Acrylic Cement Research Articles

Evaluating acrylic and glass-ionomer cement strength using the biaxial flexure test

Frequently, bone cement strengths are evaluated from uniaxial tests, such as three- or four-point flexure. Measurement of material strength in this manner may not provide an accurate characterisation of a bone cements true load-bearing capacity. In most orthopaedic applications, there exists a state of biaxial stress and so biaxial strength information is most useful. To address this issue, the biaxial flexure strength of two polymethylmethacrylate orthopaedic (PMMA) bone cements and two glass-ionomer dental cements have been determined. The biaxial strength of orthopaedic bone cements have been compared to the three-point bending strength. Furthermore, the calculated theoretical biaxial strength was compared with a value of biaxial strength utilising the finite element method. For all materials tested the calculated biaxial strength is significantly greater than the three-point bending strength. The biaxial test offers several advantages over three-point bending because it critically explores surface flaws — as it does not matter in which orientation the crack lies. However, it does minimise the volume or surface area investigated and also the edge effect. The difference in strength calculated for the two testing methods can be explained quantitatively in terms of the volume of material under stress. This work has demonstrated that the biaxial flexure test can be used for the testing of orthopaedic bone cements.

Percutaneous coaxial transpedicular biopsy of vertebral body lesions during vertebroplasty.

We evaluated the safety and histological results of percutaneous transpedicular biopsy in patients undergoing vertebroplasty for vertebral collapse. Over a 6 year period, we carried out biopsies in 46 patients who underwent percutaneous injection of acrylic surgical cement for 57 collapsed vertebrae, because the diagnosis was not clearly established on clinical or imaging grounds. All procedures were performed under fluoroscopic guidance via a coaxial bitranspedicular approach used for vertebroplasty. We performed a clinical examination and CT after every procedure and approximately 6 months thereafter. Biopsies contributed to in 55 (96.5%) of the 57 vertebral lesions. Biopsy material was inadequate in one case (1.7%) and one biopsy was a false-negative (1.7%). The accuracy of the histological results was 98.2%, allowing a correct diagnosis in 55 of the 56 procedures. Of the 37 lesions in 28 patients with a history of a tumour, the final diagnosis was osteoporotic collapse in 25 (67.6%), metastasis in nine (24.3%), and myeloma in three (8.1%). The final diagnosis in the 19 lesions in 17 patients without a known tumour was osteoporotic collapse in 12 (63.2%), metastasis in five (26.3%), and amyloidosis in two (10.5%), the latter in one patient. No complications were observed.

The influence of vacuum mixing on methylmethacrylate liberation from acrylic cement powder

Polymethylmethacrylate (PMMA) bone cement is a biomaterial used to anchor prostheses during joint replacement surgery. Residual methylmethacrylate monomer (MMA) may be related with the cytotoxic effect of PMMA. The aim of the present paper was to investigate the effect of two different cement mixing methods: hand stirring at atmospheric pressure and under partial vacuum (0.330 and 0.154 bar) on residual monomer liberation in phosphate buffer saline solution from acrylic cement powder. Residual MMA content was determined by high-performance liquid chromatography. Mathematical models were applied to experimental dissolution data revealing that monomer release was significantly reduced in bone cement powder obtained at 0.154 bar vacuum pressure compared to the other mixing conditions. The kinetic models applied are consistent with a simple diffusion mechanism of the monomer from the polymer matrix.

Design revision of a partially cemented hip stem.

