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PubMed1993

The release of cytotoxic drugs from acrylic bone cement.

The ability of cis-platinum, 5-fluorouracil, and methotrexate to leach out from various types of bone cements was examined in three different experimental systems: (1) in vitro release in physiological solution; (2) in vitro release in the presence of mouse fibrosarcoma cells; and (3) in vivo release in rabbits. The amount of drugs released was measured either spectrophotometrically by atomic absorption or by using tritium-labeled drugs. In vitro cement pellets were found to release these drugs slowly for up to six months; release was greater in the first few days, rapidly declining with time. Up to 6% of the methotrexate implanted leached out during the entire experiment. The figures for cis-platinum and 5-fluorouracil were much less: 3.3% and 3.4%, respectively. Palacos bone cement had the best leaching properties. The drugs leached out were also effective in reducing the numbers of viable mouse fibrosarcoma cells in tissue culture. In vivo, high levels of the drugs were recovered from blood drained from the operative wound of the rabbits, while very low levels of these drugs were found in the serum. Anticancer drug-loaded cement may be used effectively in the treatment of pathologic fractures and tumor surgery. This delivery method may reduce the side effects that result from systemic administration of such drugs.

Animals↗
PubMed1988

Fatigue testing of acrylic bone cements: statistical concepts and proposed test methodology.

In order to determine the fatigue behavior of a material, a standard procedure and methodology must be proposed and validated. This article describes a standard test method and statistical analysis for describing the fatigue properties of acrylic bone cement. It is proposed that bone cement fatigue data can be subjected to probability of failure (P) analysis and the establishment of a distribution function describing the data. It is also proposed that an Olgive type curve can be used to describe the stress (S) vs. cycles to failure (N) data. These two data sets can then be combined to determine the P-S-N relationship which fully describes the fatigue characteristics of the material.

Acrylates↗
PubMed1982

Changes in the bone-cement interface after total hip replacement. An in vivo animal study.

UNLABELLED: In order to study the temporal sequence of radiographic, histological, mechanical, bacteriological, and chemical changes around the femoral component following total hip replacement, a model was created by implanting plastic-on-metal total hip replacements in sheep and walking the animals on a concrete surface beginning six weeks postoperatively. This model demonstrated a decreased torsional rigidity between the prosthesis and the femoral cortex in all sheep. Failure of bonding occurred at the bone-cement interface and appears from our results to be most probably due to alterations in the functional stress of the proximal end of the femur following insertion of the femoral component rather than exothermic polymerization, toxicity of free monomer residue, or infection. CLINICAL RELEVANCE: An understanding of the causes of loosening of cemented metal femoral components in total hip replacement has been thwarted by a lack of specimens at sequential times in the loosening process. Since a patient is not operated on until the prosthetic components are completely loose, such specimens are difficult to obtain clinically. For this reason a model for examining the bone-cement interface, measured by decreased torsional rigidity of the prosthesis relative to the bone, was developed in sheep. Of all the parameters studied, those inherent in the effects (mechanical or vascular, or both) of insertion of the prosthesis itself appeared to be the most likely cause of the change in the mechanical properties of the interface. This suggests that degenerative changes of the bone-cement interface may be inevitable.

Animals↗
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↗
PubMed2002

Gene expression of bone-associated cytokines in MG63 osteoblast-like cells incubated with acrylic bone cement extracts in minimum essential medium.

This study examined the effects of in vitro challenge with four polymerized acrylic bone cements (Sulfix-60, CMW 1, CMW 2, and CMW 3) on the expression of interleukin-1beta (IL-1beta), interleukin-6 (IL-6), and transforming growth factor-beta1 (TGF-beta1) mRNAs in the osteoblast-like cell line MG63. The extracts of the cements in minimal essential medium (MEM) were tested following 1-h and 7-day curing. A semi-quantitative analysis of the cytokine-specific mRNAs was carried out by agarose gel densitometry and expression was compared with the GAPDH housekeeping gene. The ratio between cytokine gene expression and GAPDH expression was calculated. The mRNA specific for the bone-resorbing cytokines IL-1beta and IL-6 was low in basal conditions. IL-1beta mRNA increased only after incubation with the extract of CMW 1 following 1-h curing. The mRNA specific for the bone-resorbing cytokine IL-6 also increased after contact with CMW 1 at both curing times. Sulfix-60 and CMW 3 following 7-day curing, but not after 1 h, induced higher levels of IL-6 mRNA than the control. CMW 2 after 1-h curing constantly determined the expression of IL-6 mRNA, but at low levels. The mRNA specific for TGF-beta1 was also expressed by the MG63 osteoblast-like cells in basal conditions. The levels increased after contact with Sulfix-60 after 7-day curing and with CMW 1 after 1-h curing. CMW 2 after 7-day curing decreased TGF-beta1 mRNA. In conclusion, the highest expression of the cytokines IL-1beta, IL-6, and TGF-beta1 mRNA was determined by CMW 1. If the results are confirmed in vivo, the increased expression of the osteolytic cytokines induced by the bone cement might result in loosening of the prosthesis, even with all the restrictions of an in vitro study on continuous cell lines.

