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PubMed1978

Antibiotics in acrylic bone cement. In vitro studies.

The effect of combining gentamicin and cephalothin with Surgical Simplex bone cement was tested in vitro. Experiments were designed to determine (1) quantitative elution rates and period of time the antibiotics were eluted and (2) effective bactericidal qualities. Both antibiotics were eluted from polymerized acrylic cement in large quantities within 24--48 hr after coming in contact with fluid and continued to be released in smaller amounts for 21 days to more than 175 days. This varied with the antibiotic, concentration of antibiotic in the cement, surface area of cement, and volume of elution fluid. Quantitative determinations of numbers of bacteria in broth cultures demonstrated that sufficient quantities of antibiotics were released to be bactericidal to microorganisms within 45 min to 20 hr. This was dependent on the type of antibiotic, type of bacteria, concentration of antibiotic in the cement, and time of contact.

Arthroplasty↗
PubMed1982

A technique for embedding strain gages within curing bone cement.

A technique has been described to embed strain gages within curing bone cement. Both open faced and encapsulated strain gages were employed. Using a simple cantilever beam in bending test, the experimentally measured strains were linear over the range of bending strains applied and in good agreement with the calculated theoretical values.

Bone Cements↗
PubMedDate not supplied

Late hematogenous infection in total joint replacement: studies of gentamicin and bone cement in the rabbit.

Hematogenous infection of total joint replacements was experimentally produced in rabbits with cemented endoprostheses in both knees. One one side the bone cement contained gentamicin. Bacteremia was induced six to eight weeks postoperatively using a strain of Staphylococcus aureus. Twenty-five days after the induction of bacteremia approximately a third of the artificial joints were infected, whereas no bacteria were found in blood and viscera. Although the gentamicin cement still possessed anti-bacterial activity in vitro, it did not prevent hematogenous infection. Thus, gentamicin cement would not protect the joint against delayed hematogenous infection.

Animals↗
PubMed1979

Monomer release from methacrylate bone cements during simulated in vivo polymerization.

The release of monomer from methylmethacrylate bone cements was studied during immersion in an aqueous environment intended to simulate in vivo polymerization of the material. Monomer release from disk-shaped specimens into an aqueous environment was assayed by gas chromatography. The simulated intracorporal polymerization was carried out under a variety of conditions intended to encompass possible clinical variables. The majority of monomer release occurred within the first 15 min of immersion. Under conditions generally recommended for commercial cements the release into aqueous media was always less than 3% of the total monomer weight. Clinically feasible options of delaying the time from onset of mixing of the cement to insertion into the host resulted in only a 0.7 wt % difference in the amount of released monomer. Measurements for a variety of monomer/powder ratios demonstrated a minimum in the amount of released monomer at a ratio of about 0.4 ml/g. In terms of unit area covered, thin specimens released less monomer than thick specimens.

Bone Cements↗
PubMed2005

Study on modelling of PMMA bone cement polymerisation.

This contribution is concerned with the modelling of PMMA-based bone cement polymerisation process and the associated heat effect. While existing models use description in terms of the so-called polymerisation fraction to fit the experimental data, the new model is constructed in such a way as to mimic the chemical processes taking place in the cement dough. The important phenomena are identified and the mathematical formulation is proposed.

Bone Cements↗
PubMed1985

Setting properties of bone cement with added synthetic hydroxyapatite.

Synthetic hydroxyapatite powder was added to commercial bone cement to improve its physico-mechanical properties. The study of the setting properties showed the considerable effect of hydroxyapatite (HA) on the polymerization process; in particular statistical treatment of the experimental results revealed a significant relative minimum of the exothermic peak value at HA 5% weight percentage--an effect attributed to the HA 'crumbling' action on the microporosity features. The relationship between the interface (air and monomer bubbles/acrylic resin) versus dough composition was evaluated: the comparison between this last one and the corresponding internal energy variation supports the above hypothesis.

Bone Cements↗
PubMed1999

Superior compressive strength of a calcaneal fracture construct augmented with remodelable cancellous bone cement.

