological solution (test 2) was used in order to increase the bone and implant adhesiveness. Physiological solution (control 1) or connective gel (control 2) alone was given to the control groups. A topical administration of Neridronate was made on the implant surface and in the implant site. Four Bergamasca sheep were used and were sacrificed by intravenous injection of 10 cc Tanax after 8 weeks from implantation. Histologic and histomorphometric analyses were carried out. The results did not show significant differences between the test group and control group. Our data are different from other similar studies obtaining statistically significant differences. These differences could depend on the procedure of application of the drug on the implant. This study demonstrates the poor efficacy of neridronate applied topically to the implant and implant site during surgery. Further studies using different fixation techniques of the drug may be necessary to confirm the present data.

Effects of ibandronate-hydroxyapatite on resorptive activity of osteoclasts

INTRODUCTION

Bisphosphonates (BPs) can be locally used to improve the osteogenesis around hydroxyapatite (HA) implants. However, there are almost no reports discussing the effects of BPs in the bound state with HA on osteoclasts. Ibandronate is a BP widely used in clinical practice. This study was designed to evaluate the effects of ibandronate combined with HA on the morphology and resorptive activity of osteoclasts.

MATERIAL AND METHODS

The HA and ibandronate-HA were prepared. Osteoclasts were isolated from Sprague-Dawley rats and then the cells were cultured with both HA and ibandronate-HA. Then the cell morphology was inspected by inverted phase contrast microscope and transmission electron microscopy observation. The resorptive activity was tested using the dyeing agent seminaphthofluorescein and bone resorption assay.

RESULTS

Compared with the control group, the osteoclasts demonstrated morphological alterations, and the hydrogen ion concentration was significantly lower in the ibandronate-HA group. Areas of the resorption pits formed by the osteoclasts were significantly smaller, the trabecula thickness appeared thicker, and concentration of CTx was also significantly lower in the experimental group.

CONCLUSIONS

Resorptive activity of osteoclasts cultured with ibandronate-HA was weaker than that of the control group. Ibandronate on HA in the bound state could maintain its action as an inhibitor to osteoclasts.

Surface immobilized zoledronate improves screw fixation in rat bone: a new method for the coating of metal implants

Previous studies show that surface immobilized bisphosphonates improve the fixation of stainless steel screws in rat tibia after 2-8 weeks of implantation. We report here about the immobilization of a potent bisphosphonate, zoledronate, to crosslinked fibrinogen by the use of another technique, i.e. ethyl-dimethyl-aminopropylcarbodiimide (EDC)/imidazole immobilization. Bone fixation of zoledronate-coated screws was compared to screws coated with crosslinked fibrinogen only and ditto with EDC/N-hydroxy-succinimide immobilized pamidronate. Fixation in rat tibia was evaluated by a pull-out test at either 2 or 6 weeks after implantation. Both bisphosphonate coatings increased the pull-out force at both time points, and zoledronate showed a significantly higher pull-out force than pamidronate. To further evaluate the new coating technique we also performed a morphometric study, focusing on the area surrounding the implant. The zoledronate coating resulted in an increased bone density around the screws compared to controls. No pronounced increase was seen around the pamidronate coated screws. Together, the results demonstrate the possibility of obtaining a significant local therapeutic effect with minute amounts of surface immobilized zoledronate.

Sol-gel derived titania coating with immobilized bisphosphonate enhances screw fixation in rat tibia

