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Calcium phosphate cement (CPC) has potentials in orthopaedics and orthodontics but it has significant limitations such as low mechanical strength, low injectability and instability in body. Starches from five botanical sources were used as cohesion additives to prepare calcium phosphate bone cement (CPB) and the starch source showed significant impact on physicochemical properties of the CPBs. CPB modified by pregelatinised waxy maize starch (CPB-W) had the highest mechanical strength, longest setting time, and most compact structure compared with other CPBs. As the amylose content increased, the viscosity of starch modified cement paste increased, and the cured cement had lower density and mechanical strength. It appears that starch with a low amylose content significantly improves the surgical performance and mechanical strength of CPC. CPB-W also exhibited good cytocompatibility to MC3T3-E1 cells. Starch modified CPBs are considered as promising injectable bone cements for minimally invasive surgery applications like vertebroplasty and kyphoplasty. [ABSTRACT FROM AUTHOR]

Although commonly used in orthopedic surgery, bone cements often face a high risk of post-operative infection. Developing bone cement with antibacterial capability is an effective path for eliminating implant-associated infections. Herein, the potential of silver ions (Ag+) and silver nanoparticles (AgNPs) in modifying CPC for long-term antibacterial property was investigated. Ag+ ions or AgNPs of various concentrations were incorporated in starch-modified calcium phosphate bone cement (CPB) to obtain Ag+-containing (Ag+@CPB) and AgNPs-containing (AgNP@CPB) bone cements. The results showed that all silver-containing CPBs had setting times of about 25–40 min, compressive strengths of greater than 22 MPa, high cytocompatibility but inhibitory effect on Staphylococcus aureus growth. After soaking for 1 week, the mechanical properties and the cytocompatibility of all cements revealed no significant changes, but only CPB with a relatively high content of Ag+ (H-Ag+@CPB) maintained good antibacterial capability over the tested time period. In addition, all the cements showed high injectability and interdigitating capability in cancellous bone and demonstrated augmentation effect on the cannulated pedicle screws fixation in the Sawbones model. In summary, the sustainable antibacterial capability and enhanced biomechanical properties demonstrated that Ag+ ions were more suitable for the fabrication of antibacterial CPC compared to AgNPs. Also, the H-Ag+@CPB, with good injectability, high cytocompatibility, good interdigitating and biomechanical property in cancellous bone, and sustainable antibacterial effects, bears great potential for the treatments of bone infections or implant-associated infections. [Display omitted] • A silver-augmented calcium phosphate composite (Ag@CPB) was developed. • Ag@CPB has sustainable antibacterial and enhanced biomechanical properties. • Ag+@CPB has potential for tackling the implant-associated bone infections. • Ag+ ion is more suitable for preparing antibacterial CPC than AgNP. [ABSTRACT FROM AUTHOR]

Purpose: Poly(methyl methacrylate) (PMMA) cement is widely used for percutaneous kyphoplasty and vertebroplasty (PKP and PVP) but possesses formidable shortcomings due to non-degradability. Here, a biodegradable replacement is developed.Methods: Calcium phosphate cement (CPC) was redesigned by incorporating starch and BaSO4 (new cement named as CPB). The biomechanical, biocompatibility, osseointegrative and handling properties of CPB were systematically evaluated in vitro and in vivo by the models of osteoporotic sheep vertebra, rat subcutaneous implantation and rat femoral defect.Results: CPB revealed appropriate injectability and setting ability for PKP and PVP. More importantly, its biomechanical strengths measured by in vitro and in vivo models were not less than that of PMMA, while its biodegradability and osseointegrative capacities were significantly enhanced compared to PMMA.Conclusions: CPB is injectable, biomechanically robust, biodegradable and osseointegrative, demonstrating revolutionary potential for the application in PKP and PVP. [ABSTRACT FROM AUTHOR]