Twenty-six paired, fresh-frozen cadaveric feet were disarticulated at the ankle joint, and the dome of the talus was potted. Stress-risers were placed along the medial, lateral, and posterior aspects of the calcaneus, and the specimen was loaded rapidly to failure in a testing machine to produce a type-IIB displaced intra-articular fracture according to the classification system of Sanders et al. One specimen of each pair was treated with standard internal fixation with bone-grafting (the control group), and the other was treated with similar fixation but with SRS (Skeletal Repair System) calcium phosphate bone cement placed in any osseous defect. All of the specimens were cured for twenty-four hours in a bath of saline solution at 37 degrees Celsius. The specimens were tested cyclically for ten cycles from zero to 100 newtons at one hertz and for 1010 cycles from zero to 350 newtons at one hertz. The deformation per cycle (millimeters per cycle), first-cycle deformation (millimeters), number of cycles to failure, and number of specimens withstanding the cyclical testing were calculated. The specimens were examined radiographically before and after fracture and after reconstruction and testing. A large difference in the results of the cyclical testing was noted. The specimens that had been augmented with the SRS bone cement had an average deformation of 0.00195 millimeter per cycle compared with 1.013 millimeters per cycle in the control group (p < 0.005). A similar magnitude of difference was noted when the results were stratified for good and poor-quality bone. Visual examination and radiographs demonstrated that a type-IIB displaced intra-articular fracture had been created reproducibly, and computed tomographic scans showed that nearly anatomical reconstruction had been achieved in all of the specimens. The computerized tomographic scans revealed good filling of the osseous voids and no evidence of failure of the cement after cyclical loading.

Bone Cements↗
PubMed1984

Comparative fatigue behavior of different bone cements.

Tensile and fatigue studies were performed on four different preparations of acrylic bone cement: (1) surgical Simplex-P inserted into molds in the dough stage, (2) Zimmer Low Viscosity Cement (LVC) inserted in the liquid phase, (3) an experimental cement inserted in the dough phase, and (4) the same experimental cement inserted in the liquid phase. The void characteristics of the cements appeared to dictate their mechanical performance. While tests revealed no difference in the tensile strengths of the four cement preparations, small but statistically significant differences in mean fatigue life were observed. The experimental cement used in the dough stage exhibited superior fatigue characteristics when compared with Simplex and LVC. LVC had the poorest mechanical properties of the four cement groups. Since the specimen preparation procedures can markedly influence the cement void characteristics and, consequently, the mechanical properties, general statements about different cement types are offered with considerable reservations.

Bone Cements↗
PubMed2002

Residual stress due to curing can initiate damage in porous bone cement: experimental and theoretical evidence.

Residual stress due to shrinkage of polymethylmethacrylate bone cement after polymerisation is possibly one factor capable of initiating cracks in the mantle of cemented hip replacements. No relationship between residual stress and observed cracking of cement has yet been demonstrated. To investigate if any relationship exists, a physical model has been developed which allows direct observation of damage in the cement layer on the femoral side of total hip replacement. The model contains medial and lateral cement layers between a bony surface and a metal stem; the tubular nature of the cement mantle is ignored. Five specimens were prepared and examined for cracking using manual tracing of stained cracks, observed by transmission microscopy; cracks were located and measured using image analysis. A mathematical approach for the prediction of residual stress due to shrinkage was developed which uses the thermal history of the material to predict when stress-locking occurs, and estimates subsequent thermal stress. The residual stress distribution of the cement layer in the physical model was then calculated using finite element analysis. Results show maximum tensile stresses normal to the observed crack directions, suggesting a link between residual stress and pre-load cracking. The residual stress predicted depends strongly on the definition of the reference temperature for stress-locking. The highest residual stresses (4-7 MPa) are predicted for shrinkage from maximum temperature; in this case, magnitudes are sufficiently high to initiate cracks when the influence of stress raisers such as pores or interdigitation at the bone/cement interface are taken into account (up to 24 MPa when calculating stress around a pore according to the method of Harrigan and Harris (J. Biomech. 24(11) (1991) 1047-1058). We conclude that the damage accumulation failure scenario begins before weight-bearing due to cracking induced by residual stress around pores or stress raisers.

Algorithms↗
PubMed1986

Comparative in-vitro activity of antibiotics incorporated in acrylic bone cement.

We compared the persistence of antibacterial activity around antibiotic-impregnated acrylic bone cement discs which were serially transferred on seeded agar plates. On plates inoculated with Staphylococcus aureus ATCC 25923, CMW1 discs containing 2.5% by dry weight of cephalothin, coumermycin or fusidic acid (as diethanolamine fusidate) produced zones of inhibition for four to eight weeks when transferred daily. In contrast, ceftriaxone, cotrimoxazole, rifampicin and vancomycin ceased to be inhibitory within a week. Discs made of 'Palacos-R with Garamycin,' which contains gentamicin 1.25%, had an intermediate duration of activity. When Escherichia coli ATCC 25922 was used as the test organism, ceftriaxone and 'Palacos-R with Garamycin' showed activity for almost three weeks, cephalothin and cotrimoxazole were briefly inhibitory and the remainder not at all. When discs were transferred each week instead of daily, the ranking of antibiotics was similar but antibacterial activity persisted for longer. A combination of gentamicin plus fusidic acid in CMW1 was active for a much shorter time than either fusidic acid alone or 'Palacos-R with Garamycin'. We conclude that coumermycin is a promising new agent for incorporation in acrylic cement.

