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Cement-implant interface gaps explain the poor results of CMW3 for femoral stem fixation: A cadaver study of migration, fatigue and mantle morphology.

BACKGROUND: The Norwegian Arthroplasty Register reported that CMW3 cement performed poorly for femoral stem fixation. METHODS: We implanted collared, satin-finished stems (Ra = 0.35 microm) into cadaver femora using CMW3 and with Simplex as control. Cement mantle function was quantified by stem migration after 300,000 cycles of "stair climbing". Cement cracks and interface gaps were quantified in transverse sections. RESULTS: The variances of the CMW3 migrations were substantially higher than for the control (p < 0.001): subsidence for CMW3: -32 (SD 42) microm, and for Simplex: -7 (SD 9) microm (p = 0.2); retroversion for CMW3: 0.60 degrees (SD 0.25), and for Simplex: 0.37 degrees (SD 0.04) (p = 0.08). Crack length-densities were similar. CMW3 had significantly more non-apposed stem/cement interface: 52% (SD 17) versus 33% (SD 8) (p = 0.04). Migrations could be predicted by the fraction of non-apposed stem/cement interface (retroversion: R(2)=0.80, p < 0.001; subsidence: R(2) = 0.46, p = 0.02) but not by cement cracks or non-apposed cement-bone interface. INTERPRETATION: We found that increased stem/cement non-apposition resulted in increased stem migration. Early migration is known to correlate with risk of revision. Thus, the higher stem-revision risk for CMW3 cement reported by the Norwegian Arthroplasty Register may have been due to inferior and variable stem/cement apposition.

Arthroplasty, Replacement, Hip↗

Different loss of BMD using uncemented press-fit and whole polyethylene cups fixed with cement: repeated DXA studies in 96 hips randomized to 3 types of fixation.

BACKGROUND: In cemented THA, aseptic loosening of the cup is more common than loosening of the stem, while periprosthetic osteolysis of the socket resulting in difficult reconstruction problems has emerged as the most significant problem with cementless cup fixation. PATIENTS AND METHODS: 90 patients (96 hips) scheduled for THA were stratified in three groups according to the method of fixation of the acetabular component: acrylic bone cement with fluoride (Cemex-F), porous-coated press-fit cup with ceramic coating (Trilogy, uncemented) and acrylic cement with gentamicin (Palacos). All patients received the Spectron EF stem. Acetabular bone mineral density was measured with dual-energy X-ray absorptiometry (DXA) 1 week postoperatively, and after 12 and 24 months. The periprosthetic BMD was evaluated in 5 ROIs positioned around the acetabular component. RESULTS: In the uncemented sockets, the BMD had decreased proximally and medially to the cup after 2 years. The difference was significant in the proximal region as compared to the control group (Palacos). No difference was noted between the 2 groups with cemented components after 2 years. Stepwise linear regression analysis showed that loss of periprosthetic BMD in the proximal high-pressure region after 2 years increased with higher postoperative BMD and when the uncemented design had been used. INTERPRETATION: Contrary to previous studies of cemented stems, the use of fluoride cement did not influence the periprosthetic BMD 2 years after the examination. Increased loss of BMD with use of uncemented press-fit cups in the region in which osteolytic lesions are commonly found suggests that stress shielding may initiate the development of this complication. Longer follow-up will, however, be necessary to substantiate this hypothesis.

Absorptiometry, Photon↗

Stair climbing is more detrimental to the cement in hip replacement than walking.

Stair climbing may be detrimental to cemented total hip arthroplasties, because it subjects the reconstruction to high torsional loads. The current study investigated how stair climbing contributes to damage accumulation in the cement around a femoral stem compared with walking, taking into account the different frequencies of these activities during patient functioning. In finite element analyses, the damage accumulation process in the cement mantle around a Lubinus SPII stem was simulated for three different loading histories: (1) isolated walking, representative for patients who climb no stairs; (2) isolated stair climbing; (3) alternating walking and stair climbing in a ratio of nine to one cycles, representative for patients who climb many stairs. Relative to isolated walking, isolated stair climbing increased the amount of cement damage by a factor of 6. Inclusion of 10% stair climbing cycles in the loading history increased the amount of damage by 47% relative to isolated walking. Stair climbing produced damage along the entire stem, whereas isolated walking produced damage proximomedially and around the tip only. This study confirmed that stair climbing is more risky for failure of cemented femoral stems than walking. A few stair climbing cycles during daily patient functioning increases the amount of cement damage dramatically.

