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PubMed2005

Synthesis of bioactive PMMA bone cement via modification with methacryloxypropyltri-methoxysilane and calcium acetate.

Bone cement consisting of polymethylmethacrylate (PMMA) powder and methylmethacrylate (MMA) liquid is clinically used for fixation of implants such as artificial hip joints. However, it does not show bone-bonding ability, i.e., bioactivity. The lack of bioactivity would be one of factors which cause loosening between the cement and the implant. The present authors recently showed the potential of bioactive PMMA-based bone cement through modification with gamma-methacryloxypropyltrimethoxysilane (MPS) and calcium acetate. In this study, the effects of the kinds of PMMA powder on setting time, apatite formation and compressive strength were investigated in a simulated body fluid (Kokubo solution). The cement modified with calcium acetate calcined at 220 degrees C could set within 15 min when the PMMA powder had an average molecular weight of 100,000 or less. The addition of calcium acetate calcined at 120 degrees C in the PMMA powder required a much longer period for setting. The modified cements formed an apatite layer after soaking in the Kokubo solution within 1 day for cement starting from PMMA powder with a molecular weight of 100,000 or less. Compressive strengths of the modified cements were more than 70 MPa for cements starting from 100,000 and 56,000 in molecular weight. After soaking in Kokubo solution for 7 days, the modified cement consisting of PMMA powder of 100,000 in molecular weight showed a smaller decrease in compressive strength than that consisting of 56,000 in molecular weight. These results indicate that bioactive PMMA cement can be produced with appropriate setting time and mechanical strength when PMMA powders with a suitable molecular weight are used. Such a type of design of bioactive PMMA bone cement leads to a novel development of bioactive material for bone substitutes.

Acetates↗
PubMed2001

Evaluation of the effect of seven acrylic bone cements on erythrocytes and plasmatic phase of coagulation.

The haemolytic activity and the effect on the plasmatic phase of coagulation of seven bone cements were evaluated (Sulfix-60 from Sulzer Orthopedic Inc., a bone cement at low viscosity from Zimmer, a bone cement dough-type from Zimmer, Palacos R from Merck, CMW1, CMW2 and CMW3 from DePuy International Ltd.). Haemolytic activity was tested by adding the cement extracts in phosphate buffered saline to a suspension of erythrocytes. After 4 h incubation at 37 degrees C, the haemoglobin concentration was determined on the supernatants by colorimetric method. The effect on the plasmatic phase of coagulation was tested by adding the cement extracts in saline to human plasma. After 30 min incubation at room temperature activated partial thromboplastin time (APTT) was determined. All extracts induced non-significant variations of haemoglobin concentration and APTT. It was concluded that the tested cement extracts do not induce haemolysis and do not activate the intrinsic pathway of coagulation, at least in the tests that were performed.

Acrylates↗
PubMed1994

Removal of bone cement from the femoral canal using an acoustic emission-controlled milling device.

The removal of bone cement from the femoral canal in the case of hip prosthesis loosening takes a considerable amount of time and carries the additional risk of complications, thus risking bone damage and perhaps even endangering the successful reimplantation of a new prosthesis. We have demonstrated experimentally that the milling of bone and bone cement produces acoustic emission waves of different intensity. These waves can be measured by a commercial acoustic emission transducer. This method enables us to control a milling device during the removal of bone cement from deep in the femoral canal, avoiding the serious damage to the bone and thus enabling a new prosthesis to be reimplanted.

Acoustics↗
PubMed2001

Effects of bone cement volume and distribution on vertebral stiffness after vertebroplasty.

STUDY DESIGN: The biomechanical behavior of a single lumbar vertebral body after various surgical treatments with acrylic vertebroplasty was parametrically studied using finite-element analysis. OBJECTIVES: To provide a theoretical framework for understanding and optimizing the biomechanics of vertebroplasty. Specifically, to investigate the effects of volume and distribution of bone cement on stiffness recovery of the vertebral body. SUMMARY OF BACKGROUND DATA: Vertebroplasty is a treatment that stabilizes a fractured vertebra by addition of bone cement. However, there is currently no information available on the optimal volume and distribution of the filler material in terms of stiffness recovery of the damaged vertebral body. METHODS: An experimentally calibrated, anatomically accurate finite-element model of an elderly L1 vertebral body was developed. Damage was simulated in each element based on empirical measurements in response to a uniform compressive load. After virtual vertebroplasty (bone cement filling range of 1-7 cm3) on the damaged model, the resulting compressive stiffness of the vertebral body was computed for various spatial distributions of the filling material and different loading conditions. RESULTS: Vertebral stiffness recovery after vertebroplasty was strongly influenced by the volume fraction of the implanted cement. Only a small amount of bone cement (14% fill or 3.5 cm3) was necessary to restore stiffness of the damaged vertebral body to the predamaged value. Use of a 30% fill increased stiffness by more than 50% compared with the predamaged value. Whereas the unipedicular distributions exhibited a comparative stiffness to the bipedicular or posterolateral cases, it showed a medial-lateral bending motion ("toggle") toward the untreated side when a uniform compressive pressure load was applied. CONCLUSION: Only a small amount of bone cement ( approximately 15% volume fraction) is needed to restore stiffness to predamage levels, and greater filling can result in substantial increase in stiffness well beyond the intact level. Such overfilling also renders the system more sensitive to the placement of the cement because asymmetric distributions with large fills can promote single-sided load transfer and thus toggle. These results suggest that large fill volumes may not be the most biomechanically optimal configuration, and an improvement might be achieved by use of lower cement volume with symmetric placement.

