Modern issues in bone graft substitutes and advances in bone tissue technology

Synthesis and Characterization of Calcium Silicate Nanoparticles Stabilized with Amino Acids

This work presents the development of a method for the synthesis of calcium silicate nanoparticles stabilized with essential amino acids. CaSiO₃ nanoparticles were obtained through chemical precipitation. In the first stage, the optimal calcium-containing precursor was determined. The samples were examined using scanning electron microscopy. It was found that Ca(CH₃COO)₂ was the optimal calcium-containing precursor. Then, the phase composition of calcium silicate was studied using X-ray phase analysis. The results showed the presence of high-intensity bands in the diffractogram, which characterized the phase of the nanosized CaSiO₃-wollastonite. In the next stage, the influence of the type of amino acid on the microstructure of calcium silicate was studied. The amnio acids studied were valine, L-leucine, L-isoleucine, L-methionine, L-threonine, L-lysine, L-phenylalanine, and L-tryptophan. The analysis of the SEM micrographs showed that the addition of amino acids did not significantly affect the morphology of the CaSiO₃ samples. The surface of the CaSiO₃ samples, both without a stabilizer and with amino acids, was represented by irregularly shaped aggregates consisting of nanoparticles with a diameter of 50-400 nm. Further, in order to determine the optimal amino acid to use to stabilize nanoparticles, computerized quantum chemical modeling was carried out. Analysis of the data obtained showed that the most energetically favorable interaction was the CaSiO₃-L-methionine configuration, where the interaction occurs through the amino group of the amino acid; the energy value of which was -2058.497 kcal/mol. To confirm the simulation results, the samples were examined using IR spectroscopy. An analysis of the results showed that the interaction of calcium silicate with L-methionine occurs via the formation of a bond through the NH₃⁺ group of the amino acid.

Use of cement combined grafting in upper and lower extremity benign bone tumors

Objectives

This study aims to investigate the effectivity of cement combined demineralized bone matrix (DBM) treatment on new bone formation in the cortical window as well as to evaluate the effect of new bone formation on functional outcomes.

Patients and methods

Thirty-two benign bone tumor patients (15 males, 17 females; median age 38 years; range, 12 to 68 years), who were treated with cement combined DBM between February 2010 and December 2014, were evaluated retrospectively. Patient characteristics were recorded as age, gender, tumor localization, histological diagnosis, Enneking stage, tumor size, size of the cortical window, usage of prophylactic fixation, time to return to work, Musculoskeletal Tumor Society (MSTS) functional score, tumor relapse, and new bone formation on the cortical window in the computed tomography scans after one year of surgery.

Results

Median tumor volume was 17.2 cm3 (range, 2.8 to 139.6 cm3), median area of the cortical window was 8.3 cm2 (range, 1.6 to 28.4 cm2), and median postoperative one-year MSTS score was 84.5 (range, 66 to 97). MSTS scores were significantly worse with the usage of prophylactic fixation (p<0.001). There was a statistically significant difference between the usage of prophylactic fixation and cortical window size (p=0.013). There was a low-level negative correlation in terms of age and bone formation on the cortical window (p=0.046, r= -0.356) and mid-level negative correlation between cortical window size and functional scores (p=0.001, r= -0.577).

Conclusion

Application of cement combined with DBM procedure is an effective, alternative, and biological treatment in bone tumors that provides immediate stability and stimulates new bone formation on the cortical window.

Retro MTA and tricalcium phosphate/retro MTA for guided tissue regeneration of periodontal dehiscence defects in a dog model: a pilot study

Objectives

Retro MTA is a fast setting Calcium silicate cement used in endodontic regeneration procedures in recent years. Beta-tricalcium phosphate (β-TCP) is another common biomaterial used for bone augmentation procedures. The present pilot study was undertaken to evaluate and compare the efficacy of Retro MTA and a mixture of Retro MTA / β-TCP for periodontal tissue regeneration.

Materials and methods

In 4 beagle dogs, periodontal dehiscence type defects were created. In each side, one dehiscence defect was left empty as a control site and three treatment modalities were randomly applied for the others: Retro MTA covered with a collagen membrane, Retro MTA + β-TCP covered with a membrane and covering the defect with a membrane without any bone augmentation. After 8 weeks Animals were sacrificed and Histomorphometric and histologic analysis were conducted.

Results

Histologic analysis showed more cementum formation for both Retro MTA+ β-TCP (3.74 ± 0.34 mm) and Retro MTA group (3.24 ± 0.56 mm) compared to control group 1 (1. 15 ± 0.45 mm) and control group 2 (0.78 ± 0.65 mm). Formation of newly formed bone and cementum in the experimental groups were significantly higher as compared to the control groups (P < 0.0001).

Conclusions

Retro MTA or Retro MTA+ β-TCP covered with a collagen membrane resulted in regeneration of periodontal tissues. However, Retro MTA+ β-TCP showed tendency towards better results than the use of Retro MTA alone.

The Use of Tantalum Metal in Foot and Ankle Surgery

There are several reconstructive procedures in foot and ankle surgery wherein structural grafts are needed to fill defects, restore height, and maintain correction while providing an osteoconductive environment until fusion occurs. Traditionally used autografts and allografts have their disadvantages and limitations. Porous tantalum, with stiffness similar to bone and its biocompatibility, can be a viable option in foot and ankle reconstructive procedures.

Clinical assessment of 115 cases of hindfoot fusion with two different types of graft: Allograft+DBM+bone marrow aspirate versus autograft+DBM

INTRODUCTION

Nonunion is a common complication (15%) of hindfoot and ankle arthrodesis. Autograft can improve the fusion rate because of its osteoconductive, osteoinductive and osteogenic properties. However, autograft harvesting is a source of morbidity. One alternative is to combine allograft with demineralized bone matrix (DBM) and iliac bone marrow aspirate (BMA). This combination graft has similar biological properties to healthy bone. When used alone, allograft has osteoconductive and sometimes structural properties. DBM provides osteoinduction and improves the osteconductivity. BMA adds cells and thereby osteogenic potential.

