Acrylic Bone Cement Research Articles

Evaluation of a synthetic vertebral body augmentation model for rapid and reliable cyclic compression life testing of materials for balloon kyphoplasty

Screening of augmentation materials for use in balloon kyphoplasty (BKP) may be carried out using vertebral bodies (VBs) prepared from fresh cadaveric or animal model spines, but this approach has many drawbacks. Alternatively, a validated synthetic VB augmentation model may be used. In the present work, such a model-a cube (26 mm sides) of low-density polyurethane foam with a centrally located through-thickness cylindrical hole (diameter = 4 mm) completely filled with a bolus of augmentation material-was used to compare two BKP augmentation materials with very different chemistries (a high-viscosity acrylic bone cement (PMMA) and a calcium phosphate bone substitute (CP)) in cyclic compression life tests. The test conditions were considered physiologically relevant: the model was immersed in phosphate buffered saline solution, at 37 degrees C; the frequency was 3 Hz; and the maximum load was either 1150 N or 2300 N (corresponding to a maximum stress of 1.7 or 3.4 MPa). At the high load, all four PMMA and two out of seven CP specimens ran out to 1 million cycles. CP specimens consistently ran out at the low load. The use of this model for rapid and reliable ex vivo screening of BKP augmentation materials was considered both valid (because of the clear demarcation seen in the qualitative and quantitative results obtained with the two materials tested) and appropriate (that is, clinically relevant to BKP).

Biological and Biomechanical Effects of Vancomycin and Meropenem in Acrylic Bone Cement

Antibiotic-loaded bone cement is extensively used in joint arthroplasty, but increasing bacteria resistance against common antibiotics has lead to a demand for alternative drugs. However, bone cement containing new additives must be characterized both biologically and mechanically. This study evaluated elution kinetics, antibacterial activity, and mechanical properties for cement loaded with vancomycin and/or meropenem. The presence of meropenem broadened the antibacterial spectrum and enhanced the elution of vancomycin. The mechanical properties were negatively affected by 1.0 g of vancomycin, but these detrimental effects were acceptable when only 0.5 g of vancomycin were added to a cement containing 0.5 g of meropenem. Further investigations on this formulation with adjusted antibiotic amounts are, however, necessary to reach the optimal compromise between the antibacterial and the mechanical properties of the bone cement.

Reinforcement of bone cement using zirconia fibers with and without acrylic coating

Acrylic (polymethylmethacrylate or PMMA) bone cement was modified by the addition of high-strength zirconia fibers with average lengths of 200 microm and diameters of 15 microm or 30 microm. A novel emulsion polymerization process was developed to encapsulate individual fibers in PMMA. Improvements in tensile and compressive properties as well as in fracture toughness were investigated upon incorporation of uncoated and acrylic coated zirconia fibers. Bone cements were reinforced with 2% by volume of the 15 microm diameter and 5% by volume of the 30 microm fibers. Results indicate that elastic modulus and ultimate strength of bone cements reinforced with zirconia fibers were higher than controls, being the largest for cements reinforced with 30 microm diameter fibers. The fracture toughness of the cement increased by 23% and 41% by the addition of 15 microm and 30 microm fibers, respectively. Coating of individual zirconia fibers did not result in improved material properties of bone cements. The use of uncoated or acrylic coated 30 microm fibers is recommended based on the significant increases in ultimate strength and fracture toughness of the cements.

Incorporation of large amounts of gentamicin sulphate into acrylic bone cement: Effect on handling and mechanical properties, antibiotic release, and biofilm formation

Bacterial infection remains a significant complication following total joint replacement. If infection is suspected when revision surgery is being performed, a large dose of antibiotic, usually gentamicin sulphate, is often blended with the acrylic bone cement powder in an attempt to reduce the risk of recurrent infection. In this in-vitro study the effect of small and large doses of gentamicin sulphate on the handling and mechanical properties of the cement, gentamicin release from the cement, and in-vitro biofilm formation by clinical Staphylococcus spp. isolates on the cement was determined. An increase in gentamicin loading of 1, 2, 3, or 4 g, in a cement powder mass of 40 g, resulted in a significant decrease in the compressive and four-point bending strength, but a significant increase in the amount of gentamicin released over a 72h period. When overt infection was modelled, using Staphylococcus spp. clinical isolates at an inoculum of 1 x 10(7) colony-forming units/ml, an increase in the amount of gentamicin (1, 2, 3, or 4 g) added to 40 g of poly(methyl methacrylate) cement resulted in an initial decrease in bacterial colonization but this beneficial effect was no longer apparent by 72 h, with the bacterial strains forming biofilms on the cements despite the release of high levels of gentamicin. The findings suggest that orthopaedic surgeons should carefully consider the clinical consequences of blending large doses (1 g or more per 40 g of poly(methyl methacrylate)) of gentamicin into Palacos R bone cement for use in revision surgery as the increased gentamicin loading does not prevent bacterial biofilm formation and the effect on the mechanical properties could be important to the longevity of the prosthetic joint.

