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PubMed1999

Effect of porosity and environment on the mechanical behavior of acrylic bone cement modified with acrylonitrile-butadiene-styrene particles: I. Fracture toughness.

The elastomeric copolymer acrylonitrile-butadiene-styrene (ABS) was added to a conventional acrylic bone cement matrix. The results obtained show that although strength and stiffness decreased with an increasing second phase volume fraction, ductility and toughness both increased. The crack propagation became stable for specimens containing over a 5% volume fraction of the second phase. The fracture toughness increased up to 60% when the amount of ABS reached 20% (v/v). For larger amounts linear elastic fracture mechanics techniques could not be used properly. The effects of porosity and environmental conditions on the mechanical behavior were also studied. The mechanisms that control the fracture process were investigated by means of scanning electron microscopy.

Acrylic Resins↗
PubMed1989

The effect of centrifuging bone cement.

We have tested the porosity and fatigue life of five commonly used bone cements: Simplex P, LVC, Zimmer regular, CMW and Palacos R. Tests were conducted with and without centrifugation and with the monomer at room temperature and, except for LVC, at 0 degrees C. We found that the fatigue life of different specimens varied by a factor of nearly 100. It did not depend on porosity alone, but was more influenced by the basic composition of the cement. Simplex P when mixed with monomer at 0 degrees C and centrifuged for 60 seconds had the highest fatigue life and was still sufficiently liquid to use easily.

Bone Cements↗
PubMed1978

Intramedullary fixation of implants pre-coated with bone cement: a preliminary study.

A preliminary study on the feasibility of implants pre-coated with an acrylic bone cement has been performed. Four types of implants, an actual canine femoral prosthesis, a polished steel rod (0.49 cm dia. x 13 cm long) with and without pre-coating, and a sand-blasted steel rod with pre-coating were implanted into canine femurs in vitro to evaluate the interfacial shear strengths. After serial sectioning the samples in discs, push-out tests were made. The weakest interfacial shear strength was exhibited by the polished rod/cement interface (0.5 MPa) while the strongest was the "old" and "new" cement interface (23.4 MPa). The bone/cement interfacial strength was in between (1.17 MPa). The shear strength of rod/cement interface increased substantially by sand-blasting (6.84 MPa or 585% increase). The proposed method increases the modified implant's interfacial shear strength by 337% (from 1.17 to 3.84 MPa) over the conventional implants. It may furthermore reduce the setting temperature, the shrinkage, and the amount of monomer released during operation due to the reduced amount of cement at the time of implantation. The more gradual transmission of load from implant to bone and "auto-centering" of implants during operation by pre-coating, are thought to be advantageous over conventional cement fixation method.

Acrylic Resins↗
PubMed2000

Cytotoxic effect of bone cements in HL-60 cells: distinction between apoptosis and necrosis.

Ten PMMA-based bone cements used in prosthetic surgery have been studied with respect to the induction of programmed cell death (i.e., apoptosis) in HL-60 cells, which are remarkably sensitive to various apoptotic stimuli. Annexin V binding and propidium iodide (PI) exclusion were the methods for detection of early apoptotic changes, while PI entry was considered as a marker of necrosis. Hoechst 33342 staining was used to detect DNA fragmentation and Alamar blue was applied to measure oxide-reduction activity of cells. The production of reactive oxygen species (ROS) related to cell damage was verified using dichlorofluorescein-diacetate (DCFH-DA) oxidation to DCF. Under our experimental conditions, the cements tested, for the most part, were not toxic to leukemic cells at 4 and 24 h. After 24 h, three cements were able to induce cell death, with two eliciting both apoptosis and necrosis, and one cement acting mainly via apoptosis. Both processes of cell death are likely to be mediated by the production of oxygen-free radicals. These findings provide potential leads for investigation into the molecular mechanisms of cell death, which are responsible for tissue damage by cements and intolerance of cemented prostheses.

Apoptosis↗
PubMed1975

A proposed specification for acrylic bone cement.

A proposed specification covering handling characteristics and physical and chemical properties of bone cement composed primarily of methyl methacrylate has been prepared on the basis of data from the authors' studies and from various other sources. Under handling characteristics, requirements included relate to dough, handling and setting time, proper plasticity for insertion and temperature rise on setting. Mechanical properties specified include compressive strength and indentation and recovery characteristics. Maximum limits are proposed for water sorption and solubility. Suggested packaging requirements are also included.

Bone Cements↗
PubMed2002

The relationship between stress, porosity, and nonlinear damage accumulation in acrylic bone cement.

