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At least 613 records · Page 34Linked to original sources
PubMed2002

Effect of hydroxyapatite morphology/surface area on the rheology and processability of hydroxyapatite filled polyethylene composites.

The commercial success of hydroxyapatite (HA) filled polyethylene composite has generated growing interest in improving the processability of the composite. A number of synthetic procedures and post synthesis heat treatment of HA has lead to the availability of powders with widely varying morphological features. This paper addresses the effect of morphological features of HA on the rheology and processability of an injection-moulding grade HA-HDPE composite. The results showed that low surface area HA filled composite exhibited better injection processing characteristics through improved rheological responses. The effect of reducing the surface area of the filler is to require less polyethylene to wet the filler and allows more polyethylene to be involved in the flow processes. These changes reduced the temperatures and pressures required for successful processing.

Biocompatible Materials↗
PubMed2002

Measurement of polyethylene wear - a new three-dimensional methodology.

Studies in the field of polyethylene wear of the acetabular cup have been generally discussed using a two-dimensional assumption on the coronal plane; significant errors thus appear. The present study proposes a new, advanced methodology in order to accurately estimate the polyethylene wear. Through the usage of the distance between X-ray focus and film and only one follow-up, anteroposterior (AP) radiograph, a three-dimensional (3D) algorithm is introduced here. Here, 91 primary total hip joint replacements in 67 patients have been examined and three findings are obtained. Results show that the mean rate of 3D linear wear of the polyethylene estimated by the current method is 0.230+/-0.036 mm per year, that of the 2D linear wear is 0.148+/-0.028 mm per year. Moreover, the wear depth of the femoral head on the sagittal plane is 0.173+/-0.043 mm per year by the current method. This study also shows that the adoption of only one AP radiograph in the evaluation of the 3D penetration of femoral head is possible. Furthermore, the methodology proposed here is more convenient than others.

Adult↗
PubMedDate not supplied

Cutaneous toxicity studies with methoxy polyethylene glycol-350 (MPEG-350) in rats and rabbits.

The methoxy polyethylene glycols (MPEGs), also referred to as polyethylene glycol methyl ethers, are high molecular weight polymers similar in structure and nomenclature to the polyethylene glycols. Because of the potential for repeated cutaneous exposure of humans to MPEG-350 and the known toxicity of lower alkylene glycol ethers such as ethylene glycol monomethyl ether (EGME), studies were conducted to evaluate the potential toxicity and irritation of MPEG-350 following repeated, cutaneous treatment. New Zealand White rabbits were cutaneously treated with 1.0 ml of either undiluted MPEG-350 or a 50% solution of MPEG-350 in 0.1% methyl cellulose in distilled water for 9 or 90 days. CD(SD)BR rats were cutaneously treated with up to 5 g/kg/day of undiluted MPEG-350 for 14 or 28 days. The treatment area was not occluded but animals were fitted with Elizabethan collars during treatment. Rabbits were treated 6 hr/day 5 days/wk. Rats were treated for at least 19 hr/day (at weekends, the exposure time was approximately 70 hr). None of the animals died. Slight decreases in mean absolute body weight of all dose groups of male rats as compared with the concurrent control group may