High-performance liquid chromatography assay of N,N-dimethyl-p-toluidine released from bone cements: evidence for toxicity

[Chemical and physical properties of PMMA bone cements]

PMMA-based bone cements are used for anchoring artificial joints. The cements are offered as two-component systems. During mixing, a liquid paste is formed by free-radical polymerization, which completely hardens into a solid cement matrix as polymerization progresses with an increase in viscosity. Polymerization from MMA to PMMA is an exothermic process, energy is released in the form of heat. After fixation of the prosthesis and curing of the cement, the cement fills the space between the prosthesis and the bone. With the filler PMMA, a strong force-locking and interlocking mechanical bond is created. The essential properties of PMMA cements are dictated by the powder component. In vivo, the hard and brittle bone cements absorb body fluids and become more elastic and softer. The properties of various PMMA bone cements differ significantly, although the chemical acrylate base is identical.

Novel Tuning of PMMA Orthopedic Bone Cement Using TBB Initiator: Effect of Bone Cement Extracts on Bioactivity of Osteoblasts and Osteoclasts

Bone cement containing benzoyl peroxide (BPO) as a polymerization initiator are commonly used to fix orthopedic metal implants. However, toxic complications caused by bone cement are a clinically significant problem. Poly (methyl methacrylate) tri-n-butylborane (PMMA-TBB), a newly developed material containing TBB as a polymerization initiator, was found to be more biocompatible than conventional PMMA-BPO bone cements due to reduced free radical generation during polymerization. However, free radicals might not be the only determinant of cytotoxicity. Here, we evaluated the response and functional phenotypes of cells exposed to extracts derived from different bone cements. Bone cement extracts were prepared from two commercial PMMA-BPO cements and an experimental PMMA-TBB. Rat bone marrow-derived osteoblasts and osteoclasts were cultured in a medium supplemented with bone cement extracts. More osteoblasts survived and attached to the culture dish with PMMA-TBB extract than in the culture with PMMA-BPO extracts. Osteoblast proliferation and differentiation were higher in the culture with PMMA-TBB extract. The number of TRAP-positive multinucleated cells was significantly lower in the culture with PMMA-TBB extract. There was no difference in osteoclast-related gene expression in response to different bone cement extracts. In conclusion, PMMA-TBB extract was less toxic to osteoblasts than PMMA-BPO extracts. Although extracts from the different cement types did not affect osteoclast function, PMMA-TBB extract seemed to reduce osteoclastogenesis, a possible further advantage of PMMA-TBB cement. These implied that the reduced radical generation during polymerization is not the only determinant for the improved biocompatibility of PMMA-TBB and that the post-polymerization chemical elution may also be important.

Influence of Initiator Concentration on the Polymerization Course of Methacrylate Bone Cement

Background: The amount of oxidant (initiator) and reductant (co-initiator) and their ratio have a significant effect on the properties of polymethacrylate bone cement, such as maximum temperature (T_max), setting time (t_set) and compressive strength (σ). The increase in the initiating system concentration causes an increase in the number of generated radicals and a faster polymerization rate, which shortens the setting time. The influence of the redox-initiating composition on the course of polymerization (rate of polymerization and degree of double bond conversion) and the mechanical properties of bone cement will be analyzed. Methods: Bone cements were synthesized by mixing a powder phase composed of two commercially available methacrylate copolymers (Evonic) and a liquid phase containing 2-hydroxyethyl methacrylate (HEMA), methyl methacrylate (MMA), and triethylene glycol dimethacrylate (D3). As an initiating system, the benzoyl peroxide (BPO) as an oxidant (initiator) in combination with a reducing agent (co-initiator), N,N-dimethylaniline (DMA), was used. Samples were prepared with various amounts of peroxide BPO (0.05%, 0.1%, 0.2%, 0.3%, 0.5% and 0.7% by weight) with a constant amount of reducing agent DMA (0.5 wt.%), and various amounts of DMA (0.25%, 0.35% and 0.5% by weight) with a constant amount of BPO (0.3 wt.%). The polymerization kinetics were studied by differential scanning calorimetry (DSC). Doughing time and compressive strength tests were carried out according to the requirements of the ISO 5833:2002 standard. Results: The increase in polymerization rate was due to the increase in the amount of BPO. In addition, the curing time was shortened, as well as the time needed to achieve the maximum polymerization rate. The final conversion of the double bonds in the studied compositions was in the range 74-100%, and the highest value of this parameter was obtained by the system with 0.3 wt.% of BPO. The doughing times for each BPO concentration were in the range of 90-140 s. The best mechanical properties were obtained for the cement following the initiating system concentrations: 0.3 wt.% of BPO and 0.5 wt.% of DMA. Nevertheless, all tested cements met the requirements of the ISO 5833:2002 standard. Conclusions: Based on the conducted polymerization kinetic studies, the best reaction conditions are provided by an initiating system containing 0.3 wt.% of BPO oxidant (initiator) and 0.5 wt.% of DMA reductant (co-initiator). A decrease in the DMA amount caused a decrease in the polymerization rate and the amount of heat released during the reaction. The change in BPO and DMA concentrations in the composition had little effect on the doughing time of the studied bone cement. The cements showed similar doughing times, ranging from 90-225 s, which is comparable to the bone cement available on the market.