A variety of surface modifications have been tested for the enhancement of screw fixation in bone, and locally delivered anti-osteoporosis drugs such as bisphosphonates (BP) are then of interest. In this in vivo study, the impact of surface immobilized BP was compared with systemic BP delivery and screws with no BP. After due in vitro characterization, differently treated stainless steel (SS) screws were divided into four groups with 10 rats each. Three of the groups received screws coated with sol-gel derived TiO(2) and calcium phosphate (SS+TiO(2)+CaP). One of these had no further treatment, one had alendronate (BP) adsorbed to calcium phosphate mineral, and one received systemic BP treatment. The fourth group received uncoated SS screws and no BP (control). The screw pullout force was measured after 4 weeks of implantation in rat tibiae. The immobilized amount and release rate of alendronate could be controlled by different immersion times. The SS+TiO(2)+CaP coating did not increase the pullout force compared to SS alone. Surface delivered alendronate enhanced the pullout force by 93% [p = 0.000; 95% Confidence Interval (CI): 67-118%] compared to SS, and by 39% (p = 0.044; 95% CI: 7-71%) compared to systemic alendronate delivery. Both surface immobilized and systemically delivered alendronate improved implant fixation. Also, locally delivered, that is, surface immobilized alendronate showed a better fixation than systemically delivered. Using sol-gel derived TiO(2) as a platform, it is possible to administer controllable amounts of a variety of BPs.

Effects of clodronate combined with hydroxyapatite on multi-directional differentiation of mesenchymal stromal cells

INTRODUCTION

Bisphosphonates (BPs) can be locally used to improve the osteogenesis around hydroxyapatite (HA) implants. However, there are almost no reports discussing the effects of BPs in the bonding state with HA on bone mesenchymal stromal cells (BMSCs). Clodronate is a BP widely used in clinical practice. This study was designed to evaluate the effects of clodronate combined with HA on BMSCs' multi-directional differentiation.

MATERIAL AND METHODS

The HA and clodronate-HA complex were prepared. BMSCs were isolated from Sprague-Dawley rat bone marrow and then the cells were cultured with both HA and clodronate-HA. The method of transcriptional and translational assay (MTT) and multi-directional induction (including osteogenic, adipogenic, and myogenic differentiation) were used to evaluate the effect of clodronate-HA on BMSC differentiation.

RESULTS

Scanning electron microscopy indicated active proliferation of the cells on clodronate-HA and HA. MTT of BMSCs cultured on clodronate-HA and HA demonstrated no significant differences between the two groups. BMSCs differentiated into osteocytes, adipocytes, and myocytes after being cultured with both clodronate-HA and HA. This indicated that BMSCs still retained multi-directional capability. The alkaline phosphatase activity of osteogenic induced BMSCs of both groups had no significant difference. However, there was a significant difference in total protein found between them.

CONCLUSIONS

The results suggest that clodronate in the bonding state with HA has no obvious inhibition of the proliferation and activity of BMSCs on the complex, and there was no evidence of a negative effect on multi-directional capability of the BMSCs.

Immobilized-OPG-Fc on a titanium surface inhibits RANKL-dependent osteoclast differentiation in vitro

The purpose of the present study was to examine the effect of osteoprotegerin (OPG)-Fc fusion protein immobilized on a titanium surface on the initial differentiation of osteoclast precursor RAW264.7 cells. These cells were cultured on titanium specimens over which OPG-Fc was immobilized. The enhancement of tartrate-resistant acid phosphatase (TRAP) and cathepsin K mRNA expression in RAW264.7 cells exposed to receptor activator of NF-kappaB ligand (RANKL) stimulation on OPG-Fc-coated titanium was significantly lower than that in RAW264.7 cells exposed to RANKL on titanium specimens without immobilized OPG-Fc (ANOVA, P < 0.01). Preincubation of OPG-Fc-coated titanium, in a medium supplemented with 10% fetal bovine serum at 37 degrees C for two days before the cells were seeded, had no significant effect on the decrease in mRNA expression (ANOVA, P < 0.01). Taken together, these results indicate that OPG-Fc immobilized on a titanium surface blocks the differentiation of RAW264.7 cells induced by RANKL stimulation.

