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PubMed2003

Use of prepolymerized cement spacers to augment the femoral component in revision total knee arthroplasty: a clinical outcome report and laboratory experiment.

A technique for revision total knee arthroplasty managing posterior femoral condylar bone loss with prepolymerized polymethyl methacrylate cement spacers as augments to the femoral component is described in 10 consecutive cases. The maximum follow-up time is 63 months. This method allows for maintenance of the posterior joint line, which in turn facilitates appropriate flexion-extension gap balancing. The cement spacers are inexpensive compared with metal augments. An experimental study confirms that the cement spacers produce a chemical and physical bond with fresh cement. This eliminates the risk of particulate debris production between the cement augment and the fixation cement. Although the cement spacers have been produced to match one manufacturer's implants, they could be applied to other knee systems.

Arthroplasty, Replacement, Knee↗
PubMed1992

Revision arthroplasty facilitated by ultrasonic tool cement removal. An evaluation of whole bone strength in a canine model.

Ultrasonic driven tools have been developed to facilitate the removal of bone cement during revision arthroplasty. The effect on whole bone strength of cement removal by ultrasonic tools was examined in a canine femur model. Paired, fresh-frozen canine femora were divided into two groups. In group A, one femur from each pair was subjected to cement extraction with ultrasonic tools. In group B, one femur from each pair was subjected to manual cement extraction. Contralateral femora from each pair served as controls to determine the strength of intact femora. Torsional fractures were produced using a servocontrolled hydraulic testing machine (Minneapolis Testing System, Minneapolis, MN). Maximum torque, maximum angle, and energy capacity to failure were determined. Results were recorded as a reduction in percent value of the tested specimen versus the contralateral control. When comparing femora with cement removal by ultrasonic tools to the contralateral control femur, there were no statistical differences in ultimate torque (P = .83), maximum angle (P = .89), and energy capacity (P = .74) by analysis of variance. In addition, there were no significant differences between the group with ultrasonic tool cement removal and the group with manual tool removal. The authors conclude that in this canine model, removal of cement with ultrasonically driven tools has no adverse effects on whole bone strength.

Animals↗
PubMed1999

Safe removal of massive intrapelvic cement using ultrasonic instruments.

The extraction of massive intrapelvic deposits of cement in revision total hip arthroplasty presents the surgeon with a philosophical dilemma and a technical challenge. The cement is difficult to remove because of the disparity between the size of the cement mass and the defect in the acetabulum. In addition, the cement mass lies close to major intrapelvic organs, and the use of force applied with sharp cement-removing instruments poses a danger to these structures. We report on the ultrasonic technique of cement removal used to extract a massive intrapelvic cement deposit safely.

Aged↗
PubMed1999

The effect of delayed light exposure on bond strength: light-cured resin-reinforced glass ionomer cement vs light-cured resin.

Under clinical situations, the intervals between material mixing and light exposure during bracket bonding using light-cured resin-reinforced glass ionomer cement may vary for each individual bracket. This study evaluates the bond strength of light-cured resin-reinforced glass ionomer cement subjected to various time intervals between material mixing and subsequent light exposure. This investigation was conducted in two parts. The first part consisted of measuring the enamel surface temperature to define the conditions under which the second part of the study was carried out. One hundred fifteen subjects, 63 males and 52 females, participated in this study. The over-all mean temperature as measured with a noncontact infrared thermometer was 31.9 degrees C. The second part of this study assessed tensile and shear bond strengths of light-cured resin-reinforced glass ionomer cement subjected to immediate light exposure (time interval, 5 minutes) and bond strengths subjected to light exposure at 10, 20, and 40 minutes after material mixing. Light-cured resin-reinforced glass ionomer cement was then compared with light-cured composite resin. Mean tensile and shear bond strengths of light-cured resin-reinforced glass ionomer cement exposed after 40 minutes were 4.5 MPa and 20.5 MPa, respectively. This represented a reduction of approximately 20% when compared with the 5-minute group. Scheffé test showed no statistically significant differences between any two time intervals. Mean bond strengths of the light-cured resin decreased with time. Tensile and shear bond strengths of light-cured resin indicated high statistical significance within groups across time. It could therefore be concluded that the bond strength of light-cured resin-reinforced glass ionomer cement was not affected by the timing of visible light exposure; whereas, the bond strength of light-cured resin decreased as time intervals increased. Light-cured resin-reinforced glass ionomer cement may thus serve as an advantageous alternative to composite resin for bracket bonding.

