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PubMed1976

A study of the interface between bone and acrylic cement by scanning electron microscopy.

Under the scanning electron microscope, acrylic cement presents an external surface dotted with hemispherical protuberances and a cut surface of cancellous structure. The reaction of bone to acrylic has been studied, both in stable and unstable mechanical conditions. In the first instance, the bone tissue grows towards the cement with an osteogentic front that insinuates itself between the irregularities of the external surface and tends to infiltrate the apertures in it, producing a perfect anchorage which remains solid even after a long period of time. In the second instance, the contact between cement and bone is indirect, with an interposed layer of dense fibrous tissue, probably with a shock-absorbing function.

Acrylic Resins↗
PubMed1987

Bony ossicular fixation using 2-cyano-butyl-acrylate adhesive.

We investigated the effects of 2-cyano-butyl-acrylate (Histoacryl) on the ossicles of 11 of 12 adult guinea pigs. A small amount of the adhesive, placed precisely between the incus and its bony fossa in each middle ear, fixed the ossicles. Light microscopic investigation of the ears of animals killed at 3, 6, 9, and 12 months after surgery showed a bony union of the ossicle to its surrounding niche in 11 of 12 operated-on ears. Negligible inflammatory reaction was seen in areas of the middle ear not in contact with the adhesive. These observations suggest that 2-cyano-butyl-acrylate may be used to achieve a durable bony union in ossiculoplastic surgery with minimal side effects in the middle ear.

Animals↗
PubMed1997

Enhanced strength in cemented stem fixation using adhesive acrylic cement as a metal coating material.

One cause of aseptic loosening of cemented total hip arthroplasty is mechanical weakness at the interface between the metal stem and the cured bone cement. Adhesive acrylic bone cement containing 4-methacryloyloxyethyl trimellitate anhydride (4-META) was applied as a metal coating material to increase the strength of the cemented fixation. The 4-META cement has 2-3 times greater tensile bond strength to metals than does commercial acrylic bone cement. The shear strength of the coated metals fixed with bone cement was approximately 4 times greater in SUS-304 and 3 times greater in titanium (Ti) alloy than those of uncoated metals, and this strength did not decrease after 1 week's immersion in saline. The coating process using the 4-META cement can be performed at normal room temperature, so that metal stems for bone cement fixation could be coated during the course of an operation resulting in potentially improved results of total hip arthroplasty.

Biocompatible Materials↗
PubMed1999

The development and characterization of a fracture-toughened acrylic for luting total joint arthroplasties.

An autopolymerizing fracture-toughened acrylic lute was developed utilizing a toughened prepolymer and a gel-polymerization method. Samples for mechanical and chemical characterization were molded from this material and from untoughened controls. Mechanical testing showed that the mode I fracture toughness (K(IC)) of the toughened lute was increased by 163% over that of the untoughened acrylic controls while the compressive strength and modulus were decreased by 36% and 34%, respectively. The flexural properties of the experimental material were not adversely affected. Analysis of molecular weight and residual monomer data for the experimental and control materials demonstrated that the increase in toughness was due to the presence of the toughened prepolymer. The use of the gel polymerization process gave excellent homogeneity with very low porosity for the experimental polymer, but it resulted in a significant increase in the residual monomer concentration due to the absence of a dispersed phase of prepolymer remnants. This raises questions concerning tissue response to the experimental system.

Arthroplasty, Replacement↗
PubMed2002

Optimising stereoselectivity in intramolecular Diels-Alder reactions of pentadienyl acrylates: synthetic and computational investigations into the "steric directing group" approach.

