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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↗
PubMedDate not supplied

Experimental cranioplasty and skeletal augmentation using an alpha-tricalcium phosphate/dicalcium phosphate dibasic/tetracalcium phosphate monoxide cement: a preliminary short-term experiment in rabbits.

Calcium phosphate cement consisting of alpha-tricalcium phosphate (alpha-TCP), dicalcium phosphate dibasic (DCPD) and tetracalcium phosphate monoxide (TeCP) was implanted into surgically created full-thickness defects in the cranial bone (bone defect experiment) and directly onto the cranial bone under the periosteum (augmentation experiment). Three months after the implantation, the implants were retrieved with the surrounding tissues and studied histologically and micrographically to evaluate if the cement can be used as a cranioplasty and skeletal augmentation material. In the bone defect experiment, successful reconstruction of the defect was seen in 8 out of 12 specimens. Four specimens, where bleeding control was difficult at the time of implantation, showed partial loss of the cement. Histological and microradiographic studies of the successfully implanted cement revealed that new bone surrounded the implant nearly completely and united directly with the cement surface. In the augmentation experiment, the augmented area maintained the hemispherical shape and was connected tightly with the host bone. Histology and microradiography demonstrated that new bone formation was seen in the gap between the cement and the host bone, and on the outer surface (periosteum side) of the cement at the edge of the implant. From this preliminary short-term study, it could be concluded that the cement is a promising material for cranioplasty and skeletal augmentation with indications that it has good osteoconductivity.

Animals↗
PubMed2001

Reinforcement effect of short glass fibers with CaO- P(2)O(5) -SiO(2) -Al(2)O(3) glass on strength of glass-ionomer cement.

OBJECTIVES: A high strength glass-ionomer (not resin-modified) cement was developed using short fibers of CaO--P(2)O(5)--SiO(2)--Al(2)O(3) (CPSA) glass. The purpose of this study was to clarify the effect of the CPSA short fibers contained in the flexural strength of the glass-ionomer cement. METHOD: The 40 mass% short fibers of CPSA glass were added to the powder of commercial glass-ionomer cement. Beam specimens of set cement (25 x 2 x 2 mm) were prepared for measuring the flexural strength (FS). The specimens of set commercial glass-ionomer cement (GI) were used for comparison with glass ionomer cement with CPSA (FRGI). Half of all specimens were thermocycled in water for 60s of dwell time at 4 and 60 degrees C for 2500, 5000, and 10,000 cycles. The other specimens were stored in water at 37 degrees C as a control. The measurements were statistically analyzed using ANOVA. RESULTS: The initial FS of FRGI was 18.1 and that of GI was 7.7 MPa. After thermocycling, the mean FS ranged from 19.3 to 26.3 MPa and 9.8 to 11.1 MPa for FRGI and GI, respectively. After storage in water, the mean FS of FRGI and GI ranged from 20.4 to 25.9 MPa and 9.4 to 10.1 MPa, respectively. CONCLUSION: These findings suggested that glass-ionomer cement reinforced with CPSA short fibers maintains a higher strength than the conventional cement after aging.

Analysis of Variance↗
PubMed1995

In vivo effect of pressurization of polymethyl methacrylate bone-cement. Biomechanical and histologic analysis.

Sixteen goats underwent total hip arthroplasty, half with pressurized and half with unpressurized bone-cement. The animals underwent hemiarthroplasty of the contralateral hip immediately prior to sacrifice 6 weeks later. Samples were tested for interface strength and evaluated histologically. Pressurization of polymethyl methylacrylate improves the strength of the bone-cement interface in vivo, as well as in vitro. There is a regional variation in the strength of the bone-cement interface both in vivo and in vitro. The regional variation in the in vivo model is at least in part due to a biologic effect. Membranes forming at the bone-cement interface are usually fibrous and incomplete, allowing direct cement-to-bone contact. Membranes appear to be involved in the remodeling of bone. Polymethyl methacrylate causes significant necrosis of the cortex, with ensuing resorption of the cortical bone. There is a small, statistically insignificant trend toward increased resorption and decreased bone formation with pressurized cement. The amount of necrosis appears to be similar with pressurized and nonpressurized cement. Bone remodels to fill defects in the cement mantle.

Animals↗
PubMed1993

Effect of an ultrasonic device on temperatures generated in bone and on bone-cement structure.

