Comparative evaluation of polymethylmethacrylate and composite bone cements. Review of the experimental studies results

Current article is a review of experimental studies of different bone cements types and their combinations. Providing of bone fragments stable fixation at osteosynthesis in cases of difficult multifragmental fractures, arthroplasties and other implants using especially in the osteoporosis conditions is a main task of orthopaedic surgery procedures. Polymethylmethacrylate (PMMA) is the first material that is answered to these requirements. The evolution of bone cements resulted in creation of a new composite substance — combination of PMMA and β-threecalciumphosfates (β-TCPh). Combination of these two components allowed to provide high bioabsorbal, osteoconductive and osteointegrative properties along with sufficient durability. In the analyzed works the properties of composite cement CalCemex were evaluated in vivo experiment. It was found that in the case of PMMA penetration of bone tissue into the polymer structure did not occur. Under the conditions of using bone cement with β-TCF admixture, the formation of bone tissue was observed not only on the surface of the implant, but also in the external and internal pores. It is the presence of pores in CalCemex that the authors explain the possibility of penetration of cellular elements, blood vessels and bone formation. Moreover, β-TCPh is included into this material and it is bioresorbed by osteoclasts. This leads to the release of calcium and phosphorus ions and, consequently, simplifies the attachment of the newly formed bone to the bone cement. We assume that composite cement like CalCemex type is a promising material for the treatment of various types of fractures and replacement of bone defects. It should be mentioned that research in this area is ongoing and intensive work is underway to synthesize and study the results of clinical application of composite bone cements with maximum bioactive properties that will not only strengthen bone tissue but also perform osteointegrative function. Key words. Bone cement, polymethylmethacrylate, β-threecalciumphosfates, experiment.

Preparation and Characterization of Moldable Demineralized Bone Matrix/Calcium Sulfate Composite Bone Graft Materials

Demineralized bone matrix (DBM) is a decalcified allo/xenograft retaining collagen and noncollagenous proteins, which has been extensively used because of its osteoconductive and osteoinductive properties. Calcium sulfate (CaSO4, CS) is a synthetic bone substitute used in bone healing with biocompatible, nontoxic, bioabsorbable, osteoconductive, and good mechanical characteristics. This study aims to prepare a DBM/CS composite bone graft material in a moldable putty form without compromising the peculiar properties of DBM and CS. For this purpose, firstly, porcine femur was defatted using chloroform/methanol and extracted by acid for demineralization, then freeze-dried and milled/sieved to obtain DBM powder. Secondly, the α-form and β-form of calcium sulfate hemihydrate (CaSO4 •0.5H2O, CSH) were produced by heating gypsum (CaSO4 •2H2O). The morphology and particle sizes of α- and β-CSH were obtained by SEM, and their chemical properties were confirmed by EDS, FTIR and XRD. Furthermore, the DBM-based graft was mixed with α- or β-CSH at a ratio of 9:1, and glycerol/4% HPMC was added as a carrier to produce a putty. DBM/CSH putty possesses a low washout rate, good mechanical strength and biocompatibility. In conclusion, we believe that the moldable DBM/CSH composite putty developed in this study could be a promising substitute for the currently available bone grafts, and might have practical application in the orthopedics field as a potential bone void filler.

Assessment of α-calcium sulfate hemihydrate/nanocellulose composite bone graft material for bone healing in a rabbit femoral condyle model

The material properties of nanocellulose (NC) can effectively enhance the structural stability of composite materials. However, the research related to NC/α-calcium sulfate hemihydrate (CSH) composites is largely lacking. In this paper, we explore the combination of these two materials and determine their elaborate biological activities in vivo. Using α-CSH as the matrix, the composite bone graft materials were produced according to different proportions of NC. Then the mechanical strength of the composite bone graft was measured, and the results were analyzed by X-ray diffraction and scanning electron microscopy (SEM). To conduct the material in vivo evaluation, 0% (CN0) and 0.75% (CN0.75) NC/α-CSH composite bone graft materials were implanted into a femoral condyle defect model. The results indicated that NC could significantly enhance the mechanical properties of α-CSH. The SEM analysis indicated that the NC shuttled between the crystal gaps and formed a three-dimensional network structure, which was firmly combined with the crystal structure. Meanwhile, the CN0.75 scaffold remained at 12 weeks postoperation, which provided a long-term framework for new bone formation. Overall, our findings demonstrate that, with a 0.75% NC/α-CSH composite demonstrating good potential as a bone graft material for clinical bone grafting.