Adolescent↗
PubMed2003

How to determine the permeability for cement infiltration of osteoporotic cancellous bone.

Cement augmentation is an emerging surgical procedure in which bone cement is used to infiltrate and reinforce osteoporotic vertebrae. Although this infiltration procedure has been widely applied, it is performed empirically and little is known about the flow characteristics of cement during the injection process. We present a theoretical and experimental approach to investigate the intertrabecular bone permeability during the infiltration procedure. The cement permeability was considered to be dependent on time, bone porosity, and cement viscosity in our analysis. In order to determine the time-dependent permeability, ten cancellous bone cores were harvested from osteoporotic vertebrae, infiltrated with acrylic cement at a constant flow rate, and the pressure drop across the cores during the infiltration was measured. The viscosity dependence of the permeability was determined based on published experimental data. The theoretical model for the permeability as a function of bone porosity and time was then fit to the testing data. Our findings suggest that the intertrabecular bone permeability depends strongly on time. For instance, the initial permeability (60.89 mm(4)/N(*)s) reduced to approximately 63% of its original value within 18 seconds. This study is the first to analyze cement flow through osteoporotic bone. The theoretical and experimental models provided in this paper are generic. Thus, they can be used to systematically study and optimize the infiltration process for clinical practice.

Aged↗
PubMed1998

Epidural application of ionomeric cement implants. Experimental and clinical results.

During setting and hardening, the hybrid bone substitute ionomeric cement (Ionocem) achieves a stable and durable bond with the apatite of the adjacent bone without interpository soft tissue. Fluid contact during setting results in the release of aluminium ions which may reach critical levels as high as 3000 micrograms/l. On epidural application it is, therefore, essential to prevent cement constituents from gaining access to the intradural space. After the cement has hardened, the presence of aluminium is demonstrable in the adjacent bone to a maximum depth of 20 microns (EDX microanalysis). In rabbits, epidural placement of freshly mixed cement causes slight thickening of the dura. There is reason to believe that human dura, with a thickness 10 times greater, is impermeable to components of the cement. After epidural application of the freshly mixed cement in the frontobasal and laterobasal regions and at the skull cap and petrous apex, 76 patients in all have been followed for up to 6.5 years. During this period no complications have arisen and functional (and cosmetic) results are promising. The availability of preformed implants (Ionoroc, Ionocast) permitted the peridural placement of minimal quantities of freshly mixed cement. These implants were fixed to localized sites on the adjacent calvarial bone by use of Ionocem. Notwithstanding the stringent manufacturer guidelines, there have been reports in the literature that during the vulnerable stage of setting neurotoxic aluminium ions were released into the dural space with a fatal outcome in two cases. In view of potential intradural complications, such as may occur in case of dural leaks, it was considered that further application of the material adjacent to the dura was no longer warranted. The production of Ionocem was discontinued in May 1995.

Aluminum Silicates↗
PubMed2004

The effect of surface treatment of hydroxyapatite on the properties of a bioactive bone cement.