HYPOTHESIS

Given its intrinsic properties, allograft-DBM-BMA is as effective as autograft-DBM treatment while simplifying the clinical practice.

MATERIAL AND METHODS

One hundred and fifteen cases of ankle and hindfoot arthrodesis were studied in 82 patients divided in two groups: autograft-DBM vs allograft-DBM-BMA. Treatment effectiveness was assessed using clinical (time to fusion, fusion rate) and radiological (trabecular bone bridge, disappearance of joint space) criteria. A CT scan was done in 60% of cases when fusion could not be confirmed using the clinical and radiological criteria.

RESULTS

There was no significant difference between the two groups in terms of fusion rate, time to fusion, number of heterotopic ossifications, revision rate and quantity of DBM used. The nonunion rate was 18% in the autograft group and 13% in the allograft group. The infection rate was 11% in the autograft and 4% in the allograft group.

DISCUSSION

Allograft-DBM-BMA is an alternative to autograft-DBM that provides similar effectiveness without increasing the number of nonunion or complications. Osteonecrosis and surgical revision are risk factors.

LEVEL OF EVIDENCE

III retrospective study.

The Role of Heparan Sulfate and Perlecan in Bone-regenerative Procedures

Tissue engineering, grafting procedures, regeneration, and tissue remodeling are developing therapeutic modalities with great potential medical value, but these regenerative modalities are not as effective or predictable as clinicians and patients would like. Greater understanding of growth factors, cytokines, extracellular matrix molecules, and their roles in cell-mediated healing processes have made these regenerative therapies more clinically viable and will continue advancing the fields of tissue engineering and grafting. However, millions of oral and non-oral bone-grafting procedures are performed annually, and only a small percentage yield the most desirable results. Here we review the heparan-sulfate-decorated extracellular biomolecule named perlecan and the research relating to its potential as an adjunct in bone-regenerative procedures. The review includes an overview of bone graft substitutes and biological adjuncts to bone-regenerative procedures in medicine as they apply to periodontal disease, alveolar ridge augmentation, and barrier membrane therapy. Perlecan is discussed as a potential biological adjunct in terms of growth factor sequestration and delivery, and promoting cell adhesion, proliferation, differentiation, and angiogenesis. Further, we propose delivery and application schemes for perlecan and/or its domains in bone-regenerative procedures, with particular emphasis on its heparan-sulfate-decorated domain I. The perlecan molecule, with its heparan sulfate glycosylation, may provide a multi-faceted approach for the delivery of a more comprehensive stimulus than other single potential adjuncts currently available for bone-regenerative procedures.

Mechanical-chemical analyses and sub-chronic systemic toxicity of chemical treated organic bovine bone

Sequentially chemical-treated bovine bone was not only evaluated by mechanical and chemical analyses but also implanted into the gluteal muscles of rats for 12 weeks to investigate potential local pathological effects and systemic toxicities. The test (chemical treated bone) and control (heat treated bone) materials were compared using scanning electron microscope (SEM), x-ray diffraction pattern, inductively coupled plasma analysis, and bending strength test. In the SEM images, the micro-porous structure of heat-treated bone was changed to sintered ceramic-like structure. The structure of bone mineral from test and control materials was analyzed as100% hydroxyapatite. The ratio of calcium (Ca) to potassium (P), the main inorganic elements, was same even though the Ca and P percentages of the control material was relatively higher than the test material. No death or critical symptoms arose from implantation of the test (chemical treated bone) and control (physiological saline) materials during 12 weeks. The implanted sites were macroscopically examined, with all the groups showing non-irritant results. Our results indicate that chemical processed bovine bone has a better mechanical property than the heat treated bone and the implantation of this material does not produce systemic or pathological toxicity.

A historical review of common bone graft materials in foot and ankle surgery

Foot and ankle fusion is an important treatment for arthritis and deformities of the ankle and hindfoot. The literature has shown that there are improvements in fusion rates with the addition of bone graft and bone graft substitutes. Today autografts, specifically the iliac crest bone graft (ICBG), continue to be the gold standard despite significant donor site morbidity and nonunion rates, persisting around 10%. To address these drawbacks, bone graft substitutes have been developed. This article includes a historical review of the use, outcomes, and safety of autografts, allografts, and bone graft substitutes, such as ceramics, demineralized bone matrix, and platelet-derived growth factor.

Combination of poly L-lactic acid nanofiber scaffold with omentum graft for bone healing in experimental defect in tibia of rabbits

PURPOSE: To investigate the osteoconductive properties and biological performance of Poly L-lactic acid (PLLA) with omentum in bone defects. METHODS: PLLA nanofiber scaffolds were prepared via electrospinning technique. Forty four New Zealand white female rabbits randomly divided into three groups of 18 rabbits each. Created defects in right tibias were filled in group I with omentum, in group II with PLLA nanofiber scaffold and in group III with combination of the omentum and PLLA. The same defects were created in left tibia of all groups but did not receive any treatment (control group). Histological and histomorphometric evaluations were performed at two, four and six weeks after the implantation. RESULTS: Histological changes on all groups along with the time course were scored and statistical analysis showed that the average scores in group III were significantly higher than the other groups. CONCLUSION: Histomorphometric analysis of bone healing was shown to be significantly improved by the combined PLLA with omentum compared with the other groups, suggesting this biomaterial promote the healing of cortical bone, presumably by acting as an osteoconductive scaffold.

Open reduction and internal fixation of clavicular nonunions with allograft bone substitute

Background:

Biologic augmentation with allograft has shown equivalent healing rates to autograft in several nonunion models. No literature exists clearly demonstrating this in the clavicle. The purpose of this study was to evaluate the healing and complication rates of clavicle nonunions treated solely with open reduction and internal fixation (ORIF) and allograft.