The Effect of TBB, as an Initiator, on the Biological Compatibility of PMMA/MMA Bone Cement

Acrylic bone cement is widely used in orthopedic surgery for treating various conditions of the bone and joints. Bone cement consists of methyl methacrylate (MMA), polymethyl methacrylate (PMMA), and benzoyl peroxide (BPO), functioning as a liquid monomer, solid phase, and polymerization initiator, respectively. However, cell and tissue toxicity caused by bone cement has been a concern. This study aimed to determine the effect of tri-n-butyl borane (TBB) as an initiator on the biocompatibility of bone cement. Rat spine bone marrow-derived osteoblasts were cultured on two commercially available PMMA-BPO bone cements and a PMMA-TBB experimental material. After a 24-h incubation, more cells survived on PMMA-TBB than on PMMA-BPO. Cytomorphometry showed that the area of cell spread was greater on PMMA-TBB than on PMMA-BPO. Analysis of alkaline phosphatase activity, gene expression, and matrix mineralization showed that the osteoblastic differentiation was substantially advanced on the PMMA-TBB. Electron spin resonance (ESR) spectroscopy revealed that polymerization radical production within the PMMA-TBB was 1/15–1/20 of that within the PMMA-BPO. Thus, the use of TBB as an initiator, improved the biocompatibility and physicochemical properties of the PMMA-based material.

N,N-dimethyl-p-toluidine, a component in dental materials, causes hematologic toxic and carcinogenic responses in rodent model systems

Because of the potential for exposure to N,N-dimethyl-p-toluidine (DMPT) in medical devices and the lack of toxicity and carcinogenicity information available in the literature, the National Toxicology Program conducted toxicity and carcinogenicity studies of DMPT in male and female F344/N rats and B6C3F1/N mice. In these studies, a treatment-related macrocytic regenerative anemia characterized by increased levels of methemoglobin and Heinz body formation developed within a few weeks of DMPT exposure in rats and mice. DMPT induced nasal cavity, splenic, and liver toxicity in rats and mice at 3 months and 2 years. DMPT carcinogenic effects were seen in the liver of male and female rats and mice, the nasal cavity of male and female rats, and the lung and forestomach of female mice. In rodents, DMPT is distributed to many of the sites where toxic and carcinogenic effects occurred. DMPT-induced oxidative damage at these target sites may be one mechanism for the treatment-related lesions. Methemoglobinemia, as seen in these DMPT studies, is caused by oxidation of the heme moiety, and this end point served as an early alert for other target organ toxicities and carcinogenic responses that followed with longer term exposure.

Acrylamine-induced autoimmune phenomena

The objective of this study is to document a series of cases of occupationally derived autoimmune disease. Individuals with occupational exposure to acrylamides were evaluated clinically and biochemically/immunologically for evidence of autoimmune disease. Symptoms and signs and immuno-reactivity were monitored during exposure-free and re-exposure as part of the individuals' clinical evaluation. Six individuals with occupational acrylamide exposure had clinical and laboratory alterations characteristic of drug-induced autoimmune disease, specifically lupus, anti-phospholipid syndrome, Sjogren's syndrome, scleroderma, and polymyositis. The similarity of the full spectrum of disease in the reported patients to that found with procainamide strongly suggests the effects of occupational exposure. This uncontrolled study suggests the need for a full epidemiologic analysis of all individuals working with such occupational exposure, including full clinical and immunological examination.

