Calcium sulfate- and calcium phosphate-based bone substitutes. Mimicry of the mineral phase of bone

Calcium Sulfate Disks for Sustained-Release of Amoxicillin and Moxifloxacin for the Treatment of Osteomyelitis

The purpose of this in vitro study was to develop calcium sulfate (CS)-based disks infused with an antimicrobial drug, which can be used as a post-surgical treatment modality for osteomyelitis. CS powder was embedded with 10% antibiotic, amoxicillin (AMX) or moxifloxacin (MFX), to form composite disks 11 mm in diameter that were tested for their degradation and antibiotic release profiles. For the disk degradation study portion, the single drug-loaded disks were placed in individual meshes, subsequently submerged in phosphate-buffered saline (PBS), and incubated at 37 °C. The disks were weighed once every seven days and analyzed via Fourier-transform infrared spectroscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, and scanning electron microscopy. During the antibiotic release analysis, composite disks were placed in PBS solution, which was changed every 3 days, and analyzed for antibiotic activity and efficacy. The antibacterial effects of these sustained-release composites were tested by agar diffusion assay using Streptococcus mutans (S. mutans) UA 159 as an indicator strain. The degradation data showed significant increases in the degradation of all disks with the addition of antibiotics. Following PBS incubation, there were significant increases in the amount of phosphate and decreases in the amount of sulfate. The agar diffusion assay demonstrated that the released concentrations of the respective antibiotics from the disks were significantly higher than the minimum inhibitory concentration exhibited against S. mutans over a 2-3-week period. In conclusion, CS-antibiotic composite disks can potentially serve as a resorbable, osteoconductive, and antibacterial therapy in the treatment of bone defects and osteomyelitis.

Current and Future Perspectives of Bioactive Glasses as Injectable Material

This review covers recent compositions of bioactive glass, with a specific emphasis on both inorganic and organic materials commonly utilized as matrices for injectable materials. The major objective is to highlight the predominant bioactive glass formulations and their clinical applications in the biomedical field. Previous studies have highlighted the growing interest among researchers in bioactive glasses, acknowledging their potential to yield promising outcomes in this field. As a result of this increased interest, investigations into bioactive glass have prompted the creation of composite materials and, notably, the development of injectable composites as a minimally invasive method for administering the material within the human body. Injectable materials have emerged as a promising avenue to mitigate various challenges. They offer several advantages, including minimizing invasive surgical procedures, reducing patient discomfort, lowering the risk of postoperative infection and decreasing treatment expenses. Additionally, injectable materials facilitate uniform distribution, allowing for the filling of defects of any shape.

Surgical Considerations for Osteoporosis, Osteopenia, and Vitamin D Deficiency in Upper Extremity Surgery

Fragility fractures as a result of osteoporosis, osteopenia, or vitamin D deficiency are some of the most common injuries encountered in orthopedics and require careful consideration when determining the appropriate management and treatment options. A thorough perioperative evaluation can identify causes of low bone mineral density allowing for initiation of appropriate therapy. Surgical treatment of these fractures can be difficult, and techniques should be employed to ensure stable fixation. It is important to understand the potential pitfalls associated with treatment of fragility fractures to prevent avoidable complications. Postoperative management is key to preventing future injuries in this unique patient population.

Limitations and modifications in the clinical application of calcium sulfate

Calcium sulfate and calcium sulfate-based biomaterials have been widely used in non-load-bearing bone defects for hundreds of years due to their superior biocompatibility, biodegradability, and non-toxicity. However, lower compressive strength and rapid degradation rate are the main limitations in clinical applications. Excessive absorption causes a sharp increase in sulfate ion and calcium ion concentrations around the bone defect site, resulting in delayed wound healing and hypercalcemia. In addition, the space between calcium sulfate and the host bone, resulting from excessively rapid absorption, has adverse effects on bone healing or fusion techniques. This issue has been recognized and addressed. The lack of sufficient mechanical strength makes it challenging to use calcium sulfate and calcium sulfate-based biomaterials in load-bearing areas. To overcome these defects, the introduction of various inorganic additives, such as calcium carbonate, calcium phosphate, and calcium silicate, into calcium sulfate is an effective measure. Inorganic materials with different physical and chemical properties can greatly improve the properties of calcium sulfate composites. For example, the hydrolysis products of calcium carbonate are alkaline substances that can buffer the acidic environment caused by the degradation of calcium sulfate; calcium phosphate has poor degradation, which can effectively avoid the excessive absorption of calcium sulfate; and calcium silicate can promote the compressive strength and stimulate new bone formation. The purpose of this review is to review the poor properties of calcium sulfate and its complications in clinical application and to explore the effect of various inorganic additives on the physicochemical properties and biological properties of calcium sulfate.

Extrusion-based 3D printing of osteoinductive scaffolds with a spongiosa-inspired structure

Critical-sized bone defects resulting from trauma, inflammation, and tumor resections are individual in their size and shape. Implants for the treatment of such defects have to consider biomechanical and biomedical factors, as well as the individual conditions within the implantation site. In this context, 3D printing technologies offer new possibilities to design and produce patient-specific implants reflecting the outer shape and internal structure of the replaced bone tissue. The selection or modification of materials used in 3D printing enables the adaption of the implant, by enhancing the osteoinductive or biomechanical properties. In this study, scaffolds with bone spongiosa-inspired structure for extrusion-based 3D printing were generated. The computer aided design process resulted in an up scaled and simplified version of the bone spongiosa. To enhance the osteoinductive properties of the 3D printed construct, polycaprolactone (PCL) was combined with 20% (wt) calcium phosphate nano powder (CaP). The implants were designed in form of a ring structure and revealed an irregular and interconnected porous structure with a calculated porosity of 35.2% and a compression strength within the range of the natural cancellous bone. The implants were assessed in terms of biocompatibility and osteoinductivity using the osteosarcoma cell line MG63 and patient-derived mesenchymal stem cells in selected experiments. Cell growth and differentiation over 14 days were monitored using confocal laser scanning microscopy, scanning electron microscopy, deoxyribonucleic acid (DNA) quantification, gene expression analysis, and quantitative assessment of calcification. MG63 cells and human mesenchymal stem cells (hMSC) adhered to the printed implants and revealed a typical elongated morphology as indicated by microscopy. Using DNA quantification, no differences for PCL or PCL-CaP in the initial adhesion of MG63 cells were observed, while the PCL-based scaffolds favored cell proliferation in the early phases of culture up to 7 days. In contrast, on PCL-CaP, cell proliferation for MG63 cells was not evident, while data from PCR and the levels of calcification, or alkaline phosphatase activity, indicated osteogenic differentiation within the PCL-CaP constructs over time. For hMSC, the highest levels in the total calcium content were observed for the PCL-CaP constructs, thus underlining the osteoinductive properties.

Advanced applications of strontium-containing biomaterials in bone tissue engineering

Strontium (Sr) and strontium ranelate (SR) are commonly used therapeutic drugs for patients suffering from osteoporosis. Researches have showed that Sr can significantly improve the biological activity and physicochemical properties of materials in vitro and in vivo. Therefore, a large number of strontium containing biomaterials have been developed for repairing bone defects and promoting osseointegration. In this review, we provide a comprehensive overview of Sr-containing biomaterials along with the current state of their clinical use. For this purpose, the different types of biomaterials including calcium phosphate, bioactive glass, and polymers are discussed and provided future outlook on the fabrication of the next-generation multifunctional and smart biomaterials.