In a previous preclinical study the prototype version of a partially cemented hip stem, cement-locked uncemented (CLU) prosthesis, showed optimal primary stability and moderate stress shielding. However, numerical analysis suggested that the prototype design would induce relatively high stresses in the cement and a significant relative motion between cement and metal. The present study aimed to verify if these problems could be eliminated once the CLU design is improved. The revised design was analysed using a complete finite element model of an implanted human femur. To further strengthen the predictions of the finite element analysis, the cement damage induced by a severe load history was assessed experimentally in synthetic femurs implanted with the improved CLU stem or with a clinically successful fully cemented stem. The modifications made to the CLU stem design did not reduce its good primary stability but decreased the metal-cement relative micromotion. The same load induced stresses in the cement mantle of the improved CLU stem that were significantly lower than those predicted for the prototype design. Although the presence of modelling artefacts produced a highly localized stress peak of 13 MPa. 99 per cent of the cement volume was subjected to a principal tensile stress lower then 4 MPa. These levels of stress compare favourably with the tensile fatigue limit of the acrylic cement used in this study (9.7 MPa). The experimental results further supported these findings. The cemented stem showed a number of cracks per volume unit approximately ten times higher than the partially cemented stem under investigation.

Open wedge tibial osteotomy with acrylic bone cement as bone substitute

We studied the results of 245 valgus producing high tibial osteotomies performed with the use of an opening wedge technique and rigid internal fixation followed by early passive and active motion of the knee. Previous studies have used iliac bone grafts or hemicollastasis held by an external fixator for opening the osteotomy. In our series the opening was obtained by a block of cement interposed in the postero-medial part of the osteotomy. This series confirms that the opening wedge osteotomy allows good accuracy for the correction. Ninety-three percent of the knees had a correction adjusted between 180 and 187° for the hip–knee–ankle angle. Survivorship analysis showed an expected rate of survival, with conversion to a total knee on the end point, of 94% at 5 years, 85% at 10 years and 68% at 15 years. Conversion to a total knee arthroplasty was accomplished without difficulty in the patients who had this procedure done. We recommend opening wedge tibial osteotomy with acrylic cement bone cement as bone substitute, rigid internal fixation, and early motion for patients who undergo high tibial osteotomy.

Gentamicin bone cements: characterisation and release (in vitro and in vivo assays)

Due to the extended use of acrylic bone cements, its necessary to develop improved formulations in order to resolve their many drawbacks. The present work was conducted to make a physical–chemical characterisation of this kind of acrylic cement in order to introduce future changes in the formulations to: (1) improve or at least maintain their mechanical properties; (2) diminish their toxicity, and (3) control the drug release (rate and amount). From the dissolution method we can conclude that the preparation method (with or without pressure) of specimens is not responsible for the erratic release. The cumulative amount of gentamicin released was fitted to a semi-empirical equation to explain the possible release mechanism. The powder size, shape and distribution that could affect several properties of bone cement were studied with the aid of different techniques such as SEM, laser diffraction spectroscopy, and powder X-ray diffraction. From SEM micrographs, it was possible to observe that the surfaces of the specimens were very irregular with numerous small craters that may serve as conduits for eluting the antibiotic. An ‘in vitro’ drug diffusion model is proposed to elucidate the drug release mechanism. Finally an ‘in vivo’ study was performed to evaluate the antibiotic release to the neighbouring bone sites.

Preformed acrylic bone cement spacer loaded with antibiotics: use of two-stage procedure in 10 patients because of infected hips after total replacement.

In 10 patients having deep infection after total hip replacement, we used a two-stage revision procedure involving implantation of a preformed spacer with a cylindrical rod coated with acrylic cement containing antibiotics (Spacer-G). This device, which remained in situ for an average of 5 months, permitted healing of the infection in 8 cases and reimplantation of a new prosthesis (mean follow-up 35 months). During treatment, 1 dislocation occurred. The spacer maintained the gap between both bone segments and allowed a certain degree of joint mobility. Use of Spacer-G improved the quality of life of the patients during treatment and accelerated recovery of function after reimplantation.

