Comparative performance of three ceramic bone graft substitutes

Bone Graft Substitutes-What Are My Options?

We examine the range of available bone graft substitutes often used in nonunion and malunion surgery of the upper extremity. Synthetic materials such as calcium sulfate, beta-calcium phosphate ceramics, hydroxyapatite, bioactive glass, and 3D printed materials are discussed. We delve into the advantages, disadvantages, and clinical applications for each, considering factors such as biocompatibility, osteoconductivity, mechanical strength, and resorption rates. This review provides upper extremity surgeons with insights into the available array of bone graft substitutes. We hope that the reviews helps in the decision-making process to achieve optimal outcomes when treating nonunion and malunion of the upper extremity.

Vancomycin Elution Kinetics of Four Antibiotic Carriers Used in Orthopaedic Surgery: In Vitro Study over 42 Days

This study aimed to analyse and compare the vancomycin elution kinetics of four biodegradable, osteoconductive antibiotic carriers used in clinical practice within a 42-day in vitro setting. Carriers A and D already contained vancomycin (1.1 g and 0.247 g), whereas carriers B and C were mixed with vancomycin according to the manufacturer's recommendations (B: 0.83 g and C: 0.305 g). At nine time points, 50% (4.5 mL) of the elution sample was removed and substituted with the same amount of PBS. Probes were analysed with a kinetic microparticle immunoassay. Time-dependent changes in vancomycin concentrations for each carrier and differences between carriers were analysed. Mean initial antibiotic levels were highest for carrier A (37.5 mg/mL) and lowest for carrier B (5.4 mg/mL). We observed time-dependent, strongly negative linear elution kinetics for carriers A (-0.835; p < 0.001), C (-0.793; p < 0.001), and D (-0.853; p < 0.001). Vancomycin concentrations increased from 48 h to 7 d and dropped thereafter in carriers C and D whilst constantly decreasing at any time point for carrier A. Carrier B showed a shallower decrease. Mean antibiotics levels at 42 d were 1.5 mg/mL, 2.6 mg/mL, 0.1 mg/mL, and 0.1 mg/mL for carriers A, B, C, and D. Differences in mean initial and final vancomycin concentrations for carrier A were significantly larger in comparison to C (p = 0.040). A carrier consisting of allogenic bone chips showed the highest vancomycin-to-carrier ratio and the largest elution over the study period. Whilst vancomycin concentrations were still measurable at 42 days for all carriers, carrier A provided a higher drug-to-carrier ratio and a more consistent antibiotic-releasing profile.

Bone Tissue Engineering in Rat Calvarial Defects Using Induced Bone-like Tissue by rhBMPs from Immature Muscular Tissues In Vitro

This study aimed to induce bone-like tissue from immature muscular tissue (IMT) in vitro using commercially available recombinant human bone morphogenetic protein (rhBMP)-2, rhBMP-4, and rhBMP-7, and then implanting this tissue into a calvarial defect in rats to assess healing. IMTs were extracted from 20-day-old Sprague-Dawley (SD) fetal rats, placed on expanded polytetrafluoroethylene (ePTFE) with 10 ng/μL each of rhBMP-2, BMP-4, and BMP-7, and cultured for two weeks. The specimens were implanted into calvarial defects in 3-week-old SD rats for up to three weeks. Relatively strong radiopacity was observed on micro-CT two weeks after culture, and bone-like tissue, comprising osteoblastic cells and osteoids, was partially observed by H&E staining. Calcium, phosphorus, and oxygen were detected in the extracellular matrix using an electron probe micro analyzer, and X-ray diffraction patterns and Fourier transform infrared spectroscopy spectra of the specimen were found to have typical apatite crystal peaks and spectra, respectively. Furthermore, partial strong radiopacity and ossification were confirmed one week after implantation, and a dominant novel bone was observed after two weeks in the defect site. Thus, rhBMP-2, BMP-4, and BMP-7 differentiated IMT into bone-like tissue in vitro, and this induced bone-like tissue has ossification potential and promotes the healing of calvarial defects. Our results suggest that IMT is an effective tissue source for bone tissue engineering.

Integrity of the ECM Influences the Bone Regenerative Property of ECM/Dicalcium Phosphate Composite Scaffolds

Due to the limitation of clinical autologous bone supply and other issues, the development of bone regeneration materials is still a hot topic. Natural tissue-derived bone repair materials have good biocompatibility and degradability, but their structure and properties are likely to be adversely affected during terminal sterilization. In this study, a composite scaffold consisting of the acellular extracellular matrix and dicalcium phosphate (ECM/DCP) was fabricated and terminally sterilized by γ-ray irradiation. In addition, the ECM/DCP scaffold was saturated with water and was also sterilized by γ-ray irradiation (RX-ECM/DCP). Results showed that the triple helix structure of collagen was better maintained in RX-ECM/DCP than in ECM/DCP. The thermal stability of RX-DCP/ECM was much better than that of ECP/ECM. The in vitro and in vivo performances of both types of scaffolds were also evaluated. The RX-ECM/DCP scaffold exhibited better in vitro bioactivity than that of the ECM/DCP scaffold as evidenced by more mineral formation in the simulated body fluid. In addition, RX-ECM/DCP also induced more effective bone regeneration than the ECM/DCP scaffold did in a rat calvarial defect model. Results sufficiently demonstrated that the addition of water to the scaffold could protect the structure of the ECM/DCP scaffold from being damaged by γ-ray irradiation during the terminal sterilization process. In summary, this study demonstrated a means to protect the ECM structure, which in turn led to the improvement of bone regenerative properties of the materials during γ-ray irradiation of ECM-based bone repair materials.

Silicon-substituted calcium phosphate promotes osteogenic-angiogenic coupling by activating the TLR4/PI3K/AKT signaling axis

Silicon-substituted calcium phosphate (Si-CaP) is a promising bioactive material for bone tissue engineering. The mechanism of Si-CaP regulates osteogenic-angiogenic coupling during bone regeneration has not been fully elucidated. In this study, we screened the targets of Si-CaP and osteogenic-angiogenic coupling. 83 common genes were regarded as key targets for Si-CaP regulation of the osteogenic-angiogenic coupling. Then, we performed protein-protein interaction analysis, GO and KEGG enrichment analysis of these 83 targets to further predict their molecular mechanism. Our results showed that Si-CaP treatment could regulate the osteogenic-angiogenic coupling by up-regulating the expression of Toll-like receptor 4 (TLR4), and the phosphorylation of AKT which in turn activating the PI3K/AKT signaling pathway, promoting the expression of RUNX2, OPN, VEGF. In addition, we also found that TLR4 siRNA treatment could block the PI3K/AKT signaling pathway, while inhibiting the promoting effect of Si-CaP. However, although LY294002 can achieve the same inhibitory effect as TLR4 siRNA by blocking the PI3K/AKT signaling pathway, it could not affect the expression of TLR4. This indicates that TLR4 is an upstream activator of PI3K/AKT signaling pathway. These results are highly consistent with the prediction of bioinformatics. In conclusion, we have elucidated the role of TLR4/PI3K/AKT signaling axis in Si-CaP mediated osteogenic-angiogenic coupling for the first time. This study provides new data onto the regulatory role and molecular mechanism of Si-CaP in the process of osteogenic-angiogenic coupling, which strongly supports its wide application for bone tissue engineering.

3D Printed Gelatin/Sodium Alginate Hydrogel Scaffolds Doped with Nano-Attapulgite for Bone Tissue Repair

INTRODUCTION

Bone tissue engineering (BTE) is a new strategy for bone defect repair, but the difficulties in the fabrication of scaffolds with personalized structures still limited their clinical applications. The rapid development in three-dimensional (3D) printing endows it capable of controlling the porous structures of scaffolds with high structural complexity and provides flexibility to meet specific needs of bone repair.

METHODS

In this study, sodium alginate (SA)/gelatin (Gel) hydrogel scaffolds doped with different contents of nano-attapulgite were fabricated via 3D printing. The surface microstructure, hydrophilicity and mechanical properties were fully evaluated. Furthermore, mouse bone marrow-derived mesenchymal stem cells (BMSCs) were cultured with the composite hydrogels in vitro, and proliferation and osteoblastic differentiation were assessed. A rabbit tibia plateau defect model was used to evaluate the osteogenic potential of the composite hydrogel in vivo.