Alternative acrylic bone cement formulations for cemented arthroplasties: present status, key issues, and future prospects

All the commercially available plain acrylic bone cement brands that are used in cemented arthroplasties are based on poly (methyl methacrylate) and, with a few exceptions, have the same constituents. It is well known that these brands are beset with many drawbacks, such as high maximum exotherm temperature, lack of bioactivity, and volumetric shrinkage upon curing. Furthermore, concerns have been raised about a number of the constituents, such as toxicity of the activator (N,N,dimethyl-p-toluidine) and possible involvement of the radiopacifier (BaSO(4) or ZrO(2) particles) in third-body wear. Thus, over the years, many research efforts have been expended to address these drawbacks, culminating in a large number of alternative formulations, which may be grouped into 16 categories. Although there are a number of reviews of the large literature that now exists on these formulations, each covers only some of the categories and none contains a detailed discussion of the germane issues. The objective of the present work, therefore, was to present a comprehensive and critical review of the whole field. In addition to succinct descriptions of the cements in each category, there are explicative summaries of literature reports, a detailed discussion of several key issues surrounding the potential for use of these cements in cemented arthroplasties, and a presentation of numerous ideas for future studies.

Influence of strontia on various properties of surgical simplex P acrylic bone cement and experimental variants

The fact that the composition of acrylic bone cement, as used in cemented primary arthroplasties, is not optimal has been highlighted in the literature. For example: (i) deleterious effects of the radiopacifier (BaSO(4) or ZrO(2) particles in the powder) have been reported; (ii) there is an indication that pre-polymerized poly(methylmethacrylate) (PMMA) beads in the powder may be dispensed with; and (iii) there is a strong consensus that the accelerator commonly used, N,N-dimethyl-p-toluidine (DMPT), is toxic and has many other undesirable properties. At the same time, the effectiveness of drugs that contain a strontium compound in treating the effects of osteoporosis has been explained in terms of the role of strontium in bone formation and resorption. This indicates that strontium compounds may also have desirable effects on osseointegration of arthroplasties. The present study is a detailed evaluation of 24 acrylic bone cement formulations comprising different relative amounts of BaSO(4), strontia (as an alternative radiopacifier), pre-polymerized PMMA beads and DMPT. A large number of properties of the curing and cured cement were determined, including setting time, polymerization rate, fracture toughness and fatigue life. The focus was on the radiopacifier, with the finding being that many properties of formulations that contained strontia were about the same or better than those for cements that contained BaSO(4). Thus, further developmental work on strontia-containing acrylic bone cements is justified, with a view to making them candidates for use in cemented primary arthroplasties.

Influence of two changes in the composition of an acrylic bone cement on its handling, thermal, physical, and mechanical properties

This study is a contribution to the growing body of work on the influence of changes in the composition of an acrylic bone cement on various properties of the curing and cured material. The focus is on one commercially-available acrylic bone cement brand, Surgical Simplex P, and three variants of it and a series of properties, namely, setting time, maximum exotherm temperature, activation energy and frequency factor for the polymerization reaction, diffusion coefficient for the uptake of phosphate buffered saline, at 37 degrees C, ultimate compressive strength (UCS), plane-strain fracture toughness, fatigue life (under fully-reversed tension-compression stress), hardness (H) and elastic modulus (both determined using quasi-static nanoindentation), and the variation of the storage and loss moduli with frequency of the applied force in a dynamic nanoindentation test. It was found that (a) a 68% reduction in the volume of the activator, N,N dimethyl-4-toluidine, relative to the total volume of the liquid monomer (the amounts of all the constituents in the powder and of the hydroquinone in the liquid monomer remaining unchanged) led to, for example, a significant decrease in the rate of the polymerization reaction, at 37 degrees C (c') and a significant increase in H; and (b) the elimination of the pre-polymerized poly (methyl methacrylate) beads in the powder (the amounts of all the other powder constituents and those of the liquid monomer remaining unchanged) led to, for example, a significant drop in c' and a significant increase in UCS. Thus, these findings suggest a strategy for optimizing the composition of an acrylic bone cement.