Cement removal during revision arthroplasty can be a tedious, time-consuming process. The usual methods of removing cement include high-speed drills, chisels, saws and reamers, which are often associated with fracture and/or perforation of the femoral shaft. Ultrasound has been used in dentistry to remove plaque and in ophthalmology to remove cataracts and is now applied to cement removal in orthopaedic surgery. There is little data available on the effect of ultrasound on temperatures generated in bone and on its effects on the structure of bone-cement. A cement mantle was constructed in the intramedullary canal in each of six 10 cm lengths of human cadaver femora. A temperature probe was then inserted into predrilled holes and temperatures generated by the ultrasonic device were recorded under a variety of conditions. In addition, a cement cylinder was microscopically evaluated after an ultrasonic tool had been inserted. Temperatures generated by the ultrasonic tool in cadaver bone were no higher than previously reported temperatures of 140 degrees C generated by high-speed drills. Furthermore, temperatures at the bone-cement interface never exceeded 60 degrees C when saline irrigation was used in conjunction with the ultrasonic tools, and were below 40 degrees C 1 minute after deactivation of the device. Microscopic examination shows that ultrasound produced local changes in the structure of bone-cement converting it from a microscopically spherical interlocked material to one that appears homogeneous and granular.

Bone Cements↗
PubMed1996

Cost of implanting a cemented versus cementless femoral stem.

Fifty stratified unselected cases of primary uncomplicated total hip arthroplasty performed at the total joint service of a university teaching hospital were examined. In 25 cases, the femoral stem was implanted with cement, and in the other 25, a cementless stem was implanted. For cemented stems, third-generation cement technique was used, including centrifugation. The average cost to the hospital for a cementless stem was $900 greater than for a cemented stem. The total cost to the hospital for accessories used to achieve modern cement technique was over $700. The operative time for implanting a cemented stem averaged 20 minutes longer, which resulted in an additional operating time charge of $270 and an additional anesthesia charge of $100. When these charges are added to the cost of cement and accessories, the actual cost to the hospital for implanting a modern cemented stem was greater than for a corresponding cementless stem.

Bone Cements↗
PubMed1993

The evaluation of dual cement resins in orthodontic bonding.

Dual-cement resins are composite resins that are both light activated and chemically cured. They can be cured completely with a visible light source or by the catalyst and base reaction of the material. With the control of setting time, dual cements appear to offer clinicians advantages in orthodontic bonding. The purposes of the present research are to compare various dual cements in regard to orthodontic bonding and to evaluate them in relation to currently used chemically cured and light-cured composite resins for bonding stainless steel mesh-backed orthodontic brackets. Seven currently available orthodontic bonding systems (three light cured and four chemically cured) and three dual cements were evaluated. Each of the 10 groups contained 15 noncarious mandibular incisors. Mandibular incisor brackets were bonded to the teeth in accordance with the manufacturer's recommendation. After bonding, the teeth were stored for 5 days in water at 37 degrees C. An Instron machine (Instron Corp., Canton, Mass.) was used to test samples. All samples were compared with Concise orthodontic bonding composite (3M, St. Paul, Minn.). The results of this investigation show that it is possible to bond solid, mesh-backed metal orthodontic brackets to teeth with a dual cement. The shear bond strengths of the dual cements, as tested in the laboratory, should be adequate to withstand normal orthodontic forces. Increased control of the setting time of the dual cements will allow the clinician more time to correctly position brackets and to remove excess resin before curing. In addition, the clinician can be assured of complete polymerization with the chemical properties of the dual cement resins.

Analysis of Variance↗
PubMed1999

Raman microspectrometry studies of brushite cement: in vivo evolution in a sheep model.

Calcium phosphate hydraulic cements are promising synthetic bone grafting materials. Brushite-based cements were implanted for 6 and 12 months in the distal condyle of sheep femur, and their in vivo evolution was investigated by Raman microspectrometry. This new technique can probe small volumes in the cubic micrometer range. Its resolution allows a very fine analysis of crystalline changes in calcium phosphate mixtures at the microscopic level. First, Raman spectra of pure brushite, monetite, and beta-tricalcium phosphate (beta-TCP) were recorded, in order to set a data base for the basic components of brushite cements. These spectra show significant differences in the vibration mode v1 for the phosphate ion (988 and 878 cm(-1) for brushite, 988 and 900 cm(-1) for monetite, 968 and 948 cm(-1) for beta-TCP). These differences are strong enough as to allow the qualitative and quantitative analysis of these crystalline phases in the cement. Implanted sheep femur samples were harvested after 24 and 52 weeks post-op, and prepared for Raman analysis in the form of 1-mm-thick sections. Implants at 24 weeks show a core of residual cement isolated from the surrounding bone by fibroconnective tissue. No trace of brushite was detected by micro-Raman analysis in this area, but instead, a mixture of beta-TCP and Type-B carbonated apatite, the latter being very close in composition and structure to the mineral fraction of normal bone in the vicinity of the implant. Implants recovered after 52 weeks show a decrease of the bone/residual cement perimeter, whereas new trabeculations are formed in the implanted zone; the small amounts of residual cement still present are substantially transformed into Type-B carbonated apatite containing small amounts of proteins. In the same area, some beta-TCP particles are also detected showing that, contrary to brushite, the excess beta-TCP originally present in the cement is not completely metabolized. In the implanted zone already converted into trabecular bone, Raman microspectrometry shows the characteristic spectrum of normal bone.

