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PubMed1984

Effects of fat admixture on the strengths of conventional and low-viscosity bone cements.

The diametral tensile and compressive strengths of both conventional doughy and low-viscosity (LVC) bone cements were tested with sequential admixtures of up to 50% (by weight) liquified fat. The addition of as little as 5% (by weight) fat caused a significant reduction (p = 0.05) in the strengths of both cements. The LVC appeared to be affected to a greater degree by fat contaminations than did the conventional cement, although the strengths of the LVC were generally equal to or higher than those of the conventional cement. The enhanced effect of fat contamination on the LVC was thought to be due to the more fluid, tacky nature of this material during administration.

Animals↗
PubMed1993

Effect of screw diameter, insertion technique, and bone cement augmentation of pedicular screw fixation strength.

This study investigated (1) the effect of screw diameter and insertion technique in lumbar vertebrae, and insertion site in the sacrum, on the axial pullout force and transverse bending stiffness of pedicle screws, and (2) the effect of bone cement augmentation using polymethylmethacrylate (PMMA) and the biodegradable composite, poly(propylene glycol-fumarate) on axial pullout force and transverse bending stiffness of pedicle screws inserted into lumbar vertebrae. The axial pullout force and transverse bending stiffness of a 6.25-mm Steffee screw and a 6-mm Kluger screw did not differ significantly in vertebral bodies of similar equivalent bone mineral density. The axial pullout force of Schanz screws was significantly increased with a 1-mm increase in screw diameter. However, there was no significant increase in transverse bending stiffness. In the sacrum, an approach through the S1 facet produced significantly higher axial pullout forces and transverse bending stiffness than the approach described by Harrington and Dickson. PMMA and a biodegradable composite bone cement poly(propylene glycol-fumarate) both increased the axial pullout force. PMMA also increased the transverse bending stiffness.

Biomechanical Phenomena↗
PubMed1989

Bone cement for redislocated Colles' fracture. A prospective comparison with closed treatment.

Colles' fractures (not comminuted or intraarticular) that redislocated after two closed reductions were randomized into two groups. In one group the dorsal bone deficiency was filled with bone cement (methylmethacrylate) at operation; in the other, the fractures were rereduced and immobilized in a plaster cast. All the patients were followed for 2 years and examined with respect to anatomy of the fracture, wrist movement, strength, appearance, pain, and function. The operated on group were better with regard to all objectively measurable characteristics; all operated on fractures had healed radiographically, and the cement was surrounded by cortical bone.

Aged↗
PubMed2002

Use of an injectable calcium phosphate bone cement in the treatment of tibial plateau fractures: a prospective study of twenty-six cases with twenty-month mean follow-up.

OBJECTIVE: To evaluate the potential benefit of a new injectable mineral bone cement (Norian SRS, Cupertino, CA, USA) for the treatment of tibial plateau fractures OTA types 41.B2-B3 and C3. DESIGN: Prospective study with established protocol. SETTING: University hospital; university teaching hospital. PATIENTS: Twenty-six patients gave informed consent to participate in this study and were available for follow-up examinations. All patients had sustained intraarticular tibial plateau fracture types OTA B2-B3 and C3. All cases were followed with a mean follow-up time of 19.7 months (6 to 36 months, median eighteen months). INTERVENTION: Twenty-five cases were treated with open reduction, osteosynthesis with screws or plate, and injection of Norian SRS in the subchondral bone defect. One case had closed reduction, screw osteosynthesis, and percutaneous cement injection. MAIN OUTCOME MEASUREMENTS: Radiographs in two planes were evaluated prospectively at six, twelve, and twenty-six weeks postoperatively and at last follow-up using Rasmussen's radiologic score. Clinical parameters were measured at the same time intervals using Lysholm's and Tegner's knee scores. RESULTS: Two cases required early wound revisions because of sterile drainage. Two cases developed partial loss of reduction of the fracture between four and eight weeks after surgery, requiring revision surgery in one case (total complication rate 15.3 percent). No other patients had complications, and all other fractures healed without any displacement. The high mechanical strength of the cement allowed early weight bearing after a mean postoperative period of 4.5 weeks (1 to 6 weeks). CONCLUSIONS: An injectable mineral bone cement with high initial mechanical strength was used to fill bone defects in unstable tibial plateau fractures with good success. This material offers new perspectives in the treatment of tibial plateau fractures.

Adult↗
PubMed2004

Surface studies on acrylic bone cement.

Poly(methyl methacrylate) (PMMA) is used to fill the gap between the prosthesis and the surrounding bone in cemented arthroplasties. Biocompatibility problems related to bone cement application limit the clinical success of these cemented arthroplasties. Being the cement surface in close connection with the living bone, it is reasonable to assume that surface properties such as, surface composition and surface energy, will play a role in the biomaterial performance. X-ray photoelectron spectroscopy (XPS) analysis and surface energy studies were carried out during 4 months, in order to assess a possible correlation between aging time and surface changes. The aging of PMMA, in a biological model fluid, strongly influences the composition and wettability of the cement surface. These changes may be explained through the hydrolysis of PMMA ester groups and the subsequent hydrogen bonding. Although our study does not exactly reproduce the in vivo environment surrounding a prosthesis, it suggests that the changes in the composition and wettability of the surface may modulate the host response towards the implant, thus contributing to its loosening.