RESULTS

When increasing nano-ATP content, the Gel/SA/nano-ATP composite hydrogels showed better mechanical property and printability. Moreover, Gel/SA/nano-ATP composite hydrogels showed excellent bioactivity, and a significant mineralization effect was observed on the surface after being incubated in simulated body fluid (SBF) for 14 days. The Gel/SA/nano-ATP composite hydrogel also showed good biocompatibility and promoted the osteogenesis of BMSCs. Finally, histological analysis demonstrates that the Gel/SA/nano-ATP composite hydrogels could effectively enhance bone regeneration in vivo.

CONCLUSION

These properties render the Gel/SA/nano-ATP composite hydrogel scaffolds an ideal bone tissue engineering material for the repair of bone defects.

Biocompatible Customized 3D Bone Scaffolds Treated with CRFP, an Osteogenic Peptide

BACKGROUND

Currently used synthetic bone graft substitutes (BGS) are either too weak to bear the principal load or if metallic, they can support loading, but can lead to stress shielding and are unable to integrate fully. In this study, we developed biocompatible, 3D printed scaffolds derived from µCT images of the bone that can overcome these issues and support the growth of osteoblasts.

METHODS

Cylindrical scaffolds were fabricated with acrylonitrile butadiene styrene (ABS) and Stratasys^® MED 610 (MED610) materials. The 3D-printed scaffolds were seeded with Mus musculus calvaria cells (MC3T3). After the cells attained confluence, osteogenesis was induced with and without the addition of calcitonin receptor fragment peptide (CRFP) and the bone matrix production was analyzed. Mechanical compression testing was carried out to measure compressive strength, stiffness, and elastic modulus.

RESULTS

For the ABS scaffolds, there was a 9.8% increase in compressive strength (p < 0.05) in the scaffolds with no pre-coating and the treatment with CRFP, compared to non-treated scaffolds. Similarly, MED610 scaffolds treated with CRFP showed an 11.9% (polylysine pre-coating) and a 20% (no pre-coating) increase (p < 0.01) in compressive strength compared to non-treated scaffolds.

CONCLUSIONS

MED610 scaffolds are excellent BGS as they support osteoblast growth and show enhanced bone growth with enhanced compressive strength when augmented with CRFP.

Inhibition of osteoclast activities by SCPC bioceramic promotes osteoblast-mediated graft resorption and osteogenic differentiation

Maximizing vital bone in a grafted site is dependent on a number of factors. These include resorption or turnover of the graft material, stimulation of bone formation pathway without a need for biological molecules added to the site and inhibition of cellular activities that compromise the mineralization of new bone matrix. In the present study, the dissolution profile of silica-calcium phosphate composite (SCPC) in physiological solution was measured and the data were fed to (ANN-NARX) prediction model to predict the time required for complete dissolution. The inductively coupled plasma-optical emission spectrometer ionic composition analysis of the culture medium incubated for 3 days with SCPC showed 57% decrease in Ca concentration and a significant increase in the concentration of Si (13.5 ± 1.8 μg/ml), P (249.4 ± 22 μg/ml), and Na (9.3 ± 0.52 μg/ml). In conjunction with the release of Si, P, and Na ions, the bone resorptive activity of osteoclasts was inhibited as indicated by the significant decrease in multinucleated tartrate resistant acidic phosphate stained cells and the volume of resorption pits on bone slices. In contrast, addition of SCPC to hBMSC cultured in conventional medium promoted higher Runt-related transcription factor 2 (p < .05), osteocalcin (p < .01), and bone sialo protein (p < .01) than that expressed by control cells grown in the absence of SCPC. The predicted dissolution time of 200 mg of porous SCPC particles in 10 ml phosphate buffered saline is 6.9 months. An important byproduct of the dissolution is inhibition of osteoclastic activity and promotion of osteoblastic differentiation and hence bone formation.

Copper-Loaded Biodegradable Bone Wax with Antibacterial and Angiogenic Properties in Early Bone Repair

Traditional bone wax has lots of shortcomings such as the risk of infection and inflammation and the ability to hinder osteogenesis that limit its clinical applications. In this study, we designed a novel biodegradable bone wax with desirable angiogenic and antibacterial ability and low foreign body reaction by mixing calcium sulfate, poloxamer, and cupric ions. To evaluate its biocompatibility and angiogenetic effect in vitro, we cultured human umbilical vein endothelial cells (HUVECs) with the indicated bone wax to observe cell viability and vessel-like tubular formation. The bone wax was then implanted in a critical-sized bone defect rat model for 4 and 8 weeks to successfully stimulate angiogenesis in vivo. Finally, the bone wax extract was incubated with Gram-positive Staphylococcus aureus to confirm its antibacterial ability. The copper-loaded biodegradable bone wax overcomes the drawbacks of traditional bone wax and provides a new approach for the treatment of bone injuries.

Biodegradable materials for bone defect repair

Compared with non-degradable materials, biodegradable biomaterials play an increasingly important role in the repairing of severe bone defects, and have attracted extensive attention from researchers. In the treatment of bone defects, scaffolds made of biodegradable materials can provide a crawling bridge for new bone tissue in the gap and a platform for cells and growth factors to play a physiological role, which will eventually be degraded and absorbed in the body and be replaced by the new bone tissue. Traditional biodegradable materials include polymers, ceramics and metals, which have been used in bone defect repairing for many years. Although these materials have more or fewer shortcomings, they are still the cornerstone of our development of a new generation of degradable materials. With the rapid development of modern science and technology, in the twenty-first century, more and more kinds of new biodegradable materials emerge in endlessly, such as new intelligent micro-nano materials and cell-based products. At the same time, there are many new fabrication technologies of improving biodegradable materials, such as modular fabrication, 3D and 4D printing, interface reinforcement and nanotechnology. This review will introduce various kinds of biodegradable materials commonly used in bone defect repairing, especially the newly emerging materials and their fabrication technology in recent years, and look forward to the future research direction, hoping to provide researchers in the field with some inspiration and reference.

A novel tissue-engineered bone graft composed of silicon-substituted calcium phosphate, autogenous fine particulate bone powder and BMSCs promotes posterolateral spinal fusion in rabbits

Background

Autogenous bone graft is the gold standard bone grafting substrate available in spinal fusion because of its osteoconductive, osteogenic, and osteoinductive properties. However, several shortcomings including bleeding, infection, chronic pain, and nerve injury are known to be associated with the procedure. Bone tissue engineering has emerged as an alternative therapeutic strategy for bone grafts. New materials have been developed and tested that can substitute for the autogenous bone grafts used in the spinal fusion. The purpose of this study is to evaluate the role of a novel tissue-engineered bone graft with silicon-substituted calcium phosphate (Si-CaP), autogenous fine particulate bone powder (AFPBP), and bone marrow mesenchymal stem cells (BMSCs) using a rabbit posterolateral lumbar fusion model based on bone tissue engineering principles. The application of this graft can represent a novel choice for autogenous bone to reduce the amount of autogenous bone and promote spinal fusion.

Methods

BMSCs from New Zealand white rabbits were isolated and cultured in vitro. Then, BMSCs were marked by the cell tracker chloromethyl-benzamidodialkylcarbocyanine (CM-Dil). A total of 96 New Zealand White rabbits were randomly divided into four groups: (a) AFPBP, (b) Si-CaP, (c) Si-CaP/AFPBP, (d) Si-CaP/AFPBP/BMSCs.The rabbits underwent bilateral posterolateral spine arthrodesis of the L5-L6 intertransverse processes using different grafts. Spinal fusion and bone formation were evaluated at 4, 8, and 12 weeks after surgery by manual palpation, radiology, micro-computed tomography (micro-CT), histology, and scanning electronic microscopy (SEM).

