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PubMed2004

Radiofrequency ablation combined with bone cement injection for the treatment of bone malignancies.

PURPOSE: To evaluate the feasibility, safety, and effectiveness of combined treatment with radiofrequency (RF) ablation followed by bone cement injection in patients with malignant bone neoplasms. MATERIALS AND METHODS: Seventeen patients with 23 bone tumors were treated. The tumors, measuring 1.2-15 cm (mean, 4.9 +/- 3.5 cm), were located in the spine (n = 17), iliac bone (n = 3), sacrum (n = 2), and ischial bone (n = 1). All procedures were performed with computed tomographic (CT) fluoroscopic guidance. An electrode with an internally cooled tip was placed in the bone tumor through a biopsy needle and RF energy was applied, followed by cement injection. Pain relief was evaluated with use of the visual analogue scale score (VAS score). Local therapeutic effects were evaluated by contrast-enhanced MR imaging. Lack of tumor enhancement was considered to indicate necrosis. RESULTS: The procedures were technically successful in all patients except for one patient with an osteoblastic ischial lesion (22 of 23 patients; 96%). Pain was relieved within 1 week in all 13 patients who reported pain (13 of 13 patients; 100%), with a significant decrease in the VAS score from 8.4 to 1.1 (P <.001). Tumor necrosis was observed in 71% +/- 24% of the tumor volume (range, 14%-100%). Neural damage occurred in four patients in whom the tumor had invaded the posterior cortex of the vertebral body and pedicle. CONCLUSION: The combined therapy described here is both feasible and useful for the treatment of malignant bone neoplasms. The safety of the procedure depends on the tumor location. When the tumor is adjacent to the spinal cord, there is a risk of nerve injury.

Bone Cements↗
PubMed2005

Vascularisation of Norian CRS bone cement and its replacement by autologous bone when used for orbital reconstruction.

Various bone cements based on calcium phosphate have been used as adjuncts for repairing both the craniofacial and axial skeleton. Ideally these materials should provide initial strength and contour for the reconstruction, and be replaced over time by physiological absorption and bony deposition. Although there is evidence from animal models to support this, opportunities for human studies are rare. Here we offer clinical and histological evidence of this process.

Absorption↗
PubMed2004

The behavior of novel hydrophilic composite bone cements in simulated body fluids.

Composite bone cements were formulated with bioactive glass (MgO--SiO(2)--3CaO. P(2)O(5)) as the filler and hydrophilic matrix. The matrix was composed of a starch/cellulose acetate blend (SCA) as the solid component and a mixture of methylmethacrylate/acrylic acid (MMA/AA) as the liquid component. The curing parameters, mechanical properties, and bioactive behavior of these composite cements were determined. The addition of up to 30 wt % of glass improved both compressive modulus and yield strength and kept the maximum curing temperature at the same value presented by a typical acrylic-based commercial formulation. The lack of a strongly bonded interface (because no coupling agent was used) had important effects on the swelling and mechanical properties of the novel bone cements. However, bone cements containing AA did not show a bioactive behavior, because of the deleterious effect of this monomer on the calcium phosphate precipitation on the polymeric surfaces. Formulations without AA were prepared with MMA or 2-hydroxyethyl methacrylate (HEMA) as the liquid component. Only these formulations could form an apatite-like layer on their surface. These systems, therefore, are very promising: They are bioactive, hydrophilic, partially degradable, and present interesting mechanical properties. This combination of properties could facilitate the release of bioactive agents from the cement, allow bone ingrowth in the cement, and induce a press-fitting effect, improving the interfaces with both the prosthesis and the bone.

Acrylates↗
PubMed2006

Assessment of a three-dimensional measurement technique for the porosity evaluation of PMMA bone cement.

In vitro testing of bone cement has historically resulted in the belief that porosity should be minimised to help reduce the risk of prosthesis failure through aseptic loosening. Traditional porosity measurement techniques rely on the analysis of a two dimensional representation of a three dimensional structure. However, with an increasing interest in the number, size and distribution of pores in bone cement, the reliability of a two dimensional approach is questionable. The purpose of this study was to investigate the use of micro computed tomography (micro-CT) for the three dimensional measurement of bone cement porosity by comparison with two traditional techniques. Eighteen bone cement specimens were analysed for porosity using each technique. Levels of agreement between techniques were evaluated, and technique precision was assessed in terms of repeatability and sensitivity to changes in threshold. Micro-CT data was used to illustrate the effectiveness of predicting the porosity of a whole structure from a sample region; an approach often used with traditional techniques. In summary, poor agreement was found between all techniques. However, micro-CT was found to be significantly more repeatable and less sensitive to changes in threshold. The results demonstrated that porosity cannot be reliably determined using traditional techniques and that a large proportion of a specimen is required to provide an accurate porosity measurement.