Clodronate combined with a surfactant (Tween 20) does not improve osseointegration: a rabbit immunohistomorphometric study

Biphosphonates are compounds that inhibit bone reabsorption mediated by osteoclasts or the progression of periodontal disease independent on the host response to pathogenic bacteria that colonize the tooth surface. The use of biphosphonates in oral implantology is still in the experimental stage. The aim of this study is to evaluate the efficacy of a non-aminobiphosphonate combined with a surfactant to increase the ability of the drug to link to the implant and bone surfaces in the development of osseointegration in rabbits. Smooth titanium implants were devised to be used on rabbit femurs. A topical administration of clodronate combined with the surfactant (Tween 20) at different concentrations was made on the implant surface and in the implant site to increase the bone and implant adhesiveness. Placebo was given to the control group. New Zealand rabbits were used and sacrificed by CO2 after 8 weeks from the implantations. A histologic and histomorphometric analysis was carried out. Results did not show significant difference between the tests and the placebo groups. Our data are different from other similar studies obtaining statistically significant differences. These differences could depend on the efficacy of the drug used and on the procedure of application of the drug on the implant. This study demonstrates poor efficacy of clodronate applied topically to the implant and implant site during surgery to increase the percentage of osseointegration in the implant. Further studies using different fixation techniques of the drug may be necessary to confirm the present data.

In vitro behavior of layer-by-layer deposited molecular oligoelectrolyte films on Ti-6Al-4V surfaces

Layer-by-layer self-assembled films of molecular oligoelectrolytes were used to modify Ti-6Al-4V surfaces in order to test their ability as potential drug delivery system. With regard to medical application the in vitro behavior of the modified material was investigated. The Ti-6Al-4V (6% aluminium, 4% vanadium) material was treated in a layer-by-layer (LbL) process with 2, 4, 6 and 8 layers of molecular oligoelectrolytes 1 and 2 and thereby doped with a fluorescent reporter molecule 2. Human osteoblasts were cultured for a period up to 5 days on the modified material. Ti-6Al-4V surfaces without modification were used as control. In order to investigate the in vitro behavior of the coating as well as the influence of components of the coating on osteoblastic cells, respectively, cell proliferation, differentiation and attachment of hFOB cells were observed by means of cell number, osteoblastic gene expression and fluorescence microscopy. Degradation behavior of the OEM (oligoelectrolyte multilayer film) was examined using optical spectroscopy. Measurement data imply that the layer-by-layer coating was successfully assembled on the Ti surface and endures steam sterilization. The fluorescence signal in cell culture medium increased strictly linear with increasing pre-assembled number of layers on the surface. Proliferation rates of the cells in experimental groups did not differ significantly from each other (P >or= 0.783). Differentiation pattern was not significantly changed by the coating. The fluorescent reporter component of the film was absorbed by osteoblastic cells and was detected by fluorescence microscopy.

Bisphosphonate incorporation in surgical implant coatings by fast loading and co-precipitation at low drug concentrations

The objectives of the present work was to evaluate the possibility for fast loading by soaking of bisphosphonates (BPs) into hydroxylapatite (HA) implant coatings biomimetically grown on crystalline TiO(2) surfaces, and also investigate the influence of different BP loading concentrations in a buffer during co-precipitation of a calcium phosphate containing layer onto these surfaces. The co-precipitation method created coatings that contained BPs throughout most of the coating layer, but the presence of BPs in the buffer hindered the formation of a bulk HA-layer, thus resulting in very thin coatings most likely consisting of islands built up by a calcium phosphate containing BPs. The coatings biomimetically grown on TiO(2) surfaces, were shown to consist of crystalline HA. Soaking of these coatings during 15 min only in a low BPs concentration containing buffer yielded a concentration on the coating surface of the same order of magnitude as obtained with soaking during 60 min in significantly higher concentrated buffers. This could be of advantage during surgery since the operating surgeon could make a fast decision whether or not to include the drugs in the coating based on the need of the particular patient at hand. The BPs present on the surface of the fast-loaded HA coatings were found to be strongly bound, something which should be beneficial for in vivo use. Both the co-precipitation method and the fast loading by soaking method investigated here are promising techniques for loading of BPs onto surgical implants. The simplicity of both methods is an advantage since implants can have spatially complicated structures.

Bone formation on apatite-coated titanium with incorporated BMP-2/heparin in vivo

OBJECTIVE

The objective of this study was to investigate whether the in vivo osteoinductive activity of an implant material is enhanced by covering the surface of apatite with incorporated bone morphogenetic protein 2 (BMP-2) and heparin which maintains the activity of BMP-2.