Flavouring Group Evaluation 5, Revision 1 (FGE.05Rev1):Esters of branched‐ and straight‐chain aliphatic saturated primary alcohols and of one secondary alcohol, and branched‐ and straight‐chain unsaturated carboxylic acids from chemical groups 1, 2, and 5 (Commission Regulation (EC) No 1565/2000 of 18 July 2000) ‐ Opinion of the Scientific Panel on Food Additives, Flavourings, Processing Aids and Materials in contact with

Flavouring Group Evaluation 5, Revision 1 (FGE.05Rev1):Esters of branched‐ and straight‐chain aliphatic saturated primary alcohols and of one secondary alcohol, and branched‐ and straight‐chain unsaturated carboxylic acids from chemical groups 1, 2, and 5 (Commission Regulation (EC) No 1565/2000 of 18 July 2000) ‐ Opinion of the Scientific Panel on Food Additives, Flavourings, Processing Aids and Materials in contact with

Mechanische Biegefestigkeiten von explantierten Ex-vivo-Knochenzementen verglichen mit In-vitro-Proben

The mechanical properties of acrylic bone cements are an important factor in determining an efficient load transmission between prosthesis and bone to guarantee the long-term stability in cemented hip arthroplasty. Palacos and Refobacin Palacos specimens from 21 aseptically loosened femoral compoments of cemented hip arthroplasties manufactured by the first to third generation cementing technique have been mechanically tested in a standardised four-point bending test (ISO 5833). In vitro manufactured Palacos and Refobacin Palacos specimens served as a control group. The fatigue fracture surfaces were morphologically analysed with light microscopy. Under in vitro conditions manufactured specimens had higher values of bending strength, with the exception of blood contaminated ones, compared to ex vivo specimens. Ex vivo specimens of the second and third generation cementing technique had higher values than specimens of the first generation. Acrylic bone cements are subjected to a multifactorial material fatigue in vivo. Here, the art and quality of cementing technique is of eminent importance in determining the long-term stability of cemented hip arthroplasty.

Incorporation of chitosan in acrylic bone cement: Effect on antibiotic release, bacterial biofilm formation and mechanical properties

Bacterial infection remains a significant problem following total joint replacement. Efforts to prevent recurrent implant infection, including the use of antibiotic-loaded bone cement for implant fixation at the time of revision surgery, are not always successful. In this in vitro study, we investigated whether the addition of chitosan to gentamicin-loaded Palacos R bone cement increased antibiotic release and prevented bacterial adherence and biofilm formation by Staphylococcus spp. clinical isolates. Furthermore, mechanical tests were performed as a function of time post-polymerisation in pseudo-physiological conditions. The addition of chitosan to gentamicin-loaded Palacos R bone cement significantly decreased gentamicin release and did not increase the efficacy of the bone cement at preventing bacterial colonisation and biofilm formation. Moreover, the mechanical performance of cement containing chitosan was significantly reduced after 28 days of saline degradation with the compressive and bending strengths not in compliance with the minimum requirements as stipulated by the ISO standard for PMMA bone cement. Therefore, incorporating chitosan into gentamicin-loaded Palacos R bone cement for use in revision surgery has no clinical antimicrobial benefit and the detrimental effect on mechanical properties could adversely affect the longevity of the prosthetic joint.

Synthesis, mechanical properties, biocompatibility, and biodegradation of polyurethane networks from lysine polyisocyanates

Bone defects, such as compressive fractures in the vertebral bodies, are frequently treated with acrylic bone cements (e.g., PMMA). Although these biomaterials have sufficient mechanical properties for fixing the fracture, they are non-degradable and do not remodel or integrate with host tissue. In an alternative approach, biodegradable polyurethane (PUR) networks have been synthesized that are designed to integrate with host tissue and degrade to non-cytotoxic decomposition products. PUR networks have been prepared by two-component reactive liquid molding of low-viscosity quasi-prepolymers derived from lysine polyisocyanates and poly(ɛ-caprolactone- co- dl-lactide- co-glycolide) triols. The composition, thermal transitions, and mechanical properties of the biomaterials were measured. The values of Young's modulus ranged from 1.20–1.43 GPa, and the compressive yield strength varied from 82 to 111 MPa, which is comparable to the strength of PMMA bone cements. In vitro, the materials underwent controlled biodegradation to non-cytotoxic decomposition products, and supported the attachment and proliferation of MC3T3 cells. When cultured in osteogenic medium on the PUR networks, MC3T3 cells deposited mineralized extracellular matrix, as evidenced by von Kossa staining and tetracycline labeling. Considering the favorable mechanical and biological properties, as well as the low-viscosity of the reactive intermediates used to prepare the PUR networks, these biomaterials are potentially useful as injectable, biodegradable bone cements for fracture healing.