Bioactive bone cements based on a paste-paste system for orthopaedic applications have been developed. They consist of hydroxyapatite (HA) filler particles in a methacrylate matrix comprising urethane dimethacrylate (UDMA) and triethylene glycol dimethacrylate (TEGDMA). To improve the interface between inorganic filler and organic matrix the HA particles were subjected to two different surface treatment methods, using polyacrylic acid (PAA) and gamma-methacryloxypropyltrimethoxy silane (gammaMPS). The aim of the present study was to determine the influence of surface treatment on the mechanical properties, namely compressive strength (CS), diametral tensile strength (DTS) and three-point flexural strength (FS) of the cements and the effect of ageing in simulated body fluid (SBF). Comparing the mechanical properties of the two cements after fabrication, the gammaMPS-HA cement showed higher strength values for all tests conducted (CS = 185+/-19.6 MPa, DTS = 27+/-2.5 MPa, FS=50.2+/-4.9 MPa), whereas PAA-HA containing cement had strength values around 20% lower. However, poly(acrylic acid) surface treatment was found to be more effective in improving the interface, and PAA-HA cements maintained their mechanical properties after immersion in SBF whereas gammaMPS-HA cement showed a reduction in strength values post ageing. From the results of this study, it is concluded that PAA treatment of the HA filler is a viable alternative to silanation with gammaMPS which may provide increased durability in aqueous environments.

Acrylic Resins↗
PubMed2004

Mechanical characterisation of a bone defect model filled with ceramic cements.

Ceramic bone substitute materials are often used to fill defects in comminuted articular fractures. In an in vivo study [1], calcium phosphate cements have been injected into highly loaded slot defects in the proximal tibial metaphysis. During healing, cracks were formed mostly in the proximal anterior aspect of the implanted cement and wedge-like gaps formed between the tibial plateau and the cement. Mechanical ex vivo tests were done to investigate the mechanical competence of the bone cement in such a defect situation. Entirely filled defects were loaded with up to 4.5 kN until they failed. Cyclic loading of the proximal tibiae caused micro fragmentation of the cement after 1000 cycles at 1.5-2.0 kN load. This aspect was comparable to cement fragmentation observed in vivo. Large defects in highly loaded areas should therefore additionally be stabilised with metallic implants. The ceramic cement can only be used as a filler material, which can be replaced by new bone upon resorption.

Animals↗
PubMed2002

Injectable calcium phosphate cement as a filler for bone defects around oral implants: an experimental study in goats.

The aim of this study was to evaluate the clinical applicability and biological behavior of a newly developed injectable calcium phosphate (Ca-P) cement as bone filler for gaps around oral implants. Twenty-four step-like implants, creating gaps of 1 and 2 mm, were inserted into the trabecular bone of the medial femoral condyles of six goats. Four different situations were tested: (1) implant + gaps; (2) implant + gaps, but covered with a polylactic acid membrane; (3) implant + gaps that were filled with Ca-P cement; and (4) implant + gaps that were filled with Ca-P cement and covered with a membrane. All implants were left in place for 12 weeks. Histological and quantitative histomorphometrical measurements demonstrated that implants + gaps had generally poor bone contact at the implant base. Furthermore, fibrous encapsulation was observed in the gap part. In contrast, the presence of a membrane promoted bone ingrowth into the gap and also the bone contact at the implant base. Injection of Ca-P cement resulted in an almost complete filling of the gaps around the implant. The cement surface was completely covered by bone. Active resorption and remodeling of cement particles was observed, suggesting a pattern of slow resorption associated with full replacement with newly formed bone. Additional use of a membrane did not result in adjunctive benefits. Bone-to-implant contact at the implant base was comparable with the implants provided only with a membrane. In conclusion, the Ca-P cement used here showed excellent clinical handling properties combined with a superior bone behavior. On the other hand, the degradation rate of the material was still very slow. This current characteristic can hamper the final clinical applicability of the material as gap filler for periimplant or periodontal defects.

Animals↗
PubMed2000

Fluoride ion diffusion from a glass-ionomer cement.

