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PubMedDate not supplied

The effect of radiation on the shear strength of acrylic bone cement.

Bone loss due to secondary neoplastic disease of bone has frequently presented the orthopedic surgeon with difficult or insoluble problems of surgical management. Local radiation is the most effective, and widely used form of therapy for this type of metastatic disease. Levels of radiation in vitro comparable to therapeutic doses, as well as levels 6 times that commonly used in vivo on patients, demonstrate no significant effect on the mechanical properties of acrylic bone cement.

Acrylic Resins↗
PubMed1992

Revision of cemented fixation and cement-bone interface strength.

Interfacial shear strength between poly(methyl methacrylate) (PMMA) bone cement and cancellous bone was measured in bone samples from human proximal femora. Samples were prepared with fresh cement-bone, fresh cement inside a mantle of existing cement and with fresh cement-revised bone surfaces. Push-out tests to measure shear strength caused failure only at bone-cement interfaces; revised bone interfaces were 30 per cent weaker (P < 0.02) than primary interfaces. The clinical relevance is that revision of cemented joint arthroplasties may necessitate removal of components with sound cement-bone fixation. The practice of removing all traces of PMMA cement may not yield the optimal fixation; adhesion of fresh cement to freshly prepared surfaces of the existing cement might also be considered where circumstances are favourable.

Bone Cements↗
PubMed1979

Biomechanics of the femoral component of total hip prostheses with particular reference to the stress in the bone-cement.

Two-dimensional finite element analyses were used to determine the normal and shear stress distributions at the prostheses-cement and cement-bone interfaces in the femoral component of a total hip replacement. Various combinations of stem, cement and bone stiffnesses were investigated. In particular the influences of stem taper, cement stiffness, prosthesis stiffness and the effect of a plateau, on the cement stresses were examined and compared. It was particulary noticeable that the normal direct stress across the cement in the proximal region of the stem, both literally and medially, as generally compressive. It was found that the more flexible the cement the more uniform were the stress distributions. Furthermore, these stresses increase as the stiffness of the stem decreases.

Biomechanical Phenomena↗
PubMed1979

Experimental fixation of bone cement and composite resins to bone.

The aim of this study was to ascertain whether the use of liquid acrylic resin or NeoCryl XK-53 acrylic emulsion or etching of the bone surface with phosphoric acid or the application of both these methods would improve the bonding of CMW bone cement or Concise and Silar composite resin to bone. The test materials were applied to fresh cortical bovine bone. Their bonding capacity was measured by the Instron Universal Testing Machine. The surfaces of the test materials and the bone surfaces were examined by means of optic microscope or scanning electron microscope. The bonding strength of the bone cement and composite resins as such were found to be of the same magnitude. A three- to five-fold improvement was obtained with liquid acrylic intermediary material. Acid etching impaired the bonding.

Acrylic Resins↗
PubMed1992

Ultrastructure of the bone-cement and the bone-metal interface.

A review is given of the methods used to demonstrate the bone-implant interface by transmission electron microscopy (TEM). Neither method is yet refined enough to permit demonstration without artifacts of the contact between implant, cells, and organic and inorganic matrix. Published studies on certain metallic implants and bone cement demonstrate a direct contact between bone matrix and implant, without a continuous interposed layer of cells. The 1000 nm closest to the implant surface show a variable structure, the interpretation of which is unknown. The degree of mineralization within this distance of the implant has not yet been adequately studied. Without completely reliable analytic methods and comparable implantation protocols, the gradation of implant biocompatibility, based on the TEM appearance of the interface, should be performed with great caution.

Animals↗
PubMed1976

[Release of antibiotics from bone cement and penetration to infected cortical bone (author's transl)].

Addition of antibiotics to bone cement is used more and more in orthopedics and traumatology. Indications are discussed: 1. infection prophylaxis in replacement arthroplasty, 2. therapy and recidive prophylaxis in infected arthroplasty, 3. therapy of chronic osteomyelitis. Our own experiments show release of antibiotics from bone cement Palacos and penetration into cortical bone after experimental osteomyelitis. Carbenicillin and Cephalotin show high level of concentration for 2 weeks, after 3 weeks there is no concentration evident. Lincomycin and Gentamycin in the first days show high tissue levels, after decrease and increase again after second week. Gentamycin was examined during 10 months showing high levels after this time.

Animals↗
PubMed1992

Adhesive bone cement containing hydroxyapatite particle as bone compatible filler.