Injectable Self-Setting Ternary Calcium-Based Bone Cement Promotes Bone Repair

Bone defects, especially large ones, are clinically difficult to treat. The development of new bone repair materials exhibits broad application prospects in the clinical treatment of trauma. Bioceramics are considered to be one of the most promising biomaterials owing to their good biocompatibility and bone conductivity. In this study, a self-curing bone repair material having a controlled degradation rate was prepared by mixing calcium citrate, calcium hydrogen phosphate, and semi-hydrated calcium sulfate in varying proportions, and its properties were comprehensively evaluated. In vitro cell experiments and RNA sequencing showed that the composite cement activated PI3K/Akt and MAPK/Erk signaling pathways to promote osteogenesis by promoting the proliferation and osteoblastic differentiation of mesenchymal stem cells. In a rat model with femoral condyle defects, the composite bone cement showed excellent bone repair effect and promoted bone regeneration. The injectable properties of the composite cement further improved its practical applicability, and it can be applied in bone repair, especially in the repair of irregular bone defects, to achieve superior healing.

Composite Cement Materials Based on β-Tricalcium Phosphate, Calcium Sulfate, and a Mixture of Polyvinyl Alcohol and Polyvinylpyrrolidone Intended for Osteanagenesis

The primary purpose of the study, presented in this article, was to obtain a composite cement material intended for osteanagenesis. The β-tricalcium phosphate powder (β-TCP, β-Ca₃(PO₄)₂) was obtained by the liquid-phase method. Setting and hardening of the cement system were achieved by adding calcium sulfate hemihydrate (CSH, CaSO₄·1/2H₂O). An aqueous solution of polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), and a PVA/PVP mixture were used as a polymer component. The methods of capillary viscometry and Fourier-transform infrared spectroscopy (FTIR) revealed the formation of intermolecular hydrogen bonds between polymer components, which determines the good miscibility of polymers. The physicochemical properties of the synthesized materials were characterized by X-ray diffraction (XRD) and FTIR methods, and the added amount of polymers does not significantly influence the processes of phase formation and crystallization of the system. The size of crystallites CSD remained in the range of 32-36 nm, regardless of the ratio of polymer components. The influence of the composition of composites on their solubility was investigated. In view of the lower solubility of pure β-TCP, as compared to calcium sulfate dihydrate (CSD, CaSO₄·2H₂O), the solubility of composite materials is determined to a greater degree by the CSD solubility. Complexometric titration showed that the interaction between PVA and PVP impeded the diffusion of calcium ions, and at a ratio of PVA to PVP of 1/1, the smallest exit of calcium ions from the system is observed. The cytotoxicity analysis results allowed us to establish the fact that the viability of human macrophages in the presence of the samples varied from 80% to 125% as compared to the control.

Bone formation effect of highly concentrated tricalcium phosphate biocomposite screws in a rabbit osteoporosis model

The purpose of this study was to determine the efficacy of highly concentrated tricalcium phosphate (TCP) biocomposite screws on local bone formation in a rabbit model of osteoporosis induced by bilateral ovariohysterectomy (OHE). Fourteen 24-week-old female New Zealand rabbits (weight, 3-3.5 kg) were divided into two groups: (1) OHE and biodegradable poly(lactic-co-glycolic acid) (PLGA) without ß-TCP plate or screw insertion (OHE/Bio ScRew [BSR]) group and (2) OHE and biocomposite PLGA with highly concentrated ß-TCP plate and screw insertion (OHE/highly concentrated ß-triCalcium phosphate [HCCP]). Both groups underwent bilateral OHE and had two different types of screws and plates inserted at the proximal tibia. Bilateral tibiae were extracted at 25 weeks post-OHE. The extracted tibiae were scanned with ex vivo microcomputed tomography (micro-CT). Parameters including bone mineral density (BMD), trabecular bone volume (BV/TV), trabecular number (Tb.N), trabecular thickness (Tb. Th), and trabecular separation (Tb. Sp) were evaluated after staining the tibial samples with hematoxylin and eosin (H&E) and Masson's trichrome. We then performed pathological assessments. Micro-CT images revealed improved new bone formation near the implant in the OHE/HCCP group with higher values of BMD, BV/TV, and Tb.N but lower values of Tb. Th and Tb. Sp than the OHE/BSR group. Analyses of H&E and Masson's trichrome staining showed better new bone formation around the implant in the OHE/HCCP group than in the OHE/BSR group. The use of highly concentrated TCP biocomposite screw and plate might improve local bone formation and facilitate osteoconductivity in an osteoporotic rabbit model.

The Risk of Iatrogenic Hypercalcemia in Patients Undergoing Calcium Sulphate Beads Implantation in Prosthetic Joint Surgery: A Systematic Review

Calcium sulphate beads are increasingly being used in the management of prosthetic joint infections (PJI). Traditionally their use was limited to a void or dead space-filling combined with other additives such as Hydroxyapatite. Over the last decade, they have been developed to act more frequently as an antibiotics delivery system. Stimulan, a bio-absorbable form of Calcium sulfate, theoretically has an increased risk of hypercalcemia. Over the last few years, there have been published case reports which report it as an isolated cause of iatrogenic hypercalcemia. The sparsity of literature on this topic makes it difficult for surgeons to decide on the use of Calcium sulphate beads in patients with hypercalcemia predisposition in conditions like autoimmune disorders, sarcoidosis, malignancy, granulomatous diseases, heterotopic ossification, and hyperparathyroidism. The study was performed to assess the risk of hypercalcemia in patients after Calcium sulphate beads implantation in PJI. Two reviewers searched relevant literature in 3 online databases using cochrane methodology for systematic reviews. Studies reporting complications with the use of calcium sulphate beads in prosthetic joints were included. Studies reporting on less than five patients and studies reporting use in any other surgeries were excluded. The search of databases resulted in a total of 96 articles. After screening, a total of four articles were deemed suitable to be included in the analysis. A total of 1049 patients underwent calcium sulfate beads implantation, out of which 44 (4.2%) reported hypercalcemia with 41 (3.91%) transient in nature and 3 (0.28%) required management, including one with ICU admission. The result of this systematic review shows that calcium sulphate beads are safe and effective against PJI. There is a significant risk of transient hypercalcemia in susceptible patients and a low risk of symptomatic hypercalcemia.

Comparison of Outcome of Bone Autograft and Allograft in Union of Long Bone Fractures

Background and Purpose

There are few studies addressing the rate of application of bone allograft and its use; hence, the present study aimed to compare the clinical outcomes of using bone allograft and autograft in patients with long bone fracture.

Method

In this clinical trial study, all patients who underwent bone graft surgery with the diagnosed long bone fractures of upper and lower limbs at Shahid Beheshti Hospital were included in the research. Patients were divided into two groups, autograft and allograft, according to type of treatment. They were evaluated for their union, complications, and range of motion.

Results

In the present study, 124 people were studied. Among them, 100 patients were eligible and included in the study. The allograft and autograft groups did not have any statistical significant differences in terms of age, sex, location, causes of fracture, and surgical methods. Results of the present research on patients in terms of fracture site indicated that there was no significant relationship between the two groups in rate of union (P = 0.18). Allograft and autograft had no difference in terms of complications. Studied range of motion indicated that patients were not different in terms of their ranges of motion.

Conclusion

Based on findings of the present study, allograft could be a suitable substitute for the autograft. The two graft methods were similar in terms of complications, union, and ranges of motion.