The aims of this study were to observe the release of fluoride ions (F-) from GC-Fuji Lining-LC(R) glass-ionomer cement, to assess the diffusion process, and to measure fluoride diffusivity (D) in the set cement. Specimens of various dimensions and shapes, ranging from discs to cylindrical rods, were fabricated for both open and embedded modes of testing. In the open mode studies, specimens with different surface to volume ratios were selected and immersed in 37 degrees C distilled water. In the embedded mode studies, only one diametral surface of the rod-shaped specimens of different lengths and diameters was exposed. F- concentration was measured using a fluoride electrode. The storage solution was analysed at predetermined intervals hourly, daily, and weekly (up to 10 weeks). Immediately after each sampling, the old storage solution was discarded and replaced with new distilled water. F- release from the set cements was detectable (0.4-3.8 ppm, varied with sample geometry), even after a 10-week sampling interval. F- release was greater in ground set cements (0.37 ppm/mg powder) than in control samples of unmixed powder (0.01 ppm/mg powder) immersed for 1 h. Two mechanisms for F- release were proposed. One was short-term and involved rapid dissolution from the cement surface. The other was more gradual and resulted in the sustained diffusion of ions through the bulk cement, which can be modelled by applying a mathematical technique known as separation of variables to Fick's Second Law of Diffusion. The mean D of F- in embedded set cements of glass-ionomer was (1.4+/-0.5)x10-11 cm2/s, with higher apparent D observed in open mode samples [(7.6+/-1.4)x10-11 cm2/s].

Diffusion↗
PubMed2003

The interaction of glass-ionomer cements containing vinylphosphonic acid with water and aqueous lactic acid.

A glass-ionomer cement containing an acrylic acid/vinyl phosphonic acid copolymer, has been investigated for its interaction with water and with aqueous lactic acid and the results compared with those from conventional glass-ionomers based on polyacrylic acid. Cylindrical specimens (12 mm high x 6 mm diameter) were placed in 8 cm3 of aqueous lactic acid (20 mmol dm(-3); pH 2.7) for 1 week, at the end of which the pH was determined. Each specimen was then placed in a fresh 8 cm3 volume of lactic acid and the pH determined after a further week. This procedure was continued for a total of 13 weeks for each specimen. Experiments were also carried out on similar specimens exposed to 8 cm3 of water for 1 week only. Further experiments were carried out in which discs of cement were exposed to thin films (0.15 mm) of lactic acid at pH 4.5, with pH values determined at 30 s, 1, 2, 5 and 10 min. After 1 week, cements had changed the pH of the lactic acid to a mean value of 3.63 (SD 0.08) while in weeks 2-13 they changed it to a mean value of 3.31 (SD 0.11). After 1 week in aqueous lactic acid the cements had gained mass by a mean of 1.26% (SD 0.59%) compared with 1.22% (SD 0.14%) in water. After 13 weeks in lactic acid, cements had lost a mean of 2.83% (SD 0.74%) in mass. Thin films of aqueous lactic acid changed from pH 4.5-5.1 at 30 s and to a steady value of 5.6 (SD 0.3) between 2 and 10 min. These results were similar to those for conventional glass-ionomer cements based on carboxylic acid polymers. Hence, it was concluded that the presence of the vinylphosphonic acid units made no significant difference to the interaction of cements with aqueous solutions.

Glass Ionomer Cements↗
PubMed2000

Radiopacity and fatigue characterization of a novel acrylic bone cement with sodium fluoride.

Acrylic bone cement must provide good radiographic visibility and good long-term mechanical resistance in joint replacements. A new formulation of cement with 6% barium sulfate and 6% sodium fluoride was developed (Fluoride Bone Cement). Barium sulfate is a necessary addition to allow radiographic visibility although it reduces the mechanical strength of the material. Sodium fluoride promotes bone formation. However, its effect on the mechanical behavior is currently unknown while its influence on radiopacity can only be roughly estimated. The aim of this investigation was to establish if the new formulation would be suitable for clinical trials. In this respect, a mechanical (fatigue test) and radiographic (optical density measurements on x-ray films) characterization was performed on a typical commercially available cement with barium sulfate added and on the Fluoride Bone Cement. It was demonstrated that the fluoride cement has a (marginally) superior fatigue strength and comparable radiopacity to commercial radiopaque cements.

Arthroplasty, Replacement↗
PubMedDate not supplied

The effects of femoral stem and neck length on cement strains in a canine total hip replacement model.