Bone Cements↗
PubMed1978

Antibiotics in acrylic bone cement. In vivo studies.

In vivo experiments were performed to study elution rates of antibiotics combined with Surgical implex bone cement and efficacy in controlling bacterial infections. Cylinders of bone cement were implanted in animals and at the same time the surgical areas were infected with large numbers of bacteria. Gentamicin and Keflin were eluted from the cylinders in sufficient quantities to completely eliminate or markedly reduce the number of bacteria recovered from infected areas. Animals were also treated with an anti-inflammatory drug, hydrocortisone, prior to implantation of cylinders and infection. The antibiotics in the bone cement effectively destroyed the bacteria in these animals with impaired inflammatory responses as compared with control animals.

Animals↗
PubMed1996

Reinforcement of PMMA bone cement with a continuous wire coil--a 3D finite element study.

The changes in the mechanical response of a bone cement reinforcement, comprised of a continuous stainless steel coil imbedded within the PMMA bone cement matrix surrounding the distal tip of the total hip arthroplasty, was investigated. To achieve this, a 3D finite element model depicting two and one half rotations of the coil imbedded within the cement at the distal tip was constructed. Ideally, the wire coil should reduce the radial, and to a greater extent, the hoop stresses developing within the cement and at the cement-stem interface. As a means of comparison, a control model of only bone cement was also built. For the radial stresses, the control had about 4.5 times the compressive stress of the reinforced models (0.039 (+/-0.00065) MPa vs. 0.0087 (+/-0.0012) MPa) at the cement-stem interface. The tensile hoop stresses were also 4.5 times higher (4.272 (+/-0.0147) MPa and 0.95 (+/-0.0052) MPa) for the control than for the reinforced models. This indicates that the wire coil reinforcement is effective in reducing the cement mantle's radial and, more importantly, the hoop stresses which may lead to the failure of both the cement and the implant as a whole.

Bone Cements↗
PubMed2004

A novel test method for evaluation of the abrasive wear behaviour of total hip stems at the interface between implant surface and bone cement.

After total hip replacement, some cemented titanium stems show above-average early loosening rates. Increased release of wear particles and resulting reaction of the peri-prosthetic tissue were considered responsible. The objective was to develop a test method for analysing the abrasive wear behaviour of cemented stems and for generating wear particles at the interface with the bone cement. By means of the novel test device, cemented hip stems with different designs, surface topographies and material compositions using various bone cements could be investigated. Before testing, the cemented stems were disconnected from the cement mantle to simulate the situation of stem loosening (debonding). Subsequently, constant radial contact pressures were applied on to the stem surface by a force-controlled hydraulic cylinder. Oscillating micromotions of the stem (+/- 250 microm; 3 x 10(6)cycles; 5 Hz) were carried out at the cement interface initiating the wear process. The usability of the method was demonstrated by testing geometrically identical Ti-6A1-7Nb and Co-28Cr-6Mo hip stems (n= 12) with definite rough and smooth surfaces, combined with commercially available bone cement containing zirconium oxide particles. Under identical frictional conditions with the rough shot-blasted stems, clearly more wear particles were generated than with the smooth stems, whereas the material composition of the hip stems had less impact on the wear behaviour.

Biocompatible Materials↗
PubMed1979

Fracture behaviour of commercial surgical acrylic bone cements.

The resistance to slow growth of three commercial acrylic bone cements has been evaluated. It was found that small additions of 1 micrometer diameter barium sulphate particles reduced the resistance to slow crack growth of Simplex P and CMW acrylic bone cements, while a small addition of the antibiotic Gentamicin had no detectable effect on cracking in Palacos R bone cdment.

Acrylic Resins↗
PubMed1989

Use of high-performance polyethylene fibres as a reinforcing phase in poly(methylmethacrylate) bone cement.