Materials and Methods:

Nineteen clavicle nonunions treated with ORIF and allograft were evaluated retrospectively to assess healing rates and complications based on clinical symptoms and radiographic findings.

Results:

For the 19 patients included and treated with ORIF and allograft, clinical follow-up averaged 15 months. Seven patients were smokers. Although complete radiographic healing was achieved in only 68% of patients, clinical success occurred in 16 (84%) patients who demonstrated full range of motion and strength without pain. The three patients who did not demonstrate full radiographic healing were completely pain free. Five patients experienced complications (26%). Two underwent hardware removal due to persistent irritation after union. Three had a persistent painful nonunion. Each of these three patients was a smoker (P=0.08). Two proceeded to union after revision fixation. The other had hardware failure, which was removed, with a persistent nonunion and did not wish any further treatment.

Conclusion:

ORIF with allograft bone substitute is an acceptable treatment alternative to iliac crest bone graft for clavicle nonunions. However, we did not demonstrate equivalent healing rates to published results utilizing autograft. Smokers were identified to have a trend toward higher failure rates with ORIF augmented with allograft and therefore these patients may be better served by augmenting fixation with autograft.

Level of Evidence:

IV; retrospective comparative study.

Synthesis, characterization, and remodeling of weight-bearing allograft bone/polyurethane composites in the rabbit

The process of bone healing requires the restoration of both anatomy and physiology, and there is a recognized need for innovative biomaterials that facilitate remodeling throughout this complex process. While porous scaffolds with a high degree of interconnectivity are known to accelerate cellular infiltration and new bone formation, the presence of pores significantly diminishes the initial mechanical properties of the materials, rendering them largely unsuitable for load-bearing applications. In this study, a family of non-porous composites has been fabricated by reactive compression molding of mineralized allograft bone particles (MBPs) with a biodegradable polyurethane (PUR) binder, which is synthesized from a polyester polyol and a lysine-derived polyisocyanate. At volume fractions exceeding the random close-packing limit, the particulated allograft component presented a nearly continuous osteoconductive pathway for cells into the interior of the implant. By varying the molecular weight of the polyol and manipulating the surface chemistry of the MBP via surface demineralization, compressive modulus and strength values of 3-6 GPa and 107-172 MPa were achieved, respectively. When implanted in bilateral femoral condyle plug defects in New Zealand White rabbits, MBP/PUR composites exhibited resorption of the allograft and polymer components, extensive cellular infiltration deep into the interior of the implant, and new bone formation at 6 weeks. While later in vivo timepoints are necessary to determine the ultimate fate of the MBP/PUR composites, these observations suggest that allograft bone/polymer composites have potential for future development as weight-bearing devices for orthopedic applications.

Preparation and characterization of a composite of demineralized bone matrix fragments and polylactide beads for bone tissue engineering

A composite that utilizes the osteoinductivity of demineralized bone matrix (DBM) and the attractive characteristics of polylactide (PL) may be useful as a tissue-engineered bone substitute. The objective of this study was to investigate the potential of a composite system consisting of DBM fragments and PL beads to support the attachment and proliferation of multipotent mouse marrow stromal cells and to provide a structure for the cells' differentiation into the osteoblast lineage. Furthermore, the overarching goal was to provide a preliminary assessment of the DBM/PL cultures in order to facilitate the development of injectable composite DBM/PL systems in the long term. Demineralized bone matrix fragments were produced from bovine femurs and polylactide beads were produced by a single emulsion process. Differential scanning calorimetry and gel-permeation chromatography were used to characterize the PL samples. Multipotent mouse marrow stromal cells were cultured on several different substrate mixtures including 100% DBM, 70% DBM:30% PL, 50% DBM:50% PL and 100% PL. Cells were analyzed using a LIVE/DEAD(®) Viability/Cytotoxicity kit as well as scanning electron microscopy. Lactic acid and glucose levels were measured throughout the study. Osteogenic differentiation of the MSCs was assessed with an alkaline phosphatase activity (ALP) assay and RT-PCR for expression of bone sialoprotein, osteocalcin and runt-related transcription factor 2. All cell types attached more readily to DBM fragments than PL beads resulting in more lactic acid production in the samples containing mostly DBM. The ALP activity and gene expression results indicate that the optimal mixture for the D1 line of multipotent mouse marrow stromal cells differentiation into osteoblasts is 100% PL. However, it is likely that the decreased pH in the DBM containing samples resulted in an environment that was not very conducive for osteogenic differentiation.

Technical tricks when using the reamer irrigator aspirator technique for autologous bone graft harvesting

This report describes technical tricks for using the reamer irrigator aspirator to harvest autologous bone graft from the femur. This device is a focus of interest in orthopaedics because it can be used to harvest bone graft from the femoral canal and medial condyle in voluminous quantities. Moreover, according to some authors, the osteogenic potential of this graft is at least as effective as that of autogenous bone obtained from the iliac crest. The reamer irrigator aspirator device has substantially different design characteristics and technicalities compared with those of a standard reamer. First, a guidewire must be redirected into multiple areas, including the center of the distal femur and into both condyles, to harvest ample bone graft. This is accomplished by prebending the guidewire in a stronger fashion than required for regular reaming in the case of femoral nailing procedures. This bend can increase the risk for eccentric reaming as well as lodging of the suctioning device within the femoral canal. Second, the front and lateral drilling surfaces of this device are very sharp and further cleaned and maintained sharp by the irrigation process to permit the surgeon to obtain significant volumes of graft with a single passage of this device. At the same time, however, this sharp front-end cutting design can increase the risk of iatrogenic fracture if reaming is performed without caution. Third, a powerful suctioning device is connected to the reamer such that the blood loss that can occur during continuous reaming, irrigation, and aspiration must be considered with this technique. We hereby discuss these potential dangers and describe the correct use of this device with technical tricks to minimize the risk of unexpected intraoperative events.