Biological response of new activated acrylic bone cements with antiseptic properties. Histomorphometric analysis

The biological response to an acrylic bone cement cured with 4,4'-bis-dimethylamino benzydrol (BZN) as activator of reduced cytotoxicity and antiseptic properties, has been carried out and compared with that obtained for CMW 3 cement. Histomorphometrical data (undecalcified trichromic Goldner staining) were obtained by measuring the most significant variables at the bone-cement interface. Quantitative results of tissue response revealed that newly formed bone and connective tissue were maximum at 4 weeks whereas bone marrow increased with time of implantation for both cements. Statistical analysis (p < 0.05) showed no significant differences in newly formed bone and bone marrow with time and between both groups, however, connective tissue significantly decreased between 4 weeks and 12 weeks for BZN cement, and between 12 weeks and 24 weeks for CMW3. By comparing both cements at each time, lower significant percentage of connective tissue at the bone-cement interface of the BZN cement, was obtained at 12 and 24 weeks, however, a very low amount of connective tissue was found for both cements. All the results indicate that the new activated system could be applied clinically in a relatively short time, after the corresponding preclinical study.

Methyl-methacrylate bone cement surface does not promote platelet aggregation or plasma coagulation in vitro

Leakage of viscous bone cement into venous blood possibly resulting in pulmonary embolism may occur during percutaneous vertebroplasty. Our aim was to study if bone cement surface or cement liquid component could induce platelet aggregation or plasma coagulation in vitro. Two types of commonly used methyl-methacrylate bone cement, Palacos (Heraeus Kulzer, Germany) and Vertebroplastic (DePuy, Acro Med, England), were smeared on thin glass slides that were inserted over the bottom of cuvettes immediately or after 24 h, and platelet aggregation was recorded over 10 min. Bone cement liquid component, containing methyl-methacrylate monomer and N,N-dimethyl-p-toluidine, was tested in 2% and 4% final concentration. Partial thromboplastin time (PTT) was determined by the hook method in the presence of bone cement-smeared glass slides or 6% bone cement liquid. Both types of bone cement, either fresh or aged, did not promote platelet aggregation, whereas collagen-coated glass slides induced substantial platelet aggregation (65 +/- 37%). On the other hand, bone cement liquids reduced platelet aggregation induced by collagen solution to an average of less than 15% (p < 0.01). Bone cement, fresh or aged, had no effect on PTT, but bone cement liquids significantly prolonged PTT: median and 1st-3rd interquartile range 149 (96-171) s for Vertebroplastic and 132 (99-194) s for Palacos, p = 0.03 for both comparisons with normal pool plasma without additives that had PTT of 69 (62-71) s. We conclude that the surface of fresh or aged bone cement is not thrombogenic in vitro. The bone cement liquid inhibits platelet aggregation and plasma clotting in relatively high concentrations that cannot be expected in vivo.

Biocompatibility and other properties of acrylic bone cements prepared with antiseptic activators

Acrylic bone cements prepared with activators of reduced toxicity have been formulated with the aim of improving the biocompatibility of the final material. The activators used were N,N-dimethylaminobenzyl alcohol (DMOH) and 4,4'-dimethylamino benzydrol (BZN). The toxicity, cytotoxicity, and antiseptic action of these activators were first studied. DMOH and BZN presented LD50 values 3-4 times higher than DMT, were less cytotoxic against polymorphonuclear leucocytes, and possessed an antimicrobial character, with a high activity against the most representative microorganisms involved in postoperative infections. The properties of the acrylic bone cements formulated with DMOH and BZN were evaluated to determine the influence of these activators on the curing process and the physicochemical characteristics of the cements. A decrease of the peak temperature was observed for the curing with DMOH or BZN with respect to that of one commercially available formulation (CMW 3). However, residual monomer content and mechanical properties in tension and compression were comparable to those of CMW 3. The biocompatibility of acrylic bone cements containing DMOH or BZN was studied and compared with CMW 3. To that end, intramuscular and intraosseous implantation procedures were carried out and the results were obtained from the histological analysis of the surrounding tissues at different periods of time. Implantation of rods of cement into the dorsal muscle of rats showed the presence of a membrane of connective tissue, which increased in collagen fibers with time of implantation, for all formulations. The intraosseous implantation of the cements in the dough state in the femur of rabbits, revealed a higher and early osseous neoformation, with the presence of osteoid material surrounding the rest of the cured material, for the cement prepared with the activator BZN in comparison with that obtained following the implantation of the cement cured with DMOH or DMT (CMW 3).