Acrylic bone cement containing hydroxyapatite (HA) as a filler was developed using 4-methacryloyloxyethyl trimellitate anhydride (4-META) to promote adhesion both to bone and HA. The mechanical strengths of the cement did not decrease significantly with increasing HA in the cement by 4-META. However, strengths decreased with increasing HA content in the absence of 4-META. Scanning electron micrographic examination of fractured surfaces of the cement clearly showed that the HA particles adhered to the matrix resin when 4-META was added. Thus, it was important to maintain the original mechanical strengths for 4-META. The HA particles along the surface increased with increased HA content in the cement. The cement adhered to bone with a tensile bond strength was higher than 10 MPa.

Acrylic Resins↗
PubMed1992

[An experimental study of the process of bony ingrowth into inorganic bone-particle impregnated bone cement].

A composite of inorganic bone particles formed with bone cement in certain proportion was implanted in the proximal femora of 15 New Zealand rabbits. The animals were sacrificed in batches at different intervals after implantation and specimens were sectioned for scanning electron microscopic (SEM) observation and push-out test. SEM showed that the bone particles in the composite were in contact with each other and forming bony pathways. The gaps between inorganic bone particle bone cement and cortical bone were filled at first with collagen fibrils which were interwoven to form collagen fiber bundles and then mineralized to assume woven bone. The bone particles became smaller in size and were enveloped, absorbed and replaced by new bone structure gradually reaching the depth of bone cement along the pathways formed by bone particles. The shear strength of the cement-bone interface was increased subsequently.

Animals↗
PubMed1975

Characterization of bone cements.

Properties of acrylic bone cements during and after curing were determined for three brands of bone cement. Curing time and consistency were chosen for the characterization of the handling and working behavior of these materials. The performance of bone cements after curing may be related amongst other things to the following properties: water resorption, solubility/disintegration, flexural modulus of elasticity, yield stress, proportional limit, flexural strength and impact strength. Methods to determine these handling and material properties are described. The influence of radiopacifying and antibiotic additives on these properties is evaluated as well as the influence of porosity on flexural strength and impact strength. The results indicate that considerable differences in the handling properties occur. The material properties of the three brands tested do not show marked differences. Radiopacifying and antibiotic additives appear to have a negative effect on material properties; the effect of porosity as it develops during curing under simulated clinical conditions is more pronounced.

Acrylates↗
PubMed1992

The fracture toughness of titanium-fiber-reinforced bone cement.

Fracture of the poly(methyl methacrylate) bone cement mantle can lead to the loosening and ultimate failure of cemented total joint prostheses. The addition of fibers to the bone cement increases fracture resistance and may reduce, if not eliminate, in vivo fracturing. This study discusses the effect of incorporating titanium (Ti) fibers on fracture toughness. Essential characteristics of the composite bone cement included a homogeneous and uniform fiber distribution, and a minimal increase in apparent viscosity of the polymerizing cement. Ti fiber contents of 1%, 2%, and 5% by volume increased the fracture toughness over non-reinforced bone cement by up to 56%. Bone cements of two different viscosities were used as matrix material, but when reinforced with the same fiber type and content, they showed no difference in fracture toughness. Four different fiber aspect ratios (68, 125, 227, 417) were tested. At 5% fiber content, there was no statistically significant dependence of fracture toughness on fiber aspect ratio. Scanning electron microscopy revealed important toughening mechanisms such as fiber/matrix debonding, local fracture path alteration, and ductile fiber deformation and fracture. Fiber fracture was evidence that the critical fiber length was exceeded. The surfaces of the Ti fibers were rough and irregular, indicating that a high degree of mechanical interlock between matrix and fiber was likely. The energy absorption contribution of plastic deformation and ductile fracture is absent in brittle fibers, like carbon, but is a distinction of the Ti fibers used in this study.

Biocompatible Materials↗
PubMed1991

[Histamine release and cardiovascular reactions to implantation of bone cement during total hip replacement].