Results

The rate of fusion by manual palpation was higher in the Si-CaP/AFPBP/BMSCs group than the other groups at 8 weeks. The fusion rates in the Si-CaP/AFPBP/BMSCs and the AFPBP groups both reached 100%, which was higher than the Si-CaP/AFPBP group (62.5%) (P ​> ​0.05) and Si-CaP group (37.5%) (P ​< ​0.05) at 12 weeks. New bone formation was observed in all groups after implantation by radiology and micro-CT. The radiographic and CT scores increased in all groups from 4 to 12 weeks, indicating a time-dependent osteogenetic process. The Si-CaP/AFPBP/BMSCs group showed a larger amount of newly formed bone than the Si-CaP/AFPBP and Si-CaP groups at 12 weeks. Bone formation in the Si-CaP/AFPBP/BMSCs group was similar to the AFPBP group. Histology showed that new bone formation continued and increased along with the degradation and absorption of Si-CaP and AFPBP from 4 to 12 weeks in the Si-CaP, Si-CaP/AFPBP, and Si-CaP/AFPBP/BMSCs groups. At 4 weeks, a higher proportion of bone was detected in the AFPBP group (23.49%) compared with the Si-CaP/AFPBP/BMSCs group (14.66%, P ​< ​0.05). In the Si-CaP/AFPBP/BMSCs group at 8 weeks, the area percentage of new bone formation was 28.56%, which was less than the AFPBP group (33.21%, P ​< ​0.05). No difference in bone volume was observed between the Si-CaP/AFPBP/BMSCs group (44.39%) and AFPBP group (45.06%) at 12 weeks (P ​> ​0.05). At 12 weeks, new trabecular were visible in the Si-CaP/AFPBP/BMSCs group by SEM. CM-Dil-positive cells were observed at all stages. Compared with histological images, BMSCs participate in various stages of osteogenesis by transforming into osteoblasts, chondrocytes, and osteocytes.

Conclusion

This study demonstrated for the first time that Si-CaP/AFPBP/BMSCs is a novel tissue-engineered bone graft with excellent bioactivity, biocompatibility, and biodegradability. The graft could reduce the amount of autogenous bone and promote spinal fusion in a rabbit posterolateral lumbar fusion model, representing a novel alternative to autogenous bone.

The Translational potential of this article

The translational potential of this article lies in that this graft will be a novel spinal fusion graft with great potential for clinical applications.

Effect of Attapulgite-Doped Electrospun Fibrous PLGA Scaffold on Pro-Osteogenesis and Barrier Function in the Application of Guided Bone Regeneration

PURPOSE

Guided bone regeneration (GBR) therapy, which is a widely used technique in clinical practice and is effective in improving the repair of alveolar bone defects or bone mass deficiency regeneration, requires the use of membrane materials with good biocompatibility, barrier function, rigidity matching the space maintenance ability, economic benefits and excellent clinical applicability. The aim of this study was to develop an electrospun attapulgite (ATT)-doped poly (lactic-co-glycolic acid) (PLGA) scaffold (PLGA/ATT scaffold) as a novel material for GBR applications.

METHODS AND RESULTS

Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to determine the morphology and the crystalline structure of the PLGA/ATT scaffolds, respectively. Porosity and contact-angle measurements were also carried out to further characterize the physical properties of the PLGA/ATT scaffolds. The results of in vitro studies showed that bone marrow mesenchymal stem cells (BMSCs) attached more readily to and spread better over the PLGA/ATT scaffolds than the Bio-Gide membrane. Furthermore, in the in vitro osteoinductive experiments with BMSCs, the PLGA/ATT scaffolds were found to enhance the activity of alkaline phosphatase (ALP), promote the formation of mineralized bone nodules, and up-regulate the expression of several osteogenic markers-namely, runt-related transcription factor 2, alkaline phosphatase, osteopontin, and osteocalcin-which are similar to the effects of the Bio-Gide membrane. Further, in in vivo studies, the results of sequential fluorescent labeling, micro-computed tomography, and histological analysis suggest that using the PLGA/ATT scaffolds for repairing V-shaped buccal dehiscence on a dog's tooth root improved bone regeneration, which is not only similar to the result obtained using the Bio-Gide membrane but also much better than that obtained using PLGA scaffolds and the negative control.

CONCLUSION

To achieve satisfactory therapeutic results and to lower the cost of GBR treatment, this study provided a promising alternative material of bio-degradable membrane in clinical treatment.

Treatment of contaminated radial fracture in Sprague-Dawley rats by application of a degradable polymer releasing gentamicin

Fracture-related infections remain a leading cause of morbidity and mortality. We aimed to establish a simple contaminated radial osteotomy model to assess the efficacy of a biodegradable polymer poly(sebacic-co-ricinoleic acid) [p(SA-RA)] containing 20% w/w gentamicin. A unilateral transverse osteotomy was induced in Sprague-Dawley (SD) rats, followed by application of Staphylococcus aureus suspension over the fracture. After successfully establishing the contaminated open fracture model, we treated the rats either systemically (intraperitoneal cefuroxime), locally with p(SA-RA) containing gentamicin, or both. Control groups included non-contaminated group and contaminated groups that were either untreated or treated with the polymer alone. After 4 weeks, the bones were subjected to micro-CT scanning and microbiological and histopathology evaluations. Micro-CT analysis revealed similar changes in the group subjected to both local and systemic treatment as in the non-contaminated control group. Lack of detectable bacterial growth was noted in most animals of the group subjected to both local and systemic treatment, and all samples were negative for S. aureus. Histopathological evaluation revealed that all treatment modalities containing antibiotics were highly effective in reducing infection and promoting callus repair, resulting in early bone healing. While p(SA-RA) containing gentamicin treatment showed better results than cefuroxime, the combination of local and systemic treatment displayed the highest therapeutic potential in this model.

MagnetOs, Vitoss, and Novabone in a Multi-endpoint Study of Posterolateral Fusion: A True Fusion or Not?

STUDY DESIGN

This study was a multi-endpoint analysis of bone graft substitutes implanted as a standalone graft in a clinically relevant Ovine model of instrumented posterolateral spinal fusion (PLF).

OBJECTIVE

The objective of this study was to obtain high-quality evidence on the efficacy of commercial bone graft substitutes compared with autograft in instrumented PLF using a state-of-the-art model with a complete range of assessment techniques.

SUMMARY OF BACKGROUND DATA

Preclinical and clinical data on the quality of spinal fusions obtained with bone graft substitutes are often limited. Calcium phosphates with submicron topography have shown promising results in PLF, as these are able to induce bone formation in tissues distant from the host bone, which facilitates bony union.

METHODS

Nine female, skeletally mature sheep (4-5 y) underwent posterior pedicle screw/rods instrumented PLF at L2-L3 and L4-L5 using the following bone graft materials as a standalone graft per spinal segment: (1) biphasic calcium phosphate with submicron topography (BCP<µm), (2) 45S5 Bioglass (BG), and (3) collagen-β-tricalcium phosphate with a 45S5 Bioglass adjunct (TCP/BG). Autograft bone (AB) was used as a positive control treatment. Twelve weeks after implantation, the spinal segments were evaluated by fusion assessment (manual palpation, x-ray, micro-computed tomography, and histology), fusion mass volume quantification (micro-computed tomography), range of motion (ROM) testing, histologic evaluation, and histomorphometry.

RESULTS

Fusion assessment revealed equivalence between AB and BCP<µm by all fusion assessment methods, whereas BG and TCP/BG led to significantly inferior results. Fusion mass volume was highest for BCP<µm, followed by AB, BG, and TCP/BG. ROM testing determined equivalence for spinal levels treated with AB and BCP<µm, while BG and TCP/BG exhibited higher ROM. Histologic evaluation revealed substantial bone formation in the intertransverse regions for AB and BCP<µm, whereas BG and TCP/BG grafts contained fibrous tissue and minimal bone formation. Histologic observations were supported by the histomorphometry data.

CONCLUSIONS

This study reveals clear differences in efficacy between commercially available bone graft substitutes, emphasizing the importance of clinically relevant animal models with multiendpoint analyses for the evaluation of bone graft materials. The results corroborate the efficacy of calcium phosphate with submicron topography, as this was the only material that showed equivalent performance to autograft in achieving spinal fusion.