The long-term survival of cemented hip replacements depends on the ability of the cemented fixation to resist fatigue damage. Damage has been assumed to accumulate linearly (Miner's law) even though it is unlikely to be the case in such a porous brittle material. This study addresses the nonlinear stress-dependent nature of fatigue damage accumulation in acrylic bone cement. Specimens were subjected to a zero-to-tension fatigue load in water at 37 degrees C. A total of 15 specimens were tested, i.e., five specimens at each of three stress levels. The specimens were cyclically loaded to a certain fraction of their fatigue lives and the amount of microcracking present at that time was quantified by counting each crack and measuring its length. This procedure was repeated until the specimen failed. A total of 801 cracks formed in the 15 specimens. All cracks were found to initiate at pores. Crack propagation directions were distributed normally about the direction perpendicular to the applied load at the lower stress levels, but at higher stress, the distribution tended to be broader. At higher stresses, more cracks were produced per pore. The damage accumulation process in acrylic bone cement was found to be nonlinear with the degree of nonlinearity increasing with stress. Furthermore, great variability was found which was attributed to the differences in porosity between specimens. A power law equation is given which describes the predicted relationship between damage accumulation and number of loading cycles as a function of the stress level.

Bone Cements↗
PubMed1989

Influence of antibiotic impregnation on the fatigue life of Simplex P and Palacos R acrylic bone cements, with and without centrifugation.

The fatigue properties of Simplex P and Palacos R bone cements were compared to their antibiotic impregnated counterparts AKZ* and Palacos R with gentamycin. The effect of porosity reduction by centrifugation of all four cement types was also assessed. Fifteen specimens of each cement type were prepared according to manufacturer's instructions and 15 additional specimens of each cement type were prepared by mixing the powder with chilled monomer (0 degrees C) and then centrifuging the cement immediately after mixing. Fifteen fully reversed tension-compression fatigue tests were performed at 15 MPa in stress control for each cement preparation in vitro while simulating the in vivo state (37 degrees C and 100% humidity). The number of cycles to failure were recorded. There was no significant difference in the fatigue life of Palacos R and Simplex P when both cements were prepared in the standard fashion. The addition of 1/2 g of gentamycin to Palacos R did not significantly alter its fatigue properties. The addition of 0.5 g of erythromycin and 0.24 g of colistin did not decrease the fatigue life of Simplex P. Centrifugation significantly improved the fatigue properties of Simplex P and AKZ. The fatigue lives of Palacos R and Palacos R with gentamycin were not improved by centrifugation. The fatigue life of centrifuged Simplex P was significantly greater than the fatigue life of Palacos R and of Palacos R with gentamycin, whether the Palacos R based cements were centrifuged or not.

Biocompatible Materials↗
PubMed1977

Tolerance of mouse macrophages in vitro to barium sulfate used in orthopedic bone cement.

Barium sulfate, used as a radio-opaque marker in some orthopedic bone cements, has been shown to escape into the surrounding tissues. This may present a potential hazard. In particular, phagocytic cells may be exposed to relatively high internal levels of barium once the particles have been phagocytosed. Mouse peritoneal macrophages exposed to barium sulfate for periods up to 144 hr showed a marked cytoplasmic vacuolization from which they recovered only partially. Barium sulfate did not appear to damage the cell membrane as judged by lactice dehydrogenase release. In the relatively low doses and with the periods of exposure described here, barium sulfate does not appear to present a serious toxic hazard in the short term. It is possible, however, that longer exposures and larger doses may result in the death of phagocytic cells which have ingested barium sulfate.

Animals↗
PubMed2003

Calcium phosphate bone cements: a comprehensive review.

Calcium phosphate cements (CPCs) augment the healing of bone following craniofacial and maxillofacial surgery. Their ability to function as bone substitutes has accelerated the healing processes from bone fractures or defects. Although CPCs all possess the same general function, small chemical composition differences in these compounds have a profound impact on their in vivo character. The main purpose of this article is to report the differences of several major CPCs. When available, specific clinical trials are referenced. The goal is to expand the knowledge base on CPCs to better inform the clinician and researcher.

Bone Cements↗
PubMed1996

[Augmentation of the temporal fossa with Ionos bone cement].

To compensate for the loss of tissue after transferring the temporalis muscle, it is advisable to fill the temporalis fossa for aesthetic reasons. In so doing, we have used IONOS bone cement to augment the fossa after muscle transfers. Twelve procedures have been performed within the past 3 years. The average follow-up time has been 23 months. Surgery was required in 6 cases following delayed reconstruction to rehabilitate the paralyzed face after loss of facial nerve function, four times to stabilize a duraplasty at the skull base and twice for aesthetic facial augmentation. A prefabricated IONOS implant (IONOROC implant) was attached to the squama temporalis with fresh bone cement. In all cases a good aesthetic result was achieved. A temporary seroma occurred in 6 patients (50% of the cases) but resolved in 1-2 weeks without requiring further care. However, we now recommend that suction drainage be inserted for approximately 1 week after surgery. In two cases the IONOS implant had to be removed because of an infection.