Bone morphogenetic proteins in critical-size bone defects: what are the options?

The recent development of new orthopaedic devices and advanced techniques for soft-tissue reconstruction have clearly improved the outcome in trauma and orthopaedic surgery. Nevertheless, large bone defects are still difficult to treat and require a careful analysis of the situation. Individual planning of the reconstructive strategy is desirable. Bone morphogenetic proteins (BMPs) have successfully been applied in the clinical setting for the treatment of spinal fusion, fracture healing and delayed and non-unions. Following the 'diamond concept', surgeons have begun using BMPs for treatment of critical-size defects also--in most cases, 'off label'; different treatment strategies are currently being evaluated. BMPs are often used in combination with autogenic, allogenic, xenogenic or synthetic grafting materials and even with mesenchymal stem cells. In addition, gene therapy approaches present an attractive option. Experimental studies and first clinical results are promising in the use of BMPs for treatment of critical-size defects; however, there is obvious need for further controlled studies to define strategies.

The efficacy of Biobon and Ostim within metaphyseal defects using the Göttinger Minipig

INTRODUCTION

To compare bio, osteocompatibility, rate of resorption and remodeling dynamics of two clinically used bone substitutes.

MATERIALS AND METHODS

In a randomized fashion Biobon and Ostim were implanted bilaterally into the proximal metaphyseal tibiae of 18 Göttinger Minipigs in a direct right versus left "intra-individual" comparison. Fluorescent labelling was used. Microradiographic, histological and morphometric evaluation was carried out at 6, 12 and 52 weeks.

RESULTS

Both bone substitutes showed good biocompatibility, bioactivity and osteoconductivity. The degradation dynamics of both materials differed. Degradation of Ostim stopped after 6 weeks postoperatively, whereas Biobon was degraded slowly but evenly over the time intervals. Only at 6 weeks a significant (P < 0.05) difference in resorption rate was detected. Both Biobon and Ostim showed incomplete resorption after a year.

CONCLUSION

After 1 year no "restitutio ad integrum" could be observed in either group. Similar to ceramics, a thorough osseous incorporation seemed to inhibit further degradation of both bone substitute materials.

Fractures of the hip and osteoporosis: the role of bone substitutes

Failure of fixation is a common problem in the treatment of osteoporotic fractures around the hip. The reinforcement of bone stock or of fixation of the implant may be a solution. Our study assesses the existing evidence for the use of bone substitutes in the management of these fractures in osteoporotic patients. Relevant publications were retrieved through Medline research and further scrutinised. Of 411 studies identified, 22 met the inclusion criteria, comprising 12 experimental and ten clinical reports. The clinical studies were evaluated with regard to their level of evidence. Only four were prospective and randomised. Polymethylmethacrylate and calcium-phosphate cements increased the primary stability of the implant-bone construct in all experimental and clinical studies, although there was considerable variation in the design of the studies. In randomised, controlled studies, augmentation of intracapsular fractures of the neck of the femur with calcium-phosphate cement was associated with poor long-term results. There was a lack of data on the long-term outcome for trochanteric fractures. Because there were only a few, randomised, controlled studies, there is currently poor evidence for the use of bone cement in the treatment of fractures of the hip.

Mesenchymal stem cell allograft in revision foot and ankle surgery: a clinical and radiographic analysis

A review was conducted of 23 patients who underwent implantation of mesenchymal stem cell allograft for revision foot or ankle surgery. Composed of viable mesenchymal stem cells derived from cadaveric donor tissue, the graft had osteogenic, osteoinductive, and osteoconductive properties, and was capable of direct new bone formation at the site of implantation. In all of the cases, radiographic new bone formation was observed at the area of implantation and a 91.3% union rate was observed, and no evidence of graft rejection or complications associated with implantation were recorded. Wilcoxon rank sum tests were used to determine whether gender, diabetes, chronic renal insufficiency, neuropathy, number of previous surgeries, and smoking were associated with time to healing. Spearman's rank correlation coefficient was calculated in an effort to identify the influence of continuous numeric variables on the time to bone healing. Based on the outcomes observed in this retrospective study, it appears that mesenchymal stem cell allograft is a beneficial biological adjunct to bone healing, and serves as a suitable bone autograft substitute in revision foot and ankle surgery.

LEVEL OF CLINICAL EVIDENCE

4.

Biomimetic helical rosette nanotubes and nanocrystalline hydroxyapatite coatings on titanium for improving orthopedic implants

Natural bone consists of hard nanostructured hydroxyapatite (HA) in a nanostructured protein-based soft hydrogel template (ie, mostly collagen). For this reason, nanostructured HA has been an intriguing coating material on traditionally used titanium for improving orthopedic applications. In addition, helical rosette nanotubes (HRNs), newly developed materials which form through the self-assembly process of DNA base pair building blocks in body solutions, are soft nanotubes with a helical architecture that mimics natural collagen. Thus, the objective of this in vitro study was for the first time to combine the promising attributes of HRNs and nanocrystalline HA on titanium and assess osteoblast (bone-forming cell) functions. Different sizes of nanocrystalline HA were synthesized in this study through a wet chemical precipitation process following either hydrothermal treatment or sintering. Transmission electron microscopy images showed that HRNs aligned with nanocrystalline HA, which indicates a high affinity between both components. Some of the nanocrystalline HA formed dense coatings with HRNs on titanium. More importantly, results demonstrated enhanced osteoblast adhesion on the HRN/nanocrystalline HA-coated titanium compared with conventional uncoated titanium. Among all the HRN/nanocrystalline HA coatings tested, osteoblast adhesion was the greatest when HA nanometer particle size was the smallest. In this manner, this study demonstrated for the first time that biomimetic HRN/nanocrystalline HA coatings on titanium were cytocompatible for osteoblasts and, thus, should be further studied for improving orthopedic implants.

