Bone In-growth Induced by Biphasic Calcium Phosphate Ceramic in Femoral Defect of Dogs

Calcium Phosphate-Based Biomaterials for Bone Repair

Traumatic, tumoral, and infectious bone defects are common in clinics, and create a big burden on patient's families and society. Calcium phosphate (CaP)-based biomaterials have superior properties and have been widely used for bone defect repair, due to their similarities to the inorganic components of human bones. The biological performance of CaPs, as a determining factor for their applications, are dependent on their physicochemical properties. Hydroxyapatite (HAP) as the most thermally stable crystalline phase of CaP is mostly used in the form of ceramics or composites scaffolds with polymers. Nanostructured CaPs with large surface areas are suitable for drug/gene delivery systems. Additionally, CaP scaffolds with hierarchical nano-/microstructures have demonstrated excellent ability in promoting bone regeneration. This review focuses on the relationships and interactions between the physicochemical/biological properties of CaP biomaterials and their species, sizes, and morphologies in bone regeneration, including synthesis strategies, structure control, biological behavior, and the mechanisms of CaP in promoting osteogenesis. This review will be helpful for scientists and engineers to further understand CaP-based biomaterials (CaPs), and be useful in developing new high-performance biomaterials for bone repair.

Sr and Mg Doped Bi-Phasic Calcium Phosphate Macroporous Bone Graft Substitutes Fabricated by Robocasting: A Structural and Cytocompatibility Assessment

Bi-phasic calcium phosphates (BCPs) are considered prominent candidate materials for the fabrication of bone graft substitutes. Currently, supplemental cation-doping is suggested as a powerful path to boost biofunctionality, however, there is still a lack of knowledge on the structural role of such substituents in BCPs, which in turn, could influence the intensity and extent of the biological effects. In this work, pure and Mg- and Sr-doped BCP scaffolds were fabricated by robocasting from hydrothermally synthesized powders, and then preliminarily tested in vitro and thoroughly investigated physically and chemically. Collectively, the osteoblast cell culture assays indicated that all types of BCP scaffolds (pure, Sr- or Sr–Mg-doped) delivered in vitro performances similar to the biological control, with emphasis on the Sr–Mg-doped ones. An important result was that double Mg–Sr doping obtained the ceramic with the highest β-tricalcium phosphate (β-TCP)/hydroxyapatite mass concentration ratio of ~1.8. Remarkably, Mg and Sr were found to be predominantly incorporated in the β-TCP lattice. These findings could be important for the future development of BCP-based bone graft substitutes since the higher dissolution rate of β-TCP enables an easier release of the therapeutic ions. This may pave the road toward medical devices with more predictable in vivo performance.

Safety and feasibility study of using polyphosphate (PolyP) in alveolar cleft repair: a pilot study

BACKGROUND

Bone grafting is an important surgical procedure to reconstruct alveolar bone defects in patients with cleft lip and palate. Polyphosphate (PolyP) is a physiological polymer present in the blood, primarily in platelets. PolyP plays a role as a phosphate source in bone calcium phosphate deposition. Moreover, the cleavage of high-energy bonds to release phosphates provides local energy necessary for regenerative processes. In this study, polyP is complexed with calcium to form Calcium polyP microparticles (Ca-polyP MPs), which were shown to have osteoinductive properties in preclinical studies. The aim of this study was to evaluate the feasibility, safety, and osteoinductivity of Ca-polyP MPs, alone or in combination with BCP, in a first-in-human clinical trial.

METHODS

This single-blinded, parallel, prospective clinical pilot study enrolled eight adolescent patients (mean age 18.1: range 13-34 years) with residual alveolar bone cleft. Randomization in two groups (four receiving Ca-polyP MPs only, four a combination of Ca-polyP MPs and biphasic calcium phosphate (BCP)) was performed. Patient follow-up was 6 months. Outcome parameters included safety parameters and close monitoring of possible adverse effects using radiographic imaging, regular blood tests, and physical examinations. Osteoinductivity evaluation using histomorphometric analysis of biopsies was not possible due to COVID restrictions.

RESULTS

Due to surgical and feasibility reasons, eventually, only 2 patients received Ca-polyP MPs, and the others the combination graft. All patients were assessed up to day 90. Four out of eight were able to continue with the final assessment day (day 180). Three out of eight were unable to reach the hospital due to COVID-19 restrictions. One patient decided not to continue with the study. None of the patients showed any allergic reactions or any remarkable local or systematic side effects. Radiographically, patients receiving Ca-polyP MPs only were scored grade IV Bergland scale, while patients who got the BCP/Ca-polyP MPs combination had scores ranging from I to III.

CONCLUSIONS

Our results indicate that Ca-polyP MPs and the BCP/Ca-polyP MPs combination appear to be safe graft materials; however, in the current setting, Ca-polyP MPs alone may not be a sufficiently stable defect-filling scaffold to be used in alveolar cleft repair.