New radiopaque acrylic bone cement. II. Acrylic bone cement with bromine-containing monomer

Bromine-containing methacrylate, 2-(2-bromopropionyloxy) ethyl methacrylate (BPEM), had been used in the formulation of acrylic radiopaque cements. The effect of this monomer incorporated into the liquid phase of acrylic bone cement, on the curing parameters, thermal properties, water absorption, density, compression tests and radiopacity was studied. A decrease of maximum temperature and an increase of the setting time were observed with the addition of the bromine-containing monomer in the radiolucent cement composition. Adding BPEM in radiolucent acrylic bone cements composition results in the decrease of glass transition temperature and increase of its thermal stability. Acrylic bone cements modified with bromine-containing comonomer are characterized by polymerization shrinkage lower than the radiolucent cement. Addition of bromine-containing comonomer in radiolucent acrylic bone cement composition determines the increase of compressive strength. Acrylic bone cements modified with bromine-containing comonomer proved to be radiopaque.

Thermal stability of acrylic bone cement powder under shelf storage conditions: An isothermal microcalorimetric study

Heat-conduction isothermal microcalorimetry was used to measure the exothermic heat flow rate (Q) from the powder of a widely used commercially-available acrylic bone cement, Palacos R, when it interacted with ambient laboratory air, as a function of time, t, in the calorimeter, for up to 200 h. Four variants of the powder were used, these being unsterilized, sterilized using ethylene oxide gas, gamma-irradiated, in ambient air, with a minimum dosage of 2.5 Mrad, and gamma-irradiated, in ambient air, with a minimum dosage of 4.5 Mrad. In each case, the powder variant was tested after being stored on the shelf, under ambient conditions, for 2 days, 3 weeks and 9 months immediately following sterilization. Best-fit correlations between Q and t for each powder variant were determined. Then, this relationship was integrated over the period 14 h< or =t< or =200 h to give an estimate of the "effective" heat flow, Q(eff). For powder variants tested 2 days after being sterilized, the difference in their thermal stabilities (Qeff ranged from 0.19+/-0.01 to 0.62+/-0.03 microJ/g, respectively) was significant in the case of some pairs and not for others. However, for powders tested either 3 weeks or 9 months following sterilization, there was no significant difference between the means of Qeff (they ranged from 0.18+/-0.01 to 0.31+/-0.07 microJ/g) for any pair. These results suggest that an acrylic bone cement in which the powder is EtO-sterilized may be mixed with the liquid monomer for use in cemented arthroplasties after any length of time of shelf storage of the powder, under ambient conditions, whereas, for powders that are gamma-irradiated and then stored under the same conditions, at least 3 weeks should elapse before they are used in these procedures.

The influence of coating technology on the mechanical performance of montmorillonite nanoclay reinforced acrylic bone cement

One of the primary reasons for joint replacement failure is fracture of the bone cement mantle. The objective of this study was to determine the effects of improving the dispersion of montmorillonite nanoclay in acrylic bone cement (by using coating technology) on the mechanical properties of the cured nanocomposite bone cement. Statistically significant improvements were found in the fracture toughness and elastic modulus (p < 0.05) of the coated nanocomposite cement when compared with uncoated nanocomposite cement at a loading of 0.5% nanoclay. Characterisation of the cements demonstrated an improvement in nanoclay dispersion when using coated nanoclays.

Development of new bone cement utilizing low toxicity monomers.