Biocompatible Materials↗
PubMed1998

Bioactive bone cements.

Poly(methylmethacrylate) (PMMA) bone cement, used to fix implants into the bone, produces good surgical results if used correctly. However, prostheses do eventually become loose and the breakdown of the cement mantle is a factor in this failure. Limitations of PMMA cement, which lead to problems with the fixation of the implant, include its mechanical characteristics and its influence upon surrounding bone, associated with the polymerization reaction. A bioactive bone cement is particularly designed to produce a better interface between the cement and bone. However, an improvement in mechanical properties, especially fatigue, creep and fracture toughness, are an added necessary requirement to increase the lifetime of a cemented implant. The development of a bioactive cement has been conducted mainly in two ways; firstly, to improve existing PMMA cement by the addition of various bioactive agents and secondly, to design an alternative matrix for the bioactive material to be combined with. The most promising investigations which have been conducted, along with their relative benefits and drawbacks, are discussed.

Biocompatible Materials↗
PubMed1980

[Tissue reactions to bioactive bone cement].

In the field of bone surgery, bone cement has gained a considerable importance for the fixation of osteosynthesis material. This paper deals with the investigation of a new bone cement which is mixed with bioactive glass ceramic. In comparison to the conventional bone cement, all data pertaining to the material are improved, and histological examinations reveal an osseous connection to the superficially located glass ceramic particles.

Animals↗
PubMed1997

Prosthetic replacement of the hip in dogs using bioactive bone cement.

Total hip arthroplasties were performed in dogs using bioactive bone cement consisting of silane treated CaO-MgO-SiO2-P2O5-CaF2 glass powder as the filling particles and bisphenol-a-glycidyl methacrylate based resin as the organic matrix, and the outcomes were compared with the results of polymethylmethacrylate bone cement. The mechanical properties of the bioactive bone cement were stronger than the mechanical properties of polymethylmethacrylate bone cement. The bonding strength of the bioactive bone cement to bone in dogs' femora increased with time, reaching 4.7 MPa at 6 months, whereas that of polymethylmethacrylate bone cement did not increase, remaining at 1.0 MPa. Results of histologic examination showed direct bonding between the bioactive bone cement and bone, and the bony trabeculae around the cement mantle grew with time. However, in polymethylmethacrylate bone cement, an intervening soft tissue layer was evident at the bone cement interface. Direct bonding of the bioactive bone cement at the interface through an apatite layer of 30 microm in thickness was shown through observation with the scanning electron microscopy. Using this bioactive bone cement in clinical settings may help alleviate serious problems associated with cemented total hip arthroplasty, such as aseptic loosening of the implant and mechanical failure of the bone cement.

Acetabulum↗
PubMed2004

Physicochemical, mechanical, and biological properties of bone cements prepared with functionalized methacrylates.

Bone cements prepared with methyl methacrylate (MMA) as a base monomer and either methacrylic acid (MAA) or diethyl amino ethyl methacrylate (DEAEMA) as comonomers were characterized in terms of curing behavior, mechanical properties, and their in vitro biocompatibility. The curing time and setting temperature were found to be composition dependent while the residual monomer was not greatly affected by the presence of either acidic or alkaline comonomers in the bone cements. For samples with MAA comonomer, a faster curing time and higher setting temperature were observed when compared to the cement with DEAEMA comonomer. In terms of mechanical properties, the highest compressive strength was exhibited by formulations containing MAA, while the highest impact strength was shown by the formulations prepared with DEAEMA. There were no differences observed between the two formulations for tensile, shear, and bending strength values. Similarly, fatigue crack propagation studies did not reveal differences with the addition of either DEAEMA or MAA.No differences were observed in the initial number of attached primary rat femur osteoblasts on the different bone cements and positive controls. However, after 48 h there was a reduced proliferation in the cells grown on bone cements containing MAA.

Animals↗
PubMed2006

Augmentation of acrylic bone cement with multiwall carbon nanotubes.