Experimental conditions for the intramolecular cycloaddition of four related pentadienyl acrylates 3, 4, 5 and 6 are reported. In contrast with several previous reports, pentadienyl acrylates do undergo synthetically useful intramolecular Diels-Alder reactions: 3, 4, 5 and 6 cyclise at reasonable rates at temperatures of 132-180 degrees C at atmospheric pressure in moderate to good yields. The stereochemical outcome of each of these reactions was accurately measured and the results are in good agreement with transition structure populations predicted using B3LYP/6-31+G(d) theory. The parent system 3 cyclises with moderate endo selectivity; the presence of either a C5-methyl substituent or a C3-bromine atom results in a slight shift towards the trans-fused exo stereoisomer but--overall--a less selective reaction. The presence of both C3-Br and C5-CH3 substituents results in a marked improvement in stereoselectivity with the exo,lk-product predominating. Interpretation of B3LYP/6-31+G(d) transition structures allows insights into the improvement in stereoselectivity obtained by incorporating a removable "steric directing group" into a 5-methyl-1,3,8-nonatriene precursor.

Journal Article↗
PubMed2002

The relationship between stress, porosity, and nonlinear damage accumulation in acrylic bone cement.

The long-term survival of cemented hip replacements depends on the ability of the cemented fixation to resist fatigue damage. Damage has been assumed to accumulate linearly (Miner's law) even though it is unlikely to be the case in such a porous brittle material. This study addresses the nonlinear stress-dependent nature of fatigue damage accumulation in acrylic bone cement. Specimens were subjected to a zero-to-tension fatigue load in water at 37 degrees C. A total of 15 specimens were tested, i.e., five specimens at each of three stress levels. The specimens were cyclically loaded to a certain fraction of their fatigue lives and the amount of microcracking present at that time was quantified by counting each crack and measuring its length. This procedure was repeated until the specimen failed. A total of 801 cracks formed in the 15 specimens. All cracks were found to initiate at pores. Crack propagation directions were distributed normally about the direction perpendicular to the applied load at the lower stress levels, but at higher stress, the distribution tended to be broader. At higher stresses, more cracks were produced per pore. The damage accumulation process in acrylic bone cement was found to be nonlinear with the degree of nonlinearity increasing with stress. Furthermore, great variability was found which was attributed to the differences in porosity between specimens. A power law equation is given which describes the predicted relationship between damage accumulation and number of loading cycles as a function of the stress level.

Bone Cements↗
PubMed1975

Slow crack growth in acrylic bone cement.

Slow crack growth in Perspex acrylic sheet (PMMA) and Simplex acrylic bone cement in air and water has been studied from a fracture mechanics viewpoint. It has been found that the crack velocity, V, for each material depends upon the intensification of stress at the tip of the crack. Experimental measurements have been made of V as a function of the stress intensity factor, K, at the crack tip, and a derived V, K relationship has been used to predict the times-to-failure of components made from PMMA and Simplex cement. Direct measurements of time-to-failure for PMMA have shown that the predicted values give a conservative estimate of the structural lifetime of the material.

Bone Cements↗
PubMed1982

The viscosity of acrylic bone cements.

The viscosity of the acrylic bone cement used in total joint arthroplasty is an important material property for determination of the proper handling characteristics and interlock with bone. In this article the rheological properties of the three leading bone cements were determined over a three-decade range of shear rates. In addition, four other cements were tested at a single shear rate. The results indicate that all the acrylic bone cements are non-Newtonian, pseudoplastic materials with significant differences between them. It is shown that the viscosity increases at different rates with respect to increases in time. For the majority of cements there is a steady or increasing rate of viscosity change with time.

Biomechanical Phenomena↗
PubMed1995

Creep characteristics of hand- and vacuum-mixed acrylic bone cement at elevated stress levels.

Compressive creep testing of cylindrical specimens machined from two commercial self-polymerizing acrylic bone cements demonstrated measurable creep strains with higher creep strains for the hand-mixed cement specimens compared to vacuum-mixed cement ones. The average creep strains of hand-mixed cement, after 6 h of constant load, ranged from 0.11% at 10.5 MPa to 14.0% at 50 MPa of applied stress. Vacuum mixing reduced the average creep strain to 6.7% after 6 h of applied stress at 50 MPa. There were no significant differences in the creep response between the two types of acrylic cements. The difference in creep resistance of the two cements was reduced after vacuum mixing (P = .013), which also significantly reduced the cement's internal porosity.