Acrylic bone cement is self-curing cement comprising of liquid and powder component of methyl methacrylate (MMA). It has been used extensively in orthopedics; however, adverse effects were associated with its use. Hence we investigated in this paper the possibility of new cement utilizing methacrylates with lower toxicity than MMA. LD50s of candidate monomers were determined with administration to the medullary cavity of the rat's femur. 2-Ethylhexyl methacrylate (EHMA) and trimethylolpropane trimethacrylate (TMP) demonstrated greater LD50 values of 187 mg/kg and 380 mg/kg, respectively, than MMA (108 mg/kg); they were selected as the liquid components of the new cement. The copolymer of EHMA and cyclohexyl methacrylate was then selected as the powder component. With this combination, we developed the new cement (EHMA cement).Temperature rise during polymerization of EHMA cement was 9 degrees C-13 degrees C, which was significantly lower than that of conventional cement. The compression strength of the polymerized EHMA cement was 57 MPa without TMP, and 67 MPa with TMP (15 wt%). Thus we concluded that new EHMA cement was slightly inferior in the compression strength than the conventional cement. However, it was characterized by the low toxicity of utilized monomers and the low temperature rise during polymerization.

Mechanische In-vitro-Prüfung von fünfzehn kommerziellen Knochenzementen auf der Basis von Polymethylmethacrylat

INTRODUCTION The long-term stability in cemented hip arthroplasty depends not only on the mechanical properties of the acrylic bone cements but also on an improvement of cementing techniques. The bending strengths of 15 commonly used bone cements (CMW 3 Gentamycin; CMW 3; Refobacin Palacos R; Palacos R; Palamed G; Palamed; Cerafixgenta; Cerafix; Duracem; Simplex Tobramycin; Simplex P; Versabond; Sulcem; Sulcem 3 Genta; Copal) have been mechanically tested in a standardised in vitro four-point bending test (ISO 5833). The fatigue fracture surfaces were morphologically analysed with light microscopy. The highest values of bending strength were found in vacuum mixed specimens cured under pressure. The lowest values of strength were seen in with blood contaminated specimens. Fatigue cracks were often initiated from air bubbles or other inclusions such as antibiotics or blood in the bone cement. The present in vitro study highlights the supposition that the quality of the cementing technique is of eminent importance in determining the long-term stability of cemented hip arthroplasties.

Making a Cost-effective Contrast Bone Cement With or Without Antibiotics, Using Aqueous Methylene Blue for Easy Cement Removal in Revision and Primary Total Joint Arthroplasty

This simple, cost-effective technique for creating contrast bone cement with or without antibiotics by the addition of aqueous methylene blue to acrylic bone cement in revision or primary total joint arthroplasty, allows easy visualization for removal of cement from the surgical field.

PMMA bone cement containing a quaternary amine comonomer with potential antibacterial properties

An iodinated quaternary amine dimethacrylate monomer was synthesized and incorporated as a comonomer in acrylic bone cements. Bone cement is used in orthopaedic surgery and imparting antibacterial properties to the cement can be beneficial in the lowering of bacterial infection post surgery. PMMA based bone cements were modified by copolymerising the monomer methylmethacrylate (MMA) with a quaternary amine dimethacrylate by using the redox initiator activator system as used for curing commercial bone cements. The cements were prepared using the commercial PMMA bone cement CMW and the liquid component was modified with the amine to render antimicrobial properties to the cement. The physical, mechanical, and antimicrobial properties of the modified cements were evaluated; in addition, the viability of the cement to function as a orthopaedic cement was also established, especially with an advantage of it being radiopaque, due to the inclusion of the iodine containing quaternary amine. The cytotoxicity of the modified cements were tested using a human cell model and the results indicated that the cells remained metabolically active and proliferated when placed in direct contact with the experimental cement specimens. The cements and their eluants did not evoke any cytotoxic response.

Liquid monomer–powder particle interaction in acrylic bone cement

It is known that the method used to mix the liquid monomer and powder of PMMA bone cement influences the quality of the cement that is used in total joint replacements. Mixing theory indicates that the interaction between the liquid monomer and the powder is affected by a number of parameters, such as cement viscosity and degree of agitation, with this knowledge utilized in the design of cement mixing devices. Therefore, the objectives of this study were to: (i) obtain information on the interaction of the liquid monomer and the powder in the case of an PMMA bone cement, (ii) show how this knowledge can be applied to the design of an automated cement mixing device, and (iii) compare the porosity, bending modulus, and bending strength of one commercially-available cement prepared using the automated mixer and prepared using a conventional mixer that is in current clinical use. Experimental data indicated that increasing the velocity and decreasing the viscosity of the systems produced cement that improved mechanical properties, which may contribute to better mechanical integrity and, hence, reduced tendency for aseptic loosening, of cemented hip implants.