Animals↗
PubMed1999

Influence of polymeric additives on the mechanical properties of alpha-tricalcium phosphate cement.

Recently, great attention has been paid to calcium phosphate cements, because of their advantages in comparison with conventional calcium phosphate bioceramics employed for bone repairing, regarding in situ handling, and shaping abilities. Nevertheless, the calcium phosphate cements exhibit relatively low mechanical strength. The aim of this work was the improvement of the compressive strength of alpha-tricalcium phosphate-based cement. The hydraulic setting reaction of this system produces a calcium-deficient hydroxyapatite phase suitable for bone repairing: alpha-Ca3(PO4)2 + H2O --> Ca9(HPO4)(PO4)5OH. Mechanical strength can be improved using technological solutions developed for other applications, such as Portland cement and dual-setting glass-ionomers, by using polymeric additives. The additives used in this work were sodium alginate, sodium polyacrylate, and an in situ polymerization system resulting in a polyacrylamide crosslinked hydrogel. Parameters evaluated were setting time, compressive strength before and after immersion in simulated body fluid, density, porosity, crystalline phases, and microstructure. Sodium alginate and sodium polyacrylate were deleterious to both setting time and mechanical strength. When the in situ polymerization system was added, two setting reactions progressed in parallel: the conventional hydraulic reaction and the copolymerization of acrylamide and crosslinking water-soluble monomers. The initial and final setting times of the "dual-setting" cement were 9 and 35 min, respectively, and they can be regulated varying the initiator, catalyst, and monomers concentrations. The initial compressive strength of the dual-setting cement (6.8 MPa at 0 h, and 15.2 MPa at 24 h) is higher than that of unmodified cement. The major crystalline phase after setting is hydroxyapatite. The dual-setting cement seems to be suitable for clinical applications in bone repairing and remodeling.

Acrylic Resins↗
PubMed2000

Fracture and fatigue properties of acrylic bone cement: the effects of mixing method, sterilization treatment, and molecular weight.

The purpose of this study was to characterize the relative and combined effects of sterilization, molecular weight, and mixing method on the fracture and fatigue performance of acrylic bone cement. Palacos R brand bone cement powder was sterilized using ethylene oxide gas (EtO) or gamma irradiation. Nonsterile material was used as a control. Molecular weights of the bone-cement powders and cured cements were measured using gel permeation chromatography. Hand and vacuum mixing were employed to mold single edge-notched bend specimens for fracture toughness testing. Molded dog-bone specimens were used for fatigue tests. Electron microscopy was used to study fracture mechanisms. Analysis of variance and Student t-tests were used to compare fracture and fatigue performance between sterilization and mixing groups. Our results indicate that vacuum mixing improved significantly the fracture and fatigue resistance (P<.05, P<.07) over hand mixing in radiation-sterilized and EtO-sterilized groups. In vacuum-mixed cement, the degradation in molecular weight resulting from gamma irradiation decreased fracture resistance significantly when compared with EtO sterilization and control (P<.05). A corresponding decrease in fatigue resistance was observed in the cement that was degraded severely by a radiation dose of 10 MRad (P<.05). In contrast, EtO sterilization did not result in a significantly different fracture resistance when compared with unsterilized controls for vacuum-mixed cement (P>.1). For hand-mixed cement, fracture and fatigue resistance appeared to be independent of sterilization method. This independence is believed to be the result of higher porosity that compromised the mechanical properties and obscures any effect of sterilization. Our results indicate that a combination of nonionizing sterilization and vacuum mixing resulted in the best mechanical performance and is most likely to contribute to enhanced longevity in vivo.

Animals↗
PubMedDate not supplied

[Thromboembolic complications related to the use of bone cement in hip arthroplasty--pathogenesis and prophylaxis].