Acrylates↗
PubMed1991

Effect of hypotensive epidural anaesthesia on acetabular cement-bone fixation in total hip arthroplasty.

We selected 20 matched pairs of patients who had had total hip arthroplasty by the same surgeon using the same cemented technique. Matching was by age, sex, height, weight and diagnosis. One of each pair had received hypotensive epidural anaesthesia, with less than 300 ml blood loss: the other had normotensive general anaesthesia with more than 500 ml of blood loss. Early postoperative radiographs were evaluated independently by three blinded observers, using a scoring criteria which assessed the quality of the cement-bone interface. The results showed that patients who had received epidural anaesthesia had significantly better radiographic scores (p less than 0.02). Our findings suggest that hypotensive anaesthesia facilitates penetration of cement into bone.

Anesthesia, Epidural↗
PubMed1996

Hypersensitivity in aseptic loosening of total hip replacements. The role of constituents of bone cement.

Aseptic loosening is seen in a significant proportion of cemented total hip replacements (THR). In a small subgroup of patients who suffer early loosening polyethylene debris is unlikely to be responsible. We recently reported one case of allergic contact dermatitis to N,N-dimethylparatoluidine (DMT), an accelerator used in bone cement. We have therefore investigated this using skin-patch tests to a variety of substances including metals, polyethylene and the separated individual components of Simplex cement. We studied 70 patients, 15 with aseptic loosening less than two years after THR, 25 with satisfactory long-term cemented fixation, five with infected loosening of cemented THRs and 25 awaiting hip arthroplasty. We found seven positive reactions to DMT, all of them in patients with the rapid onset of aseptic loosening. Allergy to DMT is recognized in the dental profession in respect of the 'denture sore mouth' syndrome, and could also be an occupational hazard since some industrial glues contain DMT. Our results suggest the need for awareness of possible previous dental or occupational exposure of the constituents of bone cement. We recommend the use of skin-patch testing in high-risk cases.

Aged↗
PubMed2004

Cement penetration and stiffness of the cement-bone composite in the proximal tibia in a porcine model.

PURPOSE: To assess the stiffness of the cement bone composite and the depth and uniformity of cement penetration into the surface of the tibial component during total knee reconstruction in a porcine model. METHODS: The effectiveness of 3 protocols were compared: 2 commonly used cementing techniques-finger-packing of cement on the cut surface followed by impaction, and coating of the undersurface of the prosthesis with cement followed by impaction-and a new method using a tibial cement-pressurising device. Cement penetration was measured by computed tomography; stiffness was determined by hydraulic penetration testing. RESULTS: Cement penetration at a depth of 1 mm was significantly greater following coating the undersurface of the prosthesis than following finger-packing (p=0.008). There was no significant difference at deeper levels or between the tibial-pressurising device group and either of the 2 other groups at any level (p>0.3 in all cases). Differences in surface stiffness by tibial plateau region were found in tibiae that had been cemented using finger-packing and in those that had had their undersurface coated, but not in tibiae that had been cemented using the tibial-pressurising device. CONCLUSION: The tibial cement-pressurising device eliminated regional differences in stiffness seen with other cementing methods. Elimination of these differences by using this device should reduce micromotion and the incidence of aseptic loosening of tibial base plates in total knee arthroplasty.

Analysis of Variance↗
PubMed1999

Prolonged leaching time of peptide antibiotics from acrylic bone cement.

The leaching time of antibiotics in growth inhibitory concentrations from polyacrylic bone cements was determined using Escherichia coli, methicillin resistant Staphylococcus aureus, Staphylococcus epidermidis, Klebsiella pneumoniae, and Pseudomonas aeruginosa as target bacteria. The leaching time of the peptide antibiotics vancomycin and polymyxin B nonapeptide was considerably longer than that of gentamicin, novobiocin, and erythromycin. Among the nonpeptide antibiotics, the leaching time of novobiocin lasted longer than did that of gentamicin. The acylated parent polymyxin B antibiotic leached for a considerably shorter period than did the deacylated polymyxin B nonapeptide derivative, suggesting that the lipids impede the leaching process from the cement. Cement beads impregnated with polymyxin B nonapeptide and introduced into the tibia of three rabbits receiving oral novobiocin protected bone infection against a challenge of Pseudomonas aeruginosa that otherwise caused infection in tibias containing gentamicin impregnated cement beads. The peptide antibiotics alone or in combination with other antibiotics (polymyxin B nonapeptide and novobiocin) impregnated in cements for orthopaedic procedures may provide longer periods of protection against a wide range of bacterial pathogens.

