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PubMed1989

Elastic and ultimate properties of acrylic bone cement reinforced with ultra-high-molecular-weight polyethylene fibers.

A study of the fracture behavior of poly-(methyl methacrylate) (PMMA) bone cement reinforced with short ultra-high-molecular-weight polyethylene (Spectra 900) fibers is presented. Linear elastic and nonlinear elastic fracture mechanics results indicate that a significant reinforcing effect is obtained at fiber contents as low as 1% by weight, but beyond that concentration a plateau value is reached and the fracture toughness becomes insensitive to fiber content. The flexural strength and modulus are apparently not improved by the incorporation of polyethylene fibers in the acrylic cement, probably because of the presence of voids, the poor mixing practice and the weakness of the fiber/matrix interfacial bond. The present polyethylene/PMMA composite presents several advantages as compared to other composite cements, but overall the mechanical performance of this system resembles that of Kevlar 29/PMMA cement, with a few differences. Scanning electron microscopy reveals characteristic micromechanisms of energy absorption in Spectra 900/PMMA bone cement. A scheme for the strength of random fiber-reinforced composites, which is a simple extension of the Kelly and Tyson model for the strength of unidirectional composites, is presented and discussed. Young's modulus and the fracture toughness results are discussed in the framework of existing theories. More fundamental modeling treatments are needed in terms of fracture micromechanisms to understand and optimize the various mechanical properties with respect to structural parameters and cement preparation technique.

Bone Cements↗
PubMed2005

Liquid gentamicin in bone cement: a laboratory study of a potentially more cost-effective cement spacer.

BACKGROUND: Liquid gentamicin is approved by the Food and Drug Administration, is readily available, and is much less costly than tobramycin, the more commonly used antibiotic in cement spacers. The purpose of the present study was to test the mechanical properties, elution characteristics, and antibacterial activity of liquid gentamicin in an acrylic bone cement spacer. METHODS: Standardized specimens consisting of Palacos cement combined with liquid gentamicin, powdered tobramycin, or no antibiotic were fashioned, and the three groups were tested with regard to compressive and tensile strength, elution characteristics (with use of radioimmunoassays), and antibacterial activity (with use of bioassays). RESULTS: The ultimate compression strength decreased by 49% (from 64.65 +/- 3.89 MPa to 32.96 +/- 3.33 MPa) and the ultimate tension strength decreased by 46% (from 35.85 +/- 2.97 MPa to 19.20 +/- 0.36 MPa) when the specimens containing 480 mg of liquid gentamicin were compared with the controls. The addition of tobramycin had no significant effect compared with the controls. The majority of gentamicin was released from the cement during the initial twenty-four hours (mean concentration, 26.4 mcg/mL). The mean concentrations at three and six weeks were 4.15 and 0.65 mcg/mL, respectively. The bioassays confirmed the bactericidal activity of the gentamicin released from the cement. CONCLUSIONS: Liquid gentamicin in bone cement is potent and bactericidal. Although the mechanical properties of the cement are significantly diminished by the addition of liquid gentamicin, the temporary nature of the cement spacer makes its use potentially worthwhile given the substantial cost savings to the hospital and the patient.

Anti-Bacterial Agents↗
PubMed1993

The effects of bone cement powder on human adherent monocytes/macrophages in vitro.

This study reports the effects of Simplex bone cement powder (BC) on the proliferation and production of bone resorbing factors in vitro by human adherent monocytes/macrophages. Adherent peripheral blood cells were isolated from seven healthy individuals and exposed to a dispersion of BC powder (1 mg/mL), phytohemagglutinin (PHA, 40 micrograms/mL), or medium alone at different periods of cell incubation (days 0-2, 0-7, 5-7, or 10-12). Cell proliferation was quantified by incorporation of 3H-thymidine uptake. Culture supernatants were evaluated for levels of interleukin 1-like activity (IL-1) by murine thymocyte proliferation assay, prostaglandin E2 (PGE2) by radioimmunoassay, lysosomal enzyme activity (N-acetyl-beta-D-glucosaminidase and beta-glucuronidase using fluorometry, and collagen and casein degrading activity using radioactive substrates. Human adherent peripheral blood cells showed a proliferative response to PHA that coincided with cell maturation; BC did not inhibit PHA-induced cell proliferation of either adherent or nonadherent blood cells, indicating the non-toxic nature of these particles at the concentrations tested. BC stimulated increased release of the lysosomal enzyme N-acetyl-beta-D-glucosaminidase; the levels of PGE2, IL-1, collagenase, and caseinase were unchanged.

Adult↗
PubMed2000

Failure of total hip arthroplasty with Boneloc bone cement.

