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PubMed1996

Stable partial debonding of the cement interfaces indicated by a finite element model of a total hip prosthesis.

A simplified three-dimensional finite element model of the femoral component of a cemented total hip prosthesis was used to investigate whether partial debonding at the stem-cement or bone-cement interfaces propagates in a stable or unstable manner, and to assess the resultant variation of the stresses within the cement layer. The likelihood of unstable debonding under tensile failure mode was assessed both by a conventional monotonic strength criterion and by a fracture mechanics approach that took into account debonding due to fatigue loading. The model predicted that partial debonding at the cement interfaces would be stable and would not precipitate complete debonding. Among the various bonding conditions that were investigated, the maximum tensile stress within the cement layer was least with a small amount of debonding rather than with complete bonding. These results were consistent with clinical observations of nonprogressive or slowly progressive separation at cement interfaces in cemented femoral components that were otherwise well functioning and asymptomatic.

Biomechanical Phenomena↗
PubMed2006

Precooling of the femoral canal enhances shear strength at the cement-prosthesis interface and reduces the polymerization temperature.

Preheating of the femoral stem in total hip arthroplasty improves the cement-prosthesis bond by decreasing the interfacial porosity. The main concern, however, is the potential thermal osteonecrosis because of an increased polymerization temperature. In this study, the effects of femoral canal precooling on the characteristics of the cement-stem interface were evaluated in an experimental model for three test conditions: precooling of the femoral canal, preheating of the stem (44 degrees C), and a control in which stems were inserted at room temperature without thermal manipulation of the implant, cement, or bone. Compared to the control group, precooling of the femoral canal and preheating of the stem had similar effects on the cement-stem interface, with greater interfacial shear strength and a reduced porosity. Femoral canal precooling also produced a lower temperature at the cement-bone interface. No difference was found in the ultimate compressive strength of bone cement for the three preparation conditions. Based on this laboratory model, precooling of the femoral canal could improve shear strength and porosity at the stem-cement interface, minimize thermal injury, and maintain the mechanical strength of the cement.

Arthroplasty, Replacement, Hip↗
PubMed1990

Pathology of the bone-cement interface in loosening of total hip replacement.

The histopathology of the bone-cement interface in nine retrieved hip prostheses is reported. Three cases presented features similar to those observed by Charnley in highly successful implants, and they were classified as stable prostheses, although signs of periprosthetic bone resorption were already present. In this group a macrophagic reaction was evident even in the presence of a stable bone-cement interface, supporting the view that the release of particles by the cement or by the prosthetic components can precede the mechanical instability and be the primary cause of loosening. In six prostheses the connective tissue layer between the cement and the bone was thick and no bone trabecula reached the cement surface. The polymorphous features of this connective membrane probably resulted from instability and movement at the bone-cement and stem-cement interfaces. On the basis of the pathological changes observed in the study, the process of loosening must be far advanced before it is detected on radiographs; it is suggested that scintigraphy is the best noninvasive technique to demonstrate macrophage activation and increased bone remodeling around the cement in the early phases of loosening.

Aged↗
PubMed2003

[Extravertebral cement drainage with occlusion of the extradural venous plexus into the vena cava after vertebrobplasty. Case report and review of the literature].

This paper presents the case report of an 88 year old female who came to hospital suffering from a severe lower back pain. Ten days before, she had undergone a vertebroplasty with injection of cement into lumbar vertebra 3 because of an osteoporotic fracture. This treatment did not result in a reduction of the lower back pain, which was the main reason for the procedure. However, the patient claimed to have increasing pain radiating to her left leg. Furthermore, she suffered from numbness of her left leg. Clinical examination showed a lack of power in this leg according to hip flexion with a degree of 3/5. X-ray examinations showed paravertebral cement particles and led to the suspicion that the paravertebral cement had caused nerve root compression. MRI and CT myelography showed that the cement had drained into the intraspinal, extradural venous plexus (Batson's plexus). The plexus was filled out with cement between L2 and L5 on both sides. There was nearly no cement in the fractured vertebra L3, but cement had also run onto the paravertebral veins up to the vena cava, which was also involved. The cemented veins had led to a stenosis of the neuroforamina L2 and L3 on the left side. The result was compression of left L3 nerve root. After consulting with our vascular surgeons, we decided on a non-operative treatment. We prescribed a lumbar brace as external stabilisation and as an antithrombotic treatment we gave the patient weight adapted low molecular weight heparin.