Biomechanical Phenomena↗

Glenoid cementing may generate sufficient heat to endanger the surrounding bone.

Glenoid loosening is a common complication of shoulder arthroplasty. One possible cause is bone necrosis from the exothermic reaction of polymethylmethacrylate. The relationship between the amount of cement used in glenoid fixation and the risk of thermal injury to bone was examined. Glenoid arthroplasty was done on 17 fresh cadaver scapulas, recording the amount of cement used. The bone surface temperature during cement curing was measured using infrared thermography. Using these data and published thresholds for thermal necrosis, the frontal plane area of bone that would be at risk for necrosis in vivo was estimated. The average weight of cement implanted was 5.35 g (2.65-8.08 g). The maximum temperature recorded averaged 64.7 degree C (48.2 degree-76.8 degree C). The area of bone at risk correlated with the amount of cement used. This study indicates that potentially dangerous amounts of heat may be generated during cementing of glenoid components.

Arthroplasty, Replacement↗

Leakage of amalgam, composite, and Super-EBA, compared with a new retrofill material: bone cement.

An in vitro leakage study was conducted to compare the root-end sealing ability of amalgam with cavity varnish, composite with dentin bonding agent, and Super-EBA with a new retrofill material: bone cement. Eighty single-rooted teeth were instrumented and obturated with gutta percha, resected and retroprepared. The teeth were then randomly divided into 4 groups of 20, with each group receiving one of the previously mentioned retrofill materials. The bone cement group was either etched or unetched. The teeth were immersed in silver nitrate and developer for leakage assessment. The teeth were grooved and split longitudinally to measure leakage. Statistical analysis showed that amalgam leaked significantly less than Super-EBA and unetched bone cement; composite leaked significantly less than Super-EBA. Amalgam was not statistically different from composite or etched bone cement. No significant difference between composite and both bone cements was noted, nor between both bone cements and Super-EBA.

Bone Cements↗

The apical seal of root canal sealing cements using a radionuclide detection technique.

The aim of this study was to evaluate the apical seal obtained with various root canal sealing cements using a new method based on the use of a radionuclide and an external detection technique. A total of 150 maxillary incisors and canines, which had been kept in saline solution, were used. The root canals were instrumented with a stepback technique and circumferential filing. Six experimental groups and two control groups were randomly formed. Each experimental group was obturated by a lateral condensation technique with gutta-percha points and a different sealing cement (two based on zinc oxide-eugenol cement, two based on resins and two on calcium hydroxide); the positive control used gutta-percha without sealing cement, while in the negative control the apex was covered with nail varnish, leaving the root canal empty. The apical leakage was measured using an external detection technique after submerging the root apices in a solution containing the radioisotope metastable 99Tc. No leakage was observed in the negative control group. There was a large difference between the leakage observed in the positive control group and the experimental groups. The best seal was obtained using Sealapex cement, which differed significantly from AH26, Tubli-Seal and Diaket; there was no significant difference between the latter. The poorest results were obtained with Endomethasone and CRCS; there was a significant difference between these and the previous three sealing cements.

Administration, Topical↗

Biological tests of a silicophosphate cement.

The biological compatibility of a silicophosphate cement (Fluoro-Thin) and a zinc phosphate cement (de Trey's Improved) has been assessed in in vitro (cell culture) and in vivo (monkey teeth) tests. In the in vitro tests both materials were toxic when freshly prepared. In experiments with prolonged cell-material contact time, with set specimens of the materials, the zinc phosphate cement appeared to be non-toxic, whereas the silicophosphate cement was clearly toxic. The in vivo experiments confirmed that a possible pulp reaction cauded by zinc phosphate cement is of a mild nature. The silicophosphate cement, however, cauded a moderate or severe reaction in the pulp after 8 days of observation, and there was chronic inflammation in most teeth after 36 or 72 days. It was concluded, therefore, that Fluoro-Thin should not be used as a luting agent or for restorative purposes in direct contact with vital dentine.

Animals↗

Leaching from glass ionomer cements.

This study compared the electrical conductivities, pH and leached ion (F-, Ca, Al, Si) concentrations in supernatant liquids obtained from four glassionomer cements, a buffered ionomer cement, a polycarboxylate cement and a zinc phosphate cement, at three different levels of settings. The result indicated that the measured parameters are highest for the unset condition of cements and decreases as the set condition is approached, except for pH, which shows the opposite trend. Two pulp sensitive glassionomer cements, Chem Bond and Ketac Cem showed high Ca:F ratios as well as high Ca and F concentrations. Further, it is suggested that the cytotoxicity of leached F-, Si, Al and Zn at high concentration and at low pH may induce sensitivity in tooth structure.