First results are presented concerning the elastic and ultimate mechanical behaviour of p(MMA) bone cement reinforced with as-received and surface-modified Spectra 900 polyethylene fibres. Even though the surface chemistry and reactivity of the fibres was modified, the surface oxidation and surface grafting treatments of the polyethylene fibres apparently did not significantly affect the mechanical properties of the polyethylene-reinforced p(MMA) bone cement or improve the interfacial bonding. This may be attributed to the rather unfavourable area-to-volume ratio of PE fibres for such treatments, as well as to the necessarily low content of PE fibres in the bone cement which does not allow a clear differentiation between the various samples.

Bone Cements↗
PubMed1999

Influence of the modification of P/L ratio on a new formulation of acrylic bone cement.

The use of smaller powder/liquid (P/L) ratio favours the handling and wetting of poly(methyl methacrylate) (PMMA) beads in bone cement formulations. In this paper a P/L ratio of 1.86 is tested to overcome adhesion problems found in hydroxypropyl methacrylate (HPMA) modified bone cements and the influence on bone cement characteristics was analysed. The reduction of the P/L ratio leads to higher temperature peaks and shorter setting times, whereas the residual monomer content increases slightly. Water uptake obeys the diffusion laws, and the introduction of a more hydrophilic monomer gives rise to an increase of this parameter, which does not present significant changes with modification of the P/L ratio. Polymerization shrinkage is slightly greater because of the introduction of higher proportions of monomer in the formulation. Mechanical properties are similar to those obtained with conventional P/L ratios. The analysis of scanning electron microscopy (SEM) reveals an improvement of the adhesion between phases with respect to P/L = 2 formulations.

Acrylic Resins↗
PubMed1997

Bioactive bone cement: comparison of AW-GC filler with hydroxyapatite and beta-TCP fillers on mechanical and biological properties.

Three types of bioactive bone cement (designated AWC, HAC, and TCPC), each consisting of bisphenol-alpha-glycidyl methacrylate (Bis-GMA)-based resin and a bioactive filler of apatite and wollastonite containing glass-ceramic (AW-GC), sintered hydroxyapatite (HA), or beta-tricalcium phosphate (beta-TCP) powder were made in order to evaluate the influence of the bioactive filler on the mechanical and biological properties of bone cement. The proportion of filler added to the cements was 70% w/w. The compressive, bending, and tensile strengths and the fracture toughness of AWC were higher than HAC and TCPC under wet conditions. The cements were evaluated in vivo by packing them into the intramedullary canals of rat tibiae. An affinity index that equalled the length of bone in direct apposition to the cement was calculated for each cement and expressed as a percentage of the total length of the cement surface. Histological examination of rat tibiae up to 8 weeks after implantation revealed that AWC had higher bioactivity than HAC and TCPC. New bone had formed along the AWC surface within 2 weeks, and at 4 weeks newly formed bone surrounded the cement surface almost completely. In HAC- and TCPC-implanted tibiae, immature bone had formed directly toward but not along the cement surface at 2 weeks. Observation of cement-bone interfaces showed that AWC had bonded to the bone via a so-called "Ca-P-rich layer"; the cement-bone interface remained stable, and the width of the CA-P-rich layer became thicker with time. On the other hand, in HAC- and TCPC-implanted tibiae, the cement surface fillers were surrounded by new bone and were absorbed gradually to become bone matrix. The cement-bone interfaces went inside the cement with time. Our results indicate that stronger interstitial bonding between the inorganic filler and the organic matrix resin in AWC lead to higher mechanical properties; results also indicate that the more stable cement-bone interface and higher bioactivity of AWC are due to early and uniform apatite formation on the cement surface.

Animals↗
PubMed2005

Acrylic bone cement: its clinical development and current status in Japan.

This article describes the transition of annual total sales figures of bone cement in Japan during the last 12 years, bone cement-related complications, the present status of bone cement application in Japan as surveyed by the Implant Committee of the Japanese Orthopaedic Association, and its proposed precautions to be taken for the prevention of bone cement complications.

Arthroplasty↗
PubMed2003

The effect of mixing on gentamicin release from polymethylmethacrylate bone cements.

We compared the release of gentamicin from 6 different commercially available, antibiotic-loaded PMMA bone cements used for vacuum- and hand-mixed cement using a Cemvac vacuum mixing system. We also measured the release of gentamicin after manual addition of the antibiotic to different commercial, unloaded bone cements after hand-mixing. The porosity of cements was reduced in all vacuum-mixed cements, as compared with hand-mixed cements, concurrent with a statistically significant reduction (3 of 6) or increase (1 of 6) in the total amounts of gentamicin released. The total gentamicin release was studied in 3 of the brands after manual addition and mixing of the antibiotics. We found that the release of antibiotics was lower than in samples made from industrial mixing. In conclusion, the manual addition and mixing of gentamicin in PMMA bone cements leads to a lower release of antibiotics than that in corresponding commercially available antibiotic-loaded cements, while vacuum-mixing only leads to a minor reduction in antibiotic release, as compared to hand-mixing.