OBJECTIVE: To determine the effects of femoral prosthesis stem length and head size on cement strains in a canine hip replacement system. STUDY DESIGN: An in vitro experimental model. SAMPLE POPULATION: (1) Three standard and 3 1-cm shortened femoral implants with +3 femoral heads. (2) Two standard implants with +0, +3, and +6 femoral heads. METHODS: Femoral stems were embedded in polymethylmethacrylate cement. A uniaxial proximodistal-oriented strain gauge was applied to the cement on the medial and lateral aspects of the construct 1.5 cm, 6.0 cm and 7.0 cm distal to the collar. Each construct with a +3 femoral head was mounted in a materials testing system. An axial compressive load (0-200 N) was applied to the femoral head and cement strains were recorded. Additionally, 2 standard length constructs were also tested with +0 and +6 femoral heads. The effects of stem length and neck length on cement strains were assessed with analysis of variance. RESULTS: Strains increased at all locations with increasing loads for all constructs. Shorter implants had higher strains by 152% and 171%, lateral (P =.003) and medial (P =.0025) to the stem tip. No significant strain differences were noted, at any strain gauge location, between different neck lengths (P values ranged from.20 to.67). CONCLUSIONS: Although a shorter implant stem has a potential to improve implant fit, it led to significantly higher cement strains that may increase the risk for aseptic loosening. Changes in femoral neck length did not significantly affect cement strains under the conditions tested. CLINICAL RELEVANCE: Shortening of the femoral stem currently cannot be recommended in canine total hip replacement. The existing use of variable neck lengths likely does not increase the risk of failure of the femoral stem.

Animals↗
PubMedDate not supplied

[Effect of a rasp surface on cement penetration in paired cadaver femurs].

AIM: The purpose of this investigation was to study two different broach surface designs with regard to cement penetration into human cancellous bone. METHODS: In a cadaver study 15 paired human cadaver femora were prepared using broaches of identical geometry but different surface characteristics. All left femora were prepared using chipped toothed broaches, all right femora using diamond shaped broaches. Cancellous bone was irrigated with 1 liter pulsed lavage. The specimens were imbedded in specially designed pots. Bone cement was applied in a retrograde manner and subjected to a standard pressure protocol with a constant force of 3000 N. Radiographs were taken and horizontal sections were obtained at predefined levels using a diamond saw. Microradiographs were taken and analyzed using image analysis to assess cement penetration into cancellous bone. RESULTS: Pressure curves recorded during cement pressurisation were comparable. The microradiographic evaluation revealed no significant morphometric differences in the different groups with regard to cement penetration into cancellous bone. These findings were similar in all sections obtained. CONCLUSIONS: A standardized model was developed allowing comparison of cement penetration into cancellous bone depending on bone preparation. In the presence of pulsed lavage there is no significant influence of broach surface characteristics on cement penetration into cancellous bone of the upper end of the femur.

Bone Cements↗
PubMedDate not supplied

[Acute tissue toxicity of PMMA bone cements].

AIM: Local toxic reactions are one possible reason for fibrous tissue formation at the interface between bone and PMMA bone cement. Most of the numerous in vitro studies have shown severe cytotoxicity of bone cements and their components. However, in vivo investigations of the local tissue toxicity of bone cements have so far seldom been performed. METHODS: The in-vivo hens-egg chorion-allantoic-membrane test (HET-CAM), a well established replacement procedure for experiments with higher vertebrates, is used for the testing of potentially toxic solid and fluid substances. It was performed with PMMA bone cements, their components and their monomer extracts to measure in vivo biocompatibility. RESULTS: We showed that local toxic tissue reactions occurred, especially at the beginning of the processing phase of PMMA bone cements. We also proved that certain components of PMMA bone cements have poor tissue compatibility and sometimes cause severe local tissue changes. CONCLUSIONS: In the development of PMMA bone cements and when drafting the recommendations for their use, attention should be paid to their biocompatibility as well as their mechanical properties.

Animal Testing Alternatives↗
PubMed1998

[Long-term outcome after reconstruction of the cranial base with ionomer cement].