Early failure of Boneloc cemented total hip arthroplasty is well documented. However, information regarding the long term prognosis is scanty. The aim of this study was therefore to assess the long term failure rate of total hip replacement with Boneloc bone cement. Between January 1991 and March 1992, Boneloc bone cement (Polymers Recontructive A/S, Farum, Denmark) was used in 42 consecutive total hip replacements in 42 patients. The average age of the patients was 75 years. There were 25 women and 17 men. The diagnosis at operation was osteoarthritis in all cases. A cemented Muller Taperloc femoral stem was used with a cemented Muller acetabular cup (Biomet, Warsaw, USA). The follow-up time was 9 years. All patients underwent radiographic control the first postoperative year and annually after 1995. To date 21 patients have been revised for aseptic loosening at a mean of 5 years (range: one year to 8 years). Three other patients have definite radiographic evidence of loosening. The overall failure rate is therefore 24/42 = 57%. Our results confirm the previously reported poor results of Boneloc bone cement for hip arthroplasty and support the recommendation of indefinite follow-up for surviving prostheses. New prosthesis designs and new cements should have documentation, including laboratory tests and randomized clinical studies with radiostereometric evaluation. However, the ethical responsibility rests heavily on the shoulders of the clinician to make a correct analysis of the need for a new product before he begins to use it.

Aged↗
PubMed1991

Genotoxicity of acrylic bone cements.

The genotoxicity of conventional polymethylmethacrylate (PMMA) and a new formulation of bone cement: methylmethacrylate/n-decylmethacrylate/isobornylmethacrylate (MMA/DMA/IBMA) were tested by micronucleus test and reverse mutation assays of Salmonella typhimurium (Ames test). In extracts from cement pellets (37 degrees, 72 hr) with water and water/ethanol the concentration of MMA was reduced by 13-19 times with the new formulation and the concentrations of accelerators were reduced by 4-5 times. New chemical constituents (DMA, IBMA, dihydroxy-propyl-p-toluidine) were found in negligible concentrations. In the micronucleus test all three cement brands were found non-mutagenic and in the Ames test scattered increased revertant ratios were found without differences between the three brands. The new formulation does not possess any increased risk of genotoxicity.

Animals↗
PubMed1988

The effect of the extracorporeal shock wave lithotriptor on the bone-cement interface in dogs.

The extracorporeal shock wave lithotriptor (ECSWL) is a machine that generates shock waves that transfer energy through biologic materials. This study focused the wave at a composite bone-cement (polymethylmethacrylate) interface and evaluated the effects both quantitatively and qualitatively. Six matched sets of dog femora were selected. The intramedullary canals were packed uniformly with cement. One of the set was randomly selected for treatment with impulses while the other served as the control. The bone was then sectioned transversely into discs, and scanning electron microscopy and mechanical push-out studies were performed. The results indicated that the ECSWL does have a loosening effect on the bone-cement interface. Using a paired Student's t-test, the shear strength was significantly less in the treated group than in the control (p less than 0.003). Microscopically, the treated specimens revealed relative sparing of the surrounding bone. At the bone-cement interface, however, microfractures, loose bodies, and widening were seen. Revision total arthroplasty has a significant morbidity, which can be partially attributed to cement extraction. The results of this study indicate that the ECSWL may be a useful adjunct in revision surgery by facilitating the extraction of polymethylmethacrylate and thereby reducing the morbidity.

Animals↗
PubMed2001

Interleukin-6 expression by osteoblast-like MG63 cells challenged with four acrylic bone cements.

Periprosthetic osteolysis is a major clinical problem in total hip and total knee arthroplasty and polymethylmethacrylate (PMMA) is a possible etiologic factor. Recently, increasing importance was ascribed to interleukin-6 (IL-6) as an agent favouring bone resorption. The aim of the present study was to investigate the role of bone cements on IL-6 production by MG63. The effect of four acrylic bone cements (Sulfix-60, CMW 1, CMW 2, and CMW 3) on the protein release and mRNA expression of IL-6 in osteoblast-like cell line MG63 was examined using IL-1beta (0.2 microg ml(-1)) as the positive control. The extracts in minimum essential medium (MEM) of the cements were tested, following 1-h and 7-day curing. CMW 1 and CMW 2 significantly increased the IL-6 release into the culture media (p < 0.01). The cells incubated with Sulfix-60 and CMW 3 produced no significantly different levels of IL-6 than the basal production. A positive correlation was found between the concentration of IL-6 and the contents of benzoylperoxide (p = 0.0003) and barium sulphate (p < 0.0001). MG63 expressed IL-6 mRNA constitutively, as demonstrated by the positivity of the negative controls too. We conclude that CMW 1 and CMW 2 increase the production of IL-6 in MG63 cells. The response to Sulfix-60 and CMW 3 is not significantly greater than the negative control.