Aged↗
PubMed2004

[Nanoparticulate silver. A new antimicrobial substance for bone cement].

BACKGROUND: Multiresistant bacteria have become an important problem in prosthetic joint infections. Their frequent resistance against gentamicin, which is commonly used in antibiotic-loaded bone cements, makes a new prophylaxis necessary. METHODS: PMMA-cement was loaded with 1% nanoparticulate silver and its antibacterial activity tested in vitro against gentamicin-resistant MRSE and MRSA strains as well as being compared to the activity of plain and gentamicin-loaded bone cements. A quantitative elution testing was also done to study the potentially cytotoxic effects of NanoSilver cement. RESULTS: Unloaded and PMMA-cement loaded with 2% gentamicin did not exhibit any antibacterial activity against MRSE and MRSA. At 1%, NanoSilver cement completely inhibited the proliferation of MRSA and MRSE. NanoSilver bone cement did not show any significant differences compared to the non-toxic control group. CONCLUSIONS: If these promising in vitro results can be confirmed in vivo, NanoSilver bone cement may be of considerable value in total joint arthroplasty.

Animals↗
PubMed1998

Pharmacokinetics, uses, and limitations of vancomycin-loaded bone cement.

We have studied the mechanical and pharmacokinetic characteristics of an industrially-prepared bone cement containing 3 g of vancomycin per 60 g cement. A low viscosity cement was selected, to increase contact between the antibiotic and the infected surfaces. Resistance of compression (95 mPa) was well above the required standard (70 mPa) and similar to that of other cements with or without gentamicin. The concentrations in blood, urine and bone were measured in mg/l and mg/kg, and compared to the break point (BP) of susceptibility tests, which must be obtained to achieve control of infection. Diffusion tests were conducted in vitro (elution in saline from rods), and in 30 sheep femora implanted with the cement in vivo. In the animal study, bone levels during the first three months were three-fold higher than the BP (i.e., were > or = 12 mg/l) in 92% of specimens from all areas of bone studied and at all times since implantation; they exceeded five times the BP in 56% of specimens and were never lower than twice the BP. The mean level was four times the BP after six months and fell sharply during the next six months. A pharmacokinetic study in ten patients who had a primary total hip arthroplasty with vancomycin-loaded cement as prophylactic antibiotic therapy showed that blood levels were lower than 3 micrograms/ml, i.e., 30 times lower than the toxic threshold (90 micrograms/ml). Vancomycin was undetectable in urine after the tenth day. The levels in drainage fluids were five times the BP after 24 h and equal to it after four days. None of the ten patients treated prophylactically with vancomycin-loaded cement developed evidence of allergy, toxicity, intolerance or loosening during a two year period. No adverse events were recorded in 17 other patients treated with a vancomycin (2 g) plus gentamicin (0.8 g) loaded cement as adjuvant therapy for severe prosthetic infection.

Animals↗
PubMed1998

Ionomeric cement implants in the middle ear of the baboon (Papio ursinus) as a primate model.

