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PubMed1995

Micromechanisms of fatigue crack initiation and propagation in bone cements.

The micromechanisms of fatigue fracture in bone cements were explored and characterized in this investigation. Fatigue crack initiation sites were identified and the microscopic features responsible for crack initiation are illustrated. Differences in the fracture morphology of PMMA beads, in early crack growth and rapid crack growth stages, are brought out. Based on the fractographic features, a micromechanism of PMMA bead fracture is proposed.

Barium Sulfate↗

PubMed1987

Comparison of the fatigue characteristics of centrifuged and uncentrifuged Simplex P bone cement.

Fatigue test specimens of Simplex P bone cement (Howmedica Inc., Rutherford, NJ) prepared according to the manufacturer's instructions and specimens of Simplex P prepared by centrifuging the cement immediately after mixing were subjected to fully reversed tension-compression fatigue tests at initial strain levels ranging from 0.01 to 0.001. S:N curves for both cement preparations were generated and compared on the basis of regression analysis, Weibull analysis, and Student's t tests. Centrifuged Simplex P was able to withstand significantly more fatigue cycles than uncentrifuged Simplex P at all strain levels tested. Importantly, at the more physiologic strain levels of 2,000 and 1,000 microstrain, the centrifuged cement demonstrated superior fatigue life. Specifically, at the 1,000-microstrain level eight of the 11 uncentrifuged specimens fractured before undergoing 10 million cycles. Of those that failed, the average number of cycles to failure was 1.8 million with a range of 560,000 to 4 million cycles. In contrast, all 11 centrifuged specimens tested at 1,000 microstrain remained intact at 10 million cycles.

Analysis of Variance↗

PubMed1999

Polymethylmethacrylate-based bone cement modified with hydroxyapatite.

A commercial acrylic bone cement was modified by the incorporation of different weight fractions of polycrystalline hydroxyapatite (HA), and the modified formulation was investigated. The influence of the filler proportion on the flow characteristics and the mechanical behavior of the resultant composite was evaluated. The residual monomer present in the cured materials was measured by gas chromatography. The comparison of the residual monomer present in the cements with and without reinforcement demonstrated that the degree of polymerization was not affected by the addition of HA. Porosity morphology was analyzed by optical and scanning electron microscopy. Image examination revealed that the porosity and the pore size of the hardened cement increased with an increasing amount of particulate filler. Flexural, compressive, and fracture properties of the cement with varying amounts of HA reinforcement were measured. It was found that up to 15 wt% HA could be added for increases in flexural modulus and fracture toughness. HA acts as a rigid filler that enhances fracture resistance and flexural modulus. Our results show that the workability of the modified formulation limited the incorporation of the ceramic filler to a maximum value of 15 wt%.

Biocompatible Materials↗

PubMed2004

Propagation of fatigue cracks in acrylic bone cements containing different radiopaque agents.

In this work three iodine-containing monomers were proposed as new radiopaque agents for acrylic bone cements. In previous studies the addition of iodine-containing methacrylate monomers provided a statistically significant increase in tensile stress, fracture toughness and ductility, with respect to the barium sulphate (BaSO4)-containing cement. However, since fatigue resistance is one of the main properties required to ensure a good long-term performance of permanent prostheses, it is important to compare the fatigue properties of these new bone cement formulations with the radiolucent and BaSO4-containing bone cements. Because the acrylic cements have initial cracks, fatigue crack propagation studies were performed. It can be observed that these acrylic cements followed the Paris-Erdogan model. The results showed that the addition of some organic radiopacifiers (DISMA, TIBMA) increased the fatigue crack propagation resistance as compared to the radiolucent cement, being similar to the BaSO4-containing cement. The radiolucent cement showed a low crack propagation resistance.

Complex Mixtures↗

PubMed1994

Systemic and local silver accumulation after total hip replacement using silver-impregnated bone cement.

In a patient, at revisional Christiansen total hip arthroplasty, silver-impregnated bone cement was used as prophylaxis against deep infection. Five years later the patient developed serious neurological deficits, and the prosthesis was loose. The loose Christiansen prosthesis and the silver-impregnated bone cement were removed and a Charnley prosthesis inserted. Intra-operatively the concentration of silver in fluid drawn from the hip joint was assessed to be about 1000 times the normal serum reference value, and tissue samples from the acetabulum were densely impregnated with silver. During the following 2 years the serum concentration of silver decreased from more than 60 times to 20 times the normal; simultaneously the patient partially recovered from her grave muscle paralysis.

Aged↗

PubMed1999

Improvement of the mechanical properties of acrylic bone cements by substitution of the radio-opaque agent.

