A Novel Injectable Magnesium/Calcium Sulfate Hemihydrate Composite Cement for Bone Regeneration

Injectable macroporous naturally-derived apatite bone cement as a potential trabecular bone substitute

In this study, we have formulated a novel apatite bone cements derived from natural sources (i.e. eggshell and fishbone) with improved qualities that is, porosity, resorbability, biological activity, and so forth. The naturally-derived apatite bone cement (i.e. FBDEAp) was prepared by mixing hydroxyapatite (synthesized from fishbone) and tricalcium phosphate (synthesized from eggshell) as a solid phase with a liquid phase (a dilute acidic blend of cement binding accelerator and biopolymers like gelatin and chitosan) with polysorbate (as liquid porogen) to get a desired bone cement paste. The prepared cement paste sets within the clinically acceptable setting time (≤20 min), easily injectable (>85%) through hands and exhibits physiological pH stability (7.3-7.4). The pure apatite phased bone cement was confirmed by x-ray diffraction and Fourier transform infrared spectroscopy analyses. The FBDEAp bone cement possesses acceptable compressive strength (i.e. 5-7 MPa) within trabecular bone range and is resorbable up to 28% in simulated body fluid solution within 12 weeks of incubation at physiological conditions. The FBDEAp is macroporous in nature (average pore size ~50-400 μm) with interconnected pores verified by SEM and micro-CT analyses. The FBDEAp showed significantly increased MG63 cell viability (>125% after 72 h), cell adhesion, proliferation, and key osteogenic genes expression levels (up to 5-13 folds) compared to the synthetically derived, synthetic and eggshell derived as well as synthetic and fishbone derived bone cements. Thus, we strongly believe that our prepared FBDEAp bone cement can be used as potential trabecular bone substitute in orthopedics.

Fabrication of injectable antibiotic-loaded apatitic bone cements with prolonged drug delivery for treating post-surgery infections

Antibiotic-loaded bioactive bone substitutes are widely used for treating various orthopedic diseases and prophylactically to avoid post implantation infection. Calcium deficient hydroxyapatite (also known as apatitic bone cement) is a potential bioactive bone substitute in orthopedics due to its chemical composition similar to that of natural bone minerals. In this study, fabrication of mannitol (a solid porogen) incorporated injectable synthetic (Syn) and eggshell derived (ESD) apatitic bone cements loaded with antibiotics (gentamicin/meropenem/ rifampicin/vancomycin) was investigated. The release kinetics of the antibiotics were studied by fitting them with different kinetic models. All the antibiotics-loaded apatitic bone cements set within clinically accepted setting time (20 ± 2 min) and with good injectability (>70%). The antibiotics released from these bone cements were found to be controlled and sustained throughout the study time. Weibull and Gompertz (applies in least initial burst and sustain drug release rate models) were the best models to predict the release behavior. They cements had acceptable compressive strength (6-10 MPa; in the range of trabecular bone) and were biodegradable (21%-27% within 12 weeks of incubation) in vitro in simulated body fluids at physiological conditions. These bone cements showed excellent antibacterial activity from day 1 onwards and no bacterial colony was found from day 3 onwards. The viability of MG63 cells in vitro after 72 h was significantly higher after 24 h (i.e., ~110%). The cells were well attached and spread over the surface of the cements with extended morphology. The ESD antibiotic-loaded apatitic bone cements showed better injectability, degradation and cytocompatibility compared when compared to Syn antibiotic-loaded apatitic bone cements. Thus, we believe that the ESD antibiotic-loaded apatitic bone cements are suitable as potential injectable bone substitutes to avoid post-operative implant associated and other acute or chronic bone infections.

A Novel Calcium Phosphate-Based Nanocomposite for Augmentation of Cortical Bone Trajectory Screw Fixation

Purpose

To evaluate the effect of cement augmentation of cortical bone trajectory (CBT) screws using a novel calcium phosphate–based nanocomposite (CPN).