Acrylic bone cement, based on polymethylmethacrylate (PMMA), is a proven polymer having important applications in medicine and dentistry, but this polymer continues to have less than ideal resistance to mechanical fatigue and impact. A variety of materials have been added to bone cement to augment its mechanical strength, but none of these augmentative materials has proven successful. Carbon nanotubes, a new hollow multiwalled tubular material 10-40 nm in diameter, 10-100 microm long, and 50-100 times the strength of steel at 1/6 the weight, have emerged as a viable augmentation candidate because of their large surface area to volume ratio. The objective of this study was to determine if the addition of multiwall carbon nanotubes to bone cement can alter its static or dynamic mechanical properties. Bar-shaped specimens made from six different (0-10% by weight) concentrations of multiwall carbon nanotubes were tested to failure in quasi-static 3-point bending and in 4-point bending fatigue (5 Hz). Analyses of variance and the 3-Parameter Weibull model were used to analyze the material performance data. The 2 wt % MWNT concentration enhanced flexural strength by 12.8% (p=0.003) and produced a 13.1% enhancement in yield stress (p=0.002). Bending modulus increased slightly with the smaller (<5 wt % MWNT) concentrations, but increased 24.1% (p<0.001) in response to the 10 wt % loading. While the 2 wt % loading produced slightly improved quasi-static test results, it was associated with clearly superior fatigue performance (3.3x increase in the Weibull mean fatigue life). Weibull minimum fatigue life (No), Weibull modulus (alpha), and characteristic fatigue life (beta) for bone cement augmented with carbon nanotubes were enhanced versus that observed in the control group. These data unambiguously showed that the bone cement-MWNT polymer system has an enhanced fatigue life compared to "control" bone cement (no added nanotubes). It is concluded that specific multiwall carbon nanotube loadings can favorably improve the mechanical performance of bone cement.

Biocompatible Materials↗
PubMed2003

The water jet as a new tool for endoprosthesis revision surgery--an in vitro study on human bone and bone cement.

In revision surgeries of endoprostheses, the interface between implant and bone cement or bone must be loosened. Conventional tools have many disadvantages because of their size and limited range. Taking advantage of the selective and athermic cutting process, a plain water jet is already used in order to cut soft tissues. This study investigates the possibilities of both a plain and an abrasive water jet as cutting tools for revision surgery. Samples of the mid-diaphysis of human femora and bone cement (CMW3) were cut with a plain water jet (PWJ) and an abrasive water jet (AWJ) at two different jet-to-surface angles (30 degrees,90 degrees ) and at five different pressure levels (30, 40, 50, 60, 70 MPa). For a PWJ a selective pressure range was identified, where only bone cement was cut. Injecting a bio-compatible abrasive (lactose) to the jet stream resulted in significantly higher cut depths in both materials. Material removal in bone was significantly less at the smaller jet-to-surface angle for both techniques. No clear selectivity between bone and bone cement was observed for application of the AWJ. However, the material removal rate was significantly higher for bone cement than for bone at all pressure levels. The results indicate that an AWJ might be an alternative tool for cement removal. The possibility for localised cutting at interfaces could be an advantage for revision of a non-cemented prosthesis.

Aged↗
PubMed1998

Improvement of the cement mantle of the acetabular component with bone cement spacers. A retrospective analysis of 200 cemented cups.

A discontinuous or thin cement mantle of a socket is associated with increased polyethylene wear and cement fractures. In a retrospective radiological analysis we examined the quality of the cement mantle in cups without (group I = 100 Charnley-Mueller cups) and with (group II = 100 Contemporary cups, Howmedica) bone cement spacers. Under-filling (0-2 mm) and over-filling (> 8 mm) of the cement mantle were noted and classified. Statistics show significantly less under-filling of the cement mantle in group II than in group I (P = 0.001), in particular when comparing separate cup regions (thirds: P << 0.001). Furthermore, there is no significant difference in the frequency of overfilling with cement between groups I and II (P = 0.108). To sum up, utilization of an acetabular component with performed bone cement spacers considerably improves the quality of the cement mantle without additional cost.

Acetabulum↗
PubMed1999

Pressurization of bioactive bone cement in vitro.