Effect of CMW 1 bone cement on transforming growth factor-beta 1 expression by endothelial cells

The present study examined the effects of in vitro challenge with an acrylic bone cement CMW 1 on the expression of transforming growth factor-beta 1 (TGF-beta 1) in human umbilical vein endothelial cells (HUVEC). The extracts in cell culture medium of the cements were tested, after 1 h and 7-day curing. Some cultures were also stimulated with interleukin-1 beta (IL-1 beta) or all-trans retinoic acid (ATRA). The expression of mRNA was evaluated by RT-PCR with specific primers. The release of TGF-beta 1 into the conditioned medium was evaluated by enzyme immunoassay. TGF-beta 1 mRNA was constitutively expressed by endothelial cells in the culture medium after 24 h. The incubation with the extracts of CMW 1, cured both for 1 h and 7 days, induced changes neither in mRNA expression, nor in the release of TGF-beta 1 into the conditioned medium, compared to the unstimulated cells. Even stimulation with ATRA, alone or added to the extracts at both curing times, affected neither mRNA expression nor TGF-beta 1 release, compared to the cells incubated with the cement alone or with the unstimulated cultures. The mRNA expression and the release were not changed by the stimulation with IL-1beta alone or added to the extract cured for 1 h. A significant decrease compared to the unstimulated cells was observed after the addition of IL-1 beta to the extract cured for 7 days. It was concluded that CMW 1 extract did not significantly modify TGF-beta 1 expression after 1-h curing, or after 7-day curing. Incubation with CMW 1 added with ATRA did not produce any changes in TGF-beta 1 synthesis. Incubation with cement extract after 7-day curing added with IL-beta 1 produced a significant reduction in TGF-beta 1 release.

Strategies for the in vitro testing of in situ polymers

In situ polymers are used by mixing two or more compounds that are then placed directly in tissues to form a unique product. This type of reaction can generate heat, reactive oxygen species, free radicals, and other by-products of unknown toxicities, but the polymer itself is biocompatible. Many regulatory agencies require in vitro testing, however, standard guidelines (ASTM, ISO, AAMI) test polymers in a final form prior to use as a medical device. To better estimate the cytotoxicity of these in situ polymers, various means of introducing the reacting material to cells in culture were explored. Coating the material on a sterile glass cover slip then adding the cover slip to the in vitro test system immediately provided reasonable cytotoxicity data that reflected actual use conditions. For in situ polymeric devices that are more viscous, such as dental materials and bone cements, a mold was used that was placed directly into cell culture. This approach in testing in situ polymers generated in vitro toxicity data that reflects the actual use of the material.

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.

Modulation of pro- and anti-apoptotic genes in lymphocytes exposed to bone cements

The ability of bone cements to modify the apoptotic program in activated immune cells and the mechanisms by which they act were evaluated. Mononuclear cells were collected from healthy individuals, cultured for 4 and 24 h with phytohemoagglutinina-P and cement extracts and then tested to assess: (a) cell viability; (b) early apoptotic events, by Annexin V/propidium iodide staining; and (c) the expression of pro- (p53, c-myc, ICE) and anti-apoptotic (bcl-2) genes. After 4 h three cements were able to increase significantly the percentage of apoptotic cells, while after 24 h no differences were found. The proportion of dead cells was not significantly changed at either culture time. The simultaneous expression of both pro-apoptotic (ICE, c-myc, p53) and antiapoptotic genes (bcl-2) was investigated only with regard to the materials which induced significant changes in apoptosis: two cements induced the p53 expression, while the third down-regulated bcl-2. As apoptosis regulates the balance of immune response, the authors recommend that the interaction between materials and immune cells should be assessed, so that the use of pro-apoptotic materials may be avoided in patients with immune defects.