Bone Cements↗
PubMed1982

Stress relaxation and creep behaviour of normal and carbon fibre reinforced acrylic bone cement.

Room temperature compression creep and stress relaxation behaviour of normal as well as carbon fibre reinforced bone cement was studied and their properties compared. It was observed that increased deformation due to creep in 24 h was about 70% of the initial strain (due to applied constant stress fo 10.5 MN/m2) for normal PMMA and this could be reduced to 45% of the initial strain by carbon fibre reinforcement. Surgical grade PMMA, when subjected to 1% constant strain, showed an average stress-relaxation by 24% in eight hours. Percentage of stress-relaxation was somewhat more for carbon fibre reinforced bone cement even though the level of stress was much higher compared to normal PMMA.

Bone Cements↗
PubMed2002

Medical devices; reclassification of polymethylmethacrylate (PMMA) bone cement. Final rule.

The Food and Drug Administration (FDA) is announcing that it has reclassified the polymethylmethacrylate (PMMA) bone cement intended for use in arthroplastic procedures of the hip, knee, and other joints for the fixation of polymer or metallic prosthetic implants to living bone from class III to class II (special controls). The agency is also announcing that it has issued an order in the form of a letter to the Orthopedic Surgical Manufacturers Association (OSMA) reclassifying the device. The special control for the device is a guidance document entitled "Class II Special Controls Guidance Document: Polymethylmethacrylate (PMMA) Bone Cement." The agency is reclassifying this device into class II because special controls, in addition to general controls, would provide reasonable assurance of the safety and effectiveness of the device, and there is sufficient information to establish special controls.

Bone Cements↗
PubMed2002

Effect of four acrylic bone cements on transforming growth factor-beta1 expression by osteoblast-like cells MG63.

Based on the hypothesis that bone cements cause changes in the production of transforming growth factor-beta 1 (TGF-beta1) by bone cells, the effects of four acrylic bone cements (Sulfix-60, CMW 1, CMW 2 and CMW 3) were examined using the osteoblast-like cell line MG63. The extracts in MEM of the cements were tested, following 1 h- and 7 day-curing. MG63 cells seldom expressed mRNA specific for TGF-beta1 in basal conditions. The cultures expressed mRNA constantly after incubation with the extract of CMW 1 cured for 1 h. TGF-beta1 specific mRNA was seldom expressed after incubation with the other cement extracts. The release of TGF-beta1 into the conditioned medium was increased significantly by CMW 1 extract at 1 h-curing, but was not changed significantly by CMW 1 extract at 7 day-curing and by the extracts of the other cements, at both curing times. The stimulating effect of CMW 1 on the secretion of TGF-beta1, even with all the restrictions of an in vitro study of continuous cell lines, if confirmed in vivo, might favor the development of the synovial-like membrane around the implant, and therefore impair the chance of success of the prosthesis.

Acrylates↗
PubMed2001

Inflammatory responses of human primary macrophages to particulate bone cements in vitro.

We have investigated whether the particle-stimulated release of inflammatory cytokines from human primary macrophages in vitro was dependent upon the type of bone cement used. Particles of clinically relevant size were produced from Palacos R without radio-opacifier, Palacos R with BaSO4, Palacos R with ZrO2 and from CMW3 which contains BaSO4. All four preparations produced significantly greater release of tumour necrosis factor alpha, interleukin-6 and interleukin-1 beta than a negative control but there were no significant differences between them. The differences in the ability to stimulate bone resorption and in clinical performance between proprietary bone cements previously recorded are not explained by the release of the cytokines most commonly implicated in osteolysis.

Acrylic Resins↗
PubMed1995

Blood coagulation and fibrinolytic activity during femoral neck prosthetic replacement using bone cement.

To assess the blood coagulative and fibrinolytic responses during cemented femoral neck replacement, we measured these parameters in 9 patients, including anti-thrombin III (AT-III), prothrombin time (PT) and activated partial thromboplastin time (APTT) before surgery, just before packing bone cement and after the insertion of the prosthesis. We also measured thrombin-anti-thrombin III complex (TAT), plasmin-alpha 2-plasmin inhibitor complex (PIC), and D-dimer. A significant increase in APTT, and decrease in AT-III and PT were observed before the insertion of bone cement and prosthesis. The value of TAT and D-dimer increased significantly after the insertion of the prosthesis, but there were no significant changes in PIC. The data suggest that blood coagulation is activated after the insertion of bone cement and prosthesis into the femoral shaft, and in addition, the fibrinolysis is also accelerated secondary to the activation of the coagulation. Further investigations are needed to establish whether the activation of the coagulation induced by the cemented replacement exerts a great influence on the appearance of pulmonary thrombosis or circulatory depression.