STUDY DESIGN

Titanium implants were alkaline treated, heat activated, and soaked in stimulated body fluid with or without BMP-2/heparin to coat the apatite around them. Treated implant bars were then implanted in rat tibiae. After 3 weeks, nondecalcified sections were prepared and the new bone formation around the implants was examined.

RESULTS

A greater amount of bone formed on the apatite-coated implants containing BMP-2/heparin than on apatite-coated implants containing BMP, with >or=3 microg/mL heparin. Apatite-coated titanium implants with BMP-2/heparin had significantly enhanced new endosteal bone formation, with increases vertically (134%) and horizontally (124%).

CONCLUSIONS

Bone formation was stimulated around the apatite-covered titanium coated with BMP-2/heparin, which may be useful in improving implant therapy.

Biological Responses to New Advanced Surface Modifications of Endosseous Medical Implants

Implantable medical devices are increasingly important in the practice of modern medicine. However, patients with severely poor bone quality and quantity require highest implant osseointegration for the long-term success. A number of newly-developed advanced surface modifications of medical implants have recently been introduced to the medical implant system. Understanding the mechanisms by which osteogenic cells respond to such materials is therefore of major importance in developing the most effective materials to promote functional osseointegration. Diverse studies using materials with a wide range of new surface modification techniques have demonstrated the pivotal role of surface treatments in cell adhesion, proliferation and lineage specific differentiation. These events underlie the tissue responses required for bone healing following implant placement, with the interaction between adsorbed proteins on the implant surface and surrounding cells eliciting body responses to the treated implant surface. This review illustrates tissue responses to the implant material following implant placement and highlights cellular responses to new advanced implant surface modifications. Such information is of utmost importance to further develop several new advanced surface modifications to be used in the new era medical implantable devices.

Effect of combined local treatment with zoledronic acid and basic fibroblast growth factor on implant fixation in ovariectomized rats

Osteoporosis is a skeletal disorder characterized by low bone mass and deterioration of bone microarchitecture resulting in bone fragility, which impairs fixation of the implants. Zoledronic acid (ZOL) is a potential inhibitor of osteoclast-mediated bone resorption and basic fibroblast growth factor (bFGF) is a growth factor that stimulates osteoblast-mediated bone formation, and these drugs could enhance fixation of implants under osteoporotic conditions. In this study, 40 ovariectomized (OVX) rats were randomly divided into 4 groups (n=10 for each group) and underwent bilateral tibiae implantation using hydroxyapatite (HA)-coated titanium implant: Control group (distilled water immersing before implantation), ZOL group (1 mg/ml of ZOL immersing), bFGF group (20 microg/ml of bFGF immersing), and ZOL+bFGF group (1 mg/ml of ZOL and 20 microg/ml of bFGF immersing). At 3 months after implantation, all animal were sacrificed and the tibiae were harvested for histology, micro-CT examinations and biomechanical testing. Bone area and contact, determined by histomorphometric analysis, were 2.7-fold and 1.8-fold in the ZOL-treated implants, 1.9-fold and 1.8-fold in the bFGF-treated implants, 3.6-fold and 2.3-fold in the both-treated implants compared with controls (p<0.01). Such significant effects were further confirmed by microstructure parameters, the bone volume ratio and the percentage osteointegration were significantly increased by ZOL treatment (3.0-fold and 1.8-fold), bFGF treatment (1.2-fold and 1.9-fold) and ZOL+bFGF treatment (3.3-fold and 2.7-fold) (p<0.001). In addition, push-out test showed that the maximum force and the corresponding interfacial shear strength of the implants treated by ZOL, bFGF and ZOL+bFGF was 8.4-fold and 8.6-fold, 3.8-fold and 3.7-fold, 10.8-fold and 10.7-fold of the control levels, respectively (p<0.05). The combined treatment was better than either treatment alone for force, but was not different from ZOL alone for interfacial strength. The significant correlation between biomechanical and micro-CT parameters demonstrates the role of microstructure assessments in predicting mechanical fixation of implants (p<0.01). Our study suggests that locally applied ZOL or bFGF may improve implant fixation in the ovariectomized rats, and that combined treatment has more beneficial effects on osseointegration, peri-implant bone formation and maximum force than either intervention alone.

