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PubMed2006

Phase evaluation of an effervescent-added apatitic calcium phosphate bone cement.

Development of macroporosity during setting would allow fast bone ingrowth and good osteointegration of the implant. The interconnected macropores could be created in calcium phosphate cements (CPCs) through the addition of an effervescent porogen mixture to the component of the cements. But this addition could also affect other characteristics of CPCs, such as setting time, mechanical strength, extent of conversion of reactant to apatite phase, crystallinity, and chemical composition of apatite lattice. In this study, these properties were investigated in an effervescent-added calcium phosphate bone cement. From 0 to 20 wt % of an effervescent mixture was added to calcium phosphate cement (CPC) components and phase evaluations were performed after 24 h incubation at 37 degrees C and 28% relative humidity and 1, 3, 7, and 14 days immersion in a specific simulated body fluid. XRD and FTIR techniques were used to characterize the cement composition, crystallinity, and chemical groups in final CPCs. The results showed that addition of effervescent porogen affects the extent of conversion of reactant to apatite phase and crystallinity. In other words, using the effervescent porogen in CPCs could accelerate the rate of conversion of TTCP/DCPA reactant to apatite phase with smaller crystallites, so that it was the predominant phase (about 67%) after only 3 days soaking in SBF solution. The content of carbonate groups substituted for phosphate groups in apatite lattice increased when the effervescent additive was further added. The compressive strength of the set calcium phosphate cement decreased significantly with the addition of the effervescent agent and reached from 8 MPa for additive-free CPC to 1.3 MPa for 20% effervescent-added CPC. The compressive strength was improved after 3 days immersing of CPC in the simulated body fluid solution.

Apatites↗
PubMed1977

Clinical influences on bone cement monomer release.

Monomer losses for two self-curing acrylic cements were similar via laboratory serial weighing experiments. Both the P/L ratio and mixing duration substantially influenced subsequent monomer losses, but ambient temperature variation during mixing had little effect. Greater losses were encountered during the mixing and setting intervals than during the molding interval. Patient potential exposure to monomer occurs during the molding and setting intervals; therefore, handling procedures reducing losses in these intervals are important to the surgeon. The least monomer loss during both molding and setting occurred at the manufacturers' recommended P/L ratio, which strongly indicated the need to mix all contents supplied. Mixing loss increased with amount of spatulation. However, once the mass was well mixed (about 300 steady spatulations), no further decreases in the molding and setting interval losses were promoted by overmixing. Because of the lower monomer loss rate during the molding interval, postponed cement insertion may not be warranted in light of losing mechanical locking efficiency. The actual ramifications of a threefold reduction in potential patient exposure (3.5 down to 1.2 wt% of total monomer) via modified handling techniques have not yet been clinically evaluated.

Acrylates↗
PubMed1997

Reinforcement of PMMA bone cement with a continuous wire coil--a canine femur study.

The hoop and axial strains present due to loading after femoral stem implantation in canine femurs, implanted with and without a wire coil surrounding the distal tip were investigated. One stem served as the control without wire coil while the other was experimental reinforced with a wire coil. Both stems were implanted by identical methods. Ideally, the wire coil should serve to reduce the hoop and axial strains present in the distal tip of the arthroplasty. The strains were measured using 90 degrees rosette strain gages. Though the coil's position was altered slightly during implantation usable results were still obtained. At a maximum load of 44.5 N there were 32 and 19% reduction in the hoop and axial strains for the reinforced stem and the control, respectively. This experiment presents a striking difference between the control and reinforced hip arthroplasties. Equally important is that this study confirms the trends in hoop and axial strain behavior demonstrated in other works utilizing a wire coil reinforcement scheme. The simple method of applying a continuous wire coil may help to reduce the loosening of femoral stem of total hip arthroplasty by reducing strains at the tip of the stem due to the strengthening of the cement mantle.

Animals↗
PubMed1986

Effect of pressure on bone cement stiffness. An in vitro study.

Twenty-two canine femora were injected with PMMA cement at pressures varying between 0.2 and 1.3 MPa. Sections cut from the femora were tested in bending in several planes and under axial loading. Cement penetration was determined for each section. The bending and axial stiffness values were correlated with the cement penetration values. Both bending and axial stiffness were related linearly to penetration and nonlinearly to the cement intrusion pressure. The stiffness values increased with the intrusion pressure: slowly at low pressures, rapidly at medium pressures, slowly again at higher pressures, and leveling off at about 1.2 MPa. The 75 per cent of the maximum bending and axial stiffness values were achieved with a cement intrusion pressure of 0.55 MPa.