We have developed a bioactive bone cement consisting of MgO-CaO-SiO2-P2O5-CaF2 glass-ceramic powder (AW glass-ceramic powder), silica glass powder as an inorganic filler, and bisphenol-a-glycidyl methacrylate (bis-GMA) based resin as an organic matrix. The efficacy of this bioactive bone cement was investigated by evaluating its pressurization in a 5-mm hole and small pores using a simulated acetabular cavity. Two types of acetabular components were used (flanged and unflanged sockets) and a commercially available polymethylmethacrylate (PMMA) bone cement (CMW 1 Radiopaque Bone Cement) was selected as a comparative control. Bioactive bone cement exerted greater intrusion volume in 5-mm holes than PMMA bone cement in both the flanged and unflanged sockets 10 minutes after pressurization (p < 0.05). In the small pores the bioactive and PMMA bone cements exerted almost identical intrusion volumes in flanged and unflanged sockets 10 min after pressurization. The intrusion volume in the flanged socket 10 minutes after pressurization was greater than that in the unflanged socket in all groups (p < 0.05). These results show that bioactive bone cement intrudes deeper into anchor holes than PMMA bone cement.

Biocompatible Materials↗
PubMed2001

Characterization of bone cements prepared with functionalized methacrylates and hydroxyapatite.

Bone cements prepared with methyl methacrylate and either methacrylic acid or diethyl amino ethyl methacrylate as comonomers were characterized by infrared spectroscopy, nuclear magnetic resonance, gel permeation chromatography, dynamic mechanical thermal analysis, and mechanical testing. Selected formulations containing these functionalized methacrylates were filled with hydroxyapatite and studied in terms of their properties in tension, compression and bending, and X-ray diffraction. It was found that residual monomer was not greatly affected by the presence of either acid or basic comonomers in the unfilled bone cements. In contrast, molecular weight, curing times, and glass transition temperature were composition dependent. For samples with acidic comonomer, a faster curing time, higher molecular weight, and higher glass transition temperatures were observed with respect to those with the basic comonomer. X-ray diffraction revealed that the crystalline structure was not affected by the nature of comonomer in the bone cement while scanning electron microscopy showed that hydroxyapatite remained as clusters in the bone cement. The mechanical properties of filled bone cements depended mainly on composition and type of testing. Hydroxyapatite-filled bone cements fullfilled the minimum compressive strength (70 MPa) required for bone cement use. However, the minimum tensile strength (30 MPa) was only fullfilled by cements prepared without comonomer and those containing methacrylic acid. The minimum bending strength requirement (50 MPa) was not satisfied by any of the formulations studied.

Biocompatible Materials↗
PubMed1998

Viscoelastic behaviour of acrylic bone cements.

Local contact stresses at the bone-cement interface are thought to play an important role in the initiation of component loosening. A reduced-modulus bone cement can lower these local contact stresses. The viscoelastic properties of such a cement raised the question of long term subsidence of the implant system. In this study, the viscoelastic properties of a reduced-modulus bone cement were compared with standard polymethylmethacrylate, PMMA, bone cement using stress relaxation tests. Unconstrained stress relaxation tests were performed at 37 degrees C in an aqueous environment by applying 1%, 2.5%, and 5% strains on bone cement specimens and monitoring the diminishing load for 100 h. The initial rapid stress relaxation occurring over the first hour and the steady state stress relaxation occurring between 15 and 100 h were analyzed. A fast stress diminution occurred in PBMMA specimens indicating that, in a total hip arthroplasty application, PBMMA bone cement would transfer the stress quickly and distribute it over a larger area of endosteal bone surface. Steady state stress relaxation experiments showed a significant difference in 2.5% and 5% stress relaxation values (P < 0.05) between PMMA and PBMMA specimens, but not at the 1% stress values. Length measurements indicated that the viscoelastic PBMMA specimens demonstrated little recovery after 100 h of imposed strain whereas the elastic PMMA specimens showed substantial recovery. This seems to indicate relatively larger subsidence rates in unconstrained PBMMA specimens compared to PMMA specimens. In vivo, the cement is surrounded by endosteal bone at the outer side and by an implant on the inner side. Therefore, constrained creep tests are necessary to obtain the data required for an assessment of in vivo subsidence.

Biocompatible Materials↗
PubMed2000

Influence of filler content on static properties of glass-reinforced bone cement.

A commercial acrylic bone cement was modified by the incorporation of different weight fractions of glass spheres. The influence of the filler proportion on the mechanical behavior was assessed. Composite cements were prepared by replacing part of the powder phase of the cement by an equivalent weight of glass particles, which resulted in an increase in the liquid-to-powder (L/P) ratio of the polymeric matrix. Dynamic mechanical analysis revealed an increase in residual monomer content with increasing filler proportion as a consequence of the increase in L/P. Flexural, compressive, and fracture properties of the cement with varying amounts of glass particles were measured. It was found that up to 50 wt% glass particles could be added with significant increases in flexural modulus and fracture toughness. The mechanical behavior was explained in terms of both the reinforcing effect of the filler and the plasticizing effect of the monomer. Glass-filled bone cements displayed superior workability compared with the standard cement, which was attributed to a decrease in the viscosity of the initial mix and the surface characteristics of the glass particles. The observed increase in fracture toughness could be rationalized through the application of proposed mechanisms for toughening of particle-reinforced polymers.