Material and Methods

CBT screws were placed into cadaveric lumbar vertebrae. Depending on the material used for augmentation, they were divided into the following three groups: CPN, polymethylmethacrylate (PMMA), and control. Radiological imaging was used to evaluate the cement dispersion. Biomechanical tests were conducted to measure the stability of CBT screws. A rat cranial defect model was used to evaluate biodegradation and osseointegration of the CPN.

Results

After cement augmentation, the CPN tended to disperse into the distal part of the screws, whereas PMMA remained limited to the proximal part of the screws (P < 0.05). As for cement morphology, the CPN tended to form a concentrated mass, whereas PMMA arranged itself as a scattered cement cloud, but the difference was not significant (P > 0.05). The axial pullout test showed that the average maximal pullout force (Fmax) of CPN-augmented CBT screws was similar to that of the PMMA group (CPN, 1639.56 ± 358.21 N vs PMMA, 1778.45 ± 399.83 N; P = 0.745) and was significantly greater than that of the control group (1019.01 ± 371.98 N; P < 0.05). The average torque value in the CPN group was higher than that in the control group (CPN, 1.51 ± 0.78 N∙m vs control, 0.97 ± 0.58 N∙m) and lower than that in the PMMA group (1.93 ± 0.81 N∙m), but there were no statistically significant differences (P > 0.05). The CPN could be biodegraded and gradually replaced by newly formed bone tissue after 12 weeks in a rat cranial defect model.

Conclusion

The biocompatible CPN could be a valuable augmentation material to enhance CBT screw stability.

A Composite of Cubic Calcium-Magnesium Sulfate and Bioglass for Bone Repair

Calcium sulfate (CS) bone cement has been shown to have good biocompatibility and can be used as a bone filler for repairing bone defects. However, its clinical application is limited due to its low compressive strength and weak bone repair activity. To this end, in this study, cubic crystalline magnesium-doped calcium sulfate (MgCS) was prepared and mixed with 45S5 bioglass (BG) to form a composite bone cement (MgCS/BG). The results show that cubic crystal calcium sulfate helps to increase the compressive strength of the composite bone cement to more than 60 MPa. More importantly, the obtained magnesium-doped composite bone cement can promote the adhesion and differentiation of mesenchymal stem cells and has good bioactivity. Through a skull defect model, it was found that MgCS/BG can significantly enhance bone defect repair and new bone formation. This new composite MgCS/BG is very promising for future translation into clinical applications.

Bone Healing and Regeneration Potential in Rabbit Cortical Defects Using an Innovative Bioceramic Bone Graft Substitute

This study aimed to elucidate the local effect and micro-computed tomographic (μ-CT) assessment following bone implantation of an innovative bioceramic (α-calcium sulfate hemihydrate; α-CSH) on femur lateral condyle cortical bone of rabbit models. The innovative α-CSH bioceramic was synthesized through a green processing technology (microwave irradiation treatment). The bilateral implantation model was performed among 24 New Zealand White rabbits which were divided into three groups based on the type of filling materials: α-CSH, control, and blank. Treatments were performed in defects with 6 mm diameter and 7 mm depth and observed after 2, 4, 8, and 12 weeks. Material reaction and bone formation after implantation were evaluated radiographically and histopathologically. The μ-CT analysis results showed that the degradation of α-CSH and control material was similar at 4 and 8 weeks. The bone volume in the defects indicated the α-CSH increased most in 8 weeks. In histopathological evaluation, the α-CSH group was repaired with lamellar bone and well-grown bone marrow infiltration similar to the control material. Moreover, the α-CSH revealed a faster degradation rate and better healing progress than the control material under the same conditions. Therefore, the α-CSH was confirmed to be useful in promoting osteoconduction and in controlling the resorption rate in bone defects. Further, the innovative α-CSH could be considered as a promising bone substitute for utilization in bone reconstructive therapy in dental and orthopedic fields.