Spatial distribution of mineralized bone matrix produced by marrow mesenchymal stem cells in self-assembling peptide hydrogel scaffold

We evaluated the osteogenic differentiation of mesenchymal stem cells (MSCs) using a new class of synthetic self-assembling peptide hydrogels, RADA 16, as a scaffold for three-dimensional culture. MSCs derived from rat bone marrow were culture-expanded and seeded into the hydrogel and further cultured in osteogenic medium containing beta-glycerophosphate, ascorbic acid, and dexamethasone for 2-4 weeks. High alkaline phosphatase activity and osteocalcin (OC) contents were detected at both the protein and gene expression levels during the culture periods. Both calcium and the OC contents increased over time, indicating the growth of a mineralized extracellular matrix within the hydrogel. Moreover, the process of the growth of the mineralized matrix determined by three-dimensional microarchitecture images was obtained by confocal laser scanning microscopy. The findings show that MSCs can differentiate into mature osteoblasts to form mineralized matrices within the hydrogel scaffold. Importantly, the differentiation can occur three dimensionally within the hydrogel, indicating that RADA 16 can be considered attractive synthetic biomaterial for use in bone tissue engineering.

Development of a biodegradable scaffold with interconnected pores by heat fusion and its application to bone tissue engineering

Tissue engineering has been proposed as an approach to alleviate the shortage of donor tissue and organs by combining cells and a biodegradable scaffold as a temporary extracellular matrix. While numerous scaffold fabrication methods have been proposed, tissue formation is typically limited to the surface of the scaffolds in bone tissue engineering applications due to early calcification on the surface. To improve tissue formation, a novel scaffold with a hierarchical interconnected pore structure on two distinct length scales has been developed. Here we present the fabrication process and the application of the scaffold to bone tissue engineering. Porous poly(lactide-co-glycolide) (PLGA) scaffolds were made by combining solvent casting/particulate leaching with heat fusion. Porcine bone marrow-derived mesenchymal stem cells (MSCs) were differentiated into osteoblasts and cultured on these scaffolds in vitro for 2, 4, and 6 weeks. Subsequently, the constructs were assessed using histology and scanning electron microscopy. The bone marrow-derived osteoblasts attached well on these scaffolds. Cells were observed throughout the scaffolds. These initial results show promise for this scaffold to aid in the regeneration of bone.

Fracture healing: the diamond concept

Fracture healing is a complex physiological process. With the latest advances made in molecular biology and genetics it is now known that it involves the spatial and temporal coordinated action of several different cell types, proteins and the expression of hundreds of genes working towards restoring its structural integrity without scar formation. The standard tissue engineering approach to provide solutions for impaired fracture healing, bone restoration and regeneration includes the utilisation of growth factors, scaffolds and mesenchymal stem cells (triangular concept). However, although the mechanical environment is discussed and is considered as an important element in bone regeneration, its importance is often underestimated and it is not always given the necessary attention. The available scientific evidence supports the view that all the 4 known factors contributing to bone restoration should be given an equal acknowledgment and recognition. The traditional discussed triangular concept therefore should be reconsidered and be accepted as the 'diamond concept'.

Use of bone morphogenetic proteins for treatment of non-unions and future perspectives

Still a major problem in orthopedic and trauma surgery is the delayed healing or the non-union of long bone fractures. Demographic data reveal that due to the steadily rising age of the population, complications with the musculoskeletal system will increase during the next years. Bone morphogenetic proteins (BMPs) have successfully been applied in clinic for the treatment of delayed healing and non-unions. The broad difference concerning the indication, timing of treatment, dosage and application technique of BMPs calls for the need to perform further prospective studies in order to standardize the treatment and furthermore optimize the procedures or even develop new therapeutic strategies. For example, the application technique may be improved and in some cases injectable BMP preparations could be of use. Also the coating of implants with growth factors might be valuable in order to stimulate bone healing and to prevent delayed healing or non-union. This article tries to discuss some of the open questions, however can and will not reflect the absolute standard of care. To make the BMP treatment a standard of care, more clinical data and long time experiences are necessary. The intramedullary application of BMP in combination with autologous or allogenic bone grafts or bone substitutes after debridement and stabilization with implants seems to be an adequate procedure for treatment of atrophic non-unions. However, the total number of patients is too small to draw final conclusions. Further clinical studies need to be performed in the future.

Quantification of various growth factors in different demineralized bone matrix preparations

Besides autografts, allografts, and synthetic materials, demineralized bone matrix (DBM) is used for bone defect filling and treatment of non-unions. Different DBM formulations are introduced in clinic since years. However, little is known about the presents and quantities of growth factors in DBM. Aim of the present study was the quantification of eight growth factors important for bone healing in three different "off the shelf" DBM formulations, which are already in human use: DBX putty, Grafton DBM putty, and AlloMatrix putty. All three DBM formulations are produced from human donor tissue but they differ in the substitutes added. From each of the three products 10 different lots were analyzed. Protein was extracted from the samples with Guanidine HCL/EDTA method and human ELISA kits were used for growth factor quantification. Differences between the three different products were seen in total protein contend and the absolute growth factor values but also a large variability between the different lots was found. The order of the growth factors, however, is almost comparable between the materials. In the three investigated materials FGF basic and BMP-4 were not detectable in any analyzed sample. BMP-2 revealed the highest concentration extractable from the samples with approximately 3.6 microg/g tissue without a significant difference between the three DBM formulations. In DBX putty significantly more TGF-beta1 and FGFa were measurable compared to the two other DBMs. IGF-I revealed the significantly highest value in the AlloMatrix and PDGF in Grafton. No differences were accessed for VEGF. Due to the differences in the growth factor concentration between the individual samples, independently from the product formulation, further analyzes are required to optimize the clinical outcome of the used demineralized bone matrix.