Aluminum↗

Release of fluoride from conventional and metal-reinforced glass-ionomer cements.

Fluoride was extracted by 1 or 50 ml deionized water from 0.3 ml samples of two conventional and three metal-reinforced glass-ionomer cements. The fluoride concentration was determined by electrode. It was found that the fluoride concentration around the glass-ionomer cements ranged 2-3 ppm after 15 min and 3-5 ppm after 45 min. The maximum fluoride concentration attained within 24 h varied from 15-21 ppm, while the total amount of fluoride released during 100 days varied from about 2 mg fluoride to 12 mg fluoride per ml glass-ionomer cement. An alloy reinforced cement and its conventional counterpart released the highest amount of fluoride whereas a glass-cermet type released the lowest amount. Within the premises of this study it was concluded that composition and handling of the cements are of importance for the release of fluoride, and that a caries inhibitory fluoride concentration can be established in the surroundings of all of the cements.

Cermet Cements↗

Ceramic inlay movement during polymerization of resin luting cements.

In cavities with no support for inlays, polymerization contraction of the resin cement may move the ceramic inlay axially. The purpose of this study was to determine the velocity and extent of such movement. Cylindrical ceramic inlays were placed in dentin cavities filled with one of four commercially available resin composite cements. An initial standardized 200-microns-thick cement film was created. The movement of the ceramic inlay during polymerization of one of the resin cements was measured by a dial gauge. The velocity of the inlay movement decreased exponentially with time and with a velocity constant of 0.09 min-1. The majority of the movement occurred within the first 12 min after photopolymerization and probably continued for several days, reaching an estimated value of 5.8 microns. After 1-2 d of water storage, 1-2-microns contraction gaps at the cavity floors were observed microscopically for every cement used. It is concluded that in cavities without support for the inlay, about 2/3 of the resin cement contraction results in movement of the inlay and about 1/3 results in formation of gaps at the cavity floors.

Analysis of Variance↗

The tensile strength of the union between various glass ionomer cements and various composite resins.

Increasing use is being made of the glass ionomer cements as a lining for composite resin restorations, particularly when restoring posterior teeth. It has been suggested that it is possible to obtain a mechanical union between the two materials by etching the surface of the cement. This paper discusses the result of testing a broad variety of combinations of different glass ionomer cements and composite resins that have been reported on previously, and suggests that a number of factors need to be taken into account if the optimum physical properties are to be achieved from the union. There would appear to be four main factors which dictate the final strength of the union. The tensile strength of the cement itself is of primary importance and it seems the wettability of the resin bonding agent is also significant. When using some of the less heavily filled composite resins, the stresses set up by the setting contraction of the resin may be too great and, finally, the more heavily filled composite resins for restoration of posterior teeth often prove difficult to adapt to the underlying cement. With careful clinical handling, the so-called 'sandwich' technique is very useful. However, not all combinations of glass ionomer cement and composite resin will unite with sufficient strength to be successful clinically.

Chemical Phenomena↗

Predicting the failure response of cement-bone constructs using a non-linear fracture mechanics approach.

A non-linear fracture mechanics approach was used to predict the failure response of complex cement-bone constructs. A series of eight mechanical tests with a combination of tensile and shear loading along the cement-bone interface was performed. Each experiment was modeled using the finite element method with non-linear constitutive models at the cement-bone interface. Interface constitutive parameters were assigned based on the quantity of bone interdigitated with the cement. There was a strong correlation (r2 = 0.80) between experimentally measured and finite element predicted ultimate loads. The average error in predicted ultimate load was 23.9 percent. In comparison to the ultimate load predictions, correlations and errors for total energy to failure (r2 = 0.24, avg. error = 38.2 percent) and displacement at 50 percent of the ultimate load (r2 = 0.27, avg. error = 52.2 percent) were poor The results indicate that the non-linear constitutive laws could be useful in predicting the initiation and progression of interface failure of cemented bone-implant systems. However improvements in the estimation of post-yield interface properties from the quantity of bone interdigitated with cement are needed to enhance predictions of the overall failure response.

Bone Cements↗

Mechanism for erosion of glass-ionomer cements in an acidic buffer solution.