INTRODUCTION: Cemented total hip arthroplasty (THA) has to be considered a high-risk procedure with respect to cardiovascular complications. The insertion of cement and prosthesis may lead to intravasation of fat and bone marrow into the circulation. METHODS: This article represents a review on the relevant literature about thromboembolic complications associated with the use of bone cement in THA. RESULTS/DISCUSSION: The method of canal preparation and lavage is of paramount importance to reduce the potential embolic load. Additionally, thorough cleaning of the intramedullary cavity (using jet lavage) improves the cement penetration into the bone and increases the shear strength of the bone-cement interface. Modern cementing techniques include the use of high pulsatile lavage, a cement restrictor and cement pressurization. With the application of these techniques a sufficient drainage of the medullary canal should be guaranteed to minimise the risk for thromboembolic complications. During the insertion of cementless implants the intravasation of embolic material seems to be less, but it is likewise possible to have a thromboembolic complication during cementless THA. However, it is not justified as a consequence to use the thromboembolic risk as the main indication for implant choice, in particular as the overall risk of a serious fatal complication is low.

Arthroplasty, Replacement, Hip↗
PubMed2002

[Results after rebuilding the ossicular chain using the autogenous incus, ionomer-cement-and titanium implants (tympanoplasty type III)].

BACKGROUND: A defective ossicular chain can reliably be reconstructed with standardized techniques using e. g. modern alloplastic materials. The comparison of clinical and functional results have proved its worth. Prospective clinical trial as well as collecting and evaluating relevant intraoperative and postoperative findings may be helpful to find the appropriate bone substitute in each case when rebuilding middle ear structures. METHOD: In 354 middle ears (332 patients) the defective or destroyed ossicular chain was rebuilt with the carefully trimmed autogenous incus (n = 83), with ionomer-cement implants (n = 100) and with titanium prostheses (n = 171). The follow-up of the earmicroscopic findings and middle ear function extended over a period of 1.5 years postoperatively on an average (min. 3 months, max. 6 years). The modified otologic record form named "Würzburger Ohrbogen" was used for preoperative and operative data, the "Ohrnachsorgebuch" for the postoperative follow-up. RESULTS: Using incus the air bone gap was improved up to 15 dB in the main speech area. Thus the average remaining conduction deficit was less than 10 dB. The "taking" of ionomer based cement prostheses and titanium prostheses was equally good. The cement implants showed a tendency to protrusion (n = 3), 2 titanium implants were extruded. The air bone gap decreased about 10 to 35 dB using titanium total prosthesis and about 15 to 20 dB using ionomer-cement total prosthesis. The remaining air bone gap with titanium implants was slightly less than with the ionomer-cement PORP (10-15 dB). The air bone gap using the titanium TORP was diminished in a reach of 10 to 35 dB, with the ionomer cement prosthesis between 15 to 20 dB. The remaining gap in the main speech area was slightly favorable to titanium (less than 15 dB) compared with the ionomer-cement TORP. Comparing higher frequencies the air bone gap of titanium was recognizable due to its light weight, but less impressive than expected. Revision surgery (n = 50) has to be performed by reason of cholesteatoma (n = 9), adhesive process (n = 8), dislocation of alloplastic prostheses (n = 8) and because of proposed "second look" (n = 14). CONCLUSIONS: Compared with other materials autogenous implants used for reconstruction of the incus have proved their value, however a deterioration of the sound transmission may develop in the long run. The middle ear compatibility of ionomer-cement implants is similar to titanium implants. The functional results of the titanium implants seem to be slightly superior.

Adolescent↗
PubMed1996

[Ionomer cement in cochlear implant surgery--applications and long-term outcome].

Over the last ten years about 850 cochlear implant operations were performed at the ENT department of Hannover Medizinische Hochschule. In most cases, intracochlear nucleus implants were used. For about two years the intracochlear Clarion device has also been used in 150 adults and children. For several years we have used ionomeric cement (lonocap, supplied by lonos, Seefeld/Germany) to fix the electrode array in the region of the posterior wall and the facial recess. Previously, the implant package was fixed by ionomeric cement. To evaluate the outcome of cement application, we conducted a prospective study of our implant patients during the period from 1991 to 1993. During regular reexamination over a period of two years postoperatively in 244 patients (122 male and 122 female patients, average age 17.6 years), we did not observe any complication related to the cement. Nearly all revision cases (n = 8) showed a stable contact between electrode array, bone, and cement. With increasing experience, we reduced the cement application and fixed the package with vicryl sutures in a precisely drilled bony bed. Contact of the cement with neural and cerebral structures should be avoided. In our experience ionomeric cement is a helpful tool in cochlear implant surgery with long-term stability and no rejection reactions.