Co-transplantation of Wharton's jelly mesenchymal stem cell-derived osteoblasts with differentiated endothelial cells does not stimulate blood vessel and osteoid formation in nude mice models

A major challenge in bone tissue engineering is the lack of post-implantation vascular growth into biomaterials. In the skeletal system, blood vessel growth appears to be coupled to osteogenesis-suggesting the existence of molecular crosstalk between endothelial cells (ECs) and osteoblastic cells. The present study (performed in two murine ectopic models) was designed to determine whether co-transplantation of human Wharton's jelly mesenchymal stem cell-derived osteoblasts (WJMSC-OBs) and human differentiated ECs enhances bone regeneration and stimulates angiogenesis, relative to the seeding of WJMSC-OBs alone. Human WJMSC-OBs and human ECs were loaded into a silicate-substituted calcium phosphate (SiCaP) scaffold and then ectopically implanted at subcutaneous or intramuscular sites in nude mice. At both subcutaneous and intramuscular implantation sites, we observed ectopic bone formation and osteoids composed of host cells when WJMSC-OBs were seeded into the scaffold. However, the addition of ECs was associated with a lower level of osteogenesis, and we did not observe stimulation of blood vessel ingrowth. in vitro studies demonstrated that WJMSC-OBs lost their ability to secrete vascular endothelial growth factor and stromal cell-derived factor 1-including when ECs were present. In these two murine ectopic models, our cell-matrix environment combination did not seem to be optimal for inducing vascularized bone reconstruction.

Comparative Efficacy of Commonly Available Human Bone Graft Substitutes as Tested for Posterolateral Fusion in an Athymic Rat Model

Background

Insufficient data exist on bone graft substitute materials efficacy; two thirds lack any clinical data.1,2 This prospective animal study identified efficacy differences among commercially available materials of several classes.

Methods

Historically validated muscle pouch osteoinduction study (OIS) and posterolateral fusion (PLF) were performed in an athymic rat model. Grafting material products implanted were demineralized bone matrix (DBM)-based allografts (Accell EVO3, DBX Mix, DBX Strip, Grafton Crunch, Grafton Flex, Grafton Matrix, Grafton Putty, Magnifuse, and Progenix Plus), allografts (OsteoSponge, MinerOss), cellular allograft (Osteocel Plus), ceramics (Mozaik Strip), or activated ceramics (Actifuse ABX Putty, Vitoss BA). After 4 weeks, OIS specimens were evaluated ex vivo by histologic osteoinductivity. After 8 weeks, PLF ex vivo specimens were evaluated for fusion by manual palpation (F_MP), radiography (F_XR), and histology (F_HISTO).

Results

OIS: No materials exhibited a rejection reaction on histology. All DBM-based materials exhibited osteoinductive potential as new bone formation at > 88% of implanted sites. One plain allograft (OsteoSponge) formed bone at 25% of sites. No bone formed for one ceramic (Mozaik Strip), three activated ceramics (Actifuse ABX Putty), or one cellular allograft, regardless of human bone marrow aspirate (hBMA) when added. PLF: Among the 10 DBMs, 6 had F_MP of 100% (Accell EVO3, DBX Mix, DBX Strip, Grafton Flex, Grafton Putty, Magnifuse), 2 had F_MP of 94% (Grafton Crunch, Grafton Matrix), and 2 conditions had F_MP of 0% (Progenix Plus, Progenix Plus + athymic rat iliac crest bone graft [arICBG]). Ceramics (Mozaik Strip), activated ceramics (Actifuse ABX Putty, Vitoss BA), plain allograft (OsteoSponge, MinerOss (PLF study), and cellular allograft (Osteocel Plus) demonstrated 0% F_MP. ArICBG demonstrated 13% F_MP.

Conclusions

Eight DBM-based materials (Accell EVO3, DBX Mix, DBX Strip, Grafton Crunch, Grafton Flex, Grafton Matrix, Grafton Putty, Magnifuse) demonstrated excellent (> 90% F_MP) efficacy in promoting fusion via bone healing. Two DBM conditions (Progenix Plus, Progenix Plus + arICBG) showed no manual palpation fusion (F_MP). Systematically, over the 2 studies (OIS and PLF), cellular (Osteocel Plus), plain allografts (OsteoSponge, MinerOss; PLF study), ceramic (Mozaik Strip), and activated ceramics (Actifuse ABX Putty, Vitoss BA) demonstrated poor F_MP efficacy (< 10%).

Clinical Relevance

When selecting DBMs, clinicians must be cognizant of variability in DBM efficacy by product and lot. While theoretically osteoinductive, cellular allograft and activated ceramics yielded poor in vivo efficacy. Whole allograft and ceramics may provide osteoconductive scaffolding for mixed-material grafting; however, surgeons should be cautious in using them alone. Direct clinical data are needed to establish efficacy for any bone graft substitute.

Two-stage revision anterior cruciate ligament reconstruction

With the rising number of anterior cruciate ligament (ACL) reconstructions, revision ACL reconstructions are becoming increasingly common. A revision procedure may be performed to improved knee function, correct instability, and facilitate a return to normal activities. When performing a revision reconstruction, the surgeon decides between a single-stage or a two-stage revision. Two-stage revisions are rarely performed, but are particularly useful when addressing substantial tunnel-widening, active infection, and concomitant knee pathology (e.g., malalignment, other ligamentous injuries, meniscal or chondral lesions). Among these potential scenarios requiring a two-stage revision, tunnel-widening is the most common cause; the first stage involves graft removal, tunnel curettage, and bone grafting, followed by revision ACL reconstruction in the second stage. The purpose of this article is to review the preoperative planning, surgical considerations, rehabilitation, and outcomes of two-stage revision ACL reconstructions and summarize the recent literature outlining treatment results.

The Development of Gelatin/Hyaluronate Copolymer Mixed with Calcium Sulfate, Hydroxyapatite, and Stromal-Cell-Derived Factor-1 for Bone Regeneration Enhancement

In clinical practice, bone defects still remain a challenge. In recent years, apart from the osteoconductivity that most bone void fillers already provide, osteoinductivity has also been emphasized to promote bone healing. Stromal-cell-derived factor-1 (SDF-1) has been shown to have the ability to recruit mesenchymal stem cells (MSCs), which play an important role in the bone regeneration process. In this study, we developed a gelatin–hyaluronate (Gel-HA) copolymer mixed with calcium sulfate (CS), hydroxyapatite (HAP), and SDF-1 in order to enhance bone regeneration in a bone defect model. The composites were tested in vitro for biocompatibility and their ability to recruit MSCs after material characterization. For the in vivo test, a rat femoral condyle bone defect model was used. Micro computed tomography (Micro-CT), two-photon excitation microscopy, and histology analysis were performed to assess bone regeneration. As expected, enhanced bone regeneration was well observed in the group filled with Gel-HA/CS/HAP/SDF-1 composites compared with the control group in our animal model. Furthermore, detailed blood analysis of rats showed no obvious systemic toxicity or side effects after material implantation. In conclusion, the Gel-HA/CS/HAP/SDF-1 composite may be a safe and applicable material to enhance bone regeneration in bone defects.

Strontium‑containing α‑calcium sulfate hemihydrate promotes bone repair via the TGF‑β/Smad signaling pathway

Calcium phosphate-based bone substitutes have been widely used for bone repair, augmentation and reconstruction in bone implant surgery. While some of these substitutes have shown excellent biological efficacy, there remains a need to improve the performance of the current calcium phosphate-based bone substitutes. Strontium ions (Sr) can promote new osteogenesis, inhibit osteoclast formation and increase osteoconductivity. However, the therapeutic effect and mechanism of strontium-containing α-calcium sulfate hemihydrate (Sr-CaS) remains unclear. The present study created bone injuries in rats and treated the injuries with Sr-CaS. Then Cell Counting Kit-8, soft agar colony formation, flow cytometry, Transwell and Alizarin Red staining assays were performed to assess the bone cells for their proliferation, growth, apoptosis, invasion, and osteogenic differentiation abilities. The bone reconstructive states were measured by the microCT method, hematoxylin and eosin staining and Masson staining. Bone-related factors were analyzed by the reverse transcription-quantitative PCR assay; transforming growth factor (TGF)-β, mothers against decapentaplegic homolog (Smad)2/3 and β-catenin expression was measured by western blot analysis and osteocalcin (OCN) expression was assessed by immunohistochemistry. Sr-CaS did not significantly affect the proliferation and apoptosis of bone marrow stem cells (BMSCs), but did accelerate the migration and osteogenic differentiation of BMSCs in vitro. Sr-CaS promoted bone repair and significantly increased the values for bone mineral density, bone volume fraction, and trabecular thickness, but decreased trabecular spacing in vivo in a concentration-dependent manner. In addition, Sr-CaS dramatically upregulated the expression levels of genes associated with osteogenic differentiation (Runt-related transcription factor 2, Osterix, ALP, OCN and bone sialoprotein) both in vitro and in vivo. Sr-CaS also increased Smad2/3, TGF-β and phosphorylated-β-catenin protein expression in vitro and in vivo. These results indicated that materials that contain 5 or 10% Sr can improve bone defects by regulating the TGF-β/Smad signaling pathway.