Bone Cements↗
PubMed1983

Acrylic bone cement: in vitro and in vivo property-structure relationship--a selective review.

The nature and curing characteristics of acrylic bone cement are presented to give some basic understanding of the key to improving its performance in in vivo clinical use. The use of electron paramagnetic resonance (EPR) spectroscopy in the (polymerization) setting and curing/aging of bone cement under in vitro and in vivo conditions is presented. The current research effort to improve the implant fixation by precoating the prosthesis with acrylic polymers is also discussed.

Bone Cements↗
PubMed2003

Preliminary study of interfacial shear strength between PMMA precoated UHMWPE acetabular cup and PMMA bone cement.

Followed by successful demonstration of high interfacial tensile strength in a new design of cemented all-polyethylene acetabular cup, interfacial shear strength was investigated in this study, with the use of canine-size prototypes of polymethylmethacrylate (PMMA) precoated UHMWPE acetabular cups. In addition to the PMMA precoated prototypes, three different types of controls were also prepared and tested: grooved UHMWPE cups, PMMA (bone cement) cups, and noncoated, plain UHMWPE cups. The interfacial shear strength of the precoated prototypes was 10.1 +/- 0.69 MPa (n = 6), whereas it was 24.3 +/- 0.78 MPa (n = 2) for the PMMA cup, 6.95 +/- 0.21 MPa (n = 2) for the grooved UHMWPE cup, and 0.34 +/- 0.47 MPa (n = 2) for the UHMWPE cup. These results indicate benefits of the PMMA precoating to stabilize the polyethylene acetabular cup securely when applied with bone cement in simulated clinical applications. Analysis of the failed PMMA precoated UHMWPE prototype cups suggested that the chemically induced bonds between precoated PMMA layer and bone cement played a key role in developing high shear strength. After the interfacial shear test of the PMMA precoated prototypes, major disruptions at the interface between treated UHMWPE and precoated PMMA layer were observed by scanning electron microscopy (SEM), which was a unique failure pattern, not found with other prototypes.

Animals↗
PubMed1996

Treatment of pathological fractures of the humeral shaft due to bone metastases: a comparison of intramedullary locking nail and plate osteosynthesis with adjunctive bone cement.

In a retrospective study 37 patients were surgically treated for 38 fractures (27 actual and 11 impending) caused by metastatic lesions of the humerus shaft. A comparison between plate osteosynthesis with bone cement (20 cases) and intramedullary nailing (18 cases) was made. There was no mortality related to the surgical procedure. The patients' survival rate was 61% after 3 months and 44% after 6 months; six were alive after 1 year. Overall, a subjective and objective relief of pain was achieved in 92% and 79%, respectively. Restoration of arm function was improved in 95%. The operative course was complicated in six patients after plate osteosynthesis (three local and three systemic complications) and in four patients after intramedullary nailing (one local and three systemic complications). Fixation failed in four patients, instability developed twice after intramedullary fixation without bipolar static locking. No significant difference in survival rate, pain relief, restoration of function and complications were associated with methods of treatment, or with operation of actual or impending pathological fractures. Despite the poor life expectancy our results indicate that intramedullary nailing with bipolar static locking and post-operative irradiation or plate osteosynthesis with bone cement for treatment of pathological (impending) fractures of the humerus shaft are safe ways to restore arm function and improve quality of life.

Adult↗
PubMed1976

Effects of laminations and blood entrapment on the strength of acrylic bone cement.

The tensile and shear strengths of surgically mixed acrylic bone cement were measured for intact specimens and for special two-part cylindrical specimens containing single laminations perpendicular to their longitudinal axes. Laminations were formed at times ranging from 3 1/2 to 6 1/2 minutes after initial mixing of the powder and liquid for dry interfaces and for interfaces containing fresh blood at the time of lamination formation. In additon, special tests were conducted to measure the bond strength between freshly mixed and pre-polymerized acrylic. The tensile and shear strengths at the lamination interface decreased significantly when the laminations were formed late in the working life of the acrylic. The presence of blood at the interface further weakened the bond to approximately 25 per cent (tension) and 36 per cent (shear) of the virgin strengths of the material. These results support early acrylic placement with dry surgical fields. The bonding of fresh acrylic to pre-polymerized material was most effective when the material was poured into the mold before dough stage. This technique would have practical application in special cases for re-cementing revision prostheses without removing the old acrylic from within the bone.