TRIAL REGISTRATION

Indonesian Trial Registry under number INA-EW74C1N by the ethical committee of Faculty of Medicine, Hasanuddin University, Makassar, Indonesia with code number 1063/UN4.6.4.5.31/PP36/2019 .

Improved Biocompatible, Flexible Mesh Composites for Implant Applications via Hydroxyapatite Coating with Potential for 3-Dimensional Extracellular Matrix Network and Bone Regeneration

Hydroxyapatite (HA)-coated metals are biocompatible composites, which have potential for various applications for bone replacement and regeneration in the human body. In this study, we proposed the design of biocompatible, flexible composite implants by using a metal mesh as substrate and HA coating as bone regenerative stimulant derived from a simple sol-gel method. Experiments were performed to understand the effect of coating method (dip-coating and drop casting), substrate material (titanium and stainless steel) and substrate mesh characteristics (mesh size, weave pattern) on implant's performance. HA-coated samples were characterized by X-ray diffractometer, transmission electron microscope, field-emission scanning electron microscope, nanoindenter, polarization and electrochemical impedance spectroscopy, and biocompatibility test. Pure or biphasic nanorod HA coating was obtained on mesh substrates with thicknesses varying from 4.0 to 7.9 μm. Different coating procedures and number of layers did not affect crystal structure, shape, or most intense plane reflections of the HA coating. Moduli of elasticity below 18.5 GPa were reported for HA-coated samples, falling within the range of natural skull bone. Coated samples led to at least 90% cell viability and up to 99.5% extracellular matrix coverage into a 3-dimensional network (16.4% to 76.5% higher than bare substrates). Fluorescent imaging showed no antagonistic effect of the coatings on osteogenic differentiation. Finer mesh size enhanced coating coverage and adhesion, but a low number of HA layers was preferable to maintain open mesh areas promoting extracellular matrix formation. Finally, electrochemical behavior studies revealed that, although corrosion protection for HA-coated samples was generally higher than bare samples, galvanic corrosion occurred on some samples. Overall, the results indicated that while HA-coated titanium grade 1 showed the best performance as a potential implant, HA-coated stainless steel 316 with the finest mesh size constitutes an adequate, lower cost alternative.

In vitro study of alginate-gelatin scaffolds incorporated with silica NPs as injectable, biodegradable hydrogels

Porous substrates composed of biodegradable polymers and nanoparticles have found extensive use as three-dimensional (3D) scaffolds to regenerate damaged tissues through the incorporation of cells or growth factors. Here, injectable thermally responsive hydrogels based on SiO₂ nanoparticles (NPs), alginate, and gelatin biopolymers, with possible utilization for cartilage tissue engineering, are introduced. The nanocomposites contain different amounts of SiO₂ NPs for reinforcement and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC)/N-hydroxysuccinimide (NHS) for chemical crosslinking of polymer chains in the 3D hydrogel network. The cross-sectional structure of the hydrogels containing 0.25, 1.5, and 3.0% SiO₂ NPs was observed by FE-SEM, confirming porous morphology with interconnected pores. Based on the rheometer analyses, by increasing the amount of SiO₂ NPs, the mechanical strength of the gels can be found. In addition, in vitro biodegradation studies show that the hydrogels without SiO₂ are more unstable than the hydrogels containing SiO₂ NPs. In vitro biocompatibility of the products tested by MTT assay indicates that cell viability and attachment depend on the presence of SiO₂ NPs.

Thermoresponsive oxidized alginate/gelatin/SiO₂ NPs injectable hydrogels have great potential in cartilage tissue engineering due to low gelation time (120 s) and body temperature gelation (37 °C).

The Use of Biphasic Calcium Phosphate Substitute (BCP) in Mandibular Defects in Dogs: Use of CBCT to Evaluate Bone Healing

This study aimed to assess the use of cone beam computed tomography (CBCT) to follow-up bone healing of mandibular bone defects in dogs, filled with a combination of autologous blood and millimetric BCP granules. CBCT was performed ≥4 weeks postoperatively. CBCT gray-scale values were measured from multiplanar reconstructions of the defects and compared to that of normal contralateral mandibular bone and to pure BCP/blood composite time 0 (T0) value. Other parameters, determined by affecting grades according to specific criteria included: bone ridge margin restoration; biomaterial homogeneity; bone-biomaterial interface. Results: 8 dogs with 14 defects were included. Median age was 7.2 years (1-15 years). Follow-up CBCT was performed 1 to 7.5 months postoperatively (mean 3.3 months). Defect CBCT gray-scale values at follow-up were significantly greater than T0 (p < 0.05). Ratios of maximum and minimum densities of the defects to contralateral mandibular bone followed a linear correlation with time (p < 0.05). The bone ridge margin was adequately restored in all the defects and significantly correlated with time (p = 0.03). Biomaterial homogeneity was fair to good in 11 defects and significantly correlated with the bone ridge margin parameter (p = 0.05) and time (p = 0.006). There was no significant correlation with the bone-material interface. The latter was satisfactory in 12 defects and significantly correlated with time (p = 0.01) but not with the other parameters. The biomaterial was more homogeneous in smaller defects and with increasing time. CBCT allowed effective assessment of bone healing via the measurement of CBCT gray-scale values and assessment of multiple radiological variables.

