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PubMed1977

The mechanical properties of bone cements.

The mechanical properties of a number of commercially available bone cements have been investigated. Tests were carried out on specimens in compression, in bending and in tension. Using the compression test as a standard, the effects of the following variables were studied: the addition of antibiotics, strain rate, environmental temperature, and age. It was concluded that age, temperature and rate of straining have a marked effect on the strength of the cement, while the addition of small quantities of antibiotics only marginally weakens the cement.

Anti-Bacterial Agents↗
PubMed1996

In situ analysis of the degree of polymerization of bone cement by using FT-Raman spectroscopy.

A method has been developed which enables an in situ analysis of the degree of polymerization of bone cement. The concentration of monomeric double bond is monitored continuously during the entire curing process and hence the method can be used for quantitative studies of polymerization kinetics. In this study, Fourier Transform Raman (FTR) spectroscopy was utilized to investigate the degree of polymerization of a novel bone cement in situ, and the results are compared with the thermal profile obtained for polymerization.

Biocompatible Materials↗
PubMed2000

Mechanical properties of hydroxyapatite reinforced poly(ethylmethacrylate) bone cement after immersion in a physiological solution: influence of a silane coupling agent.

PEMA-based bone cement has previously been shown to possess many advantages over traditional PMMA cements. One of these is the option of adding up to 40 wt % HA without a decrease in static mechanical strength, thus providing the potential for enhanced bioactivity. Bone cement, in vivo, is subjected to an aqueous environment and therefore, it is important to understand the influence of this upon the mechanical integrity of experimental cements. In this current investigation the static and dynamic properties of PEMA cement, with and without 30 wt % untreated and silanated HA, were examined after periods of immersion in Ringer's solution. A commercial PMMA cement was also tested in a similar manner. Relatively small changes in static mechanical properties were observed after 12 weeks storage for the PEMA cements, the largest change being for the PEMA cement reinforced with silanated HA. The PMMA cement exhibited the largest change in static strength with a decrease of 16.6%. In contrast to these results, the fatigue properties of the PEMA cements were found to decrease significantly after storage in Ringer's solution, again with the largest changes to the PEMA cement reinforced with silanated HA. This effect was attributed to the reduction in efficiency of the silane coupling agent in the presence of water. The fatigue resistance of the PMMA cement was not reduced after immersion in a saline environment.

Journal Article↗
PubMed2007

Calcium phosphate bone cements, functionalized with VEGF: release kinetics and biological activity.

Calcium phosphate bone cements are of great interest for bone replacement since the nanocrystalline structure allows their remodelling into native bone tissue. A strategy to accelerate vascularization of the implant region is the functionalization with vascular endothelial growth factor (VEGF), which is known to mediate angiogenesis in vivo. In this study, the release of recombinant human VEGF (rhVEGF(165)) following physical adsorption to Biocement D (BioD) and several modifications were investigated. Our data demonstrate a high VEGF binding capacity of BioD and a sustained release with a moderate initial burst. A proliferation assay using endothelial cells revealed maintenance of biological activity of VEGF after release from BioD. Release behavior of BioD was not improved by modification with mineralized collagen type I, as well as with a combination of mineralized collagen with O-phospho-L-serine and sodium citrate, respectively. In contrast, a positive impact of these modifications on the activity of released VEGF was observed; in case of the phosphoserine- and sodium citrate-modified cements, the biological efficacy of released VEGF was even higher than that of nonreleased control VEGF. We conclude that the bone implant material BioD and, especially, the phosphoserine modification may support activation of angiogenesis by delivery of VEGF in a local and sustained manner.

Animals↗
PubMed2004

In vitro measurement of the time-related efficacy of gentamicin sulfate release from bone cements.

BACKGROUND: The aim of the present study was to establish an in vitro microbiologic monitoring system which measures the dynamics of antibiotic release from acrylic bone cement and its antibacterial efficacy. METHODS: Palacos R and Orthofix R cements containing gentamicin sulfate were tested. The in vitro elution dynamics was analyzed by plate diffusion method during a 1-year period after mixing. High but rapidly decreasing antibiotic levels were detected within the 1st week, resulting in an almost steadily low concentration by the end of the 1st month. After 1 year, it was still possible to demonstrate the inhibitory effect of the drug from both cements. Comparison of the time-related release between the antibiotics failed to find any statistically significant differences. CONCLUSION: The method described is a useful and reproducible technique for the in vitro measurement of the inhibitory activity of antibiotic released from bone cements.

Anti-Bacterial Agents↗
PubMed2002

A radiographic study of the detection limits of bone-cement remnants in total joint arthroplasty.

Management of an infected hip prosthesis typically requires that all associated cement be removed. In the absence of gross mantle loosening, the surgeon frequently resorts to intraoperative radiographs to assess the completeness of removal. For this reason, we undertook a study to determine limits of detection of retained cement by routine radiography. Polymethyl methacrylate bone-cement beads (Simplex-P; Stryker-Howmedica-Osteonics, Allendale, NJ) were fashioned into graduated sizes and placed within cadaver medullary canals using 2 different methods. Standard radiographic images were obtained. Individually and independently, we viewed these images and proposed the limit of resolution to be 2.4 to 3.2 mm. It is difficult to remove all cement based on radiographs alone. These results suggest a need to use techniques that permit visualization of the canal to ensure adequate cement removal.