Biological enhancement of tibial diaphyseal aseptic non-unions: the efficacy of autologous bone grafting, BMPs and reaming by-products

The mandatory stimulus that can optimise the healing pathway can be electrical, mechanical, biological, or a combination of all these parameters. A variety of means has been utilised for biological enhancement, including extracorporeal shock wave, electrical, ultrasound stimulation, the reaming technique of IM nailing, bone graft substitutes, osteogenic cells and bioactive molecules produced by tissue engineering techniques. The aim of this study is to present a review of the existing evidence for the efficacy of reaming, autologous bone grafting and the commercially available growth factors (BMP-2 and BMP-7) for the treatment of aseptic tibial non-unions. The gold standard method of enhancing bone healing in cases of tibial non-union remains the autologous bone graft. Autogenous bone grafts possess osteoconductive, osteoinductive properties and also osteoprogenitor cells. However, their harvesting is associated with high morbidity and many complications reaching percentages of 30%. Intramedullary reamed nailing, either used as an alternative fixation method or as an exchange to a wider implant, offers the unique biomechanical advantages of an intramedullary device, together with the osteoinductive stimulus of the by-products of reaming, and the aptitude for early weight-bearing and active rehabilitation. The safety of administration of the commercial distributed growth factors (BMP-2 and BMP-7), combined with the lack of the morbidity and the quantity restrictions that characterise autologous bone grafts, have given to this family of molecules a principal role between the other bone graft substitutes. On average the union rates reported in the 20 manuscripts that have been evaluated range from 58.3% to 100%, and the average time to union from 12.5 weeks to 48.4 weeks, indicating the significant discrepancies in the reported evidence and the multiplicity of different treatment strategies.

From the laboratory bench to the patient's bedside: an update on clinical trials with mesenchymal stem cells

Mesenchymal Stem Cells (MSCs) are non-hematopoietic multi-potent stem-like cells that are capable of differentiating into both mesenchymal and non-mesenchymal lineages. In fact, in addition to bone, cartilage, fat, and myoblasts, it has been demonstrated that MSCs are capable of differentiating into neurons and astrocytes in vitro and in vivo. MSCs are of interest because they are isolated from a small aspirate of bone marrow and can be easily expanded in vitro. As such, these cells are currently being tested for their potential use in cell and gene therapy for a number of human diseases. Nevertheless, there are still some open questions about origin, multipotentiality, and anatomical localization of MSCs. In this review, we discuss clinical trials based on the use of MSCs in cardiovascular diseases, such as treatment of acute myocardial infarction, endstage ischemic heart disease, or prevention of vascular restenosis through stem cell-mediated injury repair. We analyze data from clinical trials for treatment of osteogenesis imperfecta (OI), which is a genetic disease characterized by production of defective type I collagen. We describe progress for neurological disease treatment with MSC transplants. We discuss data on amyotrophic lateral sclerosis (ALS) and on lysosomal storage diseases (Hurler syndrome and metachromatic leukodystrophy). A section of review is dedicated to ongoing clinical trials, involving MSCs in treatment of steroid refractory Graft Versus Host Disease (GVHD); periodontitis, which is a chronic disease affecting periodontium and causing destruction of attachment apparatus, heart failure, and bone fractures. Finally, we will provide information about biotech companies developing MSC therapy.

Increased osteoblast adhesion on nanograined Ti modified with KRSR

Peptide sequences such as lysine-arginine-serine-arginine (KRSR) selectively bind transmembrane proteoglycans (e.g. heparin sulfate) of osteoblasts (bone-forming cells) and are, therefore, actively being investigated for orthopedic applications. Further, nanophase materials (or materials with grain or particle sizes less than 100 nm) are promising new materials that promote new bone growth more than compared to conventional (that is, micron grain or particle size) materials. To combine the above two promising approaches for improving orthopedic implants, the objective of this in vitro study was to functionalize titanium (Ti) surfaces (both nanophase and conventional) with KRSR peptides and study their osteoblast cell adhesive properties. Materials were characterized by X-ray photoelectron spectroscopy, scanning electron microscopy, and atomic force microscopy. Results of this in vitro study provided evidence of increased osteoblast adhesion on nanophase compared to conventional Ti whether functionalized with KRSR or not. Results further showed that the immobilization of KRSR onto Ti (both nanophase and conventional) increased osteoblast adhesion compared to respective nonfunctionalized Ti and those functionalized with the negative control peptide KSRR. Most importantly, osteoblast adhesion on nonfunctionalized nanophase Ti increased compared to conventional Ti functionalized with KRSR. Further, select initial osteoblast adhesion was observed to occur at particle boundaries for any type of nanophase and conventional Ti formulated in this study. In summary, results provided evidence that not only should nonfunctionalized nanophase Ti be further studied for improved orthopedic applications but so should nanophase Ti functionalized with KRSR.

Using hydroxyapatite nanoparticles and decreased crystallinity to promote osteoblast adhesion similar to functionalizing with RGD

Better materials are needed to promote bone growth. For this reason, the present study created nanometer crystalline hydroxyapatite (HA) and amorphous calcium phosphate compacts functionalized with the arginine-glycine-aspartic acid (RGD) peptide sequence. Crystalline HA and amorphous calcium phosphate nanoparticles were synthesized by a wet chemical process followed by a hydrothermal treatment for 2 h at 200 degrees C and 70 degrees C, respectively. Resulting particles were then pressed into compacts. For the preparation of conventional HA particles (or those with micron diameters), the aforementioned pressed compacts were sintered at 1,100 degrees C for 2 h. Peptide functionalization was conducted by means of a three step reaction procedure: silanization with 3-aminopropyltriethoxysilane (APTES), cross-linking with N-succinimidyl-3-maleimido propionate (SMP), and finally peptide immobilization. The three step reaction procedure was characterized by a novel 3-(4-carboxybenzoyl)quinoline-2-carboxaldehyde (CBQCA) fluorescence technique. For all materials, results showed that the immobilization of the cell adhesive RGD sequence increased osteoblast (bone-forming cell) adhesion compared to those non-functionalized and those functionalized with the noncell adhesive control peptide (RGE) after 4 h. However, surprisingly, results also showed that the adhesion of osteoblasts on non-functionalized amorphous nanoparticulate calcium phosphate was similar to conventional HA functionalized with RGD. Osteoblast adhesion on nanocrystalline HA (unfunctionalized and functionalized with RGD) was below that of the respective functionalized amorphous calcium phosphate but above that of the respective functionalized conventional HA. In this manner, results of this study suggest that decreasing the particulate size into the nanometer regime and reducing crystallinity of calcium phosphate based materials may promote osteoblast adhesion to the same degree as the well-established techniques of functionalizing conventional HA with RGD.