Bisphosphonate coating on titanium screws increases mechanical fixation in rat tibia after two weeks

Recently published data indicate that immobilized N-bisphosphonate enhances the pullout force and energy uptake of implanted stainless steel screws at 2 weeks in rat tibia. This study compares titanium screws with and without a bisphosphonate coating in the same animal model. The screws were first coated with an approximately 100-nm thick crosslinked fibrinogen film. Pamidronate was subsequently immobilized into this film via EDC/NHS-activated carboxyl groups within the fibrinogen matrix, and finally another N-bisphosphonate, ibandronate, was physically adsorbed. The release kinetics of immobilized (14)C-alendronate was measured in buffer up to 724 h and showed a 60% release within 8 h. Mechanical tests demonstrated a 32% (p = 0.04) and 48% (p = 0.02) larger pullout force and energy until failure after 2 weeks of implantation, compared to uncoated titanium screws. A control study with physically adsorbed pamidronate showed no effect on mechanical fixation, probably due to a too small adsorbed amount. We conclude that the fixation of titanium implants in bone can be improved by fibrinogen matrix-bound bisphosphonates.

Layer-by-layer deposition of molecular oligoelectrolytes-investigation of assembling and degradation behaviour

The assembly and degradation behavior of oligoelectrolyte multilayer films (OEMs) self assembled by layer-by-layer deposition of positively and negatively charged oligoelectrolytes 1-6 was investigated. Next to colorless oligoelectrolytes we have employed representatives involving chromophores, in particular porphyrins. This allows for the systematic observation of both assembly and disassembly of the OEMs using optical spectroscopy, where chromophore containing building blocks serve as reporter electrolytes. The OEMs investigated in this study were built in a consistent, monomolecular matter and show linear correlation between the absorption and the number of layers. Using the concept of reporter electrolytes we have introduced for the first time also the use of non-chromophoric oligoelectrolytes, such as the new synthesized cationic system 2 as building blocks for OEMs. Moreover, we have investigated for the first time the degradation behavior of OEMs. We demonstrated that two different mechanisms of degradation proceed at the same time. The direct degradation is accompanied by a second release mechanism.

Stainless steel screws coated with bisphosphonates gave stronger fixation and more surrounding bone. Histomorphometry in rats

Coating of stainless steel screws with bisphosphonate in a fibrinogen matrix leads to an enhancement of the pullout strength 2 weeks after insertion in rat tibiae. This effect then increases over time until at least 8 weeks. The pullout force reflects the mechanical properties of the bone within the threads, which acts as a screw nut. The aim of the present study was to find descriptive and morphometric histological correlates to the increased pullout strength. Because the bisphosphonates are applied via the implant surface, we also measured bone to implant contact and how far away from the surface any effects could be seen. Stainless steel screws underwent one of three treatments: uncoated control, controls coated with a layer of cross-linked fibrinogen, or screws further modified with bisphosphonates covalently linked and physically adsorbed to the fibrinogen layer. At 1 (n=33) and 8 (n=27) weeks, bone to implant contact and bone area density in the threads were measured, as well as bone area density at 250 and 500 microm from the outer edge of the threads. Additionally, removal torque for each screw treatment was measured at 2 weeks (n=28). At 8 weeks, the part of the bisphosphonate screw that was located in the marrow cavity had become surrounded with bone, whereas there was almost no bone surrounding the controls. The bone area density in the threads along the entire bisphosphonate screw was increased by 40% compared with uncoated controls, and at 250 microm distance it was more than doubled. At 1 week, coated screws had less implant-bone contact, but at 8 weeks there was no difference between uncoated and bisphosphonate-coated screws. The bisphosphonate screws had 50% increased removal torque at 2 weeks compared to uncoated screws. Howship's lacunae and osteoclasts were found near the screws with bisphosphonates at 8 weeks, suggesting that some bone remodeling took place near the implant, in spite of the presence of bisphosphonates.