Microwave processing of calcium phosphate and magnesium phosphate based orthopedic bioceramics: A state-of-the-art review

The main theme of this paper is to review microwave-assisted synthesis and processing of calcium and magnesium phosphate bioceramics. Microwave processing of advanced materials has been an active field of research for the last three decades and has been already reviewed in the literature. Microwave processing of bioceramics is being pursued for almost the same period of time. Unfortunately, to the best of our knowledge, we are not aware of any comprehensive review in the literature. Our group has been a significant contributor to the field, and we feel that it is an appropriate time for reviewing the state-of-the-art of the field. The paper is divided into several sections. After rationalizing the motivation behind writing this paper in the introduction, the second section builds on some fundamental aspects of microwave-matter interactions. The third section, representing the synthesis aspects, is subdivided into five sub-sections focusing on various calcium and magnesium phosphates in both crystalline and amorphous forms. The fourth section focuses on magnesium phosphate-based bioceramics. The fifth and the sixth section describe results on the utility of microwave assistance in developing multi-functional coatings on medical implants and orthopedic cements respectively. The subsequent section reviews results on microwave sintering of calcium and magnesium phosphates. The paper concludes with remarks on unresolved issues and future directions of research. It is expected that this comprehensive review on the interdisciplinary topic will further propel the exploration of other novel applications of microwave technology in processing biomaterials by a diverse group of scientists and engineers. STATEMENT OF SIGNIFICANCE: 1. This review highlights the broad-spectrum capabilities of microwave applications in processing orthopedic bioceramics. 2. The article covers "processing" in the broadest sense of the word, comprising of material synthesis, sintering, coating formation, and setting of orthopedic cements. It also expands beyond conventional calcium phosphates to include the emergent family of magnesium phosphates. 3. In vitro/in vivo responses of microwave-processed bioceramics are discussed thus providing an integral understanding of biological aspects of these materials. 4. The comprehensive review on this interdisciplinary topic will help researchers in various disciplines to appreciate the significance and usefulness of microwaves in biomaterials processing. Further, we also believe that it will propel the exploration of other novel applications of microwave technology in the biomaterials sector.

Femoral interference screw fixation of hamstring and quadriceps tendons for ACL reconstruction

PURPOSE

This cadaveric study compares the biomechanical properties of femoral graft fixation in ACL reconstruction of either quadriceps or hamstring tendon grafts with four different interference screws. The hypothesis was that quadriceps tendon grafts provide at least equal results concerning gap formation during cyclic loading and ultimate failure load compared to hamstring tendon grafts with four different interference screws.

METHODS

Eighty porcine femora underwent interference screw fixation of human tendon grafts for ACL reconstruction. Either quadriceps (Q) or hamstring (H) tendon grafts and four different bioabsorbable interference (Wolf (W), Storz (S), Mitek (M), Arthrex (A)) screws were used, resulting in 8 groups with 10 specimens per groups (WQ, WH, SQ, SH, MQ, MH, AQ, AH). Biomechanical analysis included pretensioning the constructs with 60 N for 30 s, then cyclic loading of 500 cycles between 60 and 250 N at 1 Hz in a servohydraulic testing machine, with measurement of elongation and stiffness including video measurements. After this, ultimate failure load and failure mode analysis were performed.

RESULTS

No statistically significant difference could be noted between the groups regarding gap formation during cyclic loading [Cycles 21-500 (mm): WQ 3.6 ± 0.8, WH 3.9 ± 1.4, SQ 3.6 ± 0.8, SH 3.3 ± 1.5, MQ 4.3 ± 0.8, MH 4.6 ± 1.0, AQ 4.8 ± 0.8, AH 4.3 ± 1.5, n.s.], stiffness during cyclic loading [Cycles 21-500 (N/mm): WQ 72.9 ± 16.9, WH 71.6 ± 20.7, SQ 69.5 ± 23.9, SH 77.4 ± 25.1, MQ 59.6 ± 11.2, MH 48.4 ± 15.4, AQ 48.8 ± 12.7, AH 51.9 ± 22.2, n.s.], and ultimate failure load [(N): WQ 474.4 ± 88.0, WH 579.3 ± 124.2, SQ 493.9 ± 105.2, SH 576.0 ± 90.4, MQ 478.6 ± 59.0, MH 543.9 ± 119.7, AQ 480.2 ± 93.8, AH 497.8 ± 74.2, n.s.].