Bone Cements↗
PubMed2003

Fatigue and fracture toughness of acrylic bone cements modified with long-chain amine activators.

The composition of acrylic bone cement has been identified as one of the important parameters affecting its mechanical properties and may, in turn, ultimately influence the longevity of a cemented arthroplasty. Our aim in this study was to determine the influence of change of one compositional variable, the activator, on the fatigue performance and fracture toughness of specimens of the fully cured cement. To that end, three sets of cements were prepared, containing either the conventional activator, 4-N,N dimethyl p-toluidine (DMPT), or novel ones that are tertiary amines based on long-chain fatty acids, that is, 4-N,N dimethylaminobenzyl oleate (DMAO) and 4-N,N dimethylaminobenzyl laurate (DMAL). In the fatigue tests, the specimens were subjected to tension-tension loading, and the results (number of cycles to failure, Nf) were analyzed using the linearized form of the three-parameter Weibull equation. The fracture toughness (KIc) tests were conducted with rectangular compact tension specimens. All fracture surfaces were subsequently examined with scanning electron microscopy. We found that the Weibull mean fatigue lives for specimens fabricated using the DMPT, DMAL, and DMAO containing cements were 272,823, 453,551, and 583,396 cycles, respectively. The corresponding values for KIc were 1.94 +/- 0.05, 2.06 +/- 0.09, and 2.00 +/- 0.07 MPa radical m, respectively. Statistical analyses showed that for both the DMAL- and DMAO-containing cements, the mean values of Nf were significantly higher compared to the corresponding value for the DMPT-containing cement (Mann-Whitney test; alpha < 0.10). This result is attributed to the higher molecular weights of the former cements compared to the latter. The same trend was found for the mean KIc values (Mann-Whitney test; alpha < 0.05), with the trend being explained in terms of the differences seen in the crack morphologies. These results thus demonstrate that these novel amines are viable alternatives to DMPT for incorporation into acrylic bone cement formulations in the future.

Amines↗
PubMed2004

The in vitro elution of gentamicin sulfate from a commercially available gentamicin-loaded acrylic bone cement, VersaBond AB.

The present study was designed to yield results that would be used to contribute to the ongoing debate about the mechanism of the in vitro elution of an antibiotic from an antibiotic-loaded acrylic bone cement. To this end, the elution rates (R) of gentamicin sulfate (expressed as a weight percentage of the initial mass of the antibiotic in the specimen, normalized with respect to the duration of the test) from statically loaded (STATIC) and dynamically loaded (+/-10 MPa; 2 Hz; until fracture; DYNAMIC) specimens fabricated from a commercially available acrylic bone cement (VersaBond AB), in phosphate-buffered saline solution at 37 degrees C, were obtained with the use of a spectrophotometric method. There was evidence of microcracking in the fracture surfaces of DYNAMIC specimens, but no such evidence in the case of STATIC specimens. The surface area of the DYNAMIC specimens, during the tensile phase of the cyclical loading, was estimated to be about 3% larger than for the STATIC specimens (1742 mm(2) versus 1696 mm(2)). The bulk porosities P of the specimens in both sets were also determined and found to not be statistically different, with P for the STATIC and DYNAMIC specimens being 8.55 +/- 0.10 and 8.88 +/- 0.18%, respectively. At the end of the test period, R was found to be 0.36 +/- 0.20 and 1.28 +/- 0.14 wt %/day for the STATIC and DYNAMIC specimens, respectively. It is suggested that the present results provide support for the postulate that the elution mechanism of gentamicin in this cement is a surface phenomenon.

Bone Cements↗
PubMed2004

Effect of a bisphosphonate, disodium pamidronate, on the quasi-static flexural properties of Palacos R acrylic bone cement.