Acrylates↗
PubMed1999

Use of hydroxyapatite bone cement to prevent cerebrospinal fluid leakage through the frontal sinus: technical report.

OBJECTIVE: To test the efficacy of a simple technique of frontal sinus obliteration during low frontal craniotomy using hydroxyapatite cement instead of more traditional methods, such as pericranial flaps, free muscle or adipose grafts, lumbar drainage, or fibrin glue. METHODS: Eight patients undergoing low frontal craniotomy for intradural surgery had the frontal sinus obliterated by careful removal of mucosa followed by filling of the sinus with hydroxyapatite bone cement. No other adjuncts for preventing cerebrospinal fluid leakage through the sinus were used. RESULTS: At an average follow-up of 9 months, there were no cerebrospinal fluid leaks, infections, instances of resorption, or cosmetic deformities. CONCLUSION: Hydroxyapatite bone cement seems to be a simple and effective method for frontal sinus obliteration and prevention of cerebrospinal fluid leakage.

Aged↗
PubMed2007

Evaluation of an accelerated aging medium for acrylic bone cement based on analysis of nanoindentation measurements on laboratory-prepared and retrieved specimens.

The thrust of the study was a critical evaluation of the efficacy of a medium (30% v/v H(2)O(2), at 60 degrees C) that has been suggested in a literature report as being suitable for simulating the oxidative aging process, seen in vivo, in the acrylic bone cement mantles of total hip and knee joint replacements. For this purpose, quasi-static and dynamic nanoindentation measurements were used to obtain material properties--elastic modulus, E; hardness, H; and the variation of the storage and loss moduli with the frequency of the applied indenting force--of PalacosR acrylic bone cement specimens after various periods of immersion (7, 14, 21, and 28 days) in the aging solution, and of specimens prepared from cement mantles retrieved from cemented total hip joint replacements after various times in vivo (0.92-21 years). Also, best-fit relationships were obtained between E and time in the H(2)O(2) solution (t), H and t, E and in vivo time (T), and H and T. This body of results points to the possibility that the aging solution is effective, although the evidence is not conclusive.

Biomechanical Phenomena↗
PubMedDate not supplied

Partial sacral resection and reconstruction with bone cement. Discussion of an operative experience.

Sacral resection is often the only way for effective palliation of the severe pain in tumors involving sacrum. However the operation hardly seems to be acceptable with the reported operative times, blood losses and complication rates. A case of retrorectal leiomyosarcoma invading sacrum, with severe pain resistant to combined irradiation and chemotherapy is reported. The tumor was removed with resection of the right two thirds of S2, S3 and S4, and the sacrum was reconstructed with bone cement. Complete relief of the pain was obtained with no postoperative complications. It is concluded that incomplete resection of the sacral vertebrae should be performed for sacral root pain palliation if other methods fail. Bone cement reconstruction seems to be a valuable alternative to muscle flaps in covering sacral defects.

Bone Cements↗
PubMed1993

Pressurization of bone cement under standard, flanged and custom acetabular components for total hip replacement.

Custom acetabular components are proposed to achieve uniform cement mantles, even in irregular acetabula presented at revision, in order to enhance fixation. One aim of developing custom components was to permit pressurization of bone cement by the components at insertion and maintain the pressure during polymerization. A model acetabulum was set up for the insertion of standard, flanged and custom components under constant force. Cement pressure was measured at the floor of the acetabulum by means of a piezoelectric diaphragm transducer. Polythene tubes were inserted in the model acetabular walls to estimate penetration of cement into cancellous bone. Insertion of the standard and flanged components caused cement pressures up to 106 kPa which decayed to less than 21 kPa as cement escaped at the rim and the components came into contact with the acetabulum. The custom component maintained a pressure of over 60 kPa during polymerization from an initial pressure of 105 kPa and examination of cement mantles on removal showed no evidence of contact. The custom component also showed enhanced penetration of cement, especially around the rim of the acetabulum. It is concluded that the custom component design achieves higher cement pressures and that better fixation will result.

Bone Cements↗