Animals↗
PubMed1999

Attachment of PMMA cement to bone: force measurements in rats.

The attachment of an implant material to bone relates to surface roughness and surface chemistry. There is a relatively low chemical bonding strength of so-called bioactive surfaces. Hydroxyapatite interfaces typically have an interfacial tensile strength of 0.15-1.5 MPa. An attachment force similar to that of bioactive surfaces might also be reached through mechanical interlock with ordinary bone cement. This study measured bone cement interfacial tensile strength for polished (R(a) 0.5 microm) and regular (R(a) 4.8 microm) vacuum mixed PMMA bone cement. Bone bonding was evaluated by a detachment test. We used unloaded cement surfaces, which could be detached from the bone. Titanium plates were developed such that a cement fill was contained within a plate, which was contained within a titanium holder. The cement surface came into contact with traumatized bone only, and the rest of the plate had no contact with tissue. The cement surface was either polished or left untreated after conventional preparation. Four weeks later, the plates were detached from the bone by a perpendicular force. The detaching load of the polished cement surface never exceeded 0.07 MPa, whereas for unpolished cement there was a load up to 0.9 MPa. The results suggest that surface irregularities and microinterlock enable an attachment that can resist tension between bone and a cement surface.

Animals↗
PubMed1979

Properties and applications of acrylic bone cement.

Mechanical properties of acrylic cement and its interface characteristics with cancellous bone have been described. Applications and techniques for optimal use of the cement in joint replacement, treatment of pathologic fractures, and implant revision procedures are presented.

Acrylates↗
PubMed2005

Acrylic bone cements modified with beta-TCP particles encapsulated with poly(ethylene glycol).

Beta-tricalcium phosphate (beta-TCP) has been encapsulated with poly(ethylene glycol) (PEG) to improve the filler/cement interface, and it was later incorporated to a poly(methyl methacrylate) bone cement in order to obtain cements with improved stability in the long term. Size and size distribution of the agglomerates forming the initial powder was drastically changed after its dispersion in a PEG aqueous solution. Whereas the initial beta-TCP particles had a 584 microm average diameter, the treated particles (TCP-PEG) presented more than 60% of the particles in a range of 2-6 microm. The effect of adding the treated particles to an acrylic cement was evaluated in terms of curing parameters, in vitro behaviour and mechanical performance. The presence of the TCP-PEG particles did not affect either peak temperature or setting time, indicating a good homogeneity of polymerising mass in contrast to the effect observed with the plain beta-TCP particles, which gave rise to higher setting times. In vitro behaviour studies revealed hydration degree values of the modified cements comparable to that of PMMA cements. Early stages of water uptake was Fickian in nature for all the experimental formulations indicating that the water absorption followed a diffusion controlled mechanism. After 3 months of storage in SBF the experimental formulations presented values of compressive strength in the range 76-78 MPa, higher than the minimum required by ISO 5833 (70 MPa) and those of tensile strength in the range 42-48 MPa, higher than the minimum reported for commercial formulations (30 MPa), but no significant differences in the strengths and elastic modulus were observed with the treatment of the filler particles. This observation was confirmed by ESEM analysis of the tensile fracture surfaces, which revealed a rather good cohesion between the bioceramic particles with some gaps around them, independently of the type of particles. The themogravimetric analysis of dry and wet specimens showed a higher dissolution rate of the plain beta-TCP particles in comparison to the encapsulated ones, indicating that the PEG adsorbed on the surface of the TCP particles could be a way to control the resorbability of the bioceramic component.

Absorption↗
PubMed2002

Effect of loading rate on the apparent fracture toughness of acrylic bone cement.

In this study, a determination is made of the effect of loading rate, v (0.1 mm min(-1) versus 1.0 mm min(-1) versus 10 mm min(-1)) on the value of the plane strain fracture toughness, K(Ic), of three commercial formulations of acrylic bone cement (Osteopal), CMW3, and Copal), that are characterized as "low-", "medium-", and "high-" viscosity brands, respectively). For all formulations, K(Ic) increases with increase in v. However, while this trend is statistically significant for CMW3 and Copal, this is not so for Osteopal. The CMW3 and Copal results are explained in terms of changes of the molecular relaxation transitions in the cement and the thermal state at the crack tip of the test specimen. Two implications of the findings are discussed. In the case of Osteopal, a recommendation for further study is made.