Blood↗
PubMed2007

Influence of the activator in an acrylic bone cement on an array of cement properties.

In all but one of the acrylic bone cement brands used in cemented arthroplasties, N,N-dimethyl-4-toluidine (DMPT) serves as the activator of the polymerization reaction. However, many concerns have been raised about this activator, all related to its toxicity. Thus, various workers have assessed a number of alternative activators, with two examples being N,N-dimethylamino-4-benzyl laurate (DMAL) and N,N-dimethylamino-4-benzyl oleate (DMAO). The results of limited characterization of cements that contain DMAL or DMAO have been reported in the literature. The present work is a comprehensive comparison of cements that contain one of these three activators, in which the values of a large array of their properties were determined. These properties range from the setting time and maximum exotherm temperature of the curing cement to the variation of the loss elastic modulus of the cured cement with frequency of the applied indenting force in dynamic nanoindentation tests. The present results, taken in conjunction with those presented in previous reports by the present authors and co-workers on other properties of these cements, indicate that both DMAL and DMPT are suitable alternatives to DMPT.

Acrylic Resins↗
PubMed1998

Effect of increasing temperature on the properties of four bone cements.

This investigation uses a laboratory model to evaluate the effects of a heated femoral stem on the biomechanical properties of four common acrylic bone cements. American Society for Testing Materials dog bone shaped acrylic cement specimens made at four test temperatures, 0 degree C, 23 degrees C, 37 degrees C and 50 degrees C, were tested for modulus, ultimate tensile strength, fracture toughness, and percent porosity. Fatigue strength was tested in Simplex P at 23 degrees C and 37 degrees C. The data allow direct comparison among four cement brands at each of the four temperature conditions. No adverse changes of the mechanical properties were found for any cement at any temperature. Modulus, fracture toughness, and fatigue strength were unaffected by increased temperature. Ultimate tensile strength increased in Simplex P and Zimmer Osteobond but was unaffected for Zimmer Regular and Palacos R cements. Percent porosity was related to temperature changes inversely in all brands studied, except for Palacos R which consistently had low porosity, unaffected by temperature variation. Fatigue strength of Simplex P was unaffected by heating to 37 degrees C. Based on this laboratory model, heating of the femoral stem could save time without sacrificing mechanical properties of acrylic bone cement.

Biomechanical Phenomena↗
PubMed1997

The in vitro and in vivo indomethacin release from self-setting bioactive glass bone cement.

The in vivo and in vitro drug release profiles from a self-setting bioactive CaO-SiO2-P2O5 glass bone cement containing indomethacin as a model drug were investigated. The cement containing 2% and 5% indomethacin (IMC) powder hardened within 5 min after mixing with ammonium phosphate buffer. After setting, in vitro drug release from drug-loaded cement pellets in a simulated body fluid (SBF) at pH 7.25 and 37 degrees C continued for two weeks. The hardened cement gradually formed low-crystallinity hydroxyapatite during the drug release test in SBF. An IMC-loaded cement device (2% and 5% drug) was implanted in the subcutaneous tissue on the back of rats. The in vivo IMC release from the cement increased and attained maximum levels (Cmax of 2% and 5% drug-loaded cements was 0.27 and 3.37 micrograms/ml, respectively) at Tmax, 3 and 0.5 d, respectively, upon subcutaneous (s.c.) administration in rats. This suggested that the s.c. administration of the cement provided IMC release for a much longer period than s.c. administration of the solution, and the plasma IMC concentration was dependent on the drug concentration in the cement. The plasma IMC concentration and the area under the curve from 2% and 5% IMC-loaded cements in rats were dependent on the concentration of IMC in the cements. The in vivo IMC concentration in plasma obtained by the deconvolution method was much lower than that delivered in SBF in vitro. Scanning electron microscopy and photomicrographs of cross sections showed that the bioactive bone cement had excellent biocompatibility with the surrounding soft tissues.

Animals↗
PubMed1996

The contribution of frictional torque to loosening at the cement-bone interface in Tharies hip replacements.