CONCLUSIONS

Quadriceps tendon grafts yield comparable biomechanical results for femoral interference screw fixation in ACL reconstruction compared to hamstring tendon grafts. From a clinical perspective, quadriceps tendon grafts should therefore be considered as a good option in ACL reconstruction in the future.

Calcium Phosphate Bioceramics: A Review of Their History, Structure, Properties, Coating Technologies and Biomedical Applications

Calcium phosphate (CaP) bioceramics are widely used in the field of bone regeneration, both in orthopedics and in dentistry, due to their good biocompatibility, osseointegration and osteoconduction. The aim of this article is to review the history, structure, properties and clinical applications of these materials, whether they are in the form of bone cements, paste, scaffolds, or coatings. Major analytical techniques for characterization of CaPs, in vitro and in vivo tests, and the requirements of the US Food and Drug Administration (FDA) and international standards from CaP coatings on orthopedic and dental endosseous implants, are also summarized, along with the possible effect of sterilization on these materials. CaP coating technologies are summarized, with a focus on electrochemical processes. Theories on the formation of transient precursor phases in biomineralization, the dissolution and reprecipitation as bone of CaPs are discussed. A wide variety of CaPs are presented, from the individual phases to nano-CaP, biphasic and triphasic CaP formulations, composite CaP coatings and cements, functionally graded materials (FGMs), and antibacterial CaPs. We conclude by foreseeing the future of CaPs.

Flexure-Based Device for Cyclic Strain-Mediated Osteogenic Differentiation

Application of low-magnitude strains to cells on small-thickness scaffolds, such as those for rodent calvarial defect models, is problematic, because general translation systems have limitations in terms of generating low-magnitude smooth signals. To overcome this limitation, we developed a cyclic strain generator using a customized, flexure-based, translational nanoactuator that enabled generation of low-magnitude smooth strains at the subnano- to micrometer scale to cells on small-thickness scaffolds. The cyclic strain generator we developed showed predictable operational characteristics by generating a sinusoidal signal of a few micrometers (4.5 μm) without any distortion. Three-dimensional scaffolds fitting the critical-size rat calvarial defect model were fabricated using poly(caprolactone), poly(lactic-co-glycolic acid), and tricalcium phosphate. Stimulation of human adipose–derived stem cells (ASCs) on these fabricated scaffolds using the cyclic strain generator we developed resulted in upregulated osteogenic marker expression compared to the nonstimulated group. These preliminary in vitro results suggest that the cyclic strain generator successfully provided mechanical stimulation to cells on small-thickness scaffolds, which influenced the osteogenic differentiation of ASCs.

Short-term evaluation of electromagnetic field pretreatment of adipose-derived stem cells to improve bone healing

An electromagnetic field is an effective stimulation tool because it promotes bone defect healing, albeit in an unknown way. Although electromagnetic fields are used for treatment after surgery, many patients prefer cell-based tissue regeneration procedures that do not require daily treatments. This study addressed the effects of an electromagnetic field on adipose-derived stem cells (ASCs) to investigate the feasibility of pretreatment to accelerate bone regeneration. After identifying a uniform electromagnetic field inside a solenoid coil, we observed that a 45 Hz electromagnetic field induced osteogenic marker expression via bone morphogenetic protein, transforming growth factor β, and Wnt signalling pathways based on microarray analyses. This electromagnetic field increased osteogenic gene expression, alkaline phosphate activity and nodule formation in vitro within 2 weeks, indicating that this pretreatment may provide osteogenic potential to ASCs on three-dimensional (3D) ceramic scaffolds. This pretreatment effect of an electromagnetic field resulted in significantly better bone regeneration in a mouse calvarial defect model over 4 weeks compared to that in the untreated group. This short-term evaluation showed that the electromagnetic field pretreatment may be a future therapeutic option for bone defect treatment.

A modified intramedullary nail interlocking design yields improved stability for fatigue cycling in a canine femur fracture model

Intramedullary nailing has evolved to become the standard of care for most diaphyseal femoral and tibial fractures, as well as an expanding number of metaphyseal fractures. Owing to the unstable nature of some fractures, the intramedullary device may be subjected to significant stresses owing to a lack of solid cortical contact after nailing. In such cases, excessive interfragmentary motion (due to construct toggle) has been shown to occur. Such motion increases the likelihood of a non- or delayed-union. In the current study, two versions of a modified, angle stable interlocking design were subjected to fatigue testing in a segmental defect fracture model representing a canine femur. As a control, a third group of constructs were stabilized with a traditional nail that allowed a small amount of toggle. All constructs were subjected to 50,000 fatigue cycles representing 12 weeks of cage activity at physiologic levels of combined axial-torsional loading. Torsional testing pre- and post-fatigue revealed 4.6 +/- 1.3 degrees of toggle in the traditional nail and no toggle with the angle stable nail designs. The stable nails were also significantly stiffer in axial compression and torsion before and after cycling. These data indicate that the enhanced stability of the modified interlocking designs can be maintained throughout fatigue cycling in a challenging fracture model.