A unidirectional porous beta-tricalcium phosphate material (Affinos®) for reconstruction of bony defects after excision of fibular bone for spinal surgery graft

The aim of this study was to elucidate the bone regeneration-inducing capability of Affinos®, a newly developed, high-porosity unidirectional porous β-TCP artificial bone. We compared the ability of Affinos® and OSferion®, a commercially available β-TCP product, to induce bone regeneration following implantation into bony defects left after fibula harvesting for spinal fusion surgery. Study subjects underwent surgery to harvest non-vascularized fibula grafts for spinal fusion surgery and were implanted with either Affinos® (19 patients) or OSferion® (15 patients, control group) at the defect site. The minimal and mean follow up periods were 6 and 11 months after surgery, respectively. X-rays of the lower leg taken 1-2 weeks after surgery and at the final follow-up visit were used to evaluate fibular-β-TCP continuity and fibula defect filling ratio. There was no significant difference in radiographic continuity in the fibula between the two groups. The fibula defect filling ratio for the Affinos® group decreased from 0.94 ± 0.17 at 1-2 weeks to 0.77 ± 0.14 at 10 months. For the OSferion® control group, the fibula defect filling ratio decreased from 0.94 ± 0.14 at 1-2 weeks to 0.52 ± 0.27 at final follow-up. The Affinos® group showed a significantly higher fibula defect filling ratio compared to that for the OSferion® group (p = 0.003). These results indicate that Affinos® has slow absorption rates and significant defect filling activity compared with OSferion®. Thus, Affinos® could be a suitable substitute to fill bony defects induced by fibula harvesting for spinal reconstruction surgery.

Bone Graft Substitutes: Current Concepts and Future Expectations

Owing to its osteoinductive and osteoconductive properties and the presence of osteogenic cells, freshly harvested autologous bone graft is the gold standard for skeletal reconstruction where there is inadequate native bone. Whereas these characteristics are difficult to replicate, engineered, commercially available bone graft substitutes aim to achieve a comparable osseoregenerative profile. This work furnishes the reader with an understanding of the predominant classes of bone graft substitutes available for reconstruction of upper extremity bone defects following trauma or oncological surgery. We review bone graft substitutes with respect to their mechanisms of action, their advantages and disadvantages, and their indications and contraindications. We provide examples of bone graft substitutes in clinical use and outline comparative costs. We also describe the future directions for this specific aspect of reconstructive surgery with a focus on the role of bioactive glass.

Buccal fat pad-derived stem cells with anorganic bovine bone mineral scaffold for augmentation of atrophic posterior mandible: An exploratory prospective clinical study

BACKGROUND

Application of adipose-derived stem cells originated from buccal fat pad (BFP) can simplify surgical procedures and diminish clinical risks compared to large autograft harvesting.

PURPOSE

This study sought to evaluate and compare the efficacy of buccal fat pad-derived stem cells (BFPSCs) in combination with anorganic bovine bone mineral (ABBM) for vertical and horizontal augmentation of atrophic posterior mandibles.

MATERIALS AND METHODS

Fourteen patients with atrophic posterior mandible were elected for this prospective exploratory study. BFP (3-5 mL) was harvested and BFPSCs were isolated and combined with ABBM at 50% ratio. The vertical and horizontal alveolar deficiencies were augmented by 50% mixture of ABBM with either BFPSCs (group 1) or particulated autologous bone (group 2). Titanium mesh was contoured to the desired 3D shape of the alveolar ridge and fixated to the host sites over the graft material of the two groups. At first, the amount of new bone areas was calculated by quantitative analysis of cone beam computed tomography (CBCT) images that were taken 6 months postoperatively according to regenerative techniques (group 1 vs group 2 without considering the type of bone defects). Second, these amounts were calculated in each group based on the type of defects.

RESULTS

Quantitative analysis of CBCT images revealed the areas of new bone formation were 169.5 ± 5.90 mm² and 166.75 ± 10.05 mm² in groups 1 and 2, respectively. The area of new bone formation for vertical defects were 164.91 ± 3.74 mm² and 169.36 ± 12.09 mm² in groups 1 and 2, respectively. The area of new bone formation for horizontal deficiencies were 170.51 ± 4.54 mm² and 166.98 ± 9.36 mm² in groups 1 and 2, respectively. There were no statistically significant differences between the two groups in any of the pair-wise comparisons (P > 0.05).

CONCLUSIONS

The findings of the present study demonstrated lack of difference in bone volume formation between BFPSCs and autologous particulate bone in combination with ABBM. If confirmed by future large-scale clinical trial, BFPSCs may provide an alternative to autogenous bone for reconstruction of alveolar ridge defects.

Biomaterials as cell carriers for augmentation of adipose tissue-derived stromal cell transplantation

Adipose tissue-derived stromal cells (ADSCs) contain lineage-committed progenitor cells that have the ability to differentiate into various cell types that may be useful for autologous cell transplantation to correct defects of skin, adipose, cartilage, bone, tendon, and blood vessels. The multipotent characteristics of ADSCs, as well as their abundance in the human body, make them an attractive potential resource for wound repair and applications to tissue engineering. ADSC transplantation has been used in combination with biomaterials, including cell sheets, hydrogel, and three-dimensional (3D) scaffolds based on chitosan, fibrin, atelocollagen, and decellularized porcine dermis, etc. Furthermore, low molecular weight heparin/protamine nanoparticles (LH/P NPs) have been used as an inducer of ADSC aggregation. The tissue engineering potential of these biomaterials as cell carriers is increased by the synergistic relationship between ADSCs and the biomaterials, resulting in the release of angiogenic cytokines and growth factors. In this review article, we describe the advantages of ADSC transplantation for tissue engineering, focusing on biomaterials as cell carriers which we have studied.

Mineralization in micropores of calcium phosphate scaffolds

With the increasing demand for novel bone repair solutions that overcome the drawbacks of current grafting techniques, the design of artificial bone scaffolds is a central focus in bone regeneration research. Calcium phosphate scaffolds are interesting given their compositional similarity with bone mineral. The majority of studies focus on bone growth in the macropores (>100 µm) of implanted calcium phosphate scaffolds where bone structures such as osteons and trabeculae can form. However, a growing body of research shows that micropores (<50 µm) play an important role not only in improving bone growth in the macropores, but also in providing additional space for bone growth. Bone growth in the micropores of calcium phosphate scaffolds offers major mechanical advantages as it improves the mechanical properties of the otherwise brittle materials, further stabilizes the implant, improves load transfer, and generally enhances osteointegration. In this paper, we review evidence in the literature of bone growth into micropores, emphasizing on identification techniques and conditions under which bone components are observed in the micropores. We also review theories on mineralization and propose mechanisms, mediated by cells or not, by which mineralization may occur in the confined micropore space of calcium phosphate scaffolds. Understanding and validating these mechanisms will allow to better control and enhance mineralization in micropores to improve the design and efficiency of bone implants. STATEMENT OF SIGNIFICANCE: The design of synthetic bone scaffolds remains a major focus for engineering solutions to repair damaged and diseased bone. Most studies focus on the design of and growth in macropores (>100 µm), however research increasingly shows the importance of microporosity (<50 µm). Micropores provide an additional space for bone growth, which provides multiple mechanical advantages to the scaffold/bone composite. Here, we review evidence of bone growth into micropores in calcium phosphate scaffolds and conditions under which growth occurs in micropores, and we propose mechanisms that enable or facilitate growth in these pores. Understanding these mechanisms will allow researchers to exploit them and improve the design and efficiency of bone implants.