Three dimensional printed nanostructure biomaterials for bone tissue engineering

The suffering from organ dysfunction due to damaged or diseased tissue/bone has been globally on the rise. Current treatment strategies for non-union bone defects include: the use of autografts, allografts, synthetic grafts and free vascularized fibular grafts. Bone tissue engineering has emerged as an alternative for fracture repair to satisfy the current unmet need of bone grafts and to alleviate the problems associated with autografts and allografts. The technology offers the possibility to induce new functional bone regeneration using synergistic combination of functional biomaterials (scaffolds), cells, and growth factors. Bone scaffolds are typically made of porous biodegradable materials that provide the mechanical support during repair and regeneration of damaged or diseased bone. Significant progress has been made towards scaffold materials for structural support, desired osteogenesis and angiogenesis abilities. Thanks for innovative scaffolds fabrication technologies, bioresorbable scaffolds with controlled porosity and tailored properties are possible today. Despite the presence of different bone scaffold fabrication methods, pore size, shape and interconnectivity have not yet been fully controlled in most of the methods. Moreover, scaffolds with tailored porosity for specific defects are still difficult to manufacture. Nevertheless, such scaffolds can be designed and fabricated using three dimensional (3D) printing approaches. 3D printing technology, as an advanced tissue scaffold fabrication method, offers the opportunity to produce complex geometries with distinct advantages. The technology has been used for the production of various types of bodily constructs such as blood vessels, vascular networks, bones, cartilages, exoskeletons, eyeglasses, cell cultures, tissues, organs and novel drug delivery devices. This review focuses on 3D printed scaffolds and their application in bone repair and regeneration. In addition, different classes of biomaterials commonly employed for the fabrication of 3D nano scaffolds for bone tissue engineering application so far are briefly discussed.

Alloplastic Bone Substitutes for Periodontal and Bone Regeneration in Dentistry: Current Status and Prospects

Various bone graft products are commercially available worldwide. However, there is no clear consensus regarding the appropriate bone graft products in different clinical situations. This review is intended to summarize bone graft products, especially alloplastic bone substitutes that are available in multiple countries. It also provides dental clinicians with detailed and accurate information concerning these products. Furthermore, it discusses the prospects of alloplastic bone substitutes based on an analysis of the current market status, as well as a comparison of trends among countries. In this review, we focus on alloplastic bone substitutes approved in the United States, Japan, and Korea for use in periodontal and bone regeneration. According to the Food and Drug Administration database, 87 alloplastic bone graft products have been approved in the United States since 1996. According to the Pharmaceuticals and Medical Devices Agency database, 10 alloplastic bone graft products have been approved in Japan since 2004. According to the Ministry of Health and Welfare database, 36 alloplastic bone graft products have been approved in Korea since 1980. The approved products are mainly hydroxyapatite, β-tricalcium phosphate, and biphasic calcium phosphate. The formulations of the products differed among countries. The development of new alloplastic bone products has been remarkable. In the near future, alloplastic bone substitutes with safety and standardized quality may be the first choice instead of autologous bone; they may offer new osteoconductive and osteoinductive products with easier handling form and an adequate resorption rate, which can be used with growth factors and/or cell transplantation. Careful selection of alloplastic bone graft products is necessary to achieve predictable outcomes according to each clinical situation.

Ceramic Biologics for Bony Fusion-a Journey from First to Third Generations

PURPOSE OF REVIEW

To provide information on characteristics and use of various ceramics in spine fusion and future directions.

RECENT FINDINGS

In most recent years, focus has been shifted to the use of ceramics in minimally invasive surgeries or implementation of nanostructured surface modification features to promote osteoinductive properties. In addition, effort has been placed on the development of bioactive synthetics. Core characteristic of bioactive synthetics is that they undergo change to simulate a beneficial response within the bone. This change is based on chemical reaction and various chemical elements present in the bioactive ceramics. Recently, a synthetic 15-amino acid polypeptide bound to an anorganic bone material which mimics the cell-binding domain of type-I collagen opened a possibility for osteogenic and osteoinductive roles of this hybrid graft material. Ceramics have been present in the spine fusion arena for several decades; however, their use has been limited. The major obstacle in published literature is small sample size resulting in low evidence and a potential for bias. In addition, different physical and chemical properties of various ceramics further contribute to the limited evidence. Although ceramics have several disadvantages, they still hold a great promise as a value-based graft material with being easily available, relatively inexpensive, and non-immunogenic.

Fabrication of Three-Dimensional Composite Scaffold for Simultaneous Alveolar Bone Regeneration in Dental Implant Installation

Dental implant surgeries involve the insertion of implant fixtures into alveolar bones to replace missing teeth. When the availability of alveolar bone at the surgical site is insufficient, bone graft particles are filled in the insertion site for successful bone reconstruction. Bone graft particles induce bone regeneration over several months at the insertion site. Subsequently, implant fixtures can be inserted at the recipient site. Thus, conventional dental implant surgery is performed in several steps, which in turn increases the treatment period and cost involved. Therefore, to reduce surgical time and minimize treatment costs, a novel hybrid scaffold filled with bone graft particles that could be combined with implant fixtures is proposed. This scaffold is composed of a three-dimensionally (3D) printed polycaprolactone (PCL) frame and osteoconductive ceramic materials such as hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP). Herein, we analyzed the porosity, internal microstructure, and hydrophilicity of the hybrid scaffold. Additionally, Saos-2 cells were used to assess cell viability and proliferation. Two types of control scaffolds were used (a 3D printed PCL frame and a hybrid scaffold without HA/β-TCP particles) for comparison, and the fabricated hybrid scaffold was verified to retain osteoconductive ceramic particles without losses. Moreover, the fabricated hybrid scaffold had high porosity and excellent microstructural interconnectivity. The in vitro Saos-2 cell experiments revealed superior cell proliferation and alkaline phosphatase assay results for the hybrid scaffold than the control scaffold. Hence, the proposed hybrid scaffold is a promising candidate for minimizing cost and duration of dental implant surgery.

Clinical Outcome After Anterior Lumbar Interbody Fusion With a New Osteoinductive Bone Substitute Material: A Randomized Clinical Pilot Study

STUDY DESIGN

Pilot, single-center, single-blinded, parallel-group, randomized clinical study.

OBJECTIVE

The aim of this study was to pilot a randomized clinical study to evaluate whether instrumented anterior lumbar interbody fusion (ALIF) with a new nanocrystalline hydroxyapatite embedded in a silica gel matrix (NH-SiO2) leads to superior radiologic and clinical outcomes at 12-month follow-up compared with instrumented ALIF with homologous bone.

SUMMARY OF BACKGROUND DATA

ALIF completed with interbody cages is an established technique for performing arthrodesis of the lumbar spine. There is ongoing discussion about which cage-filling material is most appropriate. This is the first study to assess the efficacy of NH-SiO2 in ALIF surgery.

MATERIALS AND METHODS

This randomized, clinical, pilot trial included 2 groups of 20 patients with monosegmental or multisegmental degenerative disease of the lumbar spine who were suitable to undergo monosegmental or bisegmental ALIF fusion at the level L4/L5 and L5/S1 with a carbon fiber reinforced polymer ALIF cage filled with either NH-SiO2 or homogenous bone. Primary outcome was postoperative disability as measured by the Oswestry Disability Index (ODI). Secondary outcomes were postoperative radiographic outcomes, pain, and quality of life. Patients were followed 12 months postoperatively.