Apatite-coated poly(lactic-co-glycolic acid) microspheres as an injectable scaffold for bone tissue engineering

Biodegradable polymer/ceramic composite scaffold could overcome limitations of biodegradable polymers or ceramics for bone regeneration. Injectable scaffold has raised great interest for bone regeneration in vivo, since it allows one for easy filling of irregularly shaped bone defects and implantation of osteogenic cells through minimally invasive surgical procedures The purpose of this study was to determine whether apatite-coated poly(lactic-co-glycolic acid) (PLGA) microspheres could be used as an injectable scaffold to regenerate bone in vivo. Apatite-coated PLGA microspheres were fabricated by incubating PLGA microspheres in simulated body fluid. The apatite that coated the PLGA microsphere surfaces was similar to apatite in natural bone, as demonstrated by scanning electron microscopy, X-ray diffraction spectra, energy-dispersive spectroscopy, and Fourier transformed-infrared spectroscopy analyses. Rat osteoblasts were mixed with apatite-coated PLGA microspheres and injected immediately into subcutaneous sites of athymic mice. Osteoblast transplantation with plain PLGA microspheres served as a control. Histological analysis of the implants at 6 weeks with hematoxylin and eosin staining, Masson's trichrome staining, and von Kossa staining revealed much better regeneration of bone in the apatite-coated PLGA microsphere group than the plain PLGA microsphere group. The new bone formation area and the calcium content of the implants were significantly higher in the apatite-coated PLGA microsphere group than in the plain PLGA microsphere group. This study demonstrates the feasibility of using apatite-coated PLGA microspheres as an injectable scaffold for in vivo bone tissue engineering. This scaffold may be useful for bone regeneration through minimally invasive surgical procedures in orthopedic applications.

Anabolic effects of bisphosphonates on peri-implant bone stock

The long-term durability of total joint replacements is critically dependent on adequate peri-implant bone stock, which can be compromised by wear debris-mediated osteolysis. This study investigated the effects of bisphosphonates on enhancing peri-implant bone in the presence of clinically relevant ultra-high molecular weight polyethylene (UHMWPE) wear debris. Fiber-mesh coated titanium-alloy plugs were implanted bilaterally in the femoral condyles of 36 New Zealand white rabbits. Implants in the left femora were covered with submicron UHMWPE particles during surgery. Rabbits were administered either no drug, subcutaneous alendronate weekly (1.0mg/kg/week) or a single dose of intravenous zoledronate (0.015mg/kg). A total of 6/12 rabbits in each group were sacrificed at 6 weeks and the remainder at 12 weeks postoperatively. Peri-implant bone stock was analyzed radiographically and histomorphometrically. Radiographically, both bisphosphonates significantly increased periprosthetic cortical thickness at 6 weeks (p<0.0001; alendronate: +18%; zoledronate: +11%) and at 12 weeks (p=0.001; alendronate: +17%; zoledronate:+19%). Histomorphometrically, alendronate and zoledronate raised peri-implant bone volume (BV/TV) up to 2-fold after 6 weeks without added wear debris and more than 3-fold when wear debris was present. Furthermore a 6-week bisphosphonate treatment increased osteoid thickness in the absence of wear debris (alendronate: +132%, p=0.007; zoledronate: +67%, p=0.51) and in the presence of wear debris (alendronate: +134%, p=0.023; zoledronate: +138%, p=0.016). In summary, alendronate and zoledronate treatment increased periprosthetic bone stock in a rabbit femoral model, particularly in the presence of UHMWPE wear debris. These new findings suggest that bisphosphonates may more than compensate for the well-documented negative effects of wear debris on peri-implant bone stock. The combined antiresorptive and osteoanabolic effects of bisphosphonates on periprosthetic bone stock may have an important role for critically improving the biological fixation and ultimate durability of total joint arthroplasty.