Benzimidazoles↗
PubMed1984

Use of antibiotic-containing bone cement.

Erythromycin and colistin (or other thermostable antibiotics) may legally be added to polymethylmethacrylate (PMMA) for use in the fixation of prostheses to bone. The antibiotics are leached or rapidly released from the combination in bactericidal concentrations. They do not reduce the strength characteristics of the cement below acceptable standards, nor do they change its handling characteristics. Erythromycin alone was used in 1112 total hip arthroplasties between 1971 and 1976, with an infection rate of 0.98%. Erythromycin-colistin bone cement was used in 786 total hip arthroplasties from July 1976 to December 1980, with a deep-wound infection rate of 0.4%. Erythromycin-colistin-containing bone cement is safe and effective in treatment of and prophylaxis against deep-wound infection in total joint arthroplasty.

Anti-Bacterial Agents↗
PubMed1978

Extracortical attachment of bioceramic endoprostheses to long bones without bone cement.

Dense, highly pure A12O3 ceramic not only shows excellent wear resistance and tissue biocompatibility, but also has sufficient mechanical strength for loaded endoprostheses. The necessary diameter size of the material to sustain adequate shear stresses can be achieved, if the endoprosthesis is attached extracortically to the conically truncated long bone according to the principle of the conical sleeve. Extracortical attachment of the endoprosthesis causes minor nutritive damage since long bones derive their vascular supply mainly from the medullary cavity. In this way a primary stable and loadable connection is established, which is a prerequisite for permanent anchorage of the implant through new bone formation. After experiments in 12 dogs bioceramic endoprostheses were implanted in a total of 40 human patients using this technique of extracortical attachment (12 hip joints, 24 proximal humeri, 4 special constructions). Thirty-six of these implants were stable after observation periods ranging from one to 49 months. A stable anchorage of the prostheses to the pre-existing bone through new bone formation could be demonstrated histologically. The above preliminary results show that bioceramic endoprostheses can be "incorporated" in the skeleton and possibly also withstand the functional stresses.

Adult↗
PubMed1978

[The cup osteosynthesis, a stable osteosynthesis of mandibular fractures with metal cups and bone cement (Kallokryl K)].

The author describes a method for the stable osteosynthesis of mandibular fractures, for which five different steel-cups are fabricated. The cup is filled with fresh mixed cold-curing polymethylmethacrylate and pressed to the fragments. After polymerisation the stable osteosynthesis is arised. The complete healing of the bone in 40 cases demonstrated the successful clinical use.

Bone Cements↗
PubMed1982

The efficiency of the Sudan-III-staining to identify wear particles of pmma-bone cement in tissue after total endoprostheses.

On the basis of the newly-formed capsular tissue of 80 cemented (Weber-Huggler, Müller-Charnley) and uncemented (ceramic/ceramic/titanium) total hip endoprostheses which had to be reoperated on because of aseptic loosening, the efficiency of the Sudan-III-staining reported in literature to identify polymethylmethacrylate (PMMA) bone cement particles is investigated, because the quantity as well as quality of the various wear products is discussed as possible factors of prostheses loosening. PMMA-, polyethylene and polyester particles show definite sudanophilia and orange-red coloration in the Sudan-III-stained frozen sections, so that only very large wear products utilizing the knowledge of the materials of the artificial joints used can be recognized by their forms, whereas the wear stored in the macrophages cannot be identified. Thus, Sudan-III-staining is not suitable for guaranteeing identification and determination of the amount of PMMA-wear.

Azo Compounds↗
PubMedDate not supplied

[Improving fiber adhesion by surface oxidation in carbon fiber reinforced bone cement].

The mechanical superiority of carbon fiber reinforced PMMA containing additional apatite was shown previously. For further improvement these carbon fibers were now submitted to a superficial oxidation treatment by HNO3. A closer contact between the carbon fibers and PMMA and even trabeculae-like adhesions were detected by Scanning Electron Microscopy. The fatigue strength of the carbon fiber reinforced bone cement could be increased at 17% by this oxidation treatment. This increase, however, is less than that observed in the case of other fiber reinforced composites. Most likely this is caused by the pronounced polymerisation contraction of PMMA. Further improvement of the adhesion of the fibers to cement may be achieved by different oxidation techniques, further extraction of foreign substances or graft polymerization of the carbon fibers by PMMA or other polymers.

Adhesiveness↗