Aseptic loosening is a major complication of joint replacements and is thought to be associated with a heavy macrophage infiltrate in response to wear particles. Bisphosphonates are compounds known to inhibit osteoclastic activity and are used to reduce osteolysis in Paget's disease, osteoporosis, and metastatic bone disease. Oral bisphosphonates have also been used to decrease osteolysis and therefore prevent aseptic loosening of joint replacements. It has been suggested that bisphosphonates mixed in bone cement can reduce bone resorption in joint replacement surgery. This would be an excellent therapeutic option to prevent or control osteolysis. The present aim was to study the mechanical properties of a commercially available acrylic bone cement, Palacos R, mixed with the bisphosphonate pamidronate. The liquid monomer of Palacos R was mixed with liquid pamidronate. Two groups of bone-cement strips were produced, one with added pamidronate and one without. The flexural properties of the cement strips were examined. A significant reduction in both the bending modulus and bending strength of the specimens with added pamidronate was found. In conclusion, the use of liquid pamidronate mixed with the acrylic bone cement Palacos R in order to reduce osteolysis is not recommended because of its effect on the mechanical properties of Palacos R.

Algorithms↗
PubMed2005

The influence of ultrasound on the release of gentamicin from antibiotic-loaded acrylic beads and bone cements.

Gentamicin-loaded acrylic beads are loosely placed in infected bone cavities, whereas gentamicin-loaded acrylic bone cement is used as a mechanical filler in bone to anchor prosthetic components. Both drug delivery systems are used to decrease infection rates by gentamicin release. The objective of this study is to investigate the effects of pulsed ultrasound on gentamicin release from both materials. Gentamicin release from gentamicin-loaded beads (Septopal) and from three commercially-available brands of gentamicin-loaded bone cement (CMW 1, Palacos R-G, and Palamed G) was measured after 18 h of exposure in PBS to an ultrasonic field of 46.5 kHz in a 1:3 duty cycle with an average acoustic intensity of 167 mW/cm(2). Samples not exposed to ultrasound were used as controls. Pulsed ultrasound significantly enhanced gentamicin release from gentamicin-loaded beads, whereas gentamicin release from the gentamicin-loaded bone cements was not significantly enhanced. Mercury intrusion porosimetry revealed an increased distribution of pores between 0.1 and 0.01 microm in beads after gentamicin release, while in bone cements no increase in the number of pores was found. Increased gentamicin release in beads due to ultrasound may be explained by micro-streaming in a porous structure, whereas the absence of changes in pore structure after gentamicin release in bone cement is concurrent with the lack of an enhanced release of the antibiotic by ultrasound. As an effective treatment of infections requires high local concentrations of antibiotic, increased gentamicin release due to ultrasound may be of clinical significance, especially since ultrasound has been demonstrated to increase bacterial killing by antibiotics.

Anti-Bacterial Agents↗
PubMed2005

In vitro evaluation of antibiotic release from and bacteria growth inhibition by antibiotic-loaded acrylic bone cement spacers.

The antibiotic release from and the bacteria growth inhibition by antibiotic-loaded acrylic bone cement hip spacers were studied. The cement used was Palacos R, and it was loaded with either one antibiotic powder (gentamicin, vancomycin, teicoplanin, or synercid) [monoantibiotic case] or two antibiotic powders (gentamicin + vancomycin or gentamicin + teicoplanin) [biantibiotic case] and then tested against Staphylococcus epidermidis, Staphylococcus aureus, Enterococcus faecalis, and methicillin-resistant Staphylococcus aureus (MRSA). Antibiotic elution and bacteria growth were measured every 24 h simultaneously by fluorescence polarization immunoassay and photometrically, respectively. The gentamicin + vancomycin combination achieved the longest growth inhibition on S. epidermidis and MRSA (mean of 20 and 14 days, respectively). Gentamicin + teicoplanin-loaded spacers were capable of inhibiting growth on E. faecalis and S. aureus for the longest period (11 and 16 days, respectively). The highest concentrations of gentamicin and vancomycin could be assayed during the first 4 days. Teicoplanin concentrations could be detected only during the first 72 h, synercid was not detected at all, possibly because of the limitation of the detection technique used. A greater percentage of the gentamicin was released than of the vancomycin. The aminoglycosid-glycopeptid combination showed a synergistic effect on the release of gentamicin, but not on vancomycin or teicoplanin. Biantibiotic-impregnated hip spacers proved to be superior to monoantibiotic ones. Because of important differences between the conditions used for the present tests and the in vivo environment, any recommendation with regard to the use of monoantibiotic- and biantibiotic-loaded acrylic bone cement spacers must await the results of further investigations.