Chemical Composition and Mechanical Properties of Bio-Derived Compact Bone Scaffolds

To compare the chemical composition and mechanical properties of the bio-derived compact bone scaffold (BDCBS) with the normal compact bone in human. Human compact bone were harvested and divided into control and experimental group. For the latter, BDCBS was prepared with physical and chemical methods. The major components (calcium, phosphorus, collagen protein) and heavy metal contents of the two groups were determined with biochemical assay. Histological examinations were performed to investigate the structure. Cylindroids from the normal compact bone and the BDCBS (6 in each group) were tested under compression. There was no significant difference between the two groups for major components. In addition, there were a few amounts of heavy metal components in BDCBS and control. Histological examinations confirmed the acellular structure in the BDCBS. Results from mechanical testing showed the compressive strength, elastic modulus and ultimate strain (193MPa, 13.76GPa, and 2.3%) of the BDCBS were a bit lower than those (205MPa, 15.67GPa, and 2.5% respectively) of control, but the differences were not statistically significant. In conclusion, there are almost the same matrix structure and composition with similar biomechanical properties between the BDCBS and the control. These results may underscore the potential of the BDCBS in tissue engineering bone.

Rabbit pilot study on the resorbability of three-dimensional bioactive glass fibre scaffolds

Bioactive glass composed of Na2O-K2O-MgO-CaO-B2O3-P2O5-SiO2 is used in this study to manufacture three-dimensional glass fibre scaffolds for a synthetic bone filler material for the treatment of bone defects. The glass is characterized by a large working range, which is the temperature interval at which forming of glass can take place. A preliminary in vivo study on New Zealand skeletally mature rabbit's tibia is reported here. Bone defects were prepared in the medial surfaces of the diaphyses of the tibia. For the first time melt derived three-dimensional bioactive glass fibre constructs were used to fill the cavities. The different implants investigated here were a scaffold with a porosity of 45-50%, scaffold with a porosity of 55-60% and morsels with a porosity of 55-60%. The implanted bone substitutes were dissected after 6 months and evaluated by histological and synchrotron radiation micro tomography analysis. PerioGlas and empty defects were used as positive and negative controls, respectively. The result was that the surgically created tibial defects were healed and new bone formation was found in the medullary cavities. Despite the intrinsic limitations of a pilot study, the preliminary results indicate that in 6 months the glass fibre scaffolds are completely resorbed and that the osteoconductive properties of the filling material are strictly correlated with the structural and morphological characteristics of the bone substitute.

Orthobiologics: a survey of materials and techniques

The modern study of the regenerative capabilities of skeletal tissues began in 1964, when Marshall Urist discovered that bone devoid of inorganic content and dried into a powder could be implanted into the muscle of a rabbit with resultant ectopic bone formation. Use of this technology is now commonplace, and a plethora of orthobiologic materials are available to the foot and ankle surgeon. The science has even become advanced to the point that custom bone replacements can be fabricated in vitro. This points toward an exciting future for the use of this technology by foot and ankle surgeons.

The use of circular wire external fixation in the treatment of salvage ankle arthrodesis

The authors retrospectively reviewed their experience with circular wire external fixation in the treatment of salvage ankle arthrodesis during the past 9 years. The results of 43 cases in a difficult patient population are presented with an average follow-up of 27.0 months. Thirty-three patients (80.5%) went on to achieve a solid fusion or stable pseudarthrosis. A minimum of a 4-ring frame construct was applied for an average of 96.1 days. The major complication rate was 51.2%, including 3 below-knee amputations (7.3%), 7 unstable nonunions (17.1%), 7 cases of osteomyelitis and/or deep-space infection (16.3%), 3 malunions (7.3%), and 2 tibial stress fractures (4.7%). The incidence of complications occurred similarly in patients with Charcot arthropathy, failed total ankle arthroplasty, septic fusion, posttraumatic deformity, or avascular necrosis of the talus, whereas it was relatively higher in patients who were diabetics, smokers, or had an increased body mass index. In addition, the incidence of a nonunion tended to increase with longer follow-up, suggesting that early presumption of a solid union may be erroneous. Based on our defined criteria of a stable, well-aligned fusion without severe pain or activity restrictions, 28 patients (68.3%) had a good result. Circular wire external fixation can be a viable treatment for complex ankle salvage pathology; however, it is difficult to predict the prospects of success or failure.

HA/TCP compounding of a porous CaP biomaterial improves bone formation and scaffold degradation—A long-term histological study

In the present study, two biphasic calcium phosphate biomaterials (BCP) with HA/TCP ratios of 50/50 and 30/70 were obtained from a pure HA biomaterial. The biomaterials which showed the same three-dimensional geometry were implanted into corticocancellous costal defects of sheep. In the specimens of all three biomaterials, abundant bone formation, mineral dissolution from the biomaterial scaffolds, and active cellular resorption of the scaffolds was present after 6 and 12 months. Backscattered electron microscopy showed bone invasion into the pores of the scaffolds and micromechanical interlocking at the bone/biomaterial interface without intervening soft tissue. The pattern of bone formation and scaffold resorption was different for cortical and cancellous bone. No time-based effect, however, was observed. Overall, the BCP biomaterials had formed significantly more bone than the HA biomaterial. Also, scaffold resorption, which was followed by a replacement with newly formed bone, was significantly higher in the BCP biomaterials. Although no significant differences were observed between both BCP biomaterials, the present study had confirmed the assumption that HA/TCP compounding was suitable to improve bone formation and scaffold resorption in the investigated biomaterials and at the same time maintain the osteoconductive properties of the scaffolds.