Cardiovascular reactions to acrylic bone cement in patients with total hip replacement are a common complication. Hypotension and arrhythmias are the most frequently observed symptoms. Elderly patients with fractures of the femoral neck constitute a special risk group. In some patients these reactions can be fatal. The mechanisms suggested to explain these reactions are embolism of air, polymer or fat, reaction to the heat, and toxic or vasodilating effects of the acrylic monomer. In a pilot study and in a case report a significant rise of the plasma histamine was described following cementation of the femur. We therefore performed an investigation to find whether application of bone cement to the femur caused histamine release in elective hip surgery, and, independently of this, also investigated whether premedication with H1- + H2-antagonists had any effect on the cardiovascular reactions due to bone cement implantation into the femoral shaft in elderly patients with hip fracture. METHODS. Part I. In all, 40 patients, scheduled for elective surgical hip replacement were anesthetized by general or epidural anesthesia. Patients were continuously monitored by ECG. Blood pressure was recorded noninvasively at 2-min intervals during the study. Blood samples for the determination of the plasma histamine were taken immediately before implantation of the bone cement into the femur, and 2, 5, and 10 min after. Part II. A further group of 20 patients aged greater than or equal to 70 years with fractures of the femoral neck and in whom total hip replacement was planned were included in the study. In this group, 10 patients were randomly assigned to receive 4 mg clemastine + 400 mg cimetidine i.v. about 15 min before implantation of the bone cement. All patients were operated on under general anesthesia. ECG was monitored continuously and blood pressure was monitored at 2-min intervals during the study. Changes of the blood pressure and heart rate and therapeutic interventions following the implantation of the bone cement were documented. RESULTS. Part I. In 11 of the 40 patients (27.5%) plasma histamine increased by greater than 0.5 ng/ml (9 patients greater than 1 ng/ml). In comparable groups (patients with a control systolic blood pressure less than or equal to 130 mmHg) the histamine responders showed a significantly greater reduction in systolic blood pressure (-5.7 +/- 14.7 vs -17.7 +/- 8.6 mmHg). Part II. In the control group we observed a significantly greater fall in systolic blood pressure than in premedicated patients (41.5 +/- 25.4 vs 11.0 +/- 13.4 mmHg). In the control group 7 of the 10 patients required therapeutic interventions, while in the premedicated group only one therapeutic intervention was necessary (P less than 0.05). DISCUSSION. We have demonstrated that the implantation of acrylic bone cement into the femur may increase plasma histamine by greater than 1 ng/ml. In elderly patients with preexisting cardiac diseases or/and hypovolemia even moderate histamine release can cause serious, sometimes potentially fatal, cardiovascular complications. In this special risk group with hip fractures we found a significant reduction in the frequency of cardiovascular reactions to bone cement implantation in patients premedicated with H1 + H2 antagonists. Because we also observed significant falls in systolic blood pressure in premedicated patients, we assume that the pathogenesis of cardiovascular reactions to bone cement implantation is multifactorial. It may be that potentially lethal complications only occur if two or more of the predisposing factors (hypovolemia, myocardial insufficiency, arrhythmia, embolism, histamine release) are present simultaneously. Pre- and intraoperative measures therefore have to be instituted to eliminate all possible risk factors.

Aged↗
PubMed1991

A method for histological preparation of undecalcified bone sections containing acrylic bone cement.

An improved and time reducing method is presented for the histological evaluation of bone containing polymethylmethacrylate (PMMA) bone cement. The undecalcified bone was embedded in epoxy resin and section of 50-100 microns thickness were produced using a commercially available cutting grinding system. The sections were stained with Stevenel's blue and van Gieson picrofuchsin or a modified hematoxylineosin. PMMA bone cement was not dissolved and remained enabling examination in situ of an intact cement bone interface and tissue reaction without decalcification.

Animals↗
PubMed1979

[Temporary plugging of cystic bone tumors by bone cement (author's transl)].

Methylmethacrylate bone cement was used to refill bony defects following excisional biopsy of supposed benign or semimalign bone tumors. This procedure offers several advantages: the anatomical situation at the site of the lesion will not be altered, that means the functions of the joint and the continuity and stability of the bone will be preserved; the histological examination of the tissue is possible without a hurry; the follow up of the lesion is easily possible by X-ray-examination; further therapeutic procedures can follow without restriction, for example if the histology discovered an unsuspected malignant tumor or if the follow-up revealed a recurrency. In addition a favorable effect is the necrosis of tumor cells, eventually left behind in the bone, by the action of zytotoxic monomer and heat, originated during the polymerisation of the methylmethacrylate. In benign or semimalignant bone tumors the cement has to be removed after an adequate observation period; at this occasion the cavity again is curetted and then filled with autologous bone grafts. Since 1972 we treated 13 bone lesions by this method of "temporary bone cement plugging". The lesions were 5 giant cell tumors, 2 aneurysmal bone cysts, 2 simple bone cysts, 1 osteosarcoma, 1 malignant lymphoma, and 2 metastases of hypernephroid carcinoma. In the case of osteosarcoma an amputation was performed just after the diagnosis was made. In the other cases no local recurrances up to now were seen.

Adult↗
PubMed1979

The morphology of polymethylmethacrylate (PMMA) bone cement: surface structures and causes of their origin.