Faced with an inadequate supply of autogenous materials, the otologic surgeon may have to utilize various alloplastic materials to reconstruct bony middle ear structures. Allogenic materials have fallen into disfavor clinically because of the possible spread of infections. Implantation of the hybrid bone substitute ionomeric cement in viscous or hardened physical states into the middle ears of a primate animal model was undertaken in order to be able to approximate as closely as possible conditions found clinically. The posterior meatal wall was replaced by freshly mixed ionomeric cement in nine baboons (Papio ursinus). After repositioning the meatal flap, the residual skin defect was left to secondary epithelialization. After removal of the stapes superstructure, incus and malleus head, a columella of hardened ionomeric cement was trimmed to the appropriate size and inserted between the footplate and the malleus handle. In three cases the prosthesis shaft was fixed in position with freshly mixed cement near the footplate. The time of follow-up ranged from 47 to 277 days. Gross sections were obtained without decalcification (using a Zeiss saw microtome) and stained with Giemsa solution. In no instance was there any spontaneous epithelialization of the external meatus, although occasional granulation was seen to develop at the free edge of the flap and subepithelially. Epithelialization of the alloplastic columellae occurred as early as 42 days post-implantation. Over the middle ears reconstructed with the viscous cement, there was growth of a thickened epithelium that partially tended to granulate. On light microscopy, the bony footplate area was found to be unaffected by the cement that had been applied when still fluid. Our findings indicate that reconstruction of the posterior meatal wall with the viscous ionomeric cement can be useful clinically. The material does not become dislocated but, as with all other alloplastic materials, spontaneous overgrowth of the adjacent meatal skin is unlikely to occur. The early epithelialization of the columellae and their middle ear compatibility and biostability give support to the excellent tolerability of the ionomeric cement. At present, complications occurring during otoneurological application of the material necessitated its commercial withdrawal from the market in May 1995.

Animals↗
PubMed1993

Preliminary study of factors affecting the fluoride release from glass-ionomer cements.

A study has been made on the release of fluoride from three glass-ionomer cements. The effect of the maturity of cements at the time of immersion and powder/liquid ratio were examined. It was found that fluoride release from immature cements was dependent on cement and powder/liquid ratio and that the effect was permanent. The effect of cement type and powder/liquid ratio lessened as cements were allowed to mature prior to immersion. It appears that fluoride release was dependent on the strength and maturity of the cement matrix and not fluoride content. It was concluded that the rate of fluoride release would depend largely on clinical factors rather than cement type.

Chemistry, Pharmaceutical↗
PubMed1994

Aluminium release from glass ionomer cements during early water exposure in vitro.

Aluminium is a major constituent of glass ionomer cements. During mixing and setting aluminium is released from the glass into the polyalkeonic acid solution. Part of this aluminium may not combine with the polyalkeonic acid, but may be released from the cement. The aluminium release from auto-cured and light-cured glass ionomer cements during early water exposure was studied. The former cements released more aluminium than the latter. Scanning electron microscopy (SEM) showed extensive loss of polymer matrix for the cements with the highest aluminium release. Insufficient curing of light-cured cements also resulted in loss of matrix. It is suggested that the considerable release of aluminium from glass ionomer cements during early water exposure may explain the reported lack of mineralization of predentin in the pulp beneath glass ionomer cements. This would correspond to the inhibiting effect of aluminium on bone mineralization.

Aluminum↗
PubMed1994

Suboptimal (thin) distal cement mantle thickness as a contributory factor in total hip arthroplasty femoral component failure. A retrospective radiographic analysis favoring distal stem centralization.

One hundred cemented total hip arthroplasties (THAs) were evaluated regarding the potential benefit of THA femoral component distal stem centralization, specifically regarding cement mantle thickness. Factors potentially predictive of femoral component mechanical loosening, both relating (22 factors) and not relating (41 factors) to cement, were analyzed on initial postoperative radiographs. Nine THAs with femoral component mechanical failure (group 1) were compared to (1) 88 non-failed THAs (group 2) and (2) 9 matched-paired, nonfailed THAs (group 3). Significant differences were evident regarding minimum and maximum cement mantle thickness in Gruen zone 5 and combined zones 5/6 (groups 1 vs 2 and groups 1 vs 3), with failed femoral components having thinner cement mantles. Discriminate analysis determined minimum cement mantle thickness in zone 5 to be the factor most predictive of femoral component failure. These data indicate that a suboptimal (thin) cement mantle at the medial diaphysis (Gruen zones 5 and 6) contributed to femoral component mechanical loosening in this THA series. This relationship may not pertain to femoral stems of different materials or cross-sectional characteristics. Many THA systems currently provide for a method of centralization of the femoral component distal stem as a mechanism to ensure an adequate circumferential distal cement mantle. Continued investigation into techniques directed toward centralization of the distal femoral stem is warranted by the findings of this study.