Acrylic Resins↗
PubMed2000

Tensile characteristics of ten commercial acrylic bone cements.

The mechanical properties of acrylic bone cement, used in orthopedic surgery, are very influential in determining successful long-term stability of a prosthesis. A large number of commercial formulations are available, differing in chemical composition and physical properties of both powder and monomer constituents. In this study, the static and dynamic tensile characteristics of a number of the most commonly used bone cements (Palacos R, Simplex P, CMW 1 & 3, Sulfix-60, Zimmer Dough), along with some newer formulations (Endurance, Duracem 3, Osteobondtrade mark and Boneloc), have been investigated under the same testing regimes. Testing was performed in air at room temperature. Significant differences in both static and fatigue properties were found between the various bone cements. Tensile tests revealed that Palacos R, Sulfix-60, and Simplex P had the highest values of ultimate tensile strength, closely followed by CMW 3, while Zimmer Dough cement had the lowest strength. Fatigue testing was performed under stress control, using sinusoidal loading in tension-tension, with an upper stress level of 22MPa. The two outstanding cements when tested in these cyclic conditions were Simplex P and Palacos R, with the highest values of Weibull median cycles to failure. Boneloc bone cement demonstrated the lowest cycles to failure. While the testing regimes were not designed to replicate exact conditions experienced by the bone cement mantle in vivo, there was a correlation between these results and clinical outcome.

Bone Cements↗
PubMed2004

Thermal characterization of PMMA-based bone cement curing.

In thermal characterization tests of polymethylmethacrylate bone cement performed according to the ASTM Standard Specification for Acrylic Bone Cement, time-temperature profiles of bone cement were observed to be sensitive to the thickness of the cement patty and the mold material. Due to the heat transfer from cement to the surrounding mold, such tests might underestimate the exothermic temperature of bone cement. Developing test methods to better characterize cement thermal behavior is necessary for accurate cement curing simulations. In this paper, the effects of the mold material and geometry on experimental measurements of bone cement setting temperature and setting time were evaluated by conducting the polymerization in different test molds. Finite element (FE) numerical simulations were also performed to provide a further understanding of these effects. It was found that the mold material and geometry significantly influence the values of the parameters measured using the ASTM standard. Results showed that the setting temperature measured was about 50 degrees C lower in a polytetrafluoroethylene (PTFE) mold than in a polyurethane (PU) foam mold for the 6 mm thickness cement. The measured peak temperature using PTFE molds varied about 75 degrees C for different mold heights (6mm vs. 40 mm), but only by 28 degrees C with PU molds. The measured setting time with PTFE molds varied by about 740 s for different mold heights (6 mm vs. 40 mm), while only by about 130 s for PU molds. Using PU foam materials for the test mold decreases cement heat transfer effects due to the poor heat conductivity of PU foam and provides more consistent measured results. FE parametric studies also support these observations. Poor conductivity materials, like PU foam, make better molds for the characterization of bone cement thermal behavior.

Bone Cements↗
PubMed2003

Comparison of failure characteristics of a range of cancellous bone-bone cement composites.

Over the past decade, orthopedic surgery has embraced an increase in the depth of cement penetration into the adjacent cancellous bone structure. The resultant interdigitation transforms this zone into a thick layer of continuous interpenetrating composite material. The failure behavior of the composite formed with a number of potential bone cements with different bonding ability was investigated. The cancellous bone-cement composites exhibit considerable resistance to crack extension, and in situ optical observation indicates that the contribution of the cancellous bone is analogous to that of a typical fiber bridging process. The critical stress intensity factor and the work of fracture have been used to quantify the failure characteristics of the cancellous bone-cement composites. The nature of the crack propagation through these cement-bone composites was also captured via optical microscopy, and scanning electron microscopic images were taken of the failure surfaces. The R-curve behavior, or crack extension characteristic, of the cancellous bone-cement composite was also determined. The interesting outcome is that the cancellous bone-PMMA (poly-methylmethacrylate) composite, despite the absence of chemical bonding with bone, required the highest energy to fracture. In addition, the dimensional stability of the cement has a great effect on the interface.

Animals↗