This study deals with the correlation between the polymerizing bone cement and the surrounding tissue. The surface structures of bone cements, polymerized in air, in tissue medium (in vitro) and in human bone during implantation were investigated and compared with the contours of the tissue of the implant bed. Basing on the dimensional differences it was differentiated between contours of 1st order and 2nd order: contours of 1st order are within the macroscopic range, contours of 2nd order within the microscopic range. The surface of bone cement polymerized in living human tissue differed essentially from samples polymerized under laboratory conditions. The differences are to be seen macroscopically in the coarse relief as well as microscopically in the shape and the connection of the superficial methylmethacrylate beads. Bone cements, polymerized in air show an ideal, even and closed surface. Bone cements, polymerized in tissue medium exhibit macroscopically some wrinkles, in the microscopic range their contours are either closed (samples prepolymerized at 22 degrees C) or partly open and partly closed (samples prepolymerized at 24 degrees C). The surface of bone cement implants, retrieved from human bones are characterized macroscopically by a marked wrinkled and papillary relief, microscopically by flattened beads, and most often by an irregular, rough and open surface with isolated beads giving almost the impression of a porous surface structure. The character of the surface of the bone cement originates from external, mechanical influences, from changes in the volume of the bone cement and from effects of the surrounding tissues. The surface of the bone cement implanted in human bone conforms exactly with the contour of the adjacent tissue; the tissue contour is infact a negative of the cement surface. The incomplete connection between the superficial PMMA beads seems to be of some practical value: In areas, where the PMMA beads are largely isolated, the mechanical stressability of the "polymer composite" is relatively low. Under high load, beads and bead-clusters may break off the surface. Shattering of bone cement implants possibly may start from such an open, porous surface area where PMMA beads are extensive isolated.

Acrylic Resins↗
PubMed1992

[Results of using bone cement and phenol lavage in the surgical management of giant cell bone tumors].

Authors report on experiences gained with phenol lavage used as adjuvant and filling with bone cement in the surgical treatment of giant cell tumors of the bone. The effect of the adjuvant therapy was a considerable decrease in the rate of relapses: in 11 patients 1 relapse was found only in contrary to the 15 relapses in the control material (41 per cent) after 36 excochleations. They think that with adequate indications both the phenol lavage and filling with bone cement are useful supplements to the surgical therapy.

Adolescent↗
PubMed1975

Dimensional behavior of curing bone cement masses.

The curing of bone cements is accompanied by release of polymerization heat and, hence, by a temperature rise of the curing cement mass. This temperature rise causes expansion of enclosed air bubbles and evaporation of the volatile monomer. An overall expansion of 3 to 5 vol % has been mentioned in the literature. It has often been stated that this expansion favours the fixation of metal endoprostheses in the marrow cavity of bone. To check for the influence of this expansion on linear dimensions of the cured cement mass we filled stainless steel cylinders with a precision bore of 22,000 +/- 0,005 mm and a length of 120 mm with bone cement. After curing of the cement in a environment of 37 degrees C the resulting cement rod was released from the cylinder and the diameter of the rod was measured at 37 degrees C. The influence of the "foaming effect" on the transverse dimensions of the rods was studied by curing the cement at 37 degrees C and 2 atm air pressure in a high-pressure-vessel. This method of curing eliminates porosity in the cement almost completely, so that curing shrinkage is to be expected rather than expansion of the cement mass. The results indicate that a volumetric expansion of the cement during curing of cylindrical rods in laboratory experiments, can be accompanied by a linear diametrical shrinkage of the cement mass. The explanation of this phenomenon is to be sought in the fact that the volumetric expansion takes place at a time when the cement is still plastic; by the formation of gas bubbles, the cement is forced in longitudinal direction into the cylinder and when the temperature of the mass has passed through a maximum, the cooling of the cement mass results in a thermal shrinkage of approximately 0.4% linearly. Extrapolating this laboratory result to clinical situation one might doubt whether the overall expansion of bone cements during curing will result in a permanent positive pressure on the walls of marrow cavity and whether it will contribute to a better fixation of endoprostheses than in the case of a, still hypothetical, nonporous cement.

Bone Cements↗
PubMed1979

Silver polymethyl methacrylate antibacterial bone cement.

An improved antibacterial bone cement was sought based on the addition of low concentrations of inorganic silver compounds to polymethyl methacrylate. Composites with AgCl, Ag-AgCl, Ag2O, Ag2SO4 and Ag3PO4 in concentrations of 0.05% to 1% by weight, were tested in vitro against bacterial cultures. All were effective, but Ag2SO4 was especially so, even after 7 weeks of incubation in normal saline. Compressive strength of the cement was not affected by these additions, except in the case of Ag2O. Biocompabibility tests in rabbit muscle for up to 12 weeks showed no significant difference between the Ag -PMM and plain PMM in tissue reactivity, both being minimal. These features, coupled with the broad spectrum of antibacterial activity and low allergic potential of silver, make Ag-PMM an attractive alternative to conventional organic antibiotic/bone cement composites.

Acrylic Resins↗