Management of the Infected Total Hip Arthroplasty with a Hip Prosthesis of Antibiotic-Loaded Acrylic Cement in Two-Stage Revision

Management of the Infected Total Hip Arthroplasty with a Hip Prosthesis of Antibiotic-Loaded Acrylic Cement in Two-Stage Revision

The PROSTALAC functional spacer in two-stage revision for infected knee replacements

The PROSTALAC functional spacer is made of antibiotic-loaded acrylic cement but has a small metal-on-polythene articular surface. We have used it as an interim spacer in two-stage exchange arthroplasty for infected total knee replacement. PROSTALAC allows continuous rehabilitation between stages as it maintains good alignment and stability of the knee and a reasonable range of movement. It also helps to maintain the soft-tissue planes, which facilitates the second-stage procedure. We reviewed 45 consecutive patients, treated over a period of nine years. The mean follow-up was for 48 months (20 to 112). At final review, there was no evidence of infection in 41 patients (91%); only one had a recurrent infection with the same organism. There was improvement in the Hospital for Special Surgery knee score between stages and at final review. The range of movement was maintained between stages. Complications were primarily related to the extensor mechanism and stability of the knee between stages. Both of these problems decreased with refinement of the design of the implant. The rate of cure of the infection in our patients was similar to that using other methods. Movement of the knee does not appear to hinder control of infection.

The PROSTALAC functional spacer in two-stage revision for infected knee replacements. Prosthesis of antibiotic-loaded acrylic cement.

The PROSTALAC functional spacer is made of antibiotic-loaded acrylic cement but has a small metal-on-polythene articular surface. We have used it as an interim spacer in two-stage exchange arthroplasty for infected total knee replacement. PROSTALAC allows continuous rehabilitation between stages as it maintains good alignment and stability of the knee and a reasonable range of movement. It also helps to maintain the soft-tissue planes, which facilitates the second-stage procedure. We reviewed 45 consecutive patients, treated over a period of nine years. The mean follow-up was for 48 months (20 to 112). At final review, there was no evidence of infection in 41 patients (91%); only one had a recurrent infection with the same organism. There was improvement in the Hospital for Special Surgery knee score between stages and at final review. The range of movement was maintained between stages. Complications were primarily related to the extensor mechanism and stability of the knee between stages. Both of these problems decreased with refinement of the design of the implant. The rate of cure of the infection in our patients was similar to that using other methods. Movement of the knee does not appear to hinder control of infection.

Custom-Made Total Joint Prostheses for Temporomandibular Joint Reconstruction

Jaw joint (temporomandibular joint or TMJ) disease is estimated to affect 30 million Americans, with approximately 1 million new patients diagnosed each year (1). Although many of these patients can be managed with nonsurgical therapies, some patients require surgical intervention. The TMJ is a unique joint in that it does not function independently but works in tandem with its contralateral joint. Therefore, disease affecting 1 joint can either directly or indirectly affect the functioning and health of the contralateral joint. When surgical intervention of the TMJ is required, the joint can often be reconstructed with autogenous tissues. However, certain TMJ conditions and pathology require reconstruction with a total joint prosthesis for predictable treatment outcomes. Some of these conditions include ≥2 previous TMJ surgeries; previous TMJ alloplastic implants containing Proplast/ Teflon (PT), Silastic, acrylic, or bone cements; inflammatory or resorptive TMJ pathology; connective tissue or autoimmune disease (i.e., rheumatoid arthritis, psoriatic arthritis, scleroderma, Sjogren's syndrome, lupus, and ankylosing spondylitis); fibrous or bony ankylosis; absence of TMJ structures due to pathology, trauma, or congenital deformity; and tumors involving the condyle and mandibular ramus area. Currently, the only TMJ total joint prosthesis approved by the Food and Drug Administration (FDA) is the custom-made device manufactured by TMJ Concepts, Inc. (Camarillo, Calif). The device was manufactured by the same company under the name Techmedica, Inc. from 1989 to 1993.

In vitro release studies of methylmethacrylate liberation from acrylic cement powder

Bone cement or polymethylmethacrylate (PMMA) is commonly used for anchoring cemented prosthesis to the bone. Cytotoxic effect of culture media exposed to PMMA powder may be related with long term problems associated with acrylic cement application, being the monomer (methylmethacrylate) one of the cement’s component partly responsible for the cytotoxic effect. The present work reports the studies of monomer release from acrylic bone cement powder under different experimental conditions: setting time of PMMA (in solution and air) and different culture media composition. High-performance liquid chromatography was used for the determination of residual monomer. Mathematical models were applied to experimental dissolution data revealing that monomer release is lightly affected by the studied variables. The monomer release seems to be a surface phenomena, suggesting that the possible actions of monomer will mainly be due to the initial loss of non polymerized monomer rather than to further depolymerization of the already polymerized cement.