RESULTS

Mean (±SD) 12-month ODI was 24±17 in the NH-SiO2 group and 27±19 in the homologous bone group (P=0.582). Postoperative radiography, functional outcomes, and quality-of-life indices did not differ significantly between groups at any of the regularly scheduled follow-up visits.

CONCLUSIONS

This clinical study showed similar functional, radiologic, and clinical outcomes 12 months postoperatively for instrumented ALIF procedures with the use of NH-SiO2 or homologous bone as cage filling. In the absence of any relevant differences in outcome, we postulate that the pivotal clinical study should be designed as an equivalence trial.

Biphasic Calcium Sulfate as an Alternative Grafting Material in Various Dental Applications

Various grafting materials have been used in oral and periodontal surgeries to augment and rebuild bone intraorally. Calcium sulfate, a synthetic material, also known as an alloplast, has been used for decades in orthopedics, plastic surgery, and oncologic and maxillofacial surgeries for the treatment of osseous deficiencies caused by trauma or inflammation. Biphasic calcium sulfate provides benefits as a short-term space maintainer. Use of biphasic calcium sulfate as the sole material are limited to relatively small osseous defects surrounded by at least 3 bony walls (eg, extraction sockets). Thus, for augmenting large and more complex bone deficiencies Bond Apatite, a composite graft formulation, is indicated. This work will review the various clinical applications of Bond Apatite as an alternative to other graft materials.

Long-term clinical and radiographic evaluation of the effectiveness of direct pulp-capping materials

The aim of this review was to assess the effectiveness of different direct pulp-capping (DPC) materials for human pulp-exposed teeth. An electronic search was performed on 20 February 2018. Long-term clinical and radiographic evaluations of the effectiveness of different DPC materials for use on human pulp-exposed teeth were included. Risk-of-bias assessment and data extraction were performed. From the 496 identified articles, 15 met the eligibility criteria. Among the studies included in those articles, a total of 1,322 teeth were treated with 12 types of DPC materials, and 1,136 teeth were evaluated at a final follow-up examination. For mineral trioxide aggregate (MTA) and calcium hydroxide (CH), the number of included studies, the number of treated teeth, and the mean follow-up period of studies were almost equal, and the success rates of MTA was superior to CH. Therefore, MTA is likely to be a more effective and predictable material for DPC compared to CH. However, the results were based on the included studies, which were all judged to have a high risk of bias. Therefore, more long-term clinical and radiographic studies designed with lower risk of bias are needed. Moreover, the other 10 materials were only investigated by a small number of studies; therefore, further studies are required.

Evidence of Negative Effects of Defect Size and Older Patient Age by Quantitative CT-Based 3D Image Analysis in Ultraporous Beta-Tricalcium Phosphate Grafted Extremity Bone Defects at One Year

Introduction

Synthetic bone graft materials are commonly used to fill defects after curettage of benign bone lesions. Ultraporous beta tricalcium phosphate (TCP) is a popular synthetic compound used in this situation. Prior clinical studies based on plain X-ray analysis suggest incorporation of TCP is incomplete, even when combined with bone marrow (BMA).

Purpose

The purpose was to analyze volumetric CT-based changes in defects grafted with TCP with/without BMA in a completed prospective RCT to objectively determine (1) relationship between size and age versus TCP incorporation and (2) whether there is an advantage to addition of BMA.

Methods

Twenty-one patients with CT scans at ≥1 year follow-up available for digital analysis (TCP=10, TCP w/BMA =11) form the study population. CT image stacks were evaluated by creating volumetric masks using MIMICS imaging software for total defect, graft remaining, and graft incorporated volumes graft incorporation endpoints.

Results

Overall, there was significant (p=0.0029) negative correlation (r² = 0.38) between defect size and ratio of incorporated bone to defect size. This relationship remained strong (r² = 0.56) particularly for defects > 20 cc but not for smaller defects. Bone width was also a significantly related factor (r² = 0.94), with less graft incorporation in larger bone sites, in part likely due to the linear relationship between defect size and bone width. Relationship with age was complex and closely tied to defect volume. For larger defect volumes, younger patients were more successful at graft incorporation. Although age itself was not an independently significant factor, as defect volume increased, advanced age more negatively impacted new bone formation.

Conclusions

Larger size defect and affected bone and advancing age appear to be important negative factors in synthetic graft incorporation. Results showed no advantage to addition of BMA to TCP.

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.

Bone substitute made from a Brazilian oyster shell functions as a fast stimulator for bone-forming cells in an animal model

Despite their demonstrated biocompatibility and osteogenic properties, oyster shells have been reported as a potential alternative to other commonly used materials for bone substitution. This study evaluated whether an experimental bone substitute (EBS) made from a typical oyster shell of Northeastern Brazil (Crassostrea rhizophora) has effects on bone development using an animal model. Oysters were collected from a biologically assisted vivarium, and their inner layer was used for preparing an EBS. Chemical and surface characterization of EBS was performed using Individually Coupled Plasma Optical Emission Spectrometry (ICP-OES) and Scanning Electron Microscope (SEM), respectively. Seventy-two rats were randomly assigned to groups according to the treatment of bone defects created in the submandibular area: Negative Control (-C), Positive Control (+C; Bio-Oss®) and EBS. Euthanasia occurred at 7, 21, 42 and 56 days postoperatively. The bone pieces were stained with hematoxylin and eosin (H&E). The formation of bone tissue was evaluated histologically and histomorphometrically. Data were analyzed through the Kruskal-Wallis test and ANOVA considering a significant level of 5%. The main element found in EBS was calcium (71.68%), and it presented heterogeneity in the particle size and a porosity aspect at SEM analysis. Histological results revealed the absence of inflammatory cells in all groups, being that EBS presented the most accelerated process of bone formation with a statistically significant difference between this group and the +C and -C groups in the 21-day time-point (p < 0.05). After 21 days, the bone formation process was similar between all groups (p > 0.05), showing an immature lamellar bone pattern after 56 days of experimentation (p > 0.05). Within the limitations of this study, it was possible to conclude that EBS presented good biocompatibility and promoted fast stimulation for bone-forming cells in an animal model.

Osteoinduction and -conduction through absorbable bone substitute materials based on calcium sulfate: in vivo biological behavior in a rabbit model

Calcium sulfate (CS) can be used as an antibiotically impregnated bone substitute in a variety of clinical constellations. Antibiotically loaded bone substitutes find specific application in orthopedic and trauma surgery to prevent or treat bone infections especially in relation to open bone defects. However, its use as a structural bone graft reveals some concerns due to its fast biodegradation. The addition of calcium carbonate and tripalmitin makes CS formulations more resistant to resorption leaving bone time to form during a prolonged degradation process. The aim of the present study was the evaluation of biocompatibility and degradation properties of newly formulated antibiotically impregnated CS preparations. Three different types of CS bone substitute beads were implanted into the tibial metaphysis of rabbits (CS dihydrate with tripalmitin, containing gentamicin (Group A) or vancomycin (Group B); Group C: tobramycin-loaded CS hemihydrate). Examinations were performed by means of x-ray, micro-computed tomography (micro-CT) and histology after 4, 6, 8 and 12 weeks. Regarding biocompatibility of the formulations, no adverse reactions were observed. Histology showed formation of vital bone cells attached directly to the implanted materials, while no cytotoxic effect in the surrounding of the beads was detected. All CS preparations showed osteogenesis associated to implanted material. Osteoblasts attached directly to the implant surface and revealed osteoid production, osteocytes were found in newly mineralized bone. Group C implants (Osteoset^®) were subject to quick degradation within 4 weeks, after 6-8 weeks there were only minor remnants with little osteogenesis demonstrated by histological investigations. Group A implants (Herafill^®-G) revealed similar degradation within atleast 12 weeks. In contrast, group B implants (CaSO4-V) were still detectable after 12 weeks with the presence of implant-associated osteogenesis atlatest follow-up. In all of these preparations, giant cells were found during implant degradation on surface and inside of resorption lacunae. None of the analyzed CS preparations triggered contact activation. All implants demonstrated excellent biocompatibility, with implants of Group A and B showing excellent features as osteoconductive and -inductive scaffolds able to improve mechanical stability.