Adult↗
PubMed2006

Cytokine release of mononuclear leukocytes (PBMC) after contact to a carbonated calcium phosphate bone cement.

Human leukocytes (peripheral blood mononuclear cells, PBMC) were overlaid on calcium phosphate bone cement (CBC, Norian SRS) and allowed to settle for 1 h under cell culture conditions. Subsequently, the cells were either left unstimulated (i.e. sham stimulation using cell culture medium), or stimulated with toxic shock syndrome toxin-1 (TSST-1, 10 ng/mL), staphylococcal enterotoxin B (SEB, 10 ng/mL), or concanavalin A (ConA, 2 microg/mL) for further 24 h using cell culture conditions. Supernatants were then analyzed for cytokine content (interleukin-1 receptor antagonist, IL-1ra; IL-2; IL-6; IL-10; IL-12) by enzyme-linked immunosorbent assay. While the spontaneous generation of cytokines was not influenced, the IL-2 release from stimulated PBMC was significantly decreased in contrast to other analyzed cytokines after contact to the curing CBC compared to control incubations without CBC. This decrease in IL-2 release was not due to known inhibitors of IL-2 synthesis platelet factor-4 (PF-4), IL-10, TGF-beta, or elevated calcium ion concentrations.

Bone Cements↗
PubMed1982

Effect of a cement-bone composite layer and prosthesis geometry on stresses in a prosthetically resurfaced tibia.

A comparative study of stress distributions in the component materials of a number of models of a prosthetically resurfaced tibia is presented. Although the geometry is idealized to be axisymmetric, the loadings for which the finite element analyses are performed are considered to be nonaxisymmetric, simulating more realistically the loading conditions in vivo. The different models are chosen with the view of determining the influence of changes in the prosthesis design on the induced stress distribution in the component materials. The changes considered are in the thickness of the cement and the cement-bone composite layers, and in the shape of the prosthesis. Experimentally measured values of strains are compared with the analytically predicted values to check the validity of the assumptions used in the finite element modeling. The comparison of induced stresses in the different materials reveals the desirability, from a mechanical behavior point of view, of introducing a cement-bone composite layer and using a prosthesis with domed subsurface in the fixation system. It is shown that for a model incorporating these features, considerable reduction of stresses in the cement, in its bulk and at its interface with the prosthesis plate, is achieved. The reduced stresses can be expected to have beneficial effects on the long-term behavior of the cement and its interfaces in the fixation system.

Bone Cements↗
PubMedDate not supplied

[Intraoperative fatal fat and bone marrow embolism of the lung in implantation of a hip endoprosthesis with polymethylmethacrylate bone cement].

We report on an intraoperative lethal fat embolism and bone marrow embolism of the lung caused by implantation of hip endoprosthesis using acrylic bone cement. Autopsy revealed massive fat embolism of the lung and multiple bone marrow emboli within branches of the pulmonary arteries. It is concluded that there is a close relationship between implantation of hip endoprosthesis and death because fat embolism and bone marrow embolism was the only available evidence on post mortem examination.

Aged↗
PubMed1998

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

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

Animals↗
PubMed1992

Experimental studies of the biological response to a new bone cement: II Soft tissue reactions in the rat.

The biological response to a new bone cement (London Hospital cement), which contains polyethylmethacrylate/n-butylmethacrylate, has been examined experimentally and compared with polymethylmethacrylate. The cellular reaction was identical when the polymer powders of the cements were inserted subcutaneously in rats, there being a macrophage response to the polymer beads of both materials. Experimental implantation of the two cements into the paraspinal musculature of rats showed that there was less tissue damage adjacent to the new material than to polyethylmethacrylate. There was a significantly smaller macrophage and giant cell reaction in relation to the polyethylmethacrylate/n-butylmethacrylate cement. These differences may be related to the lower heat of polymerisation of the new cement and to its smoother surface contour, as demonstrated by scanning electron microscopy.

Animals↗
PubMed2004

Injection biomechanics of bone cements used in vertebroplasty.

The incidence of osteoporotic bone fractures is growing exponentially as the western population ages and as life expectancy increases. Vertebroplasty, where acrylic or calcium phosphate cement is injected into the weakened vertebrae to augment them, is an emerging procedure for treating spinal fragility fractures. However, cement injection is currently limited because there are no clear standards for a safe, reproducible and predictable procedure. The purpose of this paper is to examine the role that bone cements play in the underlying bio-mechanisms that affect the outcomes of cement injection. Our most important finding after combining clinical, laboratory and theoretical research is that the process of cement injection poses conflicting demands on bone cements. The cements are required to be more viscous and less viscous at the same time. The challenge therefore is to develop biomaterials, techniques and/or devices that can overcome or manage the conflicting demands on cement viscosity.

Biomechanical Phenomena↗