Design issues in clinical studies of the in vivo volumetric wear rate of polyethylene bearing components.

The issue of wear of ultra-high molecular weight polyethylene bearing surfaces in total hip and knee replacements is, without doubt, one of the dominant themes in contemporary orthopaedics. Thus, an array of relevant facets of this topic have been extensively and intensively researched, spawning, in the process, a very large volume of literature. The main topics that have been studied are the place of wear in the hierarchy of degradation modes of polyethylene bearing surfaces, the role of polyethylene wear particles in the in vivo longevity of the prosthesis, the methods of determining the extent of wear of polyethylene bearing components (for example, the acetabular cup, acetabular cup liner, or tibial insert), the magnitude of the volumetric wear rate, the relationship between the results of in vitro wear-testing of polyethylene specimens or components and the clinical performance of polyethylene components, and the key factors influencing the clinical wear of polyethylene components. It is widely acknowledged that wear is one of many degradation modes that affect polyethylene bearing surfaces in vivo (other modes include creep, delamination, and burnishing) and that, under certain circumstances, it is not the predominant one. For example, polyethylene creep of the liner predominates during the initial stages of penetration of the femoral head into the acetabular cup, but additional penetration after the first twelve to eighteen months in situ is due to wear24. A consensus has emerged that wear of polyethylene bearing components is implicated in the aseptic loosening of hip and knee implants, and in the development of osteolysis around those implants, through resorption of the periprosthetic bone initiated by a foreign-body-giant-cell granulomatous tissue reaction. This biological reaction arises in response to the polyethylene and other wear particles (such as acrylic cement and metal) that are released into the periprosthetic bone. Furthermore, in the …

サルにおける両側視索核間の投射遮断による視運動性眼振に及ぼす影響について

It has been shown that the nucleus of the optic tract (NOT) is an important visuomotor relay between the retina and preoculomotor structures, and is responsible for mediating horizontal optokinetic nystagmus (OKN) in monkeys, cats, rabbits, and rats. The details between the NOT and the vestibular nucleus in the brain stem concerning the morphology of fibers-of-passage and axon terminals have been disclosed in cats and monkeys. One is that they project to the contralateral NOT via the posterior commissure. In order to evaluate the role of the commissural fibers between the NOTs, the posterior commissure was cut in the present experient. Three fuscata monkeys (M17, M19, M22) were used. A magnetic search coil was sutured to the right eye to record eye position. Several bolts were embedded and secured with dental acrylic cement to fasten the animal's head during experiments. The animal was mounted on a turn table covered by an OKN screen, onto which OKN stripes were projected from above. The animals viewed the OKN stripes under three conditions: right eye viewing, left eye viewing, and bilateral eye viewing. OKN was recorded in response to counter clockwise (CCW) and clockwise (CW) stimulation at stimulus velocities of 30°/s, 60°/s, and 90°/s. After the control experiment was completed, the posterior commissure was transected by an operator knife. After follow-up studies were completed, an anterograde tracer was injected in the left NOT to ascertain the complete block between NOTs. Rapid rise (RR) and steady state (SS) of slow-phase OKN velocity and time-constants (TC) of optokinetic afternystagmus (OKAN) were measured. In three aniamis, OKN gains elicited with monocular viewing were approximately equal to the those of binocularly-evoked OKN before and after surgery. In the three monkeys, the commissurectomy decreased RR and SS to both sides during the three weeks immediately after surgery. In M22, TC showed the tendency to decrease by only 30°/s and 60°/s after surgery. There were no significant differences in TCs of other experiments.In conclusion, gain reduction in RR and SS can be explained by decrease of inhibiting the resting rate in NOT, which is conducted via commissural fibers. This was caused by interruption due to a middle-line lesions. Furthermore, interrupting the commissural fibers has nothing to do with the velocity storage mechanism.