Arthroplasty, Replacement, Hip↗
PubMed1993

Porosity of bone cement reduced by mixing and collecting under vacuum.

Palacos R bone cement was mixed in a commercial vacuum mixing system (MITAB), and in an experimental system allowing evacuating air from the powder before mixing and collecting the cement under partial vacuum. The effect on the porosity of mixing at different pressure levels was tested. The effect of evacuating air from the powder before mixing was also analyzed. The numbers and sizes of the voids in the cement samples were measured in radiographs and under the microscope. Also, the density of the cement was measured. Vacuum mixed samples had a substantial reduction of voids, as well as an increase in density compared to mixing at atmospheric pressure. After vacuum mixing and collection, a further reduction of the porosity and increased density were seen; all the large voids within the cement were eliminated at 0.05 bar absolute pressure.

Bone Cements↗
PubMed2006

Addition of fluoride to acrylic bone cement does not improve fixation of a total hip arthroplasty stem.

UNLABELLED: Improved fixation to bone is vital for improving the long term success of cemented implants. Addition of fluoride to acrylic bone cement may be one way to improve the quality of the bone cement interface and thereby reduce the risk of loosening. Ninety patients (97 hips) with a median age of 70 years (range, 31-81 years) scheduled for total hip arthroplasty were randomized to receive a stem fixed with fluoride-containing acrylic bone cement or conventional acrylic bone cement. Fixation and bone remodeling around the femoral component was studied with radiostereometry and dual-energy xray absorptiometry up to 5 years after the operation in 73 patients (77 hips). Radiostereometric evaluation at 5 years revealed no differences in stem migration (subsidence/lift-off) or rotations. The stem subsidence inside the mantle was similar in the two groups. At 5 years the study group had lost more bone mineral in Gruen regions 5 and 7 than the controls. The Harris hip and pain score did not differ. Use of fluoride containing bone cement did not improve the stem fixation compared with a conventional cement used up to 5 years, but resulted in more pronounced loss of bone mineral density in the medial cortex. LEVEL OF EVIDENCE: Therapeutic Level I. See Guidelines for Authors for a complete description of levels of evidence.

Adult↗
PubMed1976

Fracture characteristics of acrylic bone cements. I. Fracture toughness.

The vital first phase of the overall materials study to protract the life of the total joint replacements is the identification of the fracture toughness and fatigue properties of bone cements. Information gained from fatigue testing, performed in a manner which simmulates in vivo conditions, and fracture toughness, which is a measure of the propensity of a crack to propagate, is the first step towards the prediction of the life of the total joint replacement. This study is concerned with the fracture toughness of Zimmer and Simplex-P cold-curing bone cements. Following cement fabrication conditions which closely approximate clinical procedures, fracture toughness testing was conducted on cement specimens which were immersed in bovine serum at 37 degrees C in order to simulate in vivo conditions. In addition, a similar study was completed on specimens, tested in air at ambient temperature for purposes of comparison. Results of this procedure, when analyzed by a Student's t-test at the 95% confidence level with eight degrees of freedom, indicate that both Zimmer and Simplex-P exhibit a higher fracture toughness in the simulated physiological environment. In order to determine whether the addition of barium sulfate to these cements compromises the fracture toughness, the above described testing rationale was repeated, indicating the existence of a complicated relationship between the different testing environments and barium sulfate. The importance of these results lies in the fact that an increased fracture toughness indicates that a cement will inherently exhibit a greater degree of resistance to the propagation of cracks, which could contribute to the ultimate failure of the total joint replacement.

Acrylates↗
PubMed2002

Effects of bone cement extracts on the cell-mediated immune response.

The aim of the study was to evaluate some aspects of the immunocompatibility of 10 acrylic bone cements. Mononuclear cells harvested from healthy individuals were cultured with cement extracts which were tested to assess their effect on the viability of lymphocytes, unstimulated and phytohaemoagglutinin (PHA)-stimulated, activating resting lymphocytes, and changing the reactivity of PHA-stimulated lymphocytes. After 24 h the extracts did not increase the percentage of dead cells in unstimulated or PHA-stimulated lymphocytes. The early apoptotic events of culture were evaluated after 4 and 24 h in PHA-stimulated lymphocytes: at 4 h three cements, namely Zimmer-dough type, Palacos R and CMW-1, increased significantly the percentage of apoptotic cells, while at 24 h no differences were found. Cement extracts did not activate the resting lymphocytes, whereas the response of the PHA-stimulated cells was significantly modified. All cements decreased the expression of the interleukin 2 receptor (CD25) and the lymphocyte proliferation, whereas only two materials (Zimmer-dough type, CMW 1) affected the expression of early activation antigen (CD69). These findings show that the products released from bone cement are not able, by themselves, to elicit a specific immune response; on the contrary they hamper the function of lymphocytes activated by an exogenous stimulus.