Acrylic bone cements become radio-opaque by the addition of an inorganic compound, commonly BaSO4 or ZrO2. However, the use of these additives has some negative effects such as loss of mechanical properties, risk of release and bone resorption. The use of the monomer 2,5-diiodo-8-quinolyl methacrylate (IHQM), which shows adequate polymerization and radio-opacity properties, is proposed as a new X-ray opaque, methacrylate iodine-containing agent. The aim of this study is to determine the effect of this new radio-opaque agent on the mechanical properties of acrylic bone cements. The addition of the iodine-containing methacrylate provides a statistically significant increase in the tensile strength, fracture toughness and ductility, with respect to the barium sulphate-containing cement. This effect can be attributed to the fact that the use of a radio-opaque monomer eliminates the porosity associated with the barium sulfate particles, which show no adhesion to the matrix. However, some reinforcing effect must also be attributed to the iodine-containing monomer, since the tensile and fracture toughness values reached are even higher than those shown by the radiolucent cement.

Journal Article↗

PubMed1981

Evaluation of acrylic bone cements and their performance standards.

Eight acrylic bone cement products were examined according to the methods set out in three published performance standards, viz., Australian Standard 2265 Part 1, 1979, ASTM specification F451-76, anda the ISO specification 5833/1, 1979. In addition, chemical analyses were carried out by GC, NMR, and IR spectroscopy as well as refractive index measurement, all to establish the main constituent of the products. All the products compiled to the physical, compositional, and sterility requirements of AS 2265. However, all but one sample failed to comply with the solubility requirements of ASTM F451-76. Also, none of the samples compiled with the doughing time requirements of ISO 5833/1. On further analysis, the results suggest that the water solubility and sorption requirements of ASTM F451-76 are restrictive and that the ISO doughing time test methodology requires modification. Various degrees of noncompliance to the requirement of all three specifications were noted on the labeling and in the information content of product inserts. Two additional clauses on mixing tools and radiopacity have been suggested for incorporation into the above standards.

Acrylic Resins↗

PubMed1981

Molecular and macroscopic properties of PMMA bone cement: free-radical generation and temperature change versus mixing ratio.

The molecular and macroscopic changes occurring during the polymerization of poly(methyl methacrylate) (PMMA) bone cement have been investigated. Electron paramagnetic resonance (EPR) spectroscopy was used to monitor free-radical generation and this was compared to temperature changes occurring in the cement for various ratios of polymer powder to liquid monomer (P/L ratio) used in the sample preparation. Both the concentration and the characteristic growth time of the free radicals associated with the polymerization of the bone cement depended on the P/L ratio used. Larger P/L ratio resulted in shorter characteristic growth time for the free radicals as well as a shorter time for the occurrence of the peak sample temperature. Smaller P/L ratios gave smaller maximum concentrations of free radicals and larger peak temperatures. These results are explained on the basis of (1) more initiators present at higher P/L ratios resulting in faster polymerization and (2) less initiators and more monomers present at smaller P/L ratios resulting in fewer radicals but more exothermic reactions. The free radicals present in the bone cement due to the manufacturer's sterilization process were found to be proportional to the fraction of powder used in the preparation, indicating negligible monomer loss during sample mixing.

Bone Cements↗

PubMed2003

Creep behavior of bone cement: a method for time extrapolation using time-temperature equivalence.

The clinical lifetime of poly(methyl methacrylate) (PMMA) bone cement is considerably longer than the time over which it is convenient to perform creep testing. Consequently, it is desirable to be able to predict the long term creep behavior of bone cement from the results of short term testing. A simple method is described for prediction of long term creep using the principle of time-temperature equivalence in polymers. The use of the method is illustrated using a commercial acrylic bone cement. A creep strain of approximately 0.6% is predicted after 400 days under a constant flexural stress of 2 MPa. The temperature range and stress levels over which it is appropriate to perform testing are described. Finally, the effects of physical aging on the accuracy of the method are discussed and creep data from aged cement are reported.

Journal Article↗

PubMed2000

3-D AE visualization of bone-cement fatigue locations.

This study addresses the visualization of crack locations in bone-cement material using a three-dimensional acoustic emission source location technique. Computer software based on an earthquake location technique was developed to determine AE source locations and was used to investigate material cracks formed at the tip of a notch in bone cement. The computed locations show that the cracks form linear features with dimensions between 0.1 and 0.2 mm although larger linear features (almost 3.5 mm) also are present. There is a difference of about 2.5 mm between the average of the event locations, and the location of the tip of the notch is 2.5 mm, which may be due to the finite size of the sensors (5 mm in diameter).