Anti-Bacterial Agents↗
PubMed2006

Influence of powder particle size distribution on complex viscosity and other properties of acrylic bone cement for vertebroplasty and kyphoplasty.

For use in vertebroplasty and kyphoplasty, an acrylic bone cement should possess many characteristics, such as high radiopacity, low and constant viscosity during its application, low value of the maximum temperature reached during the polymerization process (T(max)), a setting time (t(set)) that is neither too low nor too high, and high compressive strength. The objective of this study was to investigate the influence of the powder particle distribution on various properties of one acrylic bone cement; namely, residual monomer content, T(max), t(set), complex viscosity, storage and loss moduli, injectability, and quasi-static compressive strength and modulus. It was found that the formulations that possessed the most suitable complex viscosity-versus-mixing time characteristics are those in which the ratio of the large poly(methyl methacrylate) beads (of mean diameter 118.4 microm) to the small ones (of mean diameter 69.7 microm) was at least 90% w/w. For these formulations, the values of the other properties determined were acceptable.

Biocompatible Materials↗
PubMed2007

Biocompatibility of a new radiopaque iodine-containing acrylic bone cement.

Radiopacity in the vast majority of the commercially available acrylic bone cements that are used clinically is provided by particles of either BaSO(4) or ZrO(2). Literature reports have shown these agents to have a detrimental effect on some mechanical properties of the cements as well as on its biological response. We, therefore, have developed a new type of bone cement, for which radiopacity results from the presence of an iodine-containing methacrylic copolymer. The focus of the present work was the comparison of the biocompatibility of this new cement and a commercially available cement that contains barium sulfate. In vitro experiments show that both cements are cytocompatible materials, for which no toxic leachables are found. Implantation of the cements in a rabbit for three months resulted in the occasional presence of a thin fibrous tissue at the cement-bone interface, which is common for acrylic bone cements. Consideration of all the results led to the conclusion that the new cement is as biocompatible as the BaSO(4)-containing one.

Animals↗
PubMed2007

Influence of initial component temperature on the apparent viscosity and handling characteristics of acrylic (PMMA) bone cement.

The flow and polymerization characteristics of poly(methylmethacrylate) (PMMA) bone cement can be changed by manipulating the temperature of the bone cement components or the environment that they are prepared in. To quantify the effects of the initial component temperature (T(ic)) of acrylic bone cement on the rheological and handling characteristics, ASTM F451-99a compliant methods and clinically relevant testing methods were utilized. A rheometer was designed and fabricated using the dimensions of a clinical, commercially available, cement gun and nozzle. The influence on the apparent viscosity and handling characteristics (setting time, working time, and peak exotherm temperature) for a high viscosity (HV) commercially-available acrylic bone cement, Palacos R, were determined. The values of T(ic) used were 23 degrees C (room), 6 degrees C (refrigerator), and -14 degrees C (freezer). Using the apparent viscosity of a medium viscosity (MV) bone cement as a benchmark (Simplex P at room temperature), it was found that by adjusting the T(ic) the HV cement was able to mimic the flow characteristics of the MV cement. Lowering the T(ic) lowered the apparent viscosity of the bone cement. The effects of T(ic) on the polymerization of bone cement were studied in dynamic and static conditions. The dynamic test recorded temperature and torque from stirring resistance. Setting times were also determined using the ASTM exotherm mold method. The setting times determined by the dynamic testing conditions were consistently shorter than those determined by the ASTM method. Lowering the T(ic) increased the working and setting times; however, it did not have a significant effect on the peak exotherm temperature.

Bone Cements↗
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↗