Antigens, CD↗
PubMed2004

Surface treatment of injectable strontium-containing bioactive bone cement for vertebroplasty.

A novel injectable bioactive bone-bonding cement (SrHAC) composed of strontium-containing hydroxyapatite (Sr-HA) as the inorganic filler and bisphenol A diglycidylether dimethacrylate (Bis-GMA) as the organic matrix for vertebroplasty was developed previously. In this study, the Sr-HA powders were surface treated with methyl methacrylate (MMA) to improve the interface integration of the two phases. After surface treatment, the compression strength and Young's modulus, which were tested after immersion in distilled water at 37 degrees C for 24 h according to ISO 5833, were increased by 68.65 % (p <.001) and 31.02% (p <.001), respectively. The bending strength and bending stiffness of the bioactive bone cement were significantly improved by 54.44% (p <.001) and 83.90% (p <.001). In addition, the handling property of the cement was also enhanced. In vitro biomechanical testing showed that the stiffness of the fractured spine recovered to 82.5% (p <.01) of the intact condition after cementation with surface-treated SrHAC. The failure load of the spine cemented with original and MMA-treated SrHAC improved by 14.25% (p <.05) and 46.91% (p <.05) in comparison with the fractured spines. Results from this study revealed that the MMA-treated SrHAC has a better mechanical effect for orthopedic applications.

Animals↗
PubMed1988

Reduction in cement-bone interface shear strength between primary and revision arthroplasty.

This study quantified changes in the cement-bone interface shear strength between primary and first- and second-revision arthroplasties as a function of mechanical interlock between the cement and bone. There were 128 segments obtained from four pairs of fresh human femora that were prepared sequentially as for primary and first and second revisions, taking care to maintain original canal morphology. Cement was pressurized into the cavity of the anatomic specimens, and the maximum interface shear strength between the cement plug and the bone was experimentally determined for each revision. First-revision interface shear strength was reduced to 20.6% of primary strength, and second revision strength to 6.8% of primary strength.

Adult↗
PubMed2001

A new bioactive bone cement: effect of glass bead filler content on mechanical and biological properties.

A new bioactive bone cement (designated GBC), consisting of bioactive glass beads as an inorganic filler and polymethylmethacrylate (PMMA) as an organic matrix, has been developed. The purpose of the present study was to examine the effect of the amount of glass bead filler added to GBC on its mechanical and biological properties, and to decide the most suitable content of filler. Serial changes in GBC with time were also examined. The newly designed bioactive beads, consisting of MgO-CaO-SiO2-P2O5-CaF2 glass, were added to the cement in the proportions 30, 40, 50, 60, and 70 wt %. These cements were designated GBC30, GBC40, GBC50, GBC60, and GBC70, respectively. The compressive strength and the elastic modulus of bending of GBC increased as the glass bead content increased. The various types of GBC were packed into the intramedullar canals of rat tibiae to evaluate osteoconductivity, as determined by an affinity index calculated as the length of bone in direct contact with the cement expressed as a percentage of the total length of the cement surface. Rats were killed at 4 and 8 weeks after the operation and the affinity index was calculated for each type of GBC. Histologically, new bone had formed along the surface of all types of GBC within 4 weeks, even in GBC30 containing only 30 wt % of glass beads. At each time interval studied, there was a trend for the affinity index of GBC to increase as the glass bead filler content increased. There was no significant increase of affinity index between GBC60 and GBC70. The affinity indices for all types of GBC increased significantly with time up to 8 weeks. The handling properties of GBC were comparable to those of conventional PMMA bone cement. We conclude that when mechanical properties and osteoconductivity are both taken into consideration, GBC60 is the most suitable formulation; it shows excellent osteoconductivity and sufficient mechanical strength for clinical use.

Animals↗
PubMed1990

[An instrument for injection of bone cements].

The author describes the use of a specially developed instrument, which in combination with Chirana 30 ml syringe for one use facilitates the injection application of bone cement in the implantation of the femoral component of total hip arthroplasty or cervicocapital endoprosthesis of the hip. Emphasis is put on the availability of this instrument for all clinics and on the importance of the application of bone cement under pressure from the view point of longterm results of the above mentioned joint arthroplasty. No evident disadvantages in comparison with imported instruments have been found out.

Bone Cements↗
PubMed1998

Some factors controlling the injectability of calcium phosphate bone cements.

The injectability of four calcium phosphate bone cements (CPBCs) was measured using a commercial disposable syringe. It varied considerably with the cement powder composition, with the liquid/powder ratio, with the time after starting the mixing of liquid and powder, with the accelerator concentration (% Na2HPO4), and with the ageing time of the cement powder which was prepared by milling. The injectability test could be used to determine accurately the dough time of CPBCs. Relations between the setting time and the cohesion time are discussed.

Journal Article↗