Application of Biodegradable PLGA-PEG-PLGA/CPC Composite Bone Cement in the Treatment of Osteoporosis

The aim of this study was to evaluate the biological activity, safety, and effectiveness of poly(lactic acid)–poly(glycolic acid)–poly(ethylene glycol)–calcium phosphate cement (PLGA-PEG-PLGA/CPC). Methods: The PLGA-PEG-PLGA/CPC composite bone cement was used for interaction with MC3T3-E1 mouse osteoblasts in vitro and its compatibility was tested using Cell Counting Kit-8 (CCK-8). Alizarin Red staining and alkaline phosphatase activity were used to detect the osteogenic properties. Twenty healthy female New Zealand rabbits were selected to establish osteoporosis models, which were randomly divided into two groups. The experimental group was treated with 30 wt.% PLGA-PEG-PLGA/CPC, while the control group was treated with polymethyl methacrylate (PMMA) bone cement. Imaging and histomorphology of the vertebral body were analyzed after 12 weeks. The distribution and degradation of bone cement were assessed using micro-computed tomography examination and hematoxylin–eosin (HE) staining. Results: In vitro, CCK-8 revealed significant proliferation of osteoblasts in the PLGA-PEG-PLGA/CPC composite bone cement. Alizarin Red staining showed that the degree of staining increased with time. Quantitative results showed that absorbance was significantly higher in this group than in the CPC group on days 7 and 14. The alkaline phosphatase activity levels on days 7 and 14 were significantly higher in the 30 wt.% PLGA-PEG-PLGA/CPC group than in the CPC group. In vivo, postoperative micro-computed tomography and histomorphology showed that the material was evenly distributed in the vertebral body and a small amount penetrated into the trabecular bone. After 12 weeks, CPC degradation and absorption and the formation of new bone matrix were observed and the formation of a callus was obvious. Conclusion: PLGA-PEG-PLGA/CPC composite bone cement has a positive effect on the treatment of osteoporosis.

Comparison of two different screw trajectories in the treatment of oblique scaphoid fractures: A mechanical study on composite bone models

Objectives: In this mechanical study, we aimed to compare two different screw trajectories in terms of durability against axial loads on oblique scaphoid fractures using composite bone models. Materials and methods: Oblique osteotomies were made along the dorsal sulcus of 14 composite scaphoid bone models. Following this, all bone models were randomly classified. One group of bones were fixed with a screw placed perpendicular to the osteotomy line and the other group was fixed with a screw placed centrally down the long axis of the scaphoid bone. Each scaphoid bone model was positioned on a mechanical testing machine. Subsequently, axial loading tests were applied on each bone model to measure the amount of loading required to cause 2-mm displacement and failure on the osteotomy side and maximum displacement at the time of failure on scaphoid bone models. Results: There was no statistically significant difference in load to 2-mm displacement and failure between the two groups (p>0.05). Also, there was no statistically significant difference between the two groups in terms of maximum displacement seen on failure (p>0.05). Conclusion: In our study, we found that the stability of the screws which laid perpendicular to the fracture line and parallel to the long axis of the scaphoid was the same in fixing oblique scaphoid fractures.

A novel degradable tricalcium silicate/calcium polyphosphate/polyvinyl alcohol organic-inorganic composite cement for bone filling

In this study, tricalcium silicate (C3S) calcium/polyphosphate/polyvinyl alcohol organic-inorganic self-setting composites were successfully designed. A variety of tests were conducted to characterize their self-setting properties, mechanical properties, degradation properties, and related biological properties. The composite bone cements showed a short setting time (5.5–37.5 min) with a 5:5–6:4 ratio of C3S/CPP to maintain a stable compressive strength (28 MPa). In addition, PVA effectively reduced the brittleness of the inorganic phase. Degradation experiments confirmed the sustainable surface degradation of bone cement. A maximum degradation rate of 49% was reached within 56 days, and the structure remained intact without collapse. Culturing MC3T3 cells with bone cement extracts revealed that the composite bone cements had excellent biological properties in vitro. The original extract showed a proliferation promotion effect on cells, whereas most of the other original extracts of degradable bone cements were toxic to the cells. Meanwhile, extracellular matrix mineralization and alkaline phosphatase expression showed remarkable effects on cell differentiation. In addition, a good level of adhesion of cells to the surfaces of materials was observed. Taken together, these results indicate that C3S/CPP/PVA composite bone cements have great potential in bone defect filling for fast curing.