In vitro testing of ten bone cements after different time intervals from polymerization

Biological response of cells to implanted bone cement is a fundamental but often neglected issue in successful cemented implants. In this study, ten acrylic bone cements for orthopedics were assayed using two different in vitro testing methods on L929 cells. The cements were mixed as prescribed, cured for either 1 h or 7 days and then extracted in minimum essential medium (MEM) according to the ISO standard for the preparation of samples. For the evaluation of cytotoxicity, the neutral red uptake assay (NRU) and the incorporation of propidium iodide (PI) were used to detect the viability/death of cells. The two methods were shown to be well correlated (p < 0.0001) in the case of both the 1-h and the 7-day extracts. Two cements, i.e. CERIM LT and CMW2, were found to be toxic after 1-h curing through both the spectrophotometric NRU assay and the cytofluorometric assay with PI. After 7-day curing, these two cements, as well as the Zimmer-low viscosity cement, were toxic according to the NRU assay. The toxic effect of all the cements disappeared after dilution of extracts 1:2 with MEM, except in the case of CERIM LT. In the search for the component inducing the toxic effect, the possible contribution of the residual monomer was discarded on the basis of literature data and the influence of various other factors was analyzed, including the contrast medium (barium sulphate or zirconium dioxide) and the concentrations of N,N-dimethyl-paratoluidine and of benzoyl peroxide (< 1% or > or = 1%). Unlike zirconium dioxide, barium sulphate was found to damage the cells at the 1-h endpoint. Benzoyl peroxide at concentration > or = 1% was found to affect cells at the same endpoint, whereas dimethylparatoluidine had no effect regardless of the proportion.

Cytotoxic effect of bone cements in HL-60 cells: distinction between apoptosis and necrosis

Ten PMMA-based bone cements used in prosthetic surgery have been studied with respect to the induction of programmed cell death (i.e., apoptosis) in HL-60 cells, which are remarkably sensitive to various apoptotic stimuli. Annexin V binding and propidium iodide (PI) exclusion were the methods for detection of early apoptotic changes, while PI entry was considered as a marker of necrosis. Hoechst 33342 staining was used to detect DNA fragmentation and Alamar blue was applied to measure oxide-reduction activity of cells. The production of reactive oxygen species (ROS) related to cell damage was verified using dichlorofluorescein-diacetate (DCFH-DA) oxidation to DCF. Under our experimental conditions, the cements tested, for the most part, were not toxic to leukemic cells at 4 and 24 h. After 24 h, three cements were able to induce cell death, with two eliciting both apoptosis and necrosis, and one cement acting mainly via apoptosis. Both processes of cell death are likely to be mediated by the production of oxygen-free radicals. These findings provide potential leads for investigation into the molecular mechanisms of cell death, which are responsible for tissue damage by cements and intolerance of cemented prostheses.

In vitro cytokine production by mononuclear cells exposed to bone cement extracts

The authors evaluated the ability of bone cement to modify the profile of pro-inflammatory cytokines secreted by the immune cells. Peripheral blood mononuclear cells (PBMC) collected from healthy individuals were cultured with cement extracts and tested to assess the release of IL-1beta, TNFalpha, GM-CSF and IL-6 in both unstimulated and PHA-stimulated PBMC. The cytokine release of unstimulated PBMC was very poor, and in particular the IL-1beta was undetectable: the addition of cement extract increased both TNFalpha and GM-CSF release and decreased IL-6, sometimes significantly. The most recurrent observation in PHA-stimulated PBMCs exposed to bone cement extract was the increase in both IL-1beta and IL-6 release, while both the mean concentration and the index of release of TNFalpha and GM-CSF were changeable. In conclusion our results showed that leachable components of some bone cements can induce in vitro the release of pro-inflammatory cytokines which are known to be involved in the bone resorption associated with aseptic loosening of hip prostheses. These findings allowed us to identify materials endowed with the highest inflammatory power.