Bone Cements↗
PubMed1989

On the correlation between micromotion and histology of the bone-cement interface. Report of three cases of knee arthroplasty followed by roentgen stereophotogrammetric analysis.

The bone-cement interface from the tibial components in three clinically successful unicompartmental Marmor arthroplasties was studied histologically. The migratory behavior of the prostheses had been followed by roentgen stereophotogrammetic analysis (RSA) since their insertion 5-7 years prior to retrieval for reasons other than mechanical loosening. The prostheses migrated during the first 3 years, after which no further migration occurred. Clinical and RSA data thus suggest stable fixation. All interfaces were made up entirely of soft tissue. In the sagittal portion, between the prosthesis and the tibial eminence there was mostly fibrous tissue, while the region underneath the prostheses consisted largely of highly differentiated fibrocartilage. This histologic picture is compatible with a migratory pattern, as measured by RSA, of stable fixation after an initial remodelling period, which the authors believe has the potential of good long-term results.

Aged↗
PubMed1999

Measurement of non-linear microcrack accumulation rates in polymethylmethacrylate bone cement under cyclic loading.

Damage accumulation in the cement mantle used to fixate bone prosthesis is one failure scenario for joint reconstruction. It can be described as the phenomenon of numerous microcracks initiating and propagating within the material. Microcracks grow in the cement mantle causing it to gradually lose its mechanical integrity, leading to loosening of the prosthesis. In this study microcracking within acrylic bone cement was quantified over the course of a fatigue test. Identification of new cracks and the growth of pre-existing cracks was monitored at intervals during fatigue testing of five specimens at a mean cyclic stress of 7.5 MPa. Given these measurements, an average damage evolution curve was derived for acrylic bone cement. It was observed that the initiation sites for microcracks were the pore perimeters; therefore, the number of microcracks present in a sample is dependent on porosity. Variability was found within the results and the majority of the variability was accounted for by the difference in the porosity of each sample. Results have identified non-linear damage evolution. On a simplified level a power law equation can be used to describe the damage evolution process.

Journal Article↗
PubMed1989

Retrograde root filling using antibiotic-containing, radiopaque, bone cement.

An investigation is reported on the in-vitro behaviour, characteristics and properties of three gentamicin-containing radiopaque bone cements that are considered to be promising retrograde root-filling materials. Three commercially available cements, CMW-1G, CMW-3G and Palacos R with gentamicin were studied with regard to bacteriocidal properties, tissue compatibility in cell culture, and ability to seal tooth cavities as evidenced by dye diffusion. Results were compared and contrasted with those obtained with an amalgam. The antibiotic-containing cements investigated are considered to have some distinct advantages over amalgam when used as retrograde root-filling materials in vitro. Amalgam was found to have poor bacteriocidal properties and poor tissue compatibility but slightly better apical sealing abilities than the cements. No apparent drawbacks were found with the cements.

Acrylic Resins↗
PubMed2007

Continuous wave ultrasound enhances vancomycin release and antimicrobial efficacy of antibiotic-loaded acrylic bone cement in vitro and in vivo.

Although antibiotic-loaded bone cement (ALBC) is used as a drug delivery vehicle to decrease infection rates, the varied clinical effect of the antibiotic release remains controversial. The objective of this study is to investigate the enhancement of continuous wave ultrasound (CWU) on vancomycin release and antimicrobial efficacy of ALBC in vitro and in vivo. We measured vancomycin concentrations after a 0.5-h exposure of CWU. The results showed that CWU increased the drug elution by 2.57-27.44% when compared with the controls in vitro. Ultrasonic intensity and vancomycin load both had a significant effect on the cumulative drug elution at 10.5 h, with a significant interaction between each other. We also implanted ALBC specimens into hip joints of sixteen New Zealand White female rabbits after inoculations of Staphylococcus aureus around primary implants for 30 days. Vancomycin concentrations in the hip cavity and urinary elimination of vancomycin were both measured after intermittent exposures of CWU. The results showed that CWU increased local Tmax by 47.6 microg/mL and urinary elimination of vancomycin by 109.56 microg, but failed to prolong local T>MIC. On day 30 after the implantation, assessment in clinical performance, radiology, bacteriology, and histology all showed a tendency of decreased bacterial vitality and relieved inflammation in the infected hip treated by CWU. This study suggested that CWU could effectively enhance vancomycin release and antimicrobial efficacy of ALBC, which may be of clinical significance for treating prosthesis-related infections.

Animals↗
PubMed2002

Influence of pressurization on flexural strength distributions of PMMA-based bone cements.