We evaluated the results in a series of 170 osteoarthrotic hips (156 patients) at a median of 10.0 years (range, 3.0 to 16.4 years) after a Tharies resurfacing arthroplasty performed with cement. Our purpose was to assess the role of frictional torque in loosening at the cement-bone interface. The hips were divided into three groups on the basis of the diameter of the bearing surface: small (thirty-six, thirty-nine, or forty-three millimeters), medium (forty-seven millimeters), and large (fifty-one or fifty-four millimeters). Comparisons were made with Kaplan-Meier survivorship analysis, with stepwise discriminant analysis of risk factors for aseptic loosening. Revision for aseptic loosening was the end point for survivorship analysis. Despite higher frictional torques due to the increased diameter of the bearing surface and the increased average load, the larger prostheses survived significantly longer than the smaller ones (p=0.002). Stepwise covariate discriminant analysis indicated that the size of the bearing surface was the only factor identified that significantly affected survival. In six patients who had had a bilateral surface replacement with a component of a different size in each hip, the smaller prosthesis always failed first (p=0.001), at an average of seventy-seven months; the larger prosthesis failed at an average of 113 months. Nine patients had had a bilateral replacement with components of the same size, and there was no significant difference in the durations of survival of the two prostheses. Analysis of radiographs and retrieved specimens indicated that, regardless of the size of the component, the mechanism of loosening on both the acetabular and the femoral side of this so-called double-cup replacement was progressive resorption of bone induced by polyethylene wear particles that compromised the fixation of the components. More time was required for the process to disrupt++ the larger fixation area of the larger components. These data indicate that frictional torque was not the primary factor in the loosening of these prostheses with a large bearing surface and that higher friction and frictional torques can be tolerated if the generation of wear debris is sufficiently limited. These findings may be important as alternatives to polyethylene bearing surfaces are investigated.

Acetabulum↗
PubMed1990

Ionos bone cement (glass-ionomer): an experimental and clinical evaluation in joint replacement.

Ionos bone cement (glass-ionomer) was evaluated in total joint replacement procedures, initially in a baboon model, and finally in a highly selected group of patients in whom polymethyl methacrylate cement was contra-indicated. It was found that the cement has no inhibitory effect on bone tissue development. It is effectively incorporated into the bone, both structurally and functionally without the interposition of fibrous tissue. Under the functional stress situation in baboon hip and knee arthroplasties, the bone and marrow in direct contact with the cement responded favourably. A direct bone bond was demonstrated. The clinical results achieved were satisfactory, notwithstanding the complexity of the clinical problems included in the series. The continued clinical evaluation on a controlled basis has been shown to be well-justified.

Adult↗
PubMed1999

Total hip arthroplasty using bone cement containing tri-n-butylborane as the initiator.

We performed total hip arthroplasty (THA) using a special acrylic self-curing bone cement (Bonemite), which contains tri-n-butylborane as the initiator. Its maximum temperature at curing is lower than that of a conventional bone cement (CMW). Fifty-eight THAs using Bonemite and 35 THAs using CMW were followed up for more than 8 years (12.5 years on average). At the 10-year follow-up, the survival rates, using revision surgery or aseptic loosening impending revision as the endpoint for failure, were 92.2% for the patients in the Bonemite group and 91.0% for those in the CMW group. No statistical differences were observed between the patients in these two groups with regard to survival rate (p = 0.39). Bonemite showed no clear superiority compared with CMW, although the results suggest that Bonemite is safe and reliable for clinical use and stable in situ for long time.

Arthroplasty, Replacement, Hip↗
PubMed2003

Dynamic mechanical behavior of PMMA based bone cements in wet environment.

The mechanical properties of three wet commercial bone cements, namely Braxel (from Bioland), Simplex-P (from Howmedica) and CMW1-G (from DePuy) are investigated by means of stress relaxation and dynamic mechanical analysis (DMA). The geometry of loading that was used is the three point bending method (ASTM D790); all the tests were performed in a water chamber by means of temperature sweeps between 17 and 57 degrees C and spanning four frequency decades. The results show that viscoelastic properties are strongly dependent on specimen conditioning (i.e. water uptake and heat treatment). The results also show that all the cements that were analyzed show mechanical properties which are intermediate between the ones of the cancellous bone and of the metals of which prostheses are normally made. As a consequence, the cement is able to reduce the stress concentrations due to the interfacing of materials which have very different stiffnesses. Moreover, the results of the DMA, particularly the ones concerning the damping factor (tan delta), indicate that at body temperature the bone cements tested show an increased capacity of dissipation, the higher is the loading frequency, thus displaying shock absorbing properties.

Journal Article↗
PubMed1986

The bone-cement interface in hip arthroplasty. A histologic and enzyme study of stable components.

Thirteen patients were reoperated on because of a nonseptic complication of their cemented hip replacement. In each patient, one of the two components was stable, and biopsies from this bone-cement interface were obtained for histologic and enzyme histochemical studies. Microscopy revealed a spectrum of tissue reactions, ranging from a seemingly direct bone-cement contact to a fibrous membrane, up to 1.5 mm thick. The bone necrosis incurred at the primary operation had been largely resorbed and replaced by viable bone.

Acetabulum↗