231 アダプティブ p 法による人工股関節ステム形状最適化

Fatigue failure of the acrylic cement and resulting disruption of the bone-cement interface can limit the long-term clinical success of the cemented artificial hip joint. In order to overcome this problem optimal shape design prosthesis is required. This study describe a result of the design shape analysis (DSA) and the numerical shape optimization whereby the finite element method is used to determine optimal shape for the femoral stem of hip prosthesis in order to minimize the maximal value of the 1^<st> principal stress at the cement mantle.

Acute osteoporotic vertebral collapse: open study on percutaneous injection of acrylic surgical cement in 20 patients.

The aim of this study was to determine the efficacy of percutaneous vertebroplasty in treating painful spinal osteoporotic collapse. Twenty-three cases of vertebral collapse were evaluated with CT and MR imaging to determine osteoporotic origin and recent evolution. Percutaneous vertebroplasties were performed using CT guidance. The 20 patients included in the study (17 women, 3 men; 62-92 years old) had acute pain of less than 1 month's duration that hindered ambulation and required treatment with narcotic drugs. They underwent this procedure for analgesic purposes. The analogic visual scale of Huskisson was used for pain when scoring assessment. In 15 patients (75%), pain relief was complete within 24 hr after injection. Analgesic administration was stopped in 14 patients. Mild pain persisted in three (15%) of the remaining five patients. In one other patient (5%), crural pain was observed with cement leakage in the psoas muscle. In the fifth patient (5%), pain recurred after the patient was lifted. The pain was related to a new acute collapse of an adjacent vertebrae. Vertebroplasty for the treatment of osteoporotic vertebral collapse is a minimally invasive procedure that provides immediate pain relief and enables the patient to become quickly mobile.

The treatment of the infected hip replacement. The complex case.

The treatment of the infected total hip replacement remains expensive, leads to a long difficult course for the patient, and frequently results in a suboptimal functional outcome. Various treatment techniques are available, and may be suitable for the more straightforward case. These include one-stage exchange arthroplasty, two-stage exchange arthroplasty, resection arthroplasty, and debridement and irrigation. The complex infected total hip replacement encompasses numerous host and organism factors. These include unusual or multiple organisms, diagnostic difficulties, bone loss, immunocompromise, and reinfection. In the authors' experience, the problem of the complex infected hip replacement is best addressed using the prosthesis of antibiotic-loaded acrylic cement approach. This interval arthroplasty is a modular, custom-made, immediate fit, antibiotic selective, temporary spacer system that allows the surgeon to reconstruct even the most deficient bone stock safely and effectively using two-stage exchange arthroplasty. It affords the patient rapid pain relief, allows them to mobilize quickly while successfully eradicating infection in 96% of hips with severe bone loss, and sets an appropriate soft tissue environment for a relatively straightforward second stage procedure. The prosthesis of antibiotic-loaded acrylic cement system affords the benefits of two-stage exchange without the functional disadvantages of an excision arthroplasty particularly when the proximal femur is severely deficient. It allows flexibility for the interval period and the type of fixation used, and the potential for allograft reconstruction at the final stage.

Radiopaque acrylic cements prepared with a new acrylic derivative of iodo-quinoline.

A novel iodine-containing methacrylate, 2,5-diiodo-8-quinolyl methacrylate, has been synthesized and used in the preparation of acrylic radiopaque cements. The effect of incorporation of this monomer to the self-curing resins, on the curing parameters, swelling behaviour and mechanical properties was studied. The incorporation of the radiopaque compound 2,5-diiodo-8-hydroxyquinoline to the solid phase was also carried out for comparative experiments. A decrease in the peak temperature and an increase in the setting time was observed with the addition of the radiopaque monomer, however, the curing parameters did not appreciably change with the addition of the radiopaque compound to the solid phase. Swelling of the modified cements was in the same range as that of the radiolucent cement; however, the diffusion coefficients calculated according to the Fick's law were higher for the iodine-containing materials. The addition of 5 wt% of the iodine-containing methacrylate provided a significant increase in the tensile properties with respect to either control radiolucent formulations or BaSO4-containing formulations. Biocompatibility of the modified cements was studied by implantation of rods of the cements into rats and histological analysis of the surrounding tissue.