Biphasic, triphasic and multiphasic calcium orthophosphates

Biphasic, triphasic and multiphasic (polyphasic) calcium orthophosphates have been sought as biomaterials for reconstruction of bone defects in maxillofacial, dental and orthopedic applications. In general, this concept is determined by advantageous balances of more stable (frequently hydroxyapatite) and more resorbable (typically tricalcium orthophosphates) phases of calcium orthophosphates, while the optimum ratios depend on the particular applications. Therefore, all currently known biphasic, triphasic and multiphasic formulations of calcium orthophosphate bioceramics are sparingly soluble in water and, thus, after being implanted they are gradually resorbed inside the body, releasing calcium and orthophosphate ions into the biological medium and, hence, seeding new bone formation. The available formulations have already demonstrated proven biocompatibility, osteoconductivity, safety and predictability in vitro, in vivo, as well as in clinical models. More recently, in vitro and in vivo studies have shown that some of them might possess osteoinductive properties. Hence, in the field of tissue engineering biphasic, triphasic and multiphasic calcium orthophosphates represent promising biomaterials to construct various scaffolds capable of carrying and/or modulating the behavior of cells. Furthermore, such scaffolds are also suitable for drug delivery applications. This review summarizes the available information on biphasic, triphasic and multiphasic calcium orthophosphates, including their biomedical applications. New formulations are also proposed.

Human endothelial colony forming cells undergo vasculogenesis within biphasic calcium phosphate bone tissue engineering constructs

An important consideration in bone regeneration is the need for expedited neovascularization within the defect site. Formation of a vascular network is critical for cell viability and normal function leading to tissue regeneration, but spontaneous angiogenesis is too slow to yield sufficient vessel formation. In this pilot study, human umbilical cord blood (hUCB)-derived endothelial colony forming cells (ECFCs) were evaluated for in vivo vasculogenesis in the macropores of biphasic calcium phosphate (BCP)/bone morphogenetic protein-2 (BMP-2) bone tissue engineering constructs. Constructs were implanted on the abdominal wall of NOD/SCID mice for 4 weeks. This study demonstrated in vivo vasculogenesis by human ECFCs within the macropore space of BCP/BMP-2 constructs. The human ECFC-derived vessels anastomosed with the host vasculature and perfused vessels were visible in the very center of the 5mm diameter, 2.5mm tall scaffolds. Additionally, the vessels were evenly distributed throughout the construct. This study suggests that scaffolds containing ECFCs have significant potential for expedited neovascularization in bony defects.

A Computational and Cellular Solids Approach to the Stiffness-Based Design of Bone Scaffolds

We derive a cellular solids approach to the design of bone scaffolds for stiffness and pore size. Specifically, we focus on scaffolds made of stacked, alternating, orthogonal layers of hydroxyapatite rods, such as those obtained via micro-robotic deposition, and aim to determine the rod diameter, spacing and overlap required to obtain specified elastic moduli and pore size. To validate and calibrate the cellular solids model, we employ a finite element model and determine the effective scaffold moduli via numerical homogenization. In order to perform an efficient, automated execution of the numerical studies, we employ a geometry projection method so that analyses corresponding to different scaffold dimensions can be performed on a fixed, non-conforming mesh. Based on the developed model, we provide design charts to aid in the selection of rod diameter, spacing and overlap to be used in the robotic deposition to attain desired elastic moduli and pore size.

Fabrication of oxidized alginate-gelatin-BCP hydrogels and evaluation of the microstructure, material properties and biocompatibility for bone tissue regeneration

Composite hydrogel systems consisting of oxidized alginate, gelatin, and biphasic calcium phosphate were fabricated by the Schiff-base reaction and the effect of oxidation of alginate on the microstructure, material properties, and biocompatibility were evaluated. Alginate was modified by oxidizing the attached −OH groups to a −CHO group to facilitate interactions with the −NH2 groups of gelatin. The increased interactions between the functional groups had several effects on the materials properties, physical behaviors, and bio-compatibility. A higher degree of oxidation and thereby a higher extent of crosslinking between the −CHO and −NH2 groups resulted in an increase in water uptake and compressive strength, which was associated with a decrease in porosity, gelation time, bio-degradation rate, and to a smaller degree, biocompatibility. The hydrogel structure was highly porous and showed unique channel zed morphology with an extensive branching of the channels. The channels were not continuous and were divided into multiple segments by thin separators that were 5 µm thick and branched off of the 10–25 µm thick frame. The pores in the hydrogel system were interconnected and the porosity ranged from 44.45 to 67.89% with a pore size ranging from 100 to 300 µm. The compressive stress failure of the wet hydrogel was at 12.0 ± 1.2 MPa when the degree of alginate oxidation was 66.6%. The biocompatibility of the hydrogel system was excellent, although it was slightly lowered by oxidation. These hydrogels are promising biomaterials for bone regeneration with adjustable gelation and bio-degradation time, good mechanical strength, and excellent bio-compatibility.