Alendronate enhances antibiotic-impregnated bone grafts in the treatment of osteomyelitis

Bisphosphonates are systemic drugs. There is limited knowledge about their effects when applied locally and in osteomyelitis treatment. A prospective longitudinal randomised controlled study was designed in rat tibia to test the efficacy of local or systemically administered bisphosphonates for controlling the osteolytic reactions and possible effects on local infection control. Tibial osteomyelitis was induced in 72 Wistar albino rats with Staphylococcus aureus ATCC 25923 strain. Débridement was performed on all rats in all groups. No other treatment was given to the control group. Treatment groups received "plain bone grafts", "vancomycin-loaded bone grafts", "vancomycin-loaded bone grafts+systemic alendronate", "alendronate-impregnated bone grafts" and "vancomycin+alendronate-impregnated grafts". Study results were evaluated by swab cultures, radiology, quantitative computed tomography, dual-energy X-ray absorptiometry (DEXA) and histopathology. S. aureus was eradicated in groups II and IV by the sixth week. Diaphyseal widening, bone deformation, diaphyseal widening and osteolysis scores were significantly lower (p < 0.05), and bone mineral content, density measurements and DEXA scores were significantly higher (p = 0.001) with alendronate administration. Histology revealed marked osteoblastic activity. Local alendronate interfered with local infection control. Even though local alendronate at the given dose has stronger effects, the possible effects on the local inflammatory process needs to be clarified.

Surface treatments of titanium dental implants for rapid osseointegration

The osseointegration rate of titanium dental implants is related to their composition and surface roughness. Rough-surfaced implants favor both bone anchoring and biomechanical stability. Osteoconductive calcium phosphate coatings promote bone healing and apposition, leading to the rapid biological fixation of implants. The different methods used for increasing surface roughness or applying osteoconductive coatings to titanium dental implants are reviewed. Surface treatments, such as titanium plasma-spraying, grit-blasting, acid-etching, anodization or calcium phosphate coatings, and their corresponding surface morphologies and properties are described. Most of these surfaces are commercially available and have proven clinical efficacy (>95% over 5 years). The precise role of surface chemistry and topography on the early events in dental implant osseointegration remain poorly understood. In addition, comparative clinical studies with different implant surfaces are rarely performed. The future of dental implantology should aim to develop surfaces with controlled and standardized topography or chemistry. This approach will be the only way to understand the interactions between proteins, cells and tissues, and implant surfaces. The local release of bone stimulating or resorptive drugs in the peri-implant region may also respond to difficult clinical situations with poor bone quality and quantity. These therapeutic strategies should ultimately enhance the osseointegration process of dental implants for their immediate loading and long-term success.

Local alendronate increases fixation of implants inserted with bone compaction: 12-week canine study

Bone compaction has been shown to increase initial implant fixation. Furthermore, bone compaction creates a peri-implant zone of autograft that exerts osteoconductive properties. We have previously shown that locally applied bisphosphonate (alendronate) at 4-week observation can preserve the autograft generated by bone compaction. We now investigate whether the increased amount of autograft, seen at 4 weeks, can increase implant osseointegration and biomechanical fixation. Porous-coated titanium implants were bilaterally inserted with bone compaction into the proximal part of tibia of 10 dogs. On the right side, local bisphosphonate was injected into the bone cavity prior to bone compaction immediately prior to implant insertion. On the left side, saline was used as control. Observation period was 12 weeks. Locally applied bisphosphonate significantly increased biomechanical implant fixation (approximately twofold), bone-to-implant contact (1.2-fold), and peri-implant bone volume fraction (2.3-fold). This study indicates that local alendronate treatment can increase early implant osseointegration and biomechanical fixation of implants inserted by use of bone compaction. Long term effects remain unknown.

Boosting effect of bisphosphonates on osteoconductive materials: a histologic in vivo evaluation

BACKGROUND AND OBJECTIVE

The effect on bone regeneration, of adding pamidronate disodium to bovine-derived hydroxyapatite, was histologically evaluated, using the sheep bone model.

MATERIAL AND METHODS

Twenty-four intrabony defects were prepared in the lower jaw of eight sheep using trephine 6 mm burs. One cavity was left unfilled and the other two were filled with bovine-derived hydroxyapatite (BioOss) alone (control group) or with bovine-derived hydroxyapatite mixed with pamidronate disodium (Aredia) (case group), respectively. After 6 wk, the animals were killed and the coded samples observed using an optical microscope. The percentage of regenerated bone, number of osteoclasts and amount of inflammation was recorded. Statistical analysis was carried out using chi-square and Mann-Whitney U-tests.