Nitric oxide-dependent guanylyl cyclase participates in the glutamatergic neurotransmission within the rostral ventrolateral medulla of awake rats.

A well-known action of nitric oxide (NO) is to stimulate the soluble form of guanylyl cyclase, evoking an accumulation of cyclic GMP in target cells. The aim of the present study was to examine the effects of inhibition of guanylyl cyclase dependent on NO during cardiovascular responses induced by L-glutamate and S-nitrosoglutathione (SNOG) microinjected into the rostral ventrolateral medulla (RVLM) of awake rats. Three days before the experiments, adult male Wistar rats (280 to 320 g) were anesthetized for implantation of guide cannulas to the desired stereotaxic position (AP=-2.5 mm, L=1.8 mm) in relation to lambda. The cannulas were fixed to the skull with acrylic cement. Twenty-four hours before the experiments, a femoral artery and vein were cannulated for recording arterial pressure (AP) and heart rate (HR) and injection of anesthetic. Unilateral microinjections (100 nL) of L-glutamate (5 nmol/L) and SNOG (2.5 nmol/L) were made into the histologically confirmed RVLM. The cardiovascular responses to these drugs were evaluated before and after microinjection (3 nmol/L, 200 nL) of either methylene blue or oxodiazoloquinoxaline (ODQ). The hypertensive effect of L-glutamate was attenuated by 74% after methylene blue (DeltaAP=49+/-8 to 13+/-4 mm Hg) and by 80.5% after ODQ (DeltaAP=30+/-2 to 6+/-2 mm Hg). The increase in AP produced by SNOG was fully blocked by ODQ (DeltaAP=39+/-8 to 1+/-2 mm Hg). These data indicate that cyclic GMP mechanisms have a key role in glutamatergic neurotransmission in the RVLM of awake rats, and it is most probable that NO participates in this response.

Influence of sterilization on injectable bone biomaterials

Injectable biomaterials used in bone surgery include acrylic bone cements, calcium phosphate cements, and new composite-type biomaterials with a mineral content and an organic phase dispersed or dissolved in water. Cellulose derivatives, chitosan solutions, alginates, and other polymers are studied as useful modifiers and binding agents in calcium phosphate cements. We have developed proprietary polyester copolymers including lactic acid moieties and present here results concerning the effect of sterilization on the physico-chemical properties of derived bone biomaterials. Chitosan solutions show a dramatic decrease in viscosity after 25-kGy gamma sterilization. Aqueous copolylactic solutions also show, by capillary electrophoresis, that hydrolysis occurs to liberate monomers after 25-kGy gamma sterilization. Heat sterilization also degrades chitosan solutions, and ultrafiltration is difficult because of high viscosity. However, apatite-copolylactic solids can be steam sterilized without deterioration. Gelatin has been used as a natural polymer to bind apatite particles. Gel exclusion chromatography reveals crosslinking of the chains by irradiation. Standard acrylic cements contain monomers sterilized by ultrafiltration because they do not tolerate irradiation. We have used ultrafiltration to prepare aqueous copolylactic solutions without polymer hydrolysis. Implantation of calcium phosphate cement modified by copolylactic acid in a rabbit metaphyseal model defect shows progressive substitution of the biomaterial by new bone tissue. At 3 months, a mild inflammatory reaction still remains associated with the continuing resorption of the biomaterial. These results show that interesting biological properties can be obtained with products not sterilized by irradiation. Undoubtedly, many biopolymers are fragile and, like reactive monomers, need to be sterilized by special methods if they are to be used in injectable, liquid form.