Calcium-containing scaffolds induce bone regeneration by regulating mesenchymal stem cell differentiation and migration

Background

Osteoinduction and subsequent bone formation rely on efficient mesenchymal stem cell (MSC) recruitment. It is also known that migration is induced by gradients of growth factors and cytokines. Degradation of Ca²⁺-containing biomaterials mimics the bone remodeling compartment producing a localized calcium-rich osteoinductive microenvironment. The aim of our study was to determine the effect of calcium sulfate (CaSO₄) on MSC migration. In addition, to evaluate the influence of CaSO₄ on MSC differentiation and the potential molecular mechanisms involved.

Methods

A circular calvarial bone defect (5 mm diameter) was created in the parietal bone of 35 Balb-C mice. We prepared and implanted a cell-free agarose/gelatin scaffold alone or in combination with different CaSO₄ concentrations into the bone defects. After 7 weeks, we determined the new bone regenerated by micro-CT and histological analysis. In vitro, we evaluated the CaSO₄ effects on MSC migration by both wound healing and agarose spot assays. Osteoblastic gene expression after BMP-2 and CaSO₄ treatment was also evaluated by qPCR.

Results

CaSO₄ increased MSC migration and bone formation in a concentration-dependent manner. Micro-CT analysis showed that the addition of CaSO₄ significantly enhanced bone regeneration compared to the scaffold alone. The histological evaluation confirmed an increased number of endogenous cells recruited into the cell-free CaSO₄-containing scaffolds. Furthermore, MSC migration in vitro and active AKT levels were attenuated when CaSO₄ and BMP-2 were in combination. Addition of LY294002 and Wortmannin abrogated the CaSO₄ effects on MSC migration.

Conclusions

Specific CaSO₄ concentrations induce bone regeneration of calvarial defects in part by acting on the host’s undifferentiated MSCs and promoting their migration. Progenitor cell recruitment is followed by a gradual increment in osteoblast gene expression. Moreover, CaSO₄ regulates BMP-2-induced MSC migration by differentially activating the PI3K/AKT pathway. Altogether, these results suggest that CaSO₄ scaffolds could have potential applications for bone regeneration.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-017-0713-0) contains supplementary material, which is available to authorized users.

Role of Systemic and Local Antibiotics in the Treatment of Open Fractures

The orthopedic community has learned much about the treatment of open fractures from the tremendous work of Ramon Gustilo, Michael Patzakis, and others; however, open fractures continue to be very difficult challenges. Type III open fractures continue to be associated with high infection rates. Some combination of systemic and local antibiotics may be most appropriate in these high-grade open fractures. Further research is still necessary in determining optimal systemic antibiotic regimens as well as the role of local antibiotics. Any new discoveries related to novel systemic antibiotics or local antibiotic carriers will need to be evaluated related to cost.

Formulation, Delivery and Stability of Bone Morphogenetic Proteins for Effective Bone Regeneration

Bone morphogenetic proteins (BMPs) are responsible for bone formation during embryogenesis and bone regeneration and remodeling. The osteoinductive action of BMPs, especially BMP-2 and BMP-7, has led to their use in a range of insurmountable treatments where intervention is required for effective bone regeneration. Introduction of BMP products to the market, however, was not without reports of multiple complications and side effects. Aiming for optimization of the therapeutic efficacy and safety, efforts have been focused on improving the delivery of BMPs to lower the administered dose, localize the protein, and prolong its retention time at the site of action. A major challenge with these efforts is that the protein stability should be maintained. With this review we attempt to shed light on how the stability of BMPs can be affected in the formulation and delivery processes. We first provide a short overview of the current standing of the complications experienced with BMP products. We then discuss the different delivery parameters studied in association with BMPs, and their influence on the efficacy and safety of BMP treatments. In particular, the literature addressing the stability of BMPs and their possible interactions with components of the delivery system as well as their sensitivity to conditions of the formulation process is reviewed. In summary, recent developments in the fields of bioengineering and biopharmaceuticals suggest that a good understanding of the relationship between the formulation/delivery conditions and the stability of growth factors such as BMPs is a prerequisite for a safe and effective treatment.

Histologic and histomorphometric evaluation of bone regeneration using nanocrystalline hydroxyapatite and human freeze-dried bone graft : An experimental study in rabbit

PURPOSE

Bone regeneration is an important concern in periodontal treatment and implant dentistry. Different biomaterials and surgical techniques have been used for this purpose. The aim of the present study was to compare the effect of nanocrystalline hydroxyapatite and human freeze-dried bone graft (FDBG) in regeneration of rabbit calvarium bony defects by histologic and histomorphometric evaluation.

METHODS

In this experimental study, three similar defects, measuring 8 mm in diameter, were created in the calvaria of 16 white New Zealand rabbits. Two defects were filled with FDBG and nanocrystalline hydroxyapatite silica gel, while the other one remained unfilled to be considered as control. All the defects were covered with collagen membranes. During the healing period, two animals perished; so 14 rabbits were divided into two groups: half of them were euthanized after 6 weeks of healing and the other half after 12 weeks. The specimens were subjected to histologic and histomorphometric examinations for assessment of the following variables: percentage of bone formation and residual graft material, inflammation scores, patterns of bone formation and type of newly formed bone.

RESULTS

The percentages of new bone formation after 6 weeks were 14.22 ± 7.85, 21.57 ± 6.91, and 20.54 ± 10.07% in FDBG, NanoBone, and control defects. These values were 27.54 ± 20.19, 23.86 ± 6.27, and 26.48 ± 14.18% in 12-week specimens, respectively. No significant differences were found in the amount of bone formation between the groups. With regard to inflammation, the control and NanoBone groups showed significantly less inflammation compared to FDBG at the 6-week healing phase (P = 0.04); this difference was not significant in the 12-week specimens.

CONCLUSIONS

Based on the results of this experimental study, both NanoBone and FDBG exhibited a similar effect on bone formation.

PLA composites: From production to properties

Poly(lactic acid) or polylactide (PLA), a biodegradable polyester produced from renewable resources, is used for various applications (biomedical, packaging, textile fibers and technical items). Due to its inherent properties, PLA has a key-position in the market of biopolymers, being one of the most promising candidates for further developments. Unfortunately, PLA suffers from some shortcomings, whereas for the different applications specific end-use properties are required. Therefore, the addition of reinforcing fibers, micro- and/or nanofillers, and selected additives within PLA matrix is considered as a powerful method for obtaining specific end-use characteristics and major improvements of properties. This review highlights recent developments, current results and trends in the field of composites based on PLA. It presents the main advances in PLA properties and reports selected results in relation to the preparation and characterization of the most representative PLA composites. To illustrate the possibility to design the properties of composites, a section is devoted to the production and characterization of innovative PLA-based products filled with thermally-treated calcium sulfate, a by-product from the lactic acid production process. Moreover, are emphasized the last tendencies strongly evidenced in the case of PLA, i.e., the high interest to diversify its uses by moving from biomedical and packaging (biodegradation properties, "disposables") to technical applications ("durables").