Anti-Bacterial Agents↗
PubMed2004

Creep dominates tensile fatigue damage of the cement-bone interface.

Fatigue damage from activities of daily living has been considered to be a major cause of aseptic loosening in cemented total hip arthroplasty. The cement-bone interface is one region where loosening could occur, but to date the fatigue response of the interface has not been examined. Cement-bone specimens were prepared from fresh frozen human cadaver tissue using simulated in vivo conditions. Tensile fatigue tests to failure were performed in an environmental chamber. Loss of specimen stiffness (stiffness damage) and permanent displacement after unloading (creep damage) were found in all specimens. At failure, creep damage accounted for the majority (79.9+/-10.6%) of the total strain damage accumulation at failure (apparent strain, epsilon=0.0114+/-0.00488). A power law relationship between strain-damage rate and time-to-failure showed that the strain-damage rate was an excellent predictor of the fatigue life of the cement-bone interface. The S-N response of the interface was obtained as a function of the applied stress ratio and the initial apparent strain. The total motion between cement and bone (72.2+/-29.8 microm) prior to incipient failure due to both stiffness and creep fatigue damage may be sufficient to result in fibrous tissue formation and contribute to eventual clinical loosening.

Aged↗
PubMed1998

Fatigue of bone cement with simulated stem interface porosity.

Cracks in bone cement have been observed in carefully examined post-mortem preparations of cemented stems. These cracks were probably caused by fatigue, and frequently appeared to initiate at pores. Ubiquitous porosity, occurring preferentially at, or near, the stem, is most likely caused by polymerization shrinkage. Preparation of air-free cement has only a marginal influence on the interface porosity, but pre-heating the stem in order to reverse the direction of polymerization can reduce or eliminate it. To estimate the impact of interface porosity on the fatigue strength of bone cement, test plates for this study were cast in a steel mold without release foils, and with one side of the mold warmer. Sample plates so prepared from chilled, partial vacuum-mixed PALACOS, have one face essentially pore-free and the other porous, the extent and morphology of the porosity being very similar to that observed on the stem-cement interface. Four-point bending fatigue strength, determined after 60 d conditioning in Ringer's solution at 37 degrees C, was only 20 MPa (at 10(6) cycles, with the porous side under tension) compared to 30 MPa for conventionally prepared, pore-free material. This corresponds to a 10-100 fold reduction in cycles to failure in the range of stresses predicted to occur in vivo.

Journal Article↗
PubMed1985

Cefuroxime in CMW bone cement. A clinical study.

This paper presents the results of adding the antibiotic cefuroxime to CMW bone cement in a group of patients undergoing total hip or knee replacement, in which the levels of cefuroxime were assayed in the blood, wound drainage fluid, urine and surplus bone cement. It was found that very small amounts of cefuroxime, less than 5%, were recovered in the urine, serum and drainage fluid in the first week following operation, and since it is known that cefuroxime is not metabolised or excreted elsewhere in the body, it must follow that approximately 95% remains in the bone cement as a potential source of prophylaxis against infection.

Adult↗
PubMed1997

Effect of calcium carbonate on the compliance of an apatitic calcium phosphate bone cement.

Clinical requirements for calcium phosphate bone cements were formulated in terms of the initial setting time, the final setting time, the cohesion time and the ultimate compressive strength. Three cement formulations were tested. The previously developed Biocement H was made of a powder containing alpha-tertiary calcium phosphate and precipitated hydroxyapatite. Biocement B2 powder was made by adding some CaCO3 to Biocement H, whereas Biocement B1 was made by adding some CaCO3 but with simultaneous adjustment of the amount of precipitated hydroxyapatite.The liquid/ powder ratio of the cement paste and the accelerator concentrations (percentage Na2HPO4) in cement liquid were varied. For Biocement H there was no combination of L/P ratio and percentage Na2HPO4 for which all clinical requirements were satisfied. However, there was an area of full compliance for Biocements B1 and B2, of which that for B1 was the largest. Therefore, Biocement B1 may be applied in clinical situations as those in orthopaedics, plastic and reconstructive surgery and oral and maxillofacial surgery, even when early contact with blood is inevitable.

Apatites↗
PubMed2005

Acrylic bone cements: mechanical and physical properties.

Mechanical and physical properties are of particular significance for the performance of acrylic bone cement. Several mechanical test methods are described in the literature to characterize the mechanical performance of bone cements. The simulation of the in vivo situation is extremely difficult, however, because of the complex mechanism of loading in the bone. The usefulness of the different mechanical and physical test methods, several results of commercial acrylic bone cements, and the influence of different parameters, such as temperature, test environment, and preparation of specimens on these results are discussed in this article.

Bone Cements↗