Alloys↗
PubMed2005

Static and fatigue mechanical behavior of bone cement with elevated barium sulfate content for treatment of vertebral compression fractures.

The use of bone cement to treat vertebral compression fractures in a percutaneous manner requires placement of the cement under fluoroscopic image guidance. To enhance visualization of the flow during injection and to monitor and prevent leakage beyond the confines of the vertebral body, the orthopedic community has described increasing the amount of radiopacifier in the bone cement. In this study, static tensile and compressive testing, as well as fully reversed fatigue testing, was performed on three PMMA-based bone cements. Cements tested were SimplexP with 10% barium sulfate (Stryker Orthopedics, Mahwah, NJ) which served as a control; SimplexP with 36% barium sulfate prepared according to the clinical recommendation of Theodorou et al.; and KyphX HV-R with 30% barium sulfate (Kyphon Inc., Sunnyvale, CA). Static tensile and compressive testing was performed in accordance with ASTM F451-99a. Fatigue testing was conducted in accordance with ASTM F2118-01a under fully reversed, +/-10-, +/-15-, and +/-20-MPa stress ranges. Survival analysis was performed using three-parameter Weibull modeling techniques. KyphX HV-R was found to have comparable static mechanical properties and significantly greater fatigue life than either of the two control materials evaluated in the present study. The static tensile and compressive strengths for all three PMMA-based bone cements were found to be an order of magnitude greater than the expected stress levels within a treated vertebral body. The static and fatigue testing data collected in this study indicate that bone cement can be designed with barium sulfate levels sufficiently high to permit fluoroscopic visualization while retaining the overall mechanical profile of a conventional bone cement under typical in vivo loading conditions.

Barium Sulfate↗
PubMed2005

Development of a strontium-containing hydroxyapatite bone cement.

A new route was developed to synthesis a new type of strontium-containing hydroxyapatite (Sr-HAP) bone cement with precursors of tetracalcium phosphate (TTCP), strontium hydrogen phosphate (DSPA), dicalcium phosphate (DCPA), phosphate acid and water. The processing parameters and fundamental properties including pH value, setting time, compressive strength of final hardened body and the cytotoxicity for serial extracts of each cements were investigated. The result shows that the final product of the cement after setting for 24h is nonstoichiometic Sr-containing hydroxyapatite (Ca(10-m-x)Sr(x) square(m)(HPO4)y(PO4)6-y(OH)2-2m square2m, 0<x<1, nSr-HAP) and no other harmful impurities were detected. The pH value of Sr-containing cement pastes approaches to 7.0-7.6 when they are mixed with a ratio of 1:1 of powder to liquid (P/L) in weight. The setting time of the cement pastes is 4-11 min for the initial one and 10-17 min for the final one when the concentration of diluted phosphate is in a range of 0.5-1.0 mol/l. The compressive strengths of the hardened cements with different molar ratios of Sr/(Sr+Ca) after subjected an immersion in simulated body fluid (SBF) increase uniformly from 1 day to 5 days, where they get maximum values, respectively, but then decrease till to 2 weeks. Especially for the CPC-1, with a Sr/(Sr+Ca) molar ratios of 5% in cement powder composition, the largest compressive strength gained at 5 days is 66.57 MPa and the lowest one gained at 2 weeks is 44.75 MPa, which matches the value of human bones and can be expected to use in clinic application in repairing the nonloading sites on account of the positive result of cytotoxicity test of the extracts of Sr-containing calcium phosphate cement (Sr-CPC).

Animals↗
PubMed2005

Biologically mediated resorption of brushite cement in vitro.