Flexural strength distributions of standard viscosity and low viscosity bone cements based on Polymethylmethacrylate were obtained by testing the materials in four-point bending according to the ISO 5833 protocol. The cement dough was poured into a mold and was allowed to cure at atmospheric pressure. An additional set of specimens of the standard viscosity cement was prepared under pressure while the cement dough was polymerizing in the mold. Following preparation, test specimens were stored in a 37 degrees C water bath for 48 h. The two-parameter Weibull model, which was used to analyze the data, gave a good representation of the fracture loads distribution. Low viscosity cement displayed a higher mean flexural strength and a slightly lower data scatter than standard viscosity cement. The mean flexural strength of the cement increased about 60% when pressure was applied compared with the same material cured at atmospheric pressure. The Weibull modulus, m, characterizes the scattering in the measured values of strength. For the cement prepared at atmospheric pressure the m value was 8.6 while for the cement cured under pressure it was 12.3, which reveals a reduction in the data scatter. The cement tested in four-point bending displayed lower mean flexural strength compared with the cement tested in three-point bending. The influence of the load type upon the mean flexural strength was satisfactory predicted by Weibull model.

Journal Article↗
PubMed2003

The effect of varying percentage hydroxyapatite in poly(ethylmethacrylate) bone cement on human osteoblast-like cells.

Poly(ethylmethacrylate) (PEMA) bone cement has been developed, and the cements mechanical properties are improved by the incorporation of particulate fillers, such as hydroxyapatite (HA). In this in vitro study, human osteoblast-like (HOB) cells were used to examine the effect on cellular behavior of the addition of HA to PEMA using a plain PEMA control. Thymidine uptake ((3)H-TdR) and total DNA were used to assess cell growth and proliferation. Confocal laser scanning microscopy (CLSM) was used to study focal contacts and actin cytoskeletal organisation. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to assess cell morphology and cellular ultrastucture. The early time points showed preferential anchorage to the HA exposed on the cement surface, but no difference in adhesion or proliferation. These results have been attributed to increases in residual monomer with HA incorporation, as shown by proton nuclear magnetic resonance (H(1)-NMR) spectra.

Journal Article↗
PubMed2004

New method of pediatric cranioplasty for skull defect utilizing polylactic acid absorbable plates and carbonated apatite bone cement.

Cranial defect repair in the pediatric population requires a variety of special considerations. The pediatric skull has a dynamic nature that prohibits the use of rigid fixation, which is commonly applied in the adult population. A technique using a combination of polylactic acid plates and carbonated apatite bone cement has been devised by our group. Skull defects of varying sizes were repaired in 34 pediatric patients. Patients were examined on postoperative day 3 and at 3 months via three-dimensional computed tomography scans. Patients have been followed up to 60 months after surgery without complications or failures to date. This method benefits the pediatric patients undergoing cranioplasty by minimizing the insertion of long-term foreign bodies and allows the possibility for transformation of this construct into viable tissue.

Absorbable Implants↗
PubMed1984

The effect of antibiotic additions on the fracture properties of bone cements.

Two commercially developed cements (Palacos and Zimmer) were tested for fracture toughness with and without gentamicin additions. Compact tension specimens were molded under standardized conditions and divided into four groups. Each group contained specimens of both plain and both antibiotic cements. One group was tested as zero-time controls. The remaining three groups were radiation sterilized. One group was tested as zero-time sterilization controls. Another group was tested after 2 months immersion in Ringer's lactate to elute gentamicin. The last group was tested after being implanted for 2 months subcutaneously in dogs. Comparison of the fracture toughness of the two zero-time groups showed no effect of radiation sterilization on any of the four types of cement. The results from both the group immersed in Ringer's solution and the group implanted in dogs showed no significant effect on fracture toughness with gentamicin additions. Both these groups, however, did have greater toughness values than the zero-time groups, probably caused by the more complete polymerization with time. Furthermore, the Palacos cement exhibited a greater toughness than the Zimmer cement. The results of this study demonstrate that the addition of gentamicin to bone cement is not deleterious to the fracture properties.

Animals↗
PubMed2002

Effect of antibiotics on the properties of poly(methylmethacrylate)-based bone cement.

The goal of this study was to examine the relationship between gentamicin concentration in Palacos R bone cement (in the mass fraction range of 0-9.4%) and various properties of the cement. The results from the thermal, density, and static compression tests show that gentamicin favors the cement polymerization in its final steps, and forms a diphasic structure with the cement [poly(methylmethacrylate)] matrix. The static compression properties in the dry state are only slightly modified by the presence of the antibiotic. Concerning aging in water at 37 degrees C, two types of behavior can be distinguished: below a critical concentration, approximately 3-4%, the extraction of gentamicin by water is slow and there is only a slight change of static compression properties. In contrast, above this critical concentration, the gentamicin extraction is fast and almost complete after 48 weeks, and there is a considerable loss of static compression properties.

Anti-Bacterial Agents↗