To meet the requirements of minimally invasive surgical treatments for osteoporotic vertebral compression fracture, various strategies have been proposed to enhance the properties of calcium phosphate cement (CPC). Here, a new strategy was developed by incorporating poly (γ-glutamic acid) (γ-PGA) and its strontium salt into the formulation of alpha tricalcium phosphate (α-TCP)-based CPC. Effects of γ-PGA on the injectability, cohesion, setting times, mechanical compressive strengths and cytocompatibility were systematically studied. Results showed that the injectability, cohesion and setting times were considerably improved by introducing γ-PGA into the CPC. Moreover, after setting for 7 days, the compressive strengths increased from 14.6 ± 1.4 MPa for pure CPC to 35.3 ± 1.7 MPa for CPC with 8.9 wt% γ-PGA and further to 61.2 ± 5.4 MPa for CPC with 8.9 wt% γ-PGA combined with its strontium salt. In vitro osteoblast proliferation tests showed that the group of CPC modified by γ-PGA and its strontium salt had better cytocompatibility than the pure CPC group. All results suggest that optimal properties were obtained for the cement with 8.9 wt% γ-PGA added to its solid phases and using strontium salt as the reactive liquid phase, making it as a promising candidate for application in kyphoplasty. [ABSTRACT FROM AUTHOR]

Kyphoplasty is an effective minimally invasive surgical treatment of osteoporotic vertebral compression fractures. Current problems associated with kyphoplasty require better injectable bone cements with improved biodegradability and osseointegrative property as an alternative to polymethyl methacrylate (PMMA) bone cement. Calcium phosphate cements (CPCs) possess superior biodegradability and osteoconductivity but inferior injectability and mechanical strengths, rendering them unsuitable for kyphoplasty applications. Our previous studies developed a corn starch-reinforced CPC with improved handling, injectable and mechanical properties, yet for kyphoplasty applications the reinforced CPC needs to have radiopacity and further enhanced mechanical strength. This work therefore developed a CPC-Starch-BaSO 4 (CSB) system and investigated the effects of radiopaque agent BaSO 4 on injectability, radiopacity, mechanical and biocompatibility properties of the system. Results showed that the addition of BaSO 4 significantly improved radiopacity and mechanical strengths of CPC cement. In addition, in vitro evaluations including apoptosis, hemolysis and endotoxin tests and in vivo evaluation of subcutaneous implantation all revealed that CSB was biocompatible. This study demonstrates that CSB could meet the clinical requirements for minimally invasive surgery and thus have great potential for kyphoplasty applications. • Radiopaque agent barium sulfate could enhance mechanical property of calcium phosphate cement. • Good biocompatibility of calcium phosphate-starch-barium sulfate composite system • Injectable, biodegradable and osseointegration of calcium phosphate composite cement [ABSTRACT FROM AUTHOR]

Calcium phosphate cements (CPCs) with high bioactivity and bio-degradability have great potential for orthopaedic applications. However, handling performance and mechanical properties of current CPCs are not adequate for the applications in the minimally invasive surgery treating osteoporotic vertebral fracture like kyphoplasty. Here, the effects of reactant compositions, additions of seed crystals and setting liquids on the handling and mechanical properties of alpha-tricalcium phosphate (α-TCP)-based CPC were firstly studied. In order to further improve the injectability, anti-collapsibility and mechanical properties of CPC, natural bio-macromolecules including starch and poly (gamma-glutamic acid) were used as additive bio-macromolecules for enhancing such properties. Compared with pure CPC, the injectability, anti-collapsibility and compressive strength were significantly enhanced by incorporation of the bio-macromolecule additives. The results indicated starch- and poly (gamma-glutamic acid)-modified CPCs have a potential for the application of injectable bone cements for kyphoplasty and other treatments for load-bearing bones, and therefore are worth further study. [ABSTRACT FROM AUTHOR]