Evaluation of Antibiotic-Releasing Triphasic Bone Void Filler In-Vitro

Bone void fillers (BVFs) containing calcium sulfate, tricalcium phosphate (TCP), and hydroxyapatite can be loaded with antibiotics for infection treatment or prevention under surgeon-directed use. The aim of this study was to characterize the handling and elution properties of a triphasic BVF loaded with common antibiotics. BVF was mixed with vancomycin and/or tobramycin to form pellets, and the set time was recorded. A partial refreshment elution study was conducted with time points at 4, 8, and 24 h, as well as 2, 7, 14, 28, and 42 days. Effects on dissolution were evaluated in a 14-day dissolution study. Set time increased to over 1 h for groups containing tobramycin, although vancomycin had a minimal effect. Pellets continued to elute antibiotics throughout the 42-day elution study, suggesting efficacy for the treatment or prevention of orthopedic infections. BVF containing vancomycin or tobramycin showed similar dissolution at 14 days compared to BVF without antibiotics; however, BVF containing both antibiotics showed significantly more dissolution.

Tissue Engineering and Cell-Based Therapies for Fractures and Bone Defects

Bone fractures and segmental bone defects are a significant source of patient morbidity and place a staggering economic burden on the healthcare system. The annual cost of treating bone defects in the US has been estimated to be $5 billion, while enormous costs are spent on bone grafts for bone injuries, tumors, and other pathologies associated with defective fracture healing. Autologous bone grafts represent the gold standard for the treatment of bone defects. However, they are associated with variable clinical outcomes, postsurgical morbidity, especially at the donor site, and increased surgical costs. In an effort to circumvent these limitations, tissue engineering and cell-based therapies have been proposed as alternatives to induce and promote bone repair. This review focuses on the recent advances in bone tissue engineering (BTE), specifically looking at its role in treating delayed fracture healing (non-unions) and the resulting segmental bone defects. Herein we discuss: (1) the processes of endochondral and intramembranous bone formation; (2) the role of stem cells, looking specifically at mesenchymal (MSC), embryonic (ESC), and induced pluripotent (iPSC) stem cells as viable building blocks to engineer bone implants; (3) the biomaterials used to direct tissue growth, with a focus on ceramic, biodegradable polymers, and composite materials; (4) the growth factors and molecular signals used to induce differentiation of stem cells into the osteoblastic lineage, which ultimately leads to active bone formation; and (5) the mechanical stimulation protocols used to maintain the integrity of the bone repair and their role in successful cell engraftment. Finally, a couple clinical scenarios are presented (non-unions and avascular necrosis—AVN), to illustrate how novel cell-based therapy approaches can be used. A thorough understanding of tissue engineering and cell-based therapies may allow for better incorporation of these potential therapeutic approaches in bone defects allowing for proper bone repair and regeneration.

Strontium-releasing fluorapatite glass-ceramic scaffolds: Structural characterization and in vivo performance

There is increasing interest in biodegradable ceramic scaffolds for bone tissue engineering capable of in situ delivery of ionic species favoring bone formation. Strontium has been shown to be osteogenic, but strontium-containing drugs such as strontium ranelate, used in Europe for the treatment of osteoporosis, are now restricted due to clinical evidence of systemic effects. By doping fluorapatite-based glasses with strontium, we developed ceramic scaffolds with fully interconnected macroporosity and cell size similar to that of cancellous bone, that are also capable of releasing strontium. The crystallization behavior, investigated by XRD and SEM, revealed the formation of akermanite and fluorapatite at the surface of strontium-free glass-ceramic scaffolds, and strontium-substituted fluorapatite at the surface of the strontium-doped scaffolds. At 8 weeks after implantation in a rat calvarial critical size defect, scaffolds doped with the highest amount of strontium led to the highest mineral apposition rate. A significantly higher amount of newly-formed bone was found with the strontium-free glass-ceramic scaffold, and possibly linked to the presence of akermanite at the scaffold surface. We demonstrate by energy dispersive XRF analyses of skull sections that strontium was present in newly formed bone with the strontium-doped scaffolds, while a significant amount of fluorine was incorporated in newly formed bone, regardless of composition or crystallization state.

Synthesis of Hydroxyapatite, β-Tricalcium Phosphate and Biphasic Calcium Phosphate Particles to Act as Local Delivery Carriers of Curcumin: Loading, Release and In Vitro Studies

The successful synthesis of hydroxyapatite (HA), β-Tricalcium phosphate (β-TCP) and two biphasic mixtures (BCPs) of the two was performed by means of wet precipitation. The resulting crystals were characterized and the BCP composition was analyzed and identified as 13% HA-87% TCP and 41% HA-59% TCP. All samples were treated with curcumin solutions, and the degree of curcumin loading and release was found to be proportional to the TCP content of the ceramic. No further cytotoxicity was observed upon MG-63 treatment with the curcumin-loaded ceramics. Finally, the alkaline phosphatase activity of the cells was found to increase with increasing content of TCP, which provides an encouraging proof of concept for the use of curcumin-loaded synthetic biomaterials in bone remodeling.

Assessment of calcium sulfate hemihydrate-Tricalcium silicate composite for bone healing in a rabbit femoral condyle model

Calcium sulfate or plaster of Paris (POP) is considered as a bone cement with a fast degradation rate, which frequently makes it resorb before the bone defect area is completely filled by new bone. The incorporation of tricalcium silicate (C3S) into POP cement has been proven as a feasible approach to reduce the in vitro degradation rate and improve the in vitro bioactivity of the material. However, the in vivo performance of the POP/C3S composite cement is still unclear. Therefore, the aim of the present study is to assess the biodegradability and osteogenesis of POP/C3S composite cement in comparison with those of POP bone cement. To carry out the in vivo evaluation, POP and POP/C3S cements were implanted into a femoral condyle defect model in rabbits (5 mm diameter × 10 mm length) for 4, 8, and 12 weeks duration. The area of the remaining cement and new bone regeneration in bone defect were investigated and quantitatively measured using radiography, micro-computed tomography, and histological staining. For both cements, no sign of inflammation was observed. POP cement was completely degraded at the 8th week of post-implantation. By contrast, only approximately 50% by volume of POP/C3S composite cement degraded at the 12th week, which allowed a long-term framework for new bone formation. The osteogenic ability of POP/C3S composite cement was significantly superior to that of POP as indicated by the higher mineralization rate and maturity of the newly formed bone around the composite cement. In summary, our findings demonstrated that the in vivo degradation behaviors and osteogenic ability of POP cement could be improved by incorporating C3S in vivo, suggesting that POP/C3S composite cement has potential as a biodegradable cement for bone repair.

Optimized Bone Regeneration in Calvarial Bone Defect Based on Biodegradation-Tailoring Dual-shell Biphasic Bioactive Ceramic Microspheres

Bioceramic particulates capable of filling bone defects have gained considerable interest over the last decade. Herein, dual-shell bioceramic microspheres (CaP@CaSi@CaP, CaSi@CaP@CaSi) with adjustable beta-tricalcium phosphate (CaP) and beta-calcium silicate (CaSi) distribution were fabricated using a co-concentric capillary system enabling bone repair via a tailorable biodegradation process. The in vitro results showed the optimal concentration (1/16 of 200 mg/ml) of extracts of dual-shell microspheres could promote bone marrow mesenchymal cell (BMSC) proliferation and enhance the level of ALP activity and Alizarin Red staining. The in vivo bone repair and microsphere biodegradation in calvarial bone defects were compared using micro-computed tomography and histological evaluations. The results indicated the pure CaP microspheres were minimally resorbed at 18 weeks post-operatively and new bone tissue was limited; however, the dual-shell microspheres were appreciably biodegraded with time in accordance with the priority from CaSi to CaP in specific layers. The CaSi@CaP@CaSi group showed a significantly higher ability to promote bone regeneration than the CaP@CaSi@CaP group. This study indicates that the biphasic microspheres with adjustable composition distribution are promising for tailoring material degradation and bone regeneration rate, and such versatile design strategy is thought to fabricate various advanced biomaterials with tailorable biological performances for bone reconstruction.