A new concept of gentamicin loaded HAP/TCP bone substitute for prophylactic action: in vitro release validation

Infections and their consequences are a considerable problem in orthopaedic surgery. Despite intravenous prophylactic antibiotic administration, infection rates can reach in some occasions more than 1%. Indeed, the concentration in bone tissues is very low with the majority of antibiotics. Because high local dose can be obtained, the local release of gentamicin from acrylic bone cements has been shown to be efficient in preventing infections. However, for surgical procedures other than cemented prostheses no other local antibiotic releasing device is clinically available. The purpose of this study was to validate the concept of a gentamicin loaded bone substitute. About 125 mg of gentamicin were introduced into a HAP/TCP bone substitute for prophylactic purpose, to enhance the efficiency of systemic antibiotic treatments. The release rate of gentamicin from the bone substitute was investigated in vitro, in 0.9% sodium chloride solution. The rate appeared to be related to the bone substitute volume. All the gentamicin was released in less than 48 h. This release rate corresponds to the recommendations for the prophylactic use of antibiotics: the duration of the treatment should be less than 48 h, not to select antibiotic-resistant bacterial strains.

Amphiphilic bonder improves adhesion at the acrylic bone cement–bone interface of cemented acetabular components in total hip arthroplasty: in vivo tests in an ovine model

Even following the introduction of the "third generation" cementing technique, an improvement of the fixation of the acetabular component similar to that of the femoral has not been shown in clinical studies. The goal of the present study was to achieve a better stability with the use of an amphiphilic bonder while preserving the mechanically important subchondral sclerosis. In a total of 20 sheep, a cemented total hip replacement was implanted. In the treatment group (n = 10), the implantation was carried out following surface conditioning of the acetabular bed with an amphiphilic bonder. All the sheep were followed for 9 months. To assess the biocompatibility, the osseous ingrowth at the cement-bone interface was depicted with the help of an in vivo fluorescent marking of the osteoblasts. Additionally, conventional radiographs were obtained over the course of treatment. Finally, the ovine pelvic regions were split following a standardized technique allowing for histological evaluation of the cement-bone interfaces. The acetabular components of the treatment group revealed a stable cement-bone compound. In the control group, the implants were easily dislodged from their beds. This finding was consistent with the radiological and histological results, which had revealed increased, progressive lytic radiolucent lines and the interposition of fibrous tissue at the cement-bone interface in the control group compared to the treatment group. The bonder was biocompatible. Following the application of the bonder, the cemented acetabular components revealed an improved stability without signs of inflammation or neoplasia in a viable acetabular osseous bed. With the help of this technique, the in vivo longevities of cemented acetabular components can be increased in the clinical setting without sacrificing the biomechanical relevant subchondral sclerosis.

Mechanical Forces in Diabetic Kidney Disease

Nephropathy is one of the major microvascular complications of diabetes, and both hemodynamic and metabolic stimuli participate in its development and progression toward ESRD. There is now a greater understanding of the molecular pathways that are activated by high glomerular capillary pressure and hyperglycemia and how they interplay to produce kidney pathology. The observation that overexpression of glucose transporter 1 (GLUT-1) in mesangial cells could induce a "diabetic cellular phenotype" has led to the postulation that the expression of GLUT-1 could be upregulated in glomeruli that are exposed to high pressure. This review suggests a mechanism by which mechanical forces may aggravate a metabolic insult by stimulating excessive cellular glucose uptake. Proposed is the existence of a self-maintaining cycle whereby a hemodynamic stimulus on glomerular cells induces GLUT-1 overexpression followed by greater glucose uptake and activation of intracellular glucose metabolic pathways, resulting in excess TGF-beta1 production. TGF-beta1 in turn, maintains overexpression of GLUT-1, perpetuating a signaling sequence that has, as its ultimate effect, increased extracellular matrix synthesis. This mechanical and metabolic coupling suggests a novel pathophysiologic mechanism of injury in the kidney in diabetes and possibly other glomerular diseases.

Static shear strength between polished stem and seven commercial acrylic bone cements

The stem-cement interface is one of the most significant sites in cemented total hip replacement and has long been implicated in failure of the whole joint system. However, shear strength at this interface has rarely been compared across a range of commercially available bone cements. The present study seeks to address this issue by carrying out a comparative study. The results indicated that the static shear strength was more dependent on cement type than cement viscosity and volume. However, both cement type and viscosity were contributory factors on porosity and micropore size in the cement surface. There was no significant difference between Simplex P and Simplex P with Tobramycin. Although the bone cements were all hand mixed in this study, the static shear strength was significantly larger than the values recorded by other researchers, and the porosity and micropore size showed much lower values. Bone cement transfer films were detected on the stem surface, typically about 4-10 mum thick. They were considered to be an important factor contributing to high friction at the stem-cement interface after initial debonding.