Adolescent↗
PubMedDate not supplied

[Anatomic basis of the cemented femur shaft. A comparative study of straight and anatomic design].

AIM: The purpose of this study was to compare cemented anatomic stems with cemented straight stems regarding cement mantle and stem orientation in the medullary canal. METHODS: In a cadaver study, 10 anatomic SP II stems and 10 MEM straight stems were implanted in paired human femora using a standardised modern cementing technique. In one group the femoral canal was prepared using conventional broaches, in the other group diamond hollow-cutters were used. Standardised horizontal cuts were made and evaluated regarding stem orientation and cement mantle using digitised image analysis. RESULTS: All SP II stems in the "diamond group" showed good stem centralisation without cement mantle defects. In the "broach group" all diaphyseal cancellous bone had been removed and only 3/5 stems were well orientated. No reproducible stem centralisation was achieved with the straight stems. All stems showed an oblique orientation from antero-proximally to postero-distally with direct stem to bone contact. The variation from the optimal stem alignment along the canal axis showed a mean deviation of 3.1 mm in the anatomic stem group and 10 mm in the straight stem group. The canal preparation using broaches showed frequent fractures of the cancellous bone and debris interposition despite the use of jet-lavage. Most of the cancellous bone in the diaphysis had been destroyed. CONCLUSIONS: Anatomic stems show a better stem centralisation and a more even cement mantle than straight MEM stems. The use of high volume straight stems carries a significant risk of producing cement mantle defects. Diamond instruments are less traumatic than broaches for femoral canal preservation and help to preserve diaphyseal cancellous bone, which improves stem self-centralisation.

Biomechanical Phenomena↗
PubMed2001

Curing potential of dual-polymerizable resin cements in simulated clinical situations.

STATEMENT OF PROBLEM: Little is known about the ability of dual-polymerizable resin cements to polymerize when they are used in various clinical scenarios. PURPOSE: This study was conducted to determine whether any of 6 commercially available dual-polymerizable resin cements should be classified as an "all-purpose" resin cement. MATERIAL AND METHODS: . Chemical conversion values (C=C converted to C-C, or the extent of the curing reaction) of 6 commercially available dual-polymerizable resin cements were determined with infrared spectroscopy in 5 clinically relevant scenarios. Scenarios included: using each cement in a dual-polymerizable mode (mixing of 2 pastes); light polymerizing curing through Mylar sheets (dual-Mylar), which served as the control; light polymerizing through 3-mm porcelain (dual-3 mm); and no exposure to light (dual-no light). The single-component light-polymerizable product was also tested as follows: exposed directly through Mylar (light-Mylar) or exposed through 3 mm of porcelain (light-3 mm). Results. For each product, dual-Mylar treatment yielded the highest conversion value of all treatments (control for each product). For all products, dual-3 mm conversion was at least 97% of control and equivalent to control, with the exception of Lute-It!. Dual-no light conversion was less than control treatment but at least 86% of control for all products except for Variolink II (62% of control). For all products in dual-no light mode, except Choice and Variolink II, conversion was at least equal to the light-Mylar values. Only 1 product (Variolink II) did not demonstrate increased conversion values for dual-Mylar compared with light-Mylar treatments. For most other products (Calibra, Insure, and Lute-It!), conversion values for light-3 mm were significantly less than for light-Mylar. Conversion values for Nexus, Choice, and Variolink II were equivalent between light-Mylar and light-3 mm treatments. CONCLUSION: The choice of a dual-polymerizable cement should be based on its intended use because not all products polymerize adequately in every clinical situation. Although no cement met the stated criteria for an "all-purpose" cement, those tested did produce a range of product-specific results.

Analysis of Variance↗
PubMed2001

Curing potential of dual-polymerizable resin cements in simulated clinical situations.