Human bone graft cytocompatibility with mesenchymal stromal cells is comparable after thermal sterilization and washing followed by γ-irradiation: an in vitro study

Human bone allografts present a better alternative to autografts in terms of minimization of the harvesting procedure complications. Prior to the use in clinical applications, they require sterilization which aims to reduce bioburden. This often comes at the expense of their biological properties as carriers of cells. In this study, we evaluated the cytocompatibility of human bone allografts processed and sterilized by three different methods with mesenchymal stromal cells. Bone morphology, biological and biochemical properties of the extracted bone-conditioned medium and viability of cells were assessed. We found that chemical sterilization had a strong negative effect on cell viability, whereas thermal sterilization and washing with subsequent γ-irradiation both resulted in a bone graft compatible with the progenitor cells. Moreover, washing of the bone prior to sterilization allowed solid removal of cell debris and other bone marrow components. Taken together, our findings demonstrate the importance of a proper choice of the bone graft processing method for the production of the biomaterial suitable for tissue engineering.

Novel bioactive glass based injectable bone cement with improved osteoinductivity and its in vivo evaluation

Recently, more and more attention has been paid to the development of a new generation of injectable bone cements that are bioactive, biodegradable and are able to have appropriate mechanical properties for treatment of vertebral compression fractures (VCFs). In this study, a novel PSC/CS composite cement with high content of PSC (a phytic acid-derived bioactive glass) was prepared and evaluated in both vitro and vivo. The PSC/CS cement showed excellent injectability, good resistance to disintegration, radiopacity and suitable mechanical properties. The in vitro test showed that the cement was bioactive, biocompatible and could maintain its shape sustainably, which made it possible to provide a long-term mechanical support for bone regeneration. Radiography, microcomputed tomography and histology of critical sized rabbit femoral condyle defects implanted with the cements proved the resorption and osteoinductivity of the cement. Compared with the PMMA and CSPC, there were more osteocyte and trabeculae at the Bone-Cement interface in the group PSC/CS cement. The volume of the residual bone cement suggested that PSC/CS had certain ability of degradation and the resorption rate was much lower than that of the CSPC cement. Together, the results indicated that the cement was a promising bone cement to treat the VCFs.

In Vitro Biocompatibility Assessment and In Vivo Behavior of a New Osteoconductive βTCP Bone Substitute

OBJECTIVE

Beta-tricalcium phosphate (βTCP) granules (OsproLife) exhibit a pure crystalline phase and a rough microporous surface for promoting cell adhesion and microsized intragranule porosity for improving wettability and resorption necessary for bone regeneration. OsproLife is a fully resorbable, space-maintaining, and osteoconductive synthetic material for the filling of bone defects. To asses OsproLife properties, a similar synthetic biomaterial, already on the market, has been chosen as reference: Cerasorb has the same chemical composition, but different crystal structure, surface morphology, and granule size. The aim of this study is to compare the properties of OsproLife and Cerasorb.

METHODS

Chemical purity, composition and physical properties, in vitro cytotoxicity, and in vivo bone performance in a rabbit model were analyzed. βTCP OsproLife granules (test) were compared with Cerasorb (control). Histological and μCT analyses were performed at 6, 12, and 56 weeks after implantation.

RESULTS

βTCP OsproLife and Cerasorb granules result to be both biocompatible and characterized by the same osteoconductivity and resorption rate.

CONCLUSION

βTCP OsproLife granules are a promising bone substitute for dental and orthopedic applications.

Characterisation of a novel poly (ether ether ketone)/calcium sulphate composite for bone augmentation

Background

Calcium sulphate (CS) has been used in bone grafting since the 1800s. It has not replaced autograft as the gold standard, however, since its dissolution occurs rapidly in bodily fluids, meaning that the material cannot support long-term bone growth. Here, the polymer poly (ether ether ketone) (PEEK) was used to slow dissolution in in vitro physiological environments and augment the mechanical properties of the material.

Methods

PEEK/CS specimens were fabricated by combining powders of PEEK and CS with water, resulting in a hardening paste. To enhance physical interactions between phases, cylindrical specimens were heat-treated to melt and fuse the PEEK. Following analysis of physical and chemical interactions by SEM and FT-IR respectively, dynamic ageing in PBS and compression testing was undertaken to measure how the PEEK influenced the mechanical properties of the final parts. Changes in structure and chemistry were determined using helium pycnometry, SEM and analysis of powder XRD patterns.

Results

Powders of PEEK and CS hemihydrate (CSH) (CaSO₄.0.5H₂O) were combined with PEEK at 0 wt%, 2.5 wt%, 20 wt%, 40 wt% and 80 wt% and at a P:L ratio of 0.85 g/mL. The subsequently hardened structures were heat-treated, which initiated the melting of PEEK and dehydration of CSD (CaSO₄.2H₂O) to the CS anhydrite (CSA) (CaSO₄) phase, which changed colour and apparent volume. FT-IR and SEM analysis revealed heat treatment of PEEK/CS specimens facilitated both physical and chemical interactions between phases. Over a period of 21 days of ageing in PBS, the hydration of CS was determined by XRD and improved specimen longevity at all levels of PEEK wt% loading was measured compared with the control. Importantly, increasing PEEK wt% loading resulted in a marked increase in the mechanical properties of PEEK/CS specimens in terms of both compressive strength and modulus.

Conclusions

Reinforcement of CS with PEEK significantly enhanced in vitro dissolution resistance, in addition to enhancing mechanical properties. This composite therefore has significant future potential as a bone graft replacement.

Electronic supplementary material

The online version of this article (doi:10.1186/s40824-017-0093-7) contains supplementary material, which is available to authorized users.

Anterior cervical fusion with interbody cage containing beta-tricalcium phosphate: Clinical and radiological results

Aim

Beta tricalcium phosphate (beta-TCP) is an osteoconductive, resorbable material. Its clinical effectiveness has been proved in many indications. This study was clinical and radiographic study report obtained in patients undergoing anterior cervical discectomy and fusion ACDF in which PEEK cages were filled beta-TCP in an injectable form.

Material and methods

Between January 2010 and June 2011, 16 consecutive patients underwent ACDF using PEEK cages with beta-TCP. The cohort compromised 10 men and 6 women with a mean age of 45.2 years. The surgery was performed when the patient had myelopathy or radiculopathy with progressive neurological deficit, or failure of conservative treatment (a minimum of 3 months). The patients were evaluated by Odom criteria preoperatively and postoperative 3rd, 6th, 12th and 24th months. Preop and postop pain was evaluated with visual analogue scala (VAS). Disc height and fusion success rates were evaluated.

Results

Preoperative average VAS score was 7.9 (7–10) for neck pain and 8 (7–10) for arm pain. At the final follow-up, these scores became 1.5 and 1.4 for neck and arm pain, respectively. The average improvement rate was 81% for neck pain and 82.5% for arm pain. Postop ODOM's criteria main rate was 3.4. Bone fusion was achieved in 14 segments (70%) at 3rd month, 19 segments (95%) at 12th month follow-up assessment.

Conclusion

Clinical and radiological results revealed that B-TCP is a good alternative synthetic fusion material for cervical interbody fusion.

Level of evidence: Level IV, therapeutic study.

Bone Incorporation of Silicate-Substituted Calcium Phosphate in 2-Stage Revision Anterior Cruciate Ligament Reconstruction: A Histologic and Radiographic Study

PURPOSE

To evaluate the histologic and radiographic outcomes of using silicate-substituted calcium phosphate (Si-CaP) as bone graft substitute for the augmentation of tunnel defects in 2-stage revision anterior cruciate ligament (ACL) reconstruction.

METHODS

Forty patients undergoing 2-stage revision ACL reconstruction were included in a prospective, randomized controlled clinical trial between 2012 and 2015. The inclusion criteria were tunnel diameter of the tibial and/or femoral tunnel of 10 mm or greater after failed ACL reconstruction. Twenty patients received autologous bone from the iliac crest and 20 patients received Si-CaP as a bone graft substitute for tunnel grafting at the first-stage procedure. Punch biopsy specimens of the augmented tunnels were taken at the second-stage procedure, and histologic examination included quantitative analysis of the area of immature bone formation, lamellar bone, and bone marrow. Radiographic analysis included determination of the filling rates of the tunnels on postoperative computed tomography scans.

RESULTS

Forty patients with a mean age of 32 years (standard deviation [SD], 11.0 years) were analyzed. Histologic examination of the tunnels filled with Si-CaP showed that 15% (SD, 14%) of the area was covered with immature bone formation, 41% (SD, 10%) with well-organized lamellar bone, and 44% (SD, 8%) with bone marrow. In the control group (autologous bone), 58% (SD, 3%) of the area was covered with well-organized lamellar bone and 42% (SD, 3%) with bone marrow. Quantitative evaluation of the postoperative computed tomography scans showed a trend of better filling rates in patients with Si-CaP for the tibial tunnel (86% [SD, 17%] vs 78% [SD, 14%]; P = .131). Intraoperatively, Si-CaP was completely integrated into the original bone tunnel providing good stability for tunnel placement and tendon graft fixation comparable to autologous bone.