Cranioplasty Using a Novel Osteoconductive Scaffold and Platelet Gel

BACKGROUND

Commonly used materials for cranioplasty include autogenous bone grafts, methyl methacrylate, and titanium mesh. We evaluated a novel osteoconductive scaffold [N-isopropylacrylamide cross-linked with acrylic acid using γ-rays (ANa powder)] mixed with platelet gel for cranioplasty.

METHODS

ANa powder mixed with platelet gel was implanted into a 15 × 15-mm, full-thickness calvarial bone defect in 5 New Zealand white rabbits. ANa powder mixed with phosphate-buffered saline was implanted in 5 rabbits. The calvarial bone defect was left unreconstructed in another 5 rabbits. Twelve weeks after surgery, computed tomography examination was used to evaluate the radiographic evidence of bone healing in vivo. Bone specimens were then retrieved for histologic study.

RESULTS

The ANa scaffold mixed with platelet gel is biocompatible, biodegradable, and both osteoconductive and osteoinductive, leading to progressive growth of new bone into the calvarial bone defect.

CONCLUSION

The use of this novel osteoconductive scaffold combined with osteoinductive platelet gel offers a valuable alternative for the reconstruction of calvarial bone defects.

Gelatin-Modified Bone Substitute with Bioactive Molecules Enhance Cellular Interactions and Bone Regeneration

In this work, we have synthesized injectable bone cement incorporated with gelatin to enhance cellular interaction. Human osteosarcoma Saos-2 cells derived bone morphogenetic proteins (BMP's) and a bisphosphonate (zoledronic acid (0.2 mM)) were also incorporated to cement. In vitro studies conducted using Saos-2 demonstrated enhanced cell proliferation on gelatin (0.2%w/v) cement. The differentiation of C2C12 mouse myoblast cells into bone forming cells showed 6-fold increase in ALP levels on gelatin cement. Polymerase chain reaction (PCR) for bone biomarkers showed osteoinductive potential of gelatin cement. We investigated efficacy for local delivery of these bioactive molecules in enhancing bone substitution qualities of bone cements by implanting in 3.5 mm critical size defect in tibial metaphysis of wistar rats. The rats were sacrificed after 12 weeks and 16 weeks post implantation. X-ray, micro-CT, histology, and histomorphometry analysis were performed to check bone healing. The cement materials slowly resorbed from the defect site leaving HAP creating porous matrix providing surface for bone formation. The materials showed high biocompatibility and initial bridging was observed in all the animals but maximum bone formation was observed in animals implanted with cement incorporated with zoledronic acid followed by cement with BMP's compared to other groups.

Unexpected radiographic lucency following grafting of bone defects with calcium sulfate/tricalcium phosphate bone substitute

OBJECTIVE

To report the development of unexpected radiographic lucency (URL) corresponding to the use of a commercially available calcium sulfate/tricalcium phosphate composite used to treat benign osseous lesions.

MATERIALS AND METHODS

This is a retrospective comparative study of patients with and without URL after treatment with curettage and grafting with calcium sulfate/tricalcium phosphate. The charts of 87 patients meeting the inclusion criteria were reviewed for demographic, clinical, and radiographic data. The group with URL was compared to those with more typical patterns of graft incorporation.

RESULTS

Thirteen of 87 cases (15%) showed URL. There was no difference with respect to the pathologic subtype, anatomic location, or specific bone for the presence of URL. Of patients with URL, one (7.7%) required reoperation and regrafting, whereas among patients without URL, five (6.7%) had clinical complications, with one requiring reoperation and regrafting, and one requiring radiofrequency ablation.

CONCLUSIONS

The majority of patients treated with calcium sulfate/tricalcium phosphate cementing after curettage of low-grade bone lesions go on to uneventful healing in our series. In a minority of patients, URL occurs in lieu of the more typical pattern of centripetal incorporation. However, there is no increase in complications associated with URL. Based on these findings, patients should be informed of the possibility of this risk, although there appears to be little risk of clinically relevant adverse consequences. Physicians should be aware of this complication in order to avoid mistaking it for recurrence of the primary lesion.

Synchronization of calcium sulphate cement degradation and new bone formation is improved by external mechanical regulation

A major challenge faced in the bone materials of weight-bearing without internal fixture support is the mismatch of material degradation and new bone formation, leading to weakening or even failure of the overall bony structure. This study demonstrated in the rat femur model that calcium sulphate cement degradation and new bone formation could be better synchronized by external mechanical force. An ascending force in line with calcium sulphate cement degradation could achieve bone healing in 37 days with ultimate load to failure of 87.00 ± 7.30 N, similar to that of intact femur (80.46 ± 2.79 N, p = 0.369). In contrast, the healing process under either a constant force or no force illustrated significant residual defect volumes of 1.47 ± 0.44 and 4.08 ± 0.89 mm(3) (p < 0.001), and weaker ultimate loads to failure of 69.56 ± 4.74 and 59.17 ± 7.48 N, respectively (p < 0.001). Our results suggest that the mechanical regulation approach deserves further investigation and may potentially offer a clinical strategy to improve synchronization.

Spontaneous fractures in custom-made porous hydroxyapatite cranioplasty implants: is fragility the only culprit?

BACKGROUND

Although the porous hydroxyapatite (PHA) used in custom-made cranioplasty implants is a material appreciated for its biomimetic properties, before osteointegration it is initially very fragile. Nevertheless, we wondered whether this primary fragility is entirely due to brittleness or whether the surgeon's actions may influence the behavior of the material.

METHODS

To study the influence of the surgeon's behavior, we made a virtual model of a custom-made PHA cranioplasty implant and submitted it to three implant procedural variables using finite element methods. In the first test, a scenario in which the surgeon's design, validation, and positioning techniques are impeccable, the edges of the implant adhered well to the craniectomy margins. In the second test, a discrepancy between a portion of the perimeter of the craniectomy and the profile of the prosthesis was modeled, and in the third test, several gaps were simulated between the implant and the craniectomy margins.

RESULTS

Our mathematical model showed that when local and general discontinuities were included in the test scenarios, there was an increase in the load coming to bear on the cranioplasty implant, which amounted to 80 and 50 %, respectively.

CONCLUSIONS

The fragility of custom-made PHA cranioplasty implants increases if the surgeon fails to achieve a precise design and validation, and/or an accurate surgical procedure. Nevertheless, careful attention during these phases helps to maintain the strength of the implant, given the more favorable mechanical conditions, without interfering with its biomimetic capacity.

Mechanical force enhanced bony formation in defect implanted with calcium sulphate cement

To improve the osteogenic property of bone repairing materials and to accelerate bone healing are major tasks in bone biomaterials research. The objective of this study was to investigate if the mechanical force could be used to accelerate bone formation in a bony defect in vivo. The calcium sulfate cement was implanted into the left distal femoral epiphyses surgically in 16 rats. The half of rats were subjected to external mechanical force via treadmill exercise, the exercise started at day 7 postoperatively for 30 consecutive days and at a constant speed 8 m·min⁻¹ for 45 min·day⁻¹, while the rest served as a control. The rats were scanned four times longitudinally after surgery using microcomputed tomography and newly formed bone was evaluated. After sacrificing, the femurs had biomechanical test of three-point bending and histological analysis. The results showed that bone healing under mechanical force were better than the control with residual defect areas of 0.64±0.19 mm² and 1.78±0.39 mm² (P<0.001), and the ultimate loads to failure under mechanical force were 69.56±4.74 N, stronger than the control with ultimate loads to failure of 59.17±7.48 N (P=0.039). This suggests that the mechanical force might be used to improve new bone formation and potentially offer a clinical strategy to accelerate bone healing.