Background Context: Polymethylmethacrylate (PMMA) is the most commonly used filling material when performing percutaneous kyphoplasty (PKP) for the treatment of osteoporotic vertebral compression fractures. However, there are some inherent and unavoidable drawbacks with the clinical use of PMMA. PMMA bone cement tends to leak during injection, which can lead to injury of the spinal nerves and spinal cord. Moreover, the mechanical strength of PMMA-augmented vertebral bodies is extraordinary and this high level of mechanical strength might predispose to adjacent vertebral fractures. A novel biodegradable calcium phosphate-based nanocomposite (CPN) for PKP augmentation has recently been developed to potentially avoid these issues.Purpose: By comparison with PMMA, the leakage characteristics, biomechanical properties, and dispersion of CPN were evaluated when used for PKP.Study Design: Biomechanical evaluation and studies on the dispersion and anti-leakage properties of CPN and PMMA cements were performed and compared using cadaveric vertebral fracture model, sheep vertebral fracture model, and simulated rigid foam model.Methods: Sheep vertebral bodies were decalcified by ethylenediaminetetraacetic acid disodium salt (EDTA-Na2) to simulate osteoporosis in vitro. After compression to create wedge-shaped fractures using a self-designed fracture creation tool, human cadaveric vertebrae and decalcified sheep vertebrae were augmented by PKP. In addition, three L5 vertebral bodies from human cadavers were used in a contrast vertebroplasty (VP) augmentation experiment. Occurrence of cement leakage was observed and compared between CPN and PMMA during the process of vertebral augmentation. Open-cell rigid foam model (Sawbones#1522-507) was used to create a simulated leakage model for the evaluation of the leakage characteristics of CPN and PMMA with different viscosities. The augmentation effects of CPN and PMMA were evaluated in human cadaveric and decalcified sheep vertebral models and then compared to the results from solid rigid foam model (Sawbones#1522-23). The dispersion abilities of CPN and PMMA were evaluated via three methods as follows. The dispersion volume and dispersion ratio were calculated by three-dimensional reconstruction using human vertebral body CT scans; the ratio of cement area to injection volume was calculated from three-dimensional sections of micro-CT scans of a sheep vertebra; and the micro-CT images of cement dispersion in open-cell rigid foam model (Sawbones#1522-507) were compared between CPN and PMMA. This study was funded by the National Natural Science Foundation of China (No. 81622032, 190,000 dollars and No. 51672184, 90,600 dollars), Principal Project of Natural Science Research of Jiangsu Higher Education Institutions (No. 17KJA180011, 22,000 dollars), and Jiangsu Innovation and Entrepreneurship Program (146,000 dollars).Results: There was no significant difference in vertebral height between CPN and PMMA during PKP augmentation and both cements restored the vertebral height after augmentation. In PKP augmentation experiment, posterior wall cement leakage occurred in 75% of human vertebrae augmented with PMMA; however, no leakage occurred in human vertebrae augmented with CPN. Anterior leakage occurred in all vertebrae augmented by PMMA, while in only 75% of vertebra augmented by CPN. Furthermore, CPN and PMMA had completely different leakage patterns in the simulated rigid foam model whether administered at the same injection speed or under the same injection force, suggesting that CPN has anti-leakage characteristics. The augmentation in human cadaveric vertebrae was lower with CPN compared to PMMA (1,668±816 N vs. 2,212±813 N, p=.459, respectively), but this difference was not significant. The augmentation force in sheep vertebral bodies reached 1,393±433 N when augmented with PMMA, but 1,108±284 N when augmented with CPN. The dispersion of CPN was better, and the dispersion volume and ratio were greater, with CPN than with PMMA. Imaging of the open-cell rigid foam model showed completely different dispersion modes for CPN and PMMA. After injection, the PMMA cement formed a contracted clump in the open-cell rigid foam model. However, the CPN cement extended many antennae outward, appearing to spread to the surrounding area. The surface areas of the CPN cement blocks with different liquid-to-solid ratios were significantly larger than the surface area of the PMMA cement in the open-cell rigid foam model (p<.05).Conclusions: CPN has anti-leakage properties, which might be related to its high viscosity and viscoplasticity. CPN had a slightly lower augmentation force than PMMA when used in cadaveric vertebrae, decalcified sheep vertebrae, and in the standard rigid foam model. However, CPN diffused more easily into cancellous bone than did PMMA and encapsulated bone tissue during the dispersion process. The excellent dispersion of CPN generated better interdigitation with cancellous bone, which may be why the augmentation effect of CPN is similar to that of PMMA.Clinical Significance: Biodegradable CPN is a potential alternative to PMMA cement in PKP surgery, in which CPN is likely to reduce the cement leakage during the surgery and avoid the post-surgery complications caused by excessive strengths and nondegradability of PMMA cement. [ABSTRACT FROM AUTHOR]