Adult↗
PubMed1996

Does vacuum-mixing improve the fatigue properties of high-viscosity poly(methyl-methacrylate) (PMMA) bone cement? Comparison between two different evacuation methods.

The objective was to verify different reports in the literature which show an increase of stability using vacuum-mixing of bone cement, by testing the fatigue properties of bone-cement specimens (Palacos R). Evacuation of the poly(methyl-methacrylate) (PMMA) and evacuation with additional pressurization (Draenert system) were used to manufacture the specimens. Although we found improvement in the ultimate bending strength for evacuated Palacos R, an increase of fatigue stability could not be found either for vacuum-mixed cement or for vacuum-mixed and compressed cement. As fatigue failure is one of the most important factors leading to aseptic loosening of cemented alloarthroplasties, we conclude that the long-term results cannot be improved by vacuum-mixing this cement.

Biomechanical Phenomena↗
PubMed2001

The cytotoxic effect of methotrexate loaded bone cement on osteosarcoma cell lines.

We mixed various amounts of methotrexate with bone cement and measured the absorbance daily for 4 weeks. The cytotoxic effects on SaOS2 and MG63 osteosarcoma cells were examined by the MTT assay, and analysed according to the methotrexate concentration and the elapsed time. The amount of eluted methotrexate was greatest during the first day, and then decreased rapidly reaching a plateau in the third week. The number of viable tumour cells decreased significantly after 72 h, and they were hardly seen after 1 week.

Antimetabolites, Antineoplastic↗
PubMed1989

Temporary resection-arthrodesis of the knee using an intramedullary rod and bone cement.

A temporary arthrodesis of the knee, using an intramedullary Küntscher rod and bone cement, was carried out in 76 patients after resection of tumours of the distal femur or proximal tibia. In contrast to primary arthrodesis with bone grafting, this procedure allows the patient to bear weight on a stable limb a few days after operation, reduces the risk of infection and avoids the negative effect of chemotherapy on graft incorporation. In 12 cases (16%) the implant failed mechanically by fracture, or by bending or migration of the rod, at from 13 to 54 months after operation. Deep infection occurred in 11 patients (14%). A second reconstruction was carried out in 14 patients, 10 using Kotz prostheses and 4 arthrodeses with bone grafting. The operation we describe has advantages for patients with high grade tumours which require chemotherapy and resection-arthrodesis of the knee joint.

Adolescent↗
PubMed2001

Gentamicin bone cements: characterisation and release (in vitro and in vivo assays).

Due to the extended use of acrylic bone cements, its necessary to develop improved formulations in order to resolve their many drawbacks. The present work was conducted to make a physical-chemical characterisation of this kind of acrylic cement in order to introduce future changes in the formulations to: (1) improve or at least maintain their mechanical properties; (2) diminish their toxicity, and (3) control the drug release (rate and amount). From the dissolution method we can conclude that the preparation method (with or without pressure) of specimens is not responsible for the erratic release. The cumulative amount of gentamicin released was fitted to a semi-empirical equation to explain the possible release mechanism. The powder size, shape and distribution that could affect several properties of bone cement were studied with the aid of different techniques such as SEM, laser diffraction spectroscopy, and powder X-ray diffraction. From SEM micrographs, it was possible to observe that the surfaces of the specimens were very irregular with numerous small craters that may serve as conduits for eluting the antibiotic. An 'in vitro' drug diffusion model is proposed to elucidate the drug release mechanism. Finally an 'in vivo' study was performed to evaluate the antibiotic release to the neighbouring bone sites.

Acrylic Resins↗
PubMed1986

Bone-cement interface: a histological study of aseptic loosening in twelve prosthetic implants.

The histology of bone-cement interfaces was studied by using new fixation techniques that preserve the cement, as well as sectioning the samples without decalcification. This permits histological study of the unaltered morphology, and the precise topographical distribution of fibrous tissue, bone necrosis and cellular anomalies in relation to the cement. Twelve cases of implant loosening over an average 7 year follow-up period were examined. By dynamic studies with sequential fluorescent bone labelling it was possible to evaluate precisely the extent of bone damage after the application of cement. The characteristic findings were: fibrous tissue at the bone-cement interface; bone necrosis or reduced remodelling in proximity to the cement; away from the cement, normal bone remodelling is clearly demonstrated by fluorescent labelling.

Bone Cements↗