A new calcium phosphate cement is reported, which sets to form a matrix consisting of brushite, dicalcium pyrophosphate dihydrate and an amorphous phase following the mixture of beta-tricalcium phosphate with an aqueous pyrophosphoric acid solution. This reactant combination set within a clinically relevant time-frame (approximately 10 min) and exhibited a higher compressive strength (25 MPa) than previously reported brushite cements. The in vitro degradation of the beta-tricalcium phosphate-pyrophosphoric acid cement was tested in both phosphate buffered saline and bovine serum. The pyrophosphate ion containing cement reported here was found not to be hydrolysed to form hydroxyapatite in vitro like beta-tricalcium phosphate-orthophosphoric acid solution cements. This finding is significant since the formation of hydroxyapatite by hydrolysis is thought to retard in vivo degradation of brushite cements. When aged in bovine serum, the cement lost considerably more mass than when aged in phosphate buffered saline, indicating that proteins, most likely phosphatase enzymes played an important role in the degradation. As pyrophosphate ions are thought to be the source of orthophosphate ions during bone mineralisation, this new class of bone cement offers a route to new degradable synthetic bone grafting materials.

Animals↗
PubMed2005

Antibacterial and mechanical properties of bone cement impregnated with chitosan nanoparticles.

Although total joint replacement has become commonplace in recent years, bacterial infection remains a significant complication following this procedure. One approach to reduce the incidence of joint replacement infection is to add antimicrobial agents to the bone cement used to fix the implant. In this in vitro study, we investigated the use of chitosan nanoparticles (CS NP) and quaternary ammonium chitosan derivative nanoparticles (QCS NP) as bactericidal agents in poly(methyl methacrylate) (PMMA) bone cement with and without gentamicin. The antibacterial activity was tested against Staphylococcus aureus (S. aureus) and Staphylococcus epidermidis (S. epidermidis). A 10(3)-fold reduction in the number of viable bacterial cells upon contact with the surface was achievable using QCS NP at a nanoparticle/bone cement weight ratio of 15%. The inhibition of S. aureus and S. epidermidis growth on the surface of the CS NP and QCS NP-loaded bone cements was clearly shown using the LIVE/DEAD Baclight bacterial viability kits and fluorescence microscopy. The CS NP and QCS NP also provided a significant additional bactericidal effect to gentamicin-loaded bone cement. The antibacterial effectiveness remained high even after the modified bone cements had been immersed for 3 weeks in an aqueous medium. No cytotoxic effect of the CS NP- and QCS NP-loaded cements was shown in a mouse fibroblast MTT cytotoxicity assay. Mechanical tests indicated that the addition of the CS and QCS in nanoparticulate form allowed the retention of a significant degree of the bone cement's strength. These results indicate a new promising strategy for combating joint implant infection.

3T3 Cells↗
PubMed2006

Mechanical and histological evaluation of a PMMA-based bone cement modified with gamma-methacryloxypropyltrimethoxysilane and calcium acetate.

Polymethylmethacrylate (PMMA) bone cement is widely used for prosthetic fixation in orthopaedic surgery; however, the interface between bone and cement is a weak zone. We developed a bioactive PMMA cement through modification with gamma-methacryloxypropyltrimethoxysilane (MPS) and calcium acetate. The purpose of this study was to compare the handling, mechanical and histological properties of the modified bone cement with those of the conventional cement. The modified specimens exhibited higher bonding strength between bone and implant. Histological observation and micro-focus X-ray computed tomogram (micro-CT) images showed that the modified cement exhibited osteoconduction, which the conventional PMMA bone cement lacked. The modification was found to be effective in enabling osteoconduction with PMMA bone cement, thus providing stable fixation for a long period after implantation.

Acetates↗
PubMed2005

3D FEA of cemented steel, glass and carbon posts in a maxillary incisor.