In order to clarify the mechanism for erosion of glass-ionomer cements, we immersed two commercial luting cements in an acidic buffer solution under various conditions. The amounts of F, Al, Si, and Ca eluted from the cement were (1) in proportion to the square root of immersion time, (2) unrelated to shape or volume of the sample, (3) dependent on its surface area, and (4) not affected by shaking of the solution. It was concluded that the dissolution was controlled by the diffusion of those species in the cement matrix, which was influenced by the structure of the matrix and the concentration of H+ ion at the cement surface. The unreacted glass particles near the cement surface were dissolved by the long immersion, and many pores were left in the surface region.

Acids↗

In vitro studies on the potential for pulpal cytotoxicity of glass-ionomer cements.

Elution samples of glass-ionomer cement were prepared in sterile tissue culture medium either by direct contact between the fluid and standard cement samples or through a layer of human dentin, and then tested for toxicity to cultured mouse fibroblasts (L929). The directly-prepared eluates of the cements were highly cytotoxic, but those prepared through dentin were of either limited or no cytotoxicity. The degree of toxicity of some directly-prepared eluates was reduced by adjustment of the pH to neutrality. It was apparent that dentin reduced the potential for cytotoxicity of glass-ionomer cements to a large degree. Proposed mechanisms for the reduction were limited availability of water at the dentin-cement interface and thus limited dissolution of components, buffering of acid components of the cements by dentin, or other chemical interactions with dentin.

Adolescent↗

Effect of interface conditions between ultrahigh molecular weight polyethylene and polymethyl methacrylate bone cement on the mechanical behaviour of total shoulder arthroplasty.

The aim of this study was to investigate the effect of the interface condition between polymethyl methacrylate (PMMA) bone cement and the ultrahigh molecular weight (UHMWPE) glenoid component on cement stresses and glenoid component tilting in a finite element (FE) model. The background of this research is that most FE models assume bonding between the PMMA bone cement and the UHMWPE component, although it is very doubtful that this bonding is present. An FE model of a cemented glenoid component was developed and a joint compression force and subluxation force of 725 and 350 N respectively were applied. The maximal principal stresses in the cement layer ranged between 21.30 and 32.18 MPa. Glenoid component tilting ranged between 0.943 degrees and 0.513 degrees. It was found that the interface condition has a large effect on the maximal principal stresses and glenoid component tilting. Whether adhesion between the UHMWPE component and PMMA bone cement occurs is unknown beforehand and, as a result, design validation using the FE technique should be carried out both by using contact elements in combination with a coefficient of friction as well as by a full bonding at this interface.

Adhesiveness↗

The cement mantle in femoral impaction allografting. A comparison of three systems from four centres.

An analysis of the cement mantle obtained with the Exeter impaction allografting system at one centre showed that it was either deficient or absent in almost 47% of Gruen zones. We therefore examined the mantle obtained using this system at another hospital and compared the results with those from the CPT and Harris Precoat Systems at other centres. The surgical indications for the procedure and the patient details were broadly similar in all four hospitals. There was some variation in the frequency of use of cortical strut allografts, cerclage wires and wire mesh to supplement the impaction allograft. Analysis of the cement mantles showed that when uncertain Gruen zones were excluded, the incidence of zones with areas of absence or deficiency of the cement was 47% and 50%, respectively, for the two centres using the Exeter system, 21% for the CPT system and 18% for the Harris Precoat system. We measured the difference in size between the proximal allograft impactors and the definitive prosthesis for each system. The Exeter system impactors are shorter than the definitive prosthesis and taper sharply so that the cavity created is inadequate, especially distally. The CPT proximal impactors are considerably longer than the definitive prosthesis and are designed to give a mantle of approximately 2 mm medially and laterally and 1.5 mm anteriorly and posteriorly. The Harris Precoat proximal impactors allow for a mantle with a circumference of 0.75 mm in the smaller sizes and 1 mm in the larger. Many reports link the longevity of a cemented implant to the adequacy of the cement mantle. For this reason, femoral impaction systems require careful design to achieve a cement mantle which is uninterrupted in its length and adequate in its thickness. Our results suggest that some current systems require modification.

Acetabulum↗

Biomechanical evaluation of fixation of intra-articular fractures of the distal part of the radius in cadavera: Kirschner wires compared with calcium-phosphate bone cement.