STATEMENT OF PROBLEM: Little is known about the ability of dual-polymerizable resin cements to polymerize when they are used in various clinical scenarios. Purpose. This study was conducted to determine whether any of 6 commercially available dual-polymerizable resin cements should be classified as an "all-purpose" resin cement. MATERIAL AND METHODS: Chemical conversion values (C=C converted to C-C, or the extent of the curing reaction) of 6 commercially available dual-polymerizable resin cements were determined with infrared spectroscopy in 5 clinically relevant scenarios. Scenarios included: using each cement in a dual-polymerizable mode (mixing of 2 pastes); light polymerizing curing through Mylar sheets (dual-Mylar), which served as the control; light polymerizing through 3-mm porcelain (dual-3 mm); and no exposure to light (dual-no light). The single-component light-polymerizable product was also tested as follows: exposed directly through Mylar (light-Mylar) or exposed through 3 mm of porcelain (light-3 mm). RESULTS: For each product, dual-Mylar treatment yielded the highest conversion value of all treatments (control for each product). For all products, dual-3 mm conversion was at least 97% of control and equivalent to control, with the exception of Lute-It!. Dual-no light conversion was less than control treatment but at least 86% of control for all products except for Variolink II (62% of control). For all products in dual-no light mode, except Choice and Variolink II, conversion was at least equal to the light-Mylar values. Only 1 product (Variolink II) did not demonstrate increased conversion values for dual-Mylar compared with light-Mylar treatments. For most other products (Calibra, Insure, and Lute-It!), conversion values for light-3 mm were significantly less than for light-Mylar. Conversion values for Nexus, Choice, and Variolink II were equivalent between light-Mylar and light-3 mm treatments. CONCLUSION: The choice of a dual-polymerizable cement should be based on its intended use because not all products polymerize adequately in every clinical situation. Although no cement met the stated criteria for an "all-purpose" cement, those tested did produce a range of product-specific results.

Analysis of Variance↗
PubMed2001

Bone cement with reduced proportion of monomer in total hip arthroplasty: preclinical evaluation and randomized study of 47 cases with 5 years' follow-up.

Bone cement with reduced amount of monomer and low curing temperature may improve implant fixation due to reduced toxicity. We analyzed the mechanical, chemical and thermal properties of such a cement (Cemex Rx) using Palacos R as control. The in vivo performance of the 2 cements was also evaluated in a prospective randomized study of 47 hips, where either of the cement types was used to fixate Lubinus SP2 prostheses with the stem made of titanium alloy. Cemex Rx had a reduced tensile strength, probably because this cement was manually mixed, as recommended by the manufacturer. A standardized labor tory test showed lower curing temperature for Cemex, but measurements at 37 degrees and with prechilled Palacos R and Cemex Rx, as in clinical work, showed no difference. In the clinical study radiostereometric measurements of cup and stem migration showed similar values in the 2 groups up to 5 years after the operation. The cement mantle was stable in both groups, but the stems migrated similarly inside the cement mantle regardless of the type of cement used. Proximal wear was low (0.04-0.05 mm/year) and tended to be lower in the Cemex group (p = 0.02). Aluminum and vanadium levels in serum increased 5 years after the operation, but no difference was noted between the 2 groups. Collagen markers (PICP, ICTP) showed similar increases in bone turnover 6 weeks and 6 months after operation in both groups.

Aged↗
PubMed2001

No effect of methacrylate-based bone cement CMW 1 on the plasmatic phase of coagulation, red blood cells and endothelial cells in vitro.

The compatibility of a methacrylate-based bone cement (CMW 1, DePuy International Ltd, England) used for the fixation of joint prostheses was evaluated on plasma, an erythrocyte suspension and cultured human endothelial cells. The extract of the cement was tested, following 1 hour and 7 days of curing. After the contact in vitro of the extract with plasma, activated partial thromboplastin time, antithrombin III, thrombin-antithrombin complexes and fibrin degradation products were assayed. Hemolytic activity was tested by adding the cement extracts to a suspension of erythrocytes. After 4 hours of incubation at 37 degrees C, the hemoglobin concentration was determined on the supernatants by the colorimetric method. The effect of the cement on tissue factor and thrombomodulin production was evaluated on human umbilical vein endothelial cell cultures. Tissue factor was determined in cell lysates by enzyme immunoassay, following 4 hours' incubation of cultures with the cement extract. Thrombomodulin was assayed in cell lysates by enzyme immuno assay, after 24 hours' incubation with the cement extract. The response to all trans-retinoic acid (ATRA) was tested. The cement caused no significant modifications of the coagulation tests, had no hemolytic activity, did not determine tissue factor production and did not modify thrombomodulin, compared to the negative control. The response to stimulation with ATRA was similar to that of the negative control. We conclude that the cement extract does not affect the plasmatic phase of coagulation, has no effect on erythrocytes, does not induce the expression of procoagulant activity by endothelial cells and does not impair their antithrombotic property, within the limits of the tests performed.

Blood Coagulation↗