Osteogenic differentiation of human adipose-derived stem cells induced by osteoinductive calcium phosphate ceramics

Microstructure is indispensable for the osteoinduction of calcium phosphate ceramics. To study how microstructure takes its role and explore the mechanism of the osteoinduction, we evaluated attachment, proliferation, alkaline phosphatase (ALP)/DNA, protein/DNA, and mineralization of human adipose-derived stem cells cultured on two kinds of biphasic calcium phosphate (BCP) ceramic discs with the same chemistry and dimension, but different microporosity and surface area. BCP-A had been found osteoinductive in vivo while BCP-B was not. During the conventional culture, ALP/DNA and protein/DNA of the cell on BCP-A with larger surface area were significantly higher than those of the cells on BCP-B. With the adsorption of the proteins in culture medium with 50% fetal bovine serum (FBS) in advance, the increments of the ALP/DNA and protein/DNA for the BCP-A were found respectively significantly more than the increments of those for BCP-B, suggesting that the larger amount of protein adsorbed on the BCP-A was crucial. More results showed that ALP/DNA and protein/DNA of the cells on the two kinds of discs presoaked in culture medium having additional rhBMP-2 were found to be both higher than those of the cells on the discs resoaked in culture medium with 50% FBS, and that those values for BCP-A increased much more. Furthermore, larger mineral content was found on BCP-A than on BCP-B at day 7. The results indicated that by increasing microporosity and thus surface areas, osteoinductive calcium phosphate ceramics concentrate more proteins, including bone-inducing proteins, and thereafter stimulate inducible cells in soft tissues to form inductive bone.

Mesenchymal stem cells accelerate bone allograft incorporation in the presence of diabetes mellitus

Allograft (Allo) incorporation in the presence of a systemic disease like diabetes mellitus (DM) is becoming a major issue in the orthopedic community. Mesenchymal stem cells (MSC) are multipotent stem cells that may be derived from adult, whole bone marrow and have been shown to induce bone formation in segmental defects when combined with the appropriate carrier/scaffold. The objectives of this study were to analyze the effect of DM upon Allo incorporation in a segmental rat femoral defect and to also investigate MSC augmentation of Allo incorporation. Segmental (5 mm) femoral defects were created in non-DM and DM rats and treated with Allo containing demineralized bone matrix (DBM) or DBM with MSC augmentation. Histological scoring at 4 weeks demonstrated less mature bone in the DM/DBM group compared to its non-DM counterpart (p < 0.001). However, there was significantly more mature bone in the DM/MSC group when compared to the DM/DBM group at both 4 and 8 weeks (p < 0.001 and p = 0.004). Furthermore, significantly more bone formation was observed in the DM/MSC group compared to the DM/DBM group at the 4-week time point (p < 0.001). The results of this study suggest that MSC are a potential adjunct for bone regeneration when implanted in an orthotopic site in the presence of DM.

Biphasic calcium phosphate in periapical surgery

Calcium phosphate ceramics like hydroxyapatite and beta -tricalcium phosphate (beta -TCP) possess mineral composition that closely resembles that of the bone. They can be good bone substitutes due to their excellent biocompatibility. Biphasic calcium phosphate is a bone substitute which is a mixture of hydroxyapatite and beta -tricalcium phosphate in fixed ratios. Studies have demonstrated the osteoconductive potential of this composition. This paper highlights the clinical use of biphasic calcium phosphate as a bone substitute in periapical surgery.

Remodeling potentials of biphasic calcium phosphate granules in open wedge high tibial osteotomy

INTRODUCTION

Biphasic calcium phosphate (BCP) has proved to be an effective bone substitute, but it's effectiveness and remodeling potential in open wedge high tibial osteotomy (OWHTO) has not been analyzed yet. This study sought to evaluate the bone healing and remodeling potentials of BCP granules using a radiographic rating system in biplanar OWHTO.

MATERIALS AND METHODS

Fifteen patients (15 knees) underwent biplanar OWHTO. Bone gaps were filled with BCP granules. For radiographic evaluation, remodeling was divided into four phases. Phase 1 was accepted as rounded osteotomy sites, with clear distinction between BCP and bone, phase 2 was accepted as whitened osteotomy sites, with distinction between BCP and bone still visible, phase 3 was accepted as distinction between BCP and bone not visible and cloudy bone formation and phase 4 was accepted as full reformation of BCP granules (4A-BCP visible, 4B-disappearence of BCP) with no sign of osteotomy. Bone union was confirmed with clinical (full weight bearing without pain) and radiographic evaluation (cortical bridging callus on radiographs and phase 3 or greater remodeling). The time to full remodeling and the starting point of the consolidation on anteroposterior radiographs were noted. Complications were also noted at each clinical follow-up.