BACKGROUND: The purpose of this study was to compare the biomechanical efficacy of an injectable calcium-phosphate bone cement (Skeletal Repair System [SRS]) with that of Kirschner wires for the fixation of intraarticular fractures of the distal part of the radius. METHODS: Colles fractures (AO pattern, C2.1) were produced in ten pairs of fresh-frozen human cadaveric radii. One radius from each pair was randomly chosen for stabilization with SRS bone cement. These ten radii were treated with open incision, impaction of loose cancellous bone with use of a Freer elevator, and placement of the SRS bone cement by injection. In the ten control specimens, the fracture was stabilized with use of two horizontal and two oblique Kirschner wires. The specimens were cyclically loaded to a peak load of 200 newtons for 2000 cycles to evaluate the amount of settling, or radial shortening, under conditions simulating postoperative loading with the limb in a cast. Each specimen then was loaded to failure to determine its ultimate strength. RESULTS: The amount of radial shortening was highly variable among the specimens, but it was consistently higher in the Kirschner-wire constructs than in the bone fixed with SRS bone cement within each pair of radii. The range of shortening for all twenty specimens was 0.18 to 4.51 millimeters. The average amount of shortening in the SRS constructs was 50 percent of that in the Kirschner-wire constructs (0.51+/-0.34 compared with 1.01+/-1.23 millimeters; p = 0.015). With the numbers available, no significant difference in ultimate strength was detected between the two fixation groups. CONCLUSIONS: This study showed that fixation of an intra-articular fracture of the distal part of a cadaveric radius with biocompatible calcium-phosphate bone cement produced results that were biomechanically comparable with those produced by fixation with Kirschner wires. However, the constructs that were fixed with calcium-phosphate bone cement demonstrated less shortening under simulated cyclic load-bearing.

Biomechanical Phenomena↗

Charnley total hip arthroplasty with cement. Minimum twenty-five-year follow-up.

BACKGROUND: This report presents the results of the senior author's initial twenty-five-year experience with the use of Charnley total hip arthroplasty with cement. The purpose of this paper was to evaluate the long-term results of total hip arthroplasty. METHODS: Between July 1970 and April 1972, the senior author (R. C. J.) performed 330 Charnley total hip replacements with cement using a hand-packing cement technique in 262 patients. Fifty-one patients (sixty-two hips) who were alive at least twenty-five years post-operatively were evaluated from a clinical standpoint with use of a standard-terminology questionnaire. The average age of this group at the time of surgery was fifty-six years (range, thirty-five to seventy-one years) compared with sixty-five years (range, twenty-one to eighty-nine years) for the entire group. All patients were evaluated for radiographic changes at the time of their most recent follow-up. Of the fifty-one patients (sixty-two hips) who were alive at least twenty-five years postoperatively, thirty-one (thirty-six hips) had a follow-up radiograph made at a minimum of twenty-five years after the surgery. The average duration of radiographic follow-up for the fifty-one patients was 22.7 years (range, two to twenty-seven years). RESULTS: Of the sixty-two hips in the fifty-one patients who were alive at least twenty-five years postoperatively, fourteen (23 percent) had been revised. Three (5 percent) had the revision because of loosening with infection; eleven (18 percent), because of aseptic loosening; and none, because of dislocation. The prevalence of revision due to aseptic loosening of the acetabular component in all 316 hips (excluding those that were lost to follow-up or that were revised for infection or dislocation) was 6 percent (eighteen hips), whereas the prevalence in the fifty-nine hips (excluding the three revised for infection) in the patients who were alive at least twenty-five years after the arthroplasty was 15 percent (nine hips). The prevalence of revision because of aseptic loosening of the femoral component in all 316 hips was 3 percent (nine hips), and the prevalence in the fifty-nine hips in the living patients was 7 percent (four hips). In the group of living patients, osteolysis occurred in Gruen zone 1 or 7 in thirty-three hips and in Gruen zones 2 through 6 in two hips. Ballooning acetabular osteolysis occurred in five hips. Of the 327 hips for which the outcome was known after a minimum of twenty-five years, 295 (90 percent) had retained the original implants until the patient died or until the most recent follow-up examination. Of the sixty-two hips in patients who lived for at least twenty-five years after the surgery, forty-eight (77 percent) had retained the original prosthesis. CONCLUSIONS: Our follow-up study at twenty-five years following Charnley total hip arthroplasty with cement demonstrates the durability of the results of the procedure. These results should provide a means for comparison with the results of newer cementing techniques as well as those associated with newer cemented and cementless hip designs.

Aged↗