RESULTS

The results manifested a significant difference in the amount of bone formation, with the most being observed in the case group and the least in the negative-control group (p<0.001). Significantly fewer osteoclasts were observed in the case group than in the other groups (p<0.001). The amount of inflammation did not seem to differ within the case and control groups (p>0.05).

CONCLUSION

Adding pamidronate disodium to bovine-derived hydroxyapatite improves its osteoconductive and regenerative specifications. Further study should determine the systemic effects of a single local administration of these drugs, and their appropriate dose and type, with minimal risk.

Control of bisphosphonate release using hydroxyapatite granules

The efficacy of hydroxyapatite (HAp) as a carrier was investigated to establish a method of local administration of bisphosphonates (Bps), which has currently been administered systemically. HAp granules (300-500 microm in size) with different physicochemical features were prepared by altering the sintering temperature. To ascertain the physicochemical properties of the HAp granules, their crystallinity was assessed using X-ray diffraction, the surface morphology was examined under scanning electron microscopy, and the specific surface area and calcium dissolution were evaluated. Different Bps-HAp composites were subsequently prepared and the concentration of Bps released from these composites was measured. The influence of Bps-HAp composites on the rate of osteoclast survival was also evaluated. The results revealed that (1) HAp solubility depends on the sintering temperature; (2) The concentration of released Bps could be controlled by regulating the sintering temperature of HAp as a carrier; and (3) Bps released from Bps-HAp composites reduced the number of osteoclasts. These findings indicated that Bps-HAp composites could be locally administered as a drug delivery system to areas with bone resorption.

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

Patients with osteoporosis and joint disabilities represent a constant growing and challenging population to be treated in the musculoskeletal clinical field. Especially in the case of total hip arthroplasty, new solutions should be developed to compensate for the double negative factors, peri-implant osteolysis, and osteoporotic bone loss, affecting the quality of implant outcome. The goal of this study was then to establish a proof of concept for orthopedic implant used as Zoledronate delivery in osteoporotic rats, and in particular, to verify if this approach could increase the initial implant stability. Twenty-five female 6-month-old Wistar rats were ovariectomized 6 weeks before the implantation to induce osteoporosis. The animals were randomly separated in five groups representing the different Zoledronate concentrations in the HA coating: 0, 0.2, 2.1, 8.5, and 16 microg/implant. Histomorphometric measures and peri-implant bone volume fraction were assessed and mechanical stability tests were performed. Bone volume fraction and biomechanical results clearly illustrate the positive effect of Zoledronate coated implants in the osteoporotic rats. A remarkable result was to show the existence of a window of Zoledronate content (0.2 to 8.5 microg/implant) in which the mechanical fixation of the implant increased. We were able to establish the proof of concept for orthopedic implants used as a drug delivery system in osteoporotic rats. The local bisphosphonate delivery from a calcium phosphate coating allowed increase of the mechanical fixation of an orthopedic implant. This study shows that orthopedic implants containing bisphosphonates could be beneficial for osteoporotic patients in need of a total joint replacement.

Confocal laser scanning microscopy in orthopaedic research

Confocal laser scanning microscopy (CLSM) is a type of high-resolution fluorescence microscopy that overcomes the limitations of conventional widefield microscopy and facilitates the generation of high-resolution 3D images from relatively thick sections of tissue. As a comparatively non-destructive imaging technique, CLSM facilitates the in situ characterization of tissue microstructure. Images generated by CLSM have been utilized for the study of articular cartilage, bone, muscle, tendon, ligament and menisci by the foremost research groups in the field of orthopaedics including those teams headed by Bush, Errington, Guilak, Hall, Hunziker, Knight, Mow, Poole, Ratcliffe and White. Recent evolutions in techniques and technologies have facilitated a relatively widespread adoption of this imaging modality, with increased "user friendliness" and flexibility. Applications of CLSM also exist in the rapidly advancing field of orthopaedic implants and in the investigation of joint lubrication.