OBJECTIVES: A comparative study on the stress distribution in the dentine and cement layer of an endodontically treated maxillary incisor has been carried out by using Finite Element Analysis (FEA). The role of post and cement rigidity on reliability of endodontic restorations is discussed. METHODS: A 3D FEM model (13,272 elements and 15,152 nodes) of a central maxillary incisor is presented. A chewing static force of 10 N was applied at 125 degree angle with the tooth longitudinal axis at the palatal surface of the crown. Steel, carbon and glass fiber posts have been considered. The differences in occlusal load transfer ability when steel, carbon and glass posts, fixed to root canal using luting cements of different elastic moduli (7.0 and 18.7 GPa) are discussed. RESULTS AND SIGNIFICANCE: The more stiff systems (steel and carbon posts) have been evaluated to work against the natural function of the tooth. Maximum Von Mises equivalent stress values ranging from 7.5 (steel) to 5.4 and 3.6 MPa (respectively, for carbon posts fixed with high and low cement moduli) and to 2.2 MPa (either for glass posts fixed with high and low cement moduli) have been observed under a static masticatory load of 10 N. A very stiff post works against the natural function of the tooth creating zones of tension and shear both in the dentine and at the interfaces of the luting cement and the post. Stresses in static loading do not reach material (dentine and cement) failure limits, however, they significantly differ leading to different abilities of the restored systems to sustain fatigue loading. The influence of the cement layer elasticity in redistributing the stresses has been observed to be less relevant as the post flexibility is increased.

Bite Force↗
PubMed2005

Chemical and physical surface and bulk material characterization of white ProRoot MTA and two Portland cements.

OBJECTIVES: The chemical and physical properties of white ProRoot MTA were analyzed in the bulk and at the surface and compared with two common Portland cements types CEM1 and CEM2. METHODS: The main components were analyzed by X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray analysis (EDX), and the minor constituents were identified with inductively coupled plasma optical emission spectroscopy (ICP-OES). Moreover, the setting of the different cements was studied: the chemical composition of the surface of both powder and bound cement was investigated by XPS and the morphological changes were examined by scanning electron microscopy (SEM). RESULTS: In ProRoot MTA, the amount of gypsum is approximately half of that of the Portland cements. ProRoot MTA consists of less toxic heavy metals (Cu, Mn, Sr), less chromophores (Fe3+), and less Al-species, but contains about 2 at % Bi. In contrast to Portland cements, ProRoot MTA contains about 2 at.% Bi. In all three products, the amount of sulfur at the surface in the bound cements was 3 times higher than in the powder, indicating that in terms of the kinetics of the hardening reaction, a sulfate action mechanism prolongs the setting time. The Portland cements are composed of particles with a wide range of size, whereas ProRoot MTA showed a uniform and smaller particle size. SIGNIFICANCE: With regard to chemical and physical surface and bulk properties, ProRoot MTA cannot simply be substituted by the cheaper Portland cement. Both products are similar but not equal and exhibit marked differences.

Aluminum Compounds↗
PubMed2006

Tensile bond strength of dual curing resin-based cements to commercially pure titanium.

OBJECTIVES: The aim of this study was to evaluate the tensile bond strength of dual curing luting resin cements to commercially pure titanium at 10 min and 24h after removal of the oxide layer. METHODS: One hundred and twenty titanium discs were obtained by casting and polishing with silicon carbide papers. The titanium discs were sandblasted with 50 microm aluminum oxide, ultrasonic cleaned and bonded in pairs with the resin-based cements Panavia F and Rely X ARC at 10 min and 24h after the sandblasting. The tensile test was performed with a crosshead speed of 0.5mm/min in an Instron Universal testing machine. RESULTS: The Rely X ARC reached the highest tensile strength value at 24h after sandblasting (18.27 MPa), but there was no statistically significant difference between the two dual curing resin cements for both times tested. All specimens showed a mixture of cohesive fracture in the resin cement and adhesive failure. However, the predominant failure mode for Panavia F was cohesive in resin cement, and the Rely X ARC exhibited a greater proportion of specimens with adhesive failure between the alloy and resin luting cement at 10 min and 24h. SIGNIFICANCE: Both cements had, statistically, the same tensile bond strength. But in the fracture mode analysis, the adhesive predominant fracture mode of Rely X ARC cement indicates a premature clinical adhesive failure. On the other hand, the cohesive predominant fracture mode of Panavia F indicates a longer clinical adhesive bond with titanium.

Adhesiveness↗