Adjuvant treatment of chronic osteomyelitis of the tibia following exogenous trauma using OSTEOSET(®)-T: a review of 21 patients in a regional trauma centre

Surgical debridement and prolonged systemic antibiotic therapy are an established management strategy for infection after tibial fractures. Local antibiotic delivery via cement beads has shown improved outcome but requires further surgery for extraction of beads. OSTEOSET^®-T is a resorbable bone void filler composed of calcium sulphate and 4 % tobramycin that is packed easily into bone defects. This is a review of the outcomes of 21 patients treated with OSTEOSET^®-T for osteomyelitis of the tibia. This is a retrospective case note and clinical review. In all cases, the strategy was debridement, with removal of any implants, with excision back to bleeding bone. OSTEOSET^®-T pellets were packed into any contained defects or the intra-medullary canal with further bony stabilisation (n = 9) and soft tissue reconstruction (n = 7) undertaken as required. Intravenous vancomycin and meropenem were administered after sampling with substitution to targeted antibiotic therapy for between 6 weeks and 6 months. The average follow-up was 15 months. Union rate after tibial reconstruction was 100 %. Wound complications were encountered in 52 %: a wound discharge in the early post-operative period was noted in seven patients (33 %) independent of site of pellet placement. In the 14 cases without a wound leak, five developed wound complications (p = 0.06, Fisher’s exact test) either from delayed wound-healing or pin-site infections. One patient developed a transient acute kidney injury and one refractory osteomyelitis. OSTEOSET^®-T is an effective adjunct in the treatment of chronic tibial osteomyelitis following trauma based on the low incidence of relapse of infection within the period of follow-up in this study, but significant wound complications and one transient nephrotoxic event were also recorded.

A prospective randomized comparison of PEEK cage containing calcium sulphate or demineralized bone matrix with autograft in anterior cervical interbody fusion

PURPOSE

A variety of bone substitutes have been successfully used to fill PEEK cages in cervical interbody fusion in order to avoid the complications related to bone harvesting from the donor site. However, no controlled study has previously been conducted to compare the effectiveness of PEEK interbody cages containing calcium sulphate/ demineralized bone matrix (CS/DBM) with autogenous cancellous bone for the treatment of cervical spondylosis. The objective of this prospective, randomized clinical study was to evaluate the effectiveness of implanting PEEK cages containing CS/DBM for the treatment of cervical radiculopathy and/or myelopathy.

METHODS

Sixty-eight patients with cervical radiculopathy and/or myelopathy were randomly assigned to receive one- or two-level discectomy and fusion with PEEK interbody cages containing CS/DBM or autogenous iliac cancellous bone (AIB). The patients were followed up for two years postoperatively. The radiological and clinical outcomes were assessed during a two-year follow-up.

RESULTS

The mean blood loss was 75 ± 18.5 ml in the CS/DBM group and 100 ± 19.6 ml (P < 0.01) in the AIB group. The fusion rate was 94.3 % in the CS/DBM group and 100 % in the AIB group at 12-month follow-up. The fusion rate was 100 % at final follow-up in both groups. No significant difference (P > 0.05) was found regarding improvement of JOA score and segmental lordosis as well as neck and arm pain at all time intervals between the two groups. The total complication rate was significantly higher (P < 0.05) in the AIB group than in the CS/DBM group, but there was no significant difference between the two groups (P > 0.05) when comparing the complications in the neck.

CONCLUSIONS

In conclusion, the PEEK interbody fusion cage containing CS/DBM or AIB following one- or two-level discectomy had a similar outcome for cervical spondylotic radiculopathy and/or myelopathy. The rate of fusion and the recovery rate of JOA score between the two groups were the same. The filling of CS/DBM in the PEEK cage instead of AIB has the advantage of less operative blood loss and fewer complications at the donor site.

Tailored sequential drug release from bilayered calcium sulfate composites

The current standard for treating infected bony defects, such as those caused by periodontal disease, requires multiple time-consuming steps and often multiple procedures to fight the infection and recover lost tissue. Releasing an antibiotic followed by an osteogenic agent from a synthetic bone graft substitute could allow for a streamlined treatment, reducing the need for multiple surgeries and thereby shortening recovery time. Tailorable bilayered calcium sulfate (CS) bone graft substitutes were developed with the ability to sequentially release multiple therapeutic agents. Bilayered composite samples having a shell and core geometry were fabricated with varying amounts (1 or 10 wt.%) of metronidazole-loaded poly(lactic-co-glycolic acid) (PLGA) particles embedded in the shell and simvastatin directly loaded into either the shell, core, or both. Microcomputed tomography showed the overall layered geometry as well as the uniform distribution of PLGA within the shells. Dissolution studies demonstrated that the amount of PLGA particles (i.e., 1 vs. 10 wt.%) had a small but significant effect on the erosion rate (3% vs. 3.4%/d). Mechanical testing determined that introducing a layered geometry had a significant effect on the compressive strength, with an average reduction of 35%, but properties were comparable to those of mandibular trabecular bone. Sustained release of simvastatin directly loaded into CS demonstrated that changing the shell to core volume ratio dictates the duration of drug release from each layer. When loaded together in the shell or in separate layers, sequential release of metronidazole and simvastatin was achieved. By introducing a tunable, layered geometry capable of releasing multiple drugs, CS-based bone graft substitutes could be tailored in order to help streamline the multiple steps needed to regenerate tissue in infected defects.

Posterior lumbar fusion: choice of approach and adjunct techniques

The choice among the many options of approach and adjunct techniques in planning a posterior lumbar fusion can be problematic. Debates remain as to whether solid fusion has an advantage over pseudarthrosis regarding long-term symptom deterioration and whether an instrumented or a noninstrumented approach will best serve clinically and/or cost effectively, particularly in elderly patients. Increased motion resulting in higher rates of nonunion and the use of nonsteroidal anti-inflammatory drugs have been studied in animal models and are presumed risk factors, despite the lack of clinical investigation. Smoking is a proven risk factor for pseudarthrosis in both animal models and level III clinical studies. Recent long-term studies and image/clinical assessment of lumbar fusions and pseudarthrosis show that, although imaging remains a key area of difficulty in assessment, including an instrumented approach and a well-selected biologic adjunct, as well as achieving a solid fusion, all carry important long-term clinical advantages in avoiding revision surgery for nonunion.

The composite of hydroxyapatite and calcium sulphate: a review of preclinical evaluation and clinical applications

Recent publications have shown that the combination of α-calcium sulfate hemihydrate, the densest form of hydrates and hydroxyapatite (HA) particles gives good clinical outcome in various applications. It has large potential as bone substitute since the material transforms to bone throughout the entire volume and not only by creeping substitution, from the surface toward the inside. Release of important proteins for osteogenesis has been observed around implanted material and is speculated to be due to fast dissolution of the calcium sulfate phase in combination with the osteoconductive and bioactive nature of HA. In diabetic foot infection, the osteoconductive HA/calcium sulfate material has been successfully used loaded with antibiotics and since it is injectable, the application is minimally invasive, easy and precise. It is a bone substitute for the future.