BACKGROUND: Congenital, posttraumatic, inflammatory or tumours skull base lesions with CSF leakage require reconstruction to mechanically stabilize the CNS and to securely seal the CSF space. PATIENTS AND METHODS: Ionomeric cement was used from 1988 until 1994 in 44 patients for skull base reconstruction at the Department of Otolaryngology-Head and Neck Surgery, University of Würzburg. Thirty-five patients were reexamined. The longest follow-up time was 8 years. The program for the present follow-up study comprised a general ENT and neurological examination as well as CT scans of the skull base, MRI tomography of the CNS, and the determination of the aluminium plasma concentration. RESULTS: None of the patients reexamined presented with complaints. Neurological examinations and MRI tomography in all patients did not reveal any pathological finding related to ionomeric cement application. Aluminium plasma concentrations in patients who received ionomeric cement implantations were not significantly elevated when compared to controls. General ENT examinations and CT scans in thirty-two patients demonstrated regular postoperative findings. The cement at the anterior skull base was not covered completely by mucosa in three patients. In one these cases, CT scans revealed dislocation of the ionomeric cement so that revision surgery was performed for removal. None of the patients to date presented with a CSF leak. CONCLUSION: Long-term results of the present study show that ionomeric cement is a suitable material for closure of osseous skull base lesions to permanently seal the CSF space. These results, however, can only be obtained when handling and application of the material is adequate. Unfortunately, the production of ionomeric cement has been stopped since 1995 following four cases of aluminium encephalopathy reported in the literature.

Adult↗
PubMedDate not supplied

[Modified intracorporeal lithotripsy for cement removal in hip prosthesis exchange operations--experimental principles].

INTRODUCTION: Particularly problematic in total hip revision arthroplasty is the cement removal out of the depth of the femoral canal; it is also costly in time and effort. The extracorporal shock wave lithotripsy proved to be an unsuitable method. With the present paper we proved experimentally a newly developed endoscopically controlled modified intracorporal lithotripter (Swiss Orthoclast) for the removal of bone cement. METHODS: We tested the efficiency on standardized cement specimens of different manufacturers in vitro. We compared both conventional removing techniques with mallet and chisel and a pneumatically powered chisel with formalin fixed human femora. During these experiments we measured the intrafemoral pressure distally to the cement layer. RESULTS: We achieved a high energy (max. 450 mJ) and a very effective fragmentation of the cement (40 mg fragments calculated on the single impulse of 350 mJ). The endoscopic control ensures a safe control of the cement removal even in the depth of the femoral canal. No bone damage occurred macroscopically and radiologically. No heat or toxic products developed. Using the Swiss Orthoclast the intrafemoral pressure was the lowest possible (7 mbar). Even with hammer and chisel or the pneumatically powered chisel the pressure was too low (max. 55 mbar with mallet and chisel) to cause a fat embolic syndrome. CONCLUSION: As a result of these experiments we started with clinical trials (with permission of the Ethic commission) to evaluate the practicability of the modified intracorporal lithotripter (Swiss Orthoclast) for cement removal.

Arthroscopes↗
PubMed2000

Gentamicin release from polymethylmethacrylate bone cements and Staphylococcus aureus biofilm formation.

We measured the formation of a Staphylococcus aureus biofilm in vitro on unloaded and gentamicin-loaded bone cements (CMW3 and Palacos R) and related the formation to antibiotic release rates. All experiments were done in triplicate. Microbial growth on gentamicin-loaded cements occurred despite the release of antibiotic. Biofilm formation on gentamicin loaded CMW3 bone cement was one fourth to one fifth less than on the unloaded bone cement, while biofilm formation on Palacos R bone cement was not significantly affected by antibiotic loading. More gentamicin was released from CMW3 (79 mg) than from Palacos R (70 mg), but the percentage gentamicin released after one week relative to the total amount incorporated was significantly lower for CMW3 (4.7%) than for Palacos R (8.4%). After one day, subinhibitory concentrations of antibiotics were eluted from the cements. We concluded that antibiotic-loaded bone cement does not necessarily inhibit the formation of an infectious biofilm in vitro.

Anti-Bacterial Agents↗