CONCLUSIONS

Si-CaP as bone graft substitute for tunnel augmentation in 2-stage revision ACL reconstruction shows good histologic, radiographic, and intraoperative integration comparable to autologous bone.

LEVEL OF EVIDENCE

Level I, prospective randomized controlled trial.

A comparative study of tissue-engineered constructs from Acropora and Porites coral in a large animal bone defect model

Objectives

To compare the therapeutic potential of tissue-engineered constructs (TECs) combining mesenchymal stem cells (MSCs) and coral granules from either Acropora or Porites to repair large bone defects.

Materials and Methods

Bone marrow-derived, autologous MSCs were seeded on Acropora or Porites coral granules in a perfusion bioreactor. Acropora-TECs (n = 7), Porites-TECs (n = 6) and bone autografts (n = 2) were then implanted into 25 mm long metatarsal diaphyseal defects in sheep. Bimonthly radiographic follow-up was completed until killing four months post-operatively. Explants were subsequently processed for microCT and histology to assess bone formation and coral bioresorption. Statistical analyses comprised Mann-Whitney, t-test and Kruskal–Wallis tests. Data were expressed as mean and standard deviation.

Results

A two-fold increaseof newly formed bone volume was observed for Acropora-TECs when compared with Porites-TECs (14 sd 1089 mm³versus 782 sd 507 mm³; p = 0.09). Bone union was consistent with autograft (1960 sd 518 mm³). The kinetics of bioresorption and bioresorption rates at four months were different for Acropora-TECs and Porites-TECs (81% sd 5% versus 94% sd 6%; p = 0.04). In comparing the defects that healed with those that did not, we observed that, when major bioresorption of coral at two months occurs and a scaffold material bioresorption rate superior to 90% at four months is achieved, bone nonunion consistently occurred using coral-based TECs.

Discussion

Bone regeneration in critical-size defects could be obtained with full bioresorption of the scaffold using coral-based TECs in a large animal model. The superior performance of Acropora-TECs brings us closer to a clinical application, probably because of more suitable bioresorption kinetics. However, nonunion still occurred in nearly half of the bone defects.

Cite this article: A. Decambron, M. Manassero, M. Bensidhoum, B. Lecuelle, D. Logeart-Avramoglou, H. Petite, V. Viateau. A comparative study of tissue-engineered constructs from Acropora and Porites coral in a large animal bone defect model. Bone Joint Res 2017;6:208–215. DOI: 10.1302/2046-3758.64.BJR-2016-0236.R1.

Textural, Structural and Biological Evaluation of Hydroxyapatite Doped with Zinc at Low Concentrations

The present work was focused on the synthesis and characterization of hydroxyapatite doped with low concentrations of zinc (Zn:HAp) (0.01 < x_Zn < 0.05). The incorporation of low concentrations of Zn²⁺ ions in the hydroxyapatite (HAp) structure was achieved by co-precipitation method. The physico-chemical properties of the samples were characterized by X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Scanning Electron Microscopy (SEM), zeta-potential, and DLS and N₂-BET measurements. The results obtained by XRD and FTIR studies demonstrated that doping hydroxyapatite with low concentrations of zinc leads to the formation of a hexagonal structure with lattice parameters characteristic to hydroxyapatite. The XRD studies have also shown that the crystallite size and lattice parameters of the unit cell depend on the substitutions of Ca²⁺ with Zn²⁺ in the apatitic structure. Moreover, the FTIR analysis revealed that the water content increases with the increase of zinc concentration. Furthermore, the Energy Dispersive X-ray Analysis (EDAX) and XPS analyses showed that the elements Ca, P, O, and Zn were found in all the Zn:HAp samples suggesting that the synthesized materials were zinc doped hydroxyapatite, Ca_10−xZn_x(PO₄)₆(OH), with 0.01 ≤ x_Zn ≤ 0.05. Antimicrobial assays on Staphylococcus aureus and Escherichia coli bacterial strains and HepG2 cell viability assay were carried out.

Hyaluronic-Acid-Hydroxyapatite Colloidal Gels Combined with Micronized Native ECM as Potential Bone Defect Fillers

One of the grand challenges in translational regenerative medicine is the surgical placement of biomaterials. For bone regeneration in particular, malleable and injectable colloidal gelsare frequently designed to exhibit self-assembling and shear-response behavior which facilitates biomaterial placement in tissue defects. The current study demonstrated that by combining native extracellular matrix (ECM) microparticles, i.e., demineralized bone matrix (DBM) and decellularized cartilage (DCC), with hyaluronic acid (HA) and hydroxyapatite (HAP) nanoparticles, a viscoelastic colloidal gel consisting exclusively of natural materials was achieved. Rheological testing of HA-ECM suspensions and HA-HAP-ECM colloidal gels concluded either equivalent or substantially higher storage moduli (G' ≈ 100-10 000 Pa), yield stresses (τ_y ≈ 100-1000 Pa), and viscoelastic recoveries (G'_recovery ≥ 87%) in comparison with controls formulated without ECM, which indicated a previously unexplored synergy in fluid properties between ECM microparticles and HA-HAP colloidal networks. Notable rheological differences were observed between respective DBM and DCC formulations, specifically in HA-HAP-DBM mixtures, which displayed a mean 3-fold increase in G' and a mean 4-fold increase in τ_y from corresponding DCC mixtures. An initial in vitro assessment of these potential tissue fillers as substrates for cell growth revealed that all formulations of HA-ECM and HA-HAP-ECM showed no signs of cytotoxicity and appeared to promote cell viability. Both DBM and DCC colloidal gels represent promising platforms for future studies in bone and cartilage tissue engineering. Overall, the current study identified colloidal gels constructed exclusively of natural materials, with viscoelastic properties that may facilitate surgical placement for a wide variety of therapeutic applications.

Microporous density-mediated response of MSCs on 3D trimodal macro/micro/nano-porous scaffolds via fibronectin/integrin and FAK/MAPK signaling pathways

Microporous density influences cellular behaviors through mediating Fn–integrin interaction and FA formation, consequently resulting in FAK/MAPK cascade activation.

Comparison of Survival and Osteogenic Ability of Human Mesenchymal Stem Cells in Orthotopic and Ectopic Sites in Mice

Tissue constructs containing mesenchymal stem cells (MSCs) are appealing strategies for repairing large segmental bone defects, but they do not allow consistent bone healing and early cell death was identified as a cause of failure. However, little is known about cell survival in the clinical microenvironment encountered during bone healing process. Osteoconductive coral scaffold with or without luciferase-labeled human MSCs were implanted either in a critical segmental femoral bone defect stabilized by plate or subcutaneously in 44 mice. Cell survival was evaluated by serial bioluminescence imaging (BLI) and osteogenic capabilities by histology and microcomputed tomography. Comparisons between groups were performed with two-way analysis of variance test. Twenty mice were sacrificed 2 weeks after surgery for short-term evaluation and 24 mice at 10 weeks for long-term evaluation. BLI provided evidence of fast and continuous cell death: 85% decrease of the BLI signal over the first 2 weeks in both locations; in fact, less than 2% of the initial cell number was present in all constructs analyzed 4 weeks postimplantation and less than 1% of the initial cell number by 8 weeks postimplantation. By 2 weeks postimplantation, the amount of newly formed bone was self-limited and was similar to ectopic and orthotopic groups. By 10 weeks postimplantation, bone formation was significantly enhanced in the presence of MSCs in orthotopic site and the amount of newly formed bone in cell-containing constructs implanted in orthotopic locations was significantly higher than that observed in the ectopic group. Our results indicated that hMSCs promote bone formation despite early and massive cell death when loaded on coral scaffolds. Interestingly, bone formation was higher in orthotopic than ectopic site despite the same survival pattern. Ectopic implantation of cell-containing constructs is suitable to evaluate cell survival, but assessment of bone formation ability requires orthotopic implantation.