Hydroxyapatite-Based Biomaterials Versus Autologous Bone Graft in Spinal Fusion: An In Vivo Animal Study

STUDY DESIGN

An in vivo study was designed to compare the efficacy of biomimetic magnesium-hydroxyapatite (MgHA) and of human demineralized bone matrix (HDBM), both dispersed in a mixture of biomimetic MgHA nanoparticles, with that of an autologous bone graft.

OBJECTIVE

The objective of this study was to evaluate 2 new bone substitutes as alternatives to a bone autograft for spinal fusion, determining their osteoinductive and osteoconductive properties, and their capacity of remodeling, using a large animal model.

SUMMARY OF BACKGROUND DATA

Spinal fusion is a common surgical procedure and it is performed for different conditions. A successful fusion requires potentially osteogenic, osteoinductive, and osteoconductive biomaterials.

METHODS

A posterolateral spinal fusion model involved 18 sheep, bilaterally implanting test materials between the vertebral transverse processes. The animals were divided into 2 groups: 1 fusion level was treated with MgHA (group 1) or with HDBM-MgHA (group 2). The other fusion level received bone autografts in both groups.

RESULTS

Radiographical, histological, and microtomographic results indicated good osteointegration between the spinous process and the vertebral foramen for both materials. Histomorphometry revealed no significant differences between MgHA and autologous bone for all the parameters examined, whereas significantly lower values of bone volume were observed between HDBM-MgHA and autologous bone. Moreover, the normalization of the histomorphometric data with autologous bone revealed that MgHA showed a significantly higher value of bone volume and a lower value of trabecular number, more similar to autologous bone than HDBM-MgHA.

CONCLUSION

The study showed that the use of MgHA in an ovine model of spinal fusion led to the deposition of new bone tissue without qualitative and quantitative differences with respect to new bone formed with autologous bone, whereas the HDBM-MgHA led to a reduced deposition of newly formed bone tissue.

LEVEL OF EVIDENCE

N/A.

Drug release from calcium sulfate-based composites

To help reduce the need for autografts, calcium sulfate (CS)-based bone graft substitutes are being developed to provide a stable platform to aid augmentation while having the ability to release a broad range of bioactive agents. CS has an excellent reputation as a biocompatible and osteoconductive substance, but addition of bioactive agents may further enhance these properties. Samples were produced with either directly loaded small, hydrophobic molecule (i.e., simvastatin), directly loaded hydrophilic protein (i.e., lysozyme), or 1 and 10 wt % of fast-degrading poly(β-amino ester) (PBAE) particles containing protein. Although sustained release of directly loaded simvastatin was achieved, direct loading of small amounts of lysozyme resulted in highly variable release. Direct loading of a larger amount of protein generated a large burst, 65% of total loading, followed by sustained release of protein. Release of lysozyme from 1 wt % of PBAE particles embedded into CS was more controllable than when directly loaded, and for 10 wt % of protein-loaded PBAE particles, a higher burst was followed by sustained release, comparable to the results for the high direct loading. Compression testing determined that incorporation of directly loaded drug or drug-loaded PBAE particles weakened CS. In particular, PBAE particles had a significant effect on the strength of the composites, with a 25 and 80% decrease in strength for 1 and 10 wt % particle loadings, respectively. CS-based composites demonstrated the ability to sustainably release both macromolecules and small molecules, supporting the potential for these materials to release a range of therapeutic agents.

Effects of Heat Treatment on the Mechanical and Degradation Properties of 3D-Printed Calcium-Sulphate-Based Scaffolds

Three-dimensional printing (3DP) has been employed to fabricate scaffolds with advantages of fully controlled geometries and reproducibility. In this study, the scaffold structure design was established through investigating the minimum feature size and powder size distribution. It was then fabricated from the 3DP plaster-based powders (CaSO4·1/2H2O). Scaffolds produced from this material demonstrated low mechanical properties and a rapid degradation rate. This study investigated the effects of heat treatment on the mechanical and in vitro degradation properties of the CaSO4 scaffolds. The occurrence of dehydration during the heating cycle offered moderate improvements in the mechanical and degradation properties. By using a heat treatment protocol of 200°C for 30 min, compressive strength increased from 0.36 ± 0.13 MPa (pre-heat-treated) to 2.49 ± 0.42 MPa (heat-treated). Heat-treated scaffolds retained their structure and compressive properties for up to two days in a tris-buffered solution, while untreated scaffolds completely disintegrated within a few minutes. Despite the moderate improvements observed in this study, the heat-treated CaSO4 scaffolds did not demonstrate mechanical and degradation properties commensurate with the requirements for bone-tissue-engineering applications.

Bioerodible calcium sulfate/poly(β-amino ester) hydrogel composites

The capacity to quickly regenerate or augment bone lost as a result of resorption is crucial to ensure suitable application of prosthetics for restoring masticatory function. Calcium sulfate hemihydrate (CS)-based bone graft substitute composites containing poly(β-amino ester) (PBAE) biodegradable hydrogel particles were developed to act as a 'tenting' barrier to soft tissue infiltration, potentially providing adequate space to enable vertical bone regeneration. CS has long been recognized as an osteoconductive biomaterial with an excellent reputation as a biocompatible substance. Composite samples were fabricated with varying amounts (1 or 10 wt%) and sizes (53-150 or 150-250 μm) of gel particles embedded in CS. The swelling and degradation rates of PBAE gels alone were rapid, resulting in complete degradation in less than 24h, an important characteristic to aid in controlled release of drug. MicroCT images revealed a homogeneous distribution of gel particles within the CS matrix. All CS samples degraded via surface erosion, with the amount of gel particles (i.e., 10 wt% gel particles) having only a small, but significant, effect on the dissolution rate (4% vs. 5% per day). Compression testing determined that the amount, but not the size, of gel particles had a significant effect on the overall strength of the composites. As much as a 75% drop in strength was seen with a 10 wt% loading of particles. A pilot study using PBAE particles loaded with the multipotential drug curcumin demonstrated sustained release of drug from CS composites. By adjusting the amount and/or size of the biodegradable gel particles embedded in CS, mechanical strength and degradation rates of the composites, as well as the drug release kinetics, can be tuned to fabricate, multi-functional 'space-making' bone grafting substitutes.

In Vitro Bacterial Adherence to Teicoplanin and Calcium Sulfate-Soaked Bone Cement

The aim of this study was to assess in vitro the improvement in release kinetics for teicoplanin and the inhibition of bacterial adhesion on calcium sulfate-soaked PMMA discs. Calcium sulfate has been used in vivo and shown to be biocompatible, and prevention of bacterial adhesion may be expected with calcium sulfate-soaked polymethylmethacrylate (PMMA). Discs were made by adding teicoplanin and calcium sulfate in powder form to PMMA powder. The antibiotic concentration eluted from PMMA discs was assayed by agar diffusion assay. Nonadherent bacteria were removed by washing and adherent bacteria were detached by sonication. The suspension including nonadherent bacteria was seeded on sheep blood agar plate and incubated for 24 h at 37 degrees C for the growth of microorganisms. The teicoplanin released from discs containing calcium sulfate was higher than that released from discs which had not been soaked with calcium sulfate. The count of bacteria adhering to the calcium sulfate-soaked discs was lower than that from the discs without calcium sulfate. In conclusion, the addition of calcium sulfate to teicoplanin-loaded PMMA bone cement may provide local antibiotic concentrations higher than MIC values due to increased antibiotic release. Furthermore, calcium sulfate was found to be effective in reducing bacterial adherence to treated discs.