Osteoinductivity of commercially available demineralized bone matrix. Preparations in a spine fusion model

BACKGROUND

Although autogenous bone is the most widely used graft material for spinal fusion, demineralized bone matrix preparations are available as alternatives or supplements to autograft. They are prepared by acid extraction of most of the mineralized component, with retention of the collagen and noncollagenous proteins, including growth factors. Differences in allograft processing methods among suppliers might yield products with different osteoinductive activities. The purpose of this study was to compare the efficacy of three different commercially available demineralized bone matrix products for inducing spinal fusion in an athymic rat model.

METHODS

Sixty male athymic rats underwent spinal fusion and were divided into three groups of eighteen animals each. Group I received Grafton Putty; Group II, DBX Putty; and Group III, AlloMatrix Injectable Putty. A control group of six animals (Group IV) underwent decortication alone. Six animals from each of the three experimental groups were killed at each of three intervals (two, four, and eight weeks), and the six animals from the control group were killed at eight weeks. At each of the time-points, radiographic and histologic analysis and manual testing of the explanted spines were performed.

RESULTS

The spines in Group I demonstrated higher rates of radiographically evident fusion at eight weeks than did the spines in Group III or Group IV (p < 0.05). Manual testing of the spines at four weeks revealed variable fusion rates (five of six in Group I, two of six in Group II, and none of six in Group III). At eight weeks, all six spines in Group I, three of the six in Group II, and no spine in Group III or IV had fused. Histologic analysis of the spines in Groups I, II, and III demonstrated varying amounts of residual demineralized bone matrix and new bone formation. Group-I spines demonstrated the most new bone formation.

CONCLUSIONS

This study demonstrated differences in the osteoinductive potentials of commercially available demineralized bone matrices in this animal model.

Arthrodesis of the navicular

Isolated arthrodesis of the navicular complex is a means of restoring the integrity of the medial column. This facilitates pain relief and improved function. This option should be considered in the treatment of degenerative disease in these joints. Grade III PTTI may be managed with arthrodesis of the navicular complex , provided degenerative changes are limited to the talonavicular-naviculocuneiform joints. This procedure must include concomitant correction of the hindfoot. Osseous necrosis or bone loss that is due to severe degeneration may be managed successfully with cancellous or structural grafting that is sufficient to maintain the length of the medial column. If extensive grafting increases the risk of nonunion, the navicular or its remnants can be excised and a talocuneiform fusion may be performed. Successful management of conditions that affect the navicular complex requires meticulous attention to restoration of medical column. Optical results also demand consideration of overall alignment and condition of adjacent joints.

Site-specific delivery of acidic fibroblast growth factor stimulates angiogenic and osteogenic responsesin vivo

A major clinical problem in orthopedics is the healing of nonunion fractures. Limitations of this bone repair process include insufficient angiogenesis and mineralization. Integrating appropriate biomaterials with site-specific neovascularization and osteogenesis at the wound site has been the focus of several clinically relevant therapeutic strategies. As an extracellular protein, acidic fibroblast growth factor (FGF-1) induces, coordinates, and sustains site-specific molecular responses associated with angiogenesis and osteogenesis. To establish the ability of this growth factor to coordinate bone regenerative process in vivo, site-specific delivery of FGF-1, entrapped in a fibrin/hydroxyapatite composite, was evaluated. Kinetic analysis in vivo revealed the biocomposite was capable of delivering biologically active FGF-1. Release kinetics revealed an initial delivery of 87.5 ng/h of active FGF-1 in the first 20 h, followed by a reduced delivery of 28 ng/h during the next 20 h. In situ immunohistological analyses demonstrated that FGF-1-containing implants induced increased angiogenesis and infiltration of cells expressing osteogenic related markers (i.e., osteopontin, osteocalcin). Collectively, these efforts support that site-specific delivery of active FGF-1 in a fibrin/hydroxyapatite composite is competent to induce not only angiogenesis but also osteogenic cellular responses.

Functional outcomes of bone graft substitutes for benign bone tumors

Benign bone tumors are frequently treated surgically by intralesional excision with grafting. Due to the significant morbidity associated with autogenous graft, there is interest in bone graft substitutes. Ninety-eight consecutive patients with benign bone tumors treated by intralesional excision with bone graft substitutes were retrospectively reviewed. Functional scores using the International Symposium of Limb Salvage (ISOLS) system were obtained at most recent follow-up. The mean functional score was 28.3 out of 30 (94%). Three patients suffered fractures that ultimately healed with management. There were no local recurrences. Based on results of this study, bone graft substitutes are a reasonable alternative to autogenous grafting with a successful functional outcome.

Use of demineralized bone matrix in ankle/hindfoot fusion

Sixty-three patients who underwent complex ankle or hindfoot fusion had demineralized bone matrix placed in their fusion site to stimulate fusion. Thirty-seven patients had Grafton putty, a demineralized bone matrix product, and 26 patients had Orthoblast, a demineralized bone matrix mixed with crushed cancellous allograft bone placed to stimulate their fusion site. All patients were followed clinically and radiographically to fusion or nonunion. Of the 37 patients who had Grafton putty placed to stimulate ankle or hindfoot fusion, five (14%) developed a nonunion. Of the 26 patients who had Orthoblast placed to stimulate fusion, two (8%) developed a nonunion. These differences were not statistically significant. Nonunion rates of approximately 10% continue to be reported for ankle and hindfoot fusion procedures. In an attempt to minimize this complication, various bone graft substitutes have been used. We found no difference in efficacy of the two demineralized bone matrix compounds, and were not able to demonstrate a superior union rate compared to historical controls.