Animals↗

PubMed2007

Influence of changes in the composition of an acrylic bone cement on its polymerization kinetics.

It has been suggested in the literature that a lower polymerization rate of an acrylic bone cement is favorable for the in vivo longevity of a cemented arthroplasty. The present work was a study of the influence of three changes in the composition of an acrylic bone cement (when taken separately) on the cement polymerization rate at 37 degrees C (assumed to be the temperature in the bone bed during a cemented arthroplasty) [k']. The changes were the amount of copolymer as a proportion of the total powder weight (in cements in which there is a copolymer in the powder), the amount of DMPT as a proportion of the total volume of the liquid monomer, and the accelerator. k' was calculated using values of the activation energy and the frequency factor (assuming the polymerization reaction is Arrhenius in nature) that were computed from measurements made using the nonisothermal mode of differential scanning calorimetry. Statistical analysis (one-way ANOVA, with Bonferroni correction, and factorial ANOVA) of the k' values showed that the change in accelerator had a significant influence on k'. The importance of this finding, together with results from two relevant literature reports, is discussed within the context of the use of modified bone cements in cemented arthroplasties.

Arthroplasty, Replacement↗

PubMed2000

A comparison of 2 modern femoral cementing techniques: analysis by cement-bone interface pressure measurements, computerized image analysis, and static mechanical testing.

Modern cementing techniques aim to improve microinterlock and to reduce aseptic loosening. The Norwegian and Swedish Arthroplasty Registers have shown an increased risk of revision using reduced-viscosity cement. We have compared 2 modern cementing techniques using retrograde insertion of normal-viscosity and reduced-viscosity cements. Laboratory-simulated arthroplasty was performed in paired human femora. Performance was evaluated by measuring pressures generated during cementation, cement penetration, and shear strength of the prosthesis-cement and bone-cement interfaces. Large differences exist between these 2 modern techniques. Despite no statistical differences between the pressure measurements with the 2 techniques, greater penetration of reduced-viscosity cement was found proximally, with a trend toward increased penetration of the more viscous cement distally. Areas of greater cement penetration with reduced-viscosity cement proximally produced higher values of ultimate shear strength. Both techniques showed a progressive increase in the shear strength as the level of the section progressed toward the tip of the prosthesis. There is a trend with both techniques for the distal fixation to be stronger.

Arthroplasty, Replacement, Hip↗

PubMed2005

Effect of interface conditions between ultrahigh molecular weight polyethylene and polymethyl methacrylate bone cement on the mechanical behaviour of total shoulder arthroplasty.

The aim of this study was to investigate the effect of the interface condition between polymethyl methacrylate (PMMA) bone cement and the ultrahigh molecular weight (UHMWPE) glenoid component on cement stresses and glenoid component tilting in a finite element (FE) model. The background of this research is that most FE models assume bonding between the PMMA bone cement and the UHMWPE component, although it is very doubtful that this bonding is present. An FE model of a cemented glenoid component was developed and a joint compression force and subluxation force of 725 and 350 N respectively were applied. The maximal principal stresses in the cement layer ranged between 21.30 and 32.18 MPa. Glenoid component tilting ranged between 0.943 degrees and 0.513 degrees. It was found that the interface condition has a large effect on the maximal principal stresses and glenoid component tilting. Whether adhesion between the UHMWPE component and PMMA bone cement occurs is unknown beforehand and, as a result, design validation using the FE technique should be carried out both by using contact elements in combination with a coefficient of friction as well as by a full bonding at this interface.

Adhesiveness↗

PubMed2004

Alternative materials to acrylic bone cement for delivery of depot antibiotics in orthopaedic infections.

Acrylic bone cement has considerable laboratory and clinical data validating it as a delivery material for depot administration of antibiotics. However, an alternate material that does not require a secondary procedure for removal is desired. Many biodegradable materials have been evaluated as alternatives including protein-based materials (collagen, fibrin, thrombin, clotted blood), bone-graft, bone-graft substitutes and extenders (hydroxyapatite, beta-tricalcium phosphate, calcium sulfate, bioglass), and synthetic polymers (polyhanhydride, polylactide, polyglycolide, polyhydroxybutyrate-co-hydroxyvalerate, polyhydroxyalkanoate). Various forms and combinations of these materials have been investigated worldwide, characterizing their elution properties and performance in treating osteomyelitis in animal models. Many of these have had limited clinical evaluation. Outside the United States, some of these materials are used clinically. In the United States, none have been approved. None are commercially available for clinical use. Morselized cancellous bone and calcium sulfate are the two materials that have been used clinically in the United States on a physician-prescribed, hand-mixed, basis. Considering the limited clinical data that currently are available, the use of these materials still is experimental. Clinical application should be cautious, limiting the total antibiotic load. Until definitive data are available, a prudent dose would be no higher than one that would have acceptable toxicity risk if administered intravenously over 24 hours.