RESULTS

Mean follow-up was 27.2 months. The mean age was 55.8 years. At clinical follow-up, there were no wound healing problems, no loss of corrections, no infections, and no complications. All osteotomies successfully healed. According to the radiologic classification system, at the 6th week, 73.3% (11/15) of patients were in phase 1 and the remaining 26.7% (4/15) were in phase 2. At 12-month follow-up, 46.7 (7/15) of the patients were still in phase 3. After 2 years, all radiographs showed to be in phase 4A. Radiographic union was noted to progress from lateral to medial and finally central.

CONCLUSIONS

BCP can be successfully used as a bone substitute. The radiographic remodeling and consolidation process of BCP was found to be different from that of beta-tricalcium phosphate. In our patients with more than 2 years of follow-up, BCP granules did not completely remodel. As a result, this clinical study demonstrated that calcium phosphate granules containing hydroxyapatite had a long period of "creeping substitution" that lasts longer than 2 years.

Fracture healing in India: Available therapies, indications, and protocols

The availability of fracture healing therapies to the general public is limited in India. The infrastructure of the health system in India, involving both public and private sectors, does not provide adequate opportunity for rural and low-income inhabitants to access needed care. Also the lack of funding from the government and the overall lack of physicians place a large strain on the system. This paper will take an in-depth look at the state of the current health care system and how it affects bone stimulation therapy in India. The Indian Journal of Orthopaedics was used as a reference for the bone stimulation therapies currently utilized in India. A general search of the therapies and technologies was performed to determine protocols and indications. A table of fracture healing therapies and technologies was composed which provides a description of each therapy, as well as its specific indications and protocols. This information was then used by the authors to hypothesize the most feasible methods of fracture healing to meet the Indian demographic. Based on an assessment of the health system of India, the most practical methods of bone stimulation therapy were determined. It was also determined that nearly all forms of therapy could be made available if sufficient resources were set aside for it. Bone stimulation therapy in India remains a large void in the health care system.

BMP-2 incorporated in a tricalcium phosphate bone substitute enhances bone remodeling in sheep

Bone morphogenetic protein-2 (BMP-2) is a well-known osteoinductive protein, which requires a carrier for local application. As an alternative to the previously described carriers, an in situ hardening, resorbable, and osteoconductive beta-tricalcium phosphate cement (TCP) is tested. Trepanation defects in the bovine distal femoral epiphysis are filled with a composite consisting of TCP and 200 microg rhBMP-2 per cm3 TCP, autologous bone graft, pure TCP, or left empty. A radiological follow-up is performed after 7 weeks and 3 months. The sheep are euthanized and bone samples are analyzed by microradiography, histology, and histomorphometry. Microradiography and histology show similar results for pure TCP and the composite. The defects are filled with trabecular bone and newly formed bone is in close contact with the remaining TCP-particles. The majority of the cement is resorbed, in the composite group the amount of remaining cement particles is reduced. Defects treated with autologous bone graft are filled completely, while untreated defects shows only a small amount of bone originating from the rim of the defect. Histomorphometry of the defects treated with pure TCP shows a significantly increased bone content in comparison to defects treated with the composite or autologous bone graft. Analysis of the remaining cement particles shows significantly less cement in the TCP/rhBMP-2 group in comparison to pure TCP. The sum of bone and cement content in the rhBMP-2 group shows amounts comparable to the calcified structures found following autologous bone grafting. The addition of rhBMP-2 to the TCP leads to faster remodeling of the defect comparable to autologous bone graft, while defects treated with pure TCP are not completely remodeled.

Review: Mineralization of Synthetic Polymer Scaffolds for Bone Tissue Engineering

It has repeatedly been shown that demineralization improves the ability of bone auto- and allografts to regenerate natural bone tissue. Conversely, much work in the field of bone tissue engineering has used composite materials consisting of a mineralized phase or materials designed to mineralize rapidly in situ. In this review, we seek to examine these disparate roles of mineralization and the underlying factors that cause this discordance and to examine methods and principles of the mineralization of synthetic polymer scaffolds. Biomimetic approaches to mineralization and phosphorus-containing materials are highlighted, and a brief section focusing on drug-delivery strategies using mineralized scaffolds is included.

Growth of osteoblast-like cells on biomimetic apatite-coated chitosan scaffolds

Porous scaffold materials that can provide a framework for the cells to adhere, proliferate, and create extracellular matrix are considered to be suitable materials for bone regeneration. Interconnected porous chitosan scaffolds were prepared by freeze-drying method, and were mineralized by calcium and phosphate solution by double-diffusion method to form nanoapatite in chitosan matrix. The mineralized chitosan scaffold contains hydroxyapatite nanocrystals on the surface and also within the pore channels of the scaffold. To assess the effect of apatite and porosity of the scaffolds on cells, human osteoblast (SaOS-2) cells were cultured on unmineralized and mineralized chitosan scaffolds. The cell growth on the mineralized scaffolds and on the pure chitosan scaffold shows a similar growth trend. The total protein content and alkaline phosphatase enzyme activity of the cells grown on scaffolds were quantified, and were found to increase over time in mineralized scaffold after 1 and 3 weeks of culture. The electron microscopy of the cell-seeded scaffolds showed that most of the outer macropores became sealed off by a continuous layer of cells. The cells spanned around the pore wall and formed extra cellular matrix, consisting mainly of collagen in mineralized scaffolds. The hydroxyproline content also confirmed the formation of the collagen matrix by cells in mineralized scaffolds. This study demonstrated that the presence of apatite nanocrystals in chitosan scaffolds does not significantly influence the growth of cells, but does induce the formation of extracellular matrix and therefore has the potential to serve for bone tissue engineering.

Biodegradable Composite Implants

Biodegradable implants are established in the field of operative sports medicine. So-called composite implants are increasingly used. The idea to improve biocompatibility and osteoconductivity of biodegradable polymers by modifying them with a ceramic component, has led to the development of these composite implants. Today, an increasing variety of composite implants are available. They have substantially different material characteristics, which depend on matrix polymer choice and the additional ceramic. The material characteristics influence the mechanical properties, in vivo degradation, the osseous replacement and the host-tissue response. It is important to understand their biologic base for a better knowledge of the advantages and risks associated with using composite implants in the field of operative sports medicine. The purpose of this review is to focus on current developments in biodegradable composite implants and their biologic base.

Autologous human-derived bone marrow cells exposed to a novel TGF-β1 fusion protein for the treatment of critically sized tibial defect

We report the first clinical case of transplantation of autologous bone marrow-derived cells in vitro exposed to a novel recombinant human transforming growth factor (rhTGF)-β1 fusion protein bearing a collagen-binding domain (rhTGF-β1-F2), dexamethasone (DEX) and β-glycerophosphate (β-GP). When such culture-expanded cells were loaded into porous ceramic scaffolds and transplanted into the bone defect of a 69-year-old man, they differentiated into bone tissue. Marrow cells were obtained from the iliac crest and cultured in collagen gels impregnated with rhTGF-β1-F2. Cells were selected under serum-restricted conditions in rhTGF-β1-F2-containing medium for 10 days, expanded in 20% serum for 22 days and osteoinduced for 3 additional days in DEX/β-GP-supplemented medium. We found that the cell number harvested from rhTGF-β1-F2-treated cultures was significantly higher (2.3- to 3-fold) than that from untreated cultures. rhTGF-β1-F2 treatment also significantly increased alkaline phosphatase activity (2.2- to 5-fold) and osteocalcin synthesis, while calcium was only detected in rhTGF-β1-F2-treated cells. Eight weeks after transplantation, most of the scaffold pores were filled with bone and marrow tissue. When we tested the same human cells treated in vitro in a rat model using diffusion chambers, there was subsequent development of cartilage and bone following the subcutaneous transplantation of rhTGF-β1-F2-treated cells. This supports the suggestion that such cells were marrow-derived cells, with chondrogenic and osteogenic potential, whereas the untreated cells were not under the same conditions. The ability for differentiation into cartilage and bone tissues, combined with an extensive proliferation capacity, makes such a marrow-derived stem cell population valuable to induce bone regeneration at skeletal defect sites.

Biomimetic mineral-organic composite scaffolds with controlled internal architecture

Bone and cartilage generation by three-dimensional scaffolds is one of the promising techniques in tissue engineering. One approach is to generate histologically and functionally normal tissue by delivering healthy cells in biocompatible scaffolds. These scaffolds provide the necessary support for cells to proliferate and maintain their differentiated function, and their architecture defines the ultimate shape. Rapid prototyping (RP) is a technology by which a complex 3-dimensional (3D) structure can be produced indirectly from computer aided design (CAD). The present study aims at developing a 3D organic-inorganic composite scaffold with defined internal architecture by a RP method utilizing a 3D printer to produce wax molds. The composite scaffolds consisting of chitosan and hydroxyapatite were prepared using soluble wax molds. The behaviour and response of MC3T3-E1 pre-osteoblast cells on the scaffolds was studied. During a culture period of two and three weeks, cell proliferation and in-growth were observed by phase contrast light microscopy, histological staining and electron microscopy. The Giemsa and Gömöri staining of the cells cultured on scaffolds showed that the cells proliferated not only on the surface, but also filled the micro pores of the scaffolds and produced extracellular matrix within the pores. The electron micrographs showed that the cells covering the surface of the struts were flattened and grew from the periphery into the middle region of the pores.