Animals↗

PubMed1990

Development and application of antibiotic-loaded bone cement beads.

The authors presented an overview of the development of antibiotic-loaded bone cement beads and their indications for usage, method of application, advantages, disadvantages, and causes of failure. This method of treatment for bone and soft tissue infections of the foot is not a panacea and should be used only in selected cases. The vascular status and the physiologic ability of the patient to heal a peripheral wound or infection are the basis for the success of this method of therapy. European literature makes little mention of adjunctive systemic antibiotic therapy with local antibiotic-loaded bone cement bead use. It is the authors' opinion that clinical judgment should be used to determine the necessity for such therapy.

Anti-Bacterial Agents↗

PubMed2005

Fibrin gel-immobilized primary osteoblasts in calcium phosphate bone cement: in vivo evaluation with regard to application as injectable biological bone substitute.

Osteogenic injectable bone substitutes may be useful for many applications. We developed a novel injectable bone substitute based on osteoblast-fibrin glue suspension and calcium phosphate bone cement (BC). Human osteoblasts were isolated from trabecular bone samples and cultured under standard conditions. Osteoblasts were suspended in fibrinogen solution (FS). BC was cured with thrombin solution. 8 x 4 mm injectable bone discs were prepared using silicon molds and a custom-made applicator device. Discs containing BC, BC/FS, or BC/FS/osteoblasts were implanted subcutaneously into athymic nude mice. After 3, 9 and 24 weeks, specimens were explanted and subjected to morphologic and biomechanical evaluation. In vitro fibrin gel-embedded osteoblasts displayed a differentiated phenotype as evidenced by alkaline phosphatase, collagen type 1 and von Kossa stains. A proportion of osteoblasts appeared morphologically intact over a 3-day in vitro period following application into the BC. BC/FS and BC/FS/osteoblast discs were sparsely infiltrated with vascularized connective tissue. There was no bone formation in implants from all groups. However, positive von Kossa staining only in BC/FS/osteoblast groups suggests engraftment of at least some of the transplanted cells. Biomechanical evaluation demonstrated initial stability of the composites. Young's modulus and maximal load did not differ significantly in the BC/FS and BC/FS/osteoblast groups. The practicability of osteoblast-containing injectable bone could be demonstrated. The dense microstructure and the suboptimal initial vascularization of the composites may explain the lack of bone formation. Modifications with regard to enhanced osteoblast survival are mandatory for a possible application as injectable osteogenic bone replacement system.

Adult↗

PubMedDate not supplied

[Diagnosis of recurrence and therapy of recurrence with in situ bone cement filling in the treatment of giant cell tumor].

Bone-cement plugging allows immediate weight bearing and early detection in case of recurrence of giant cell tumor. A recurrence might be treated by either total or partial removal of the old plug and new curettage followed by a second cement plug. The method allows to plan the final surgery for a time which is likely free of risk of recurrence and which appears appropriate in terms of private time scheduling. In addition it saves the valuable autogenous graft.

Adolescent↗

PubMed1998

The apparent fracture toughness of acrylic bone cement: effect of three variables.

In cemented arthroplasties, pores are almost invariably present at one or more of the so-called 'weak-link' zones (namely, the bone-cement interface, the cement mantle and the cement-implant interface). In the clinical milieu, arthroplasties are frequently subjected to cyclical loading. These conditions underscore the significance of the apparent fracture toughness (KISR) of the cement. The present work is an investigation of the effect of three variables on KISR of three commercial formulations of bone cement (namely, CMW3, PalacosR and Osteopal) measured using straight-sided chevron notched short rod specimens. For CMW3, the effect of mixing method was studied, with all cement constituents having been stored at ambient laboratory environment prior to being mixed. The highest KISR was obtained from material that was obtained from exposing the cement constituents to a passive vacuum for 20 s and then mixing them in a machine that subjected them to simultaneous mechanical mixing and centrifugation. For Palacos R, the effects of two variables [storage temperature of the cement constituents prior to being mixed (4 degrees C versus 21 degrees C) and mixing method (hand mixing versus vacuum mixing)] (taken individually) were studied. It was found that only mixing method exerts a significant effect on KISR. When room-temperature stored constituents were vacuum mixed, the KISR values for a low-viscosity cement (Osteopal) and a medium-viscosity cement of very similar composition (Palacos R) are not significantly different, indicating that the fracture resistance of bone cement is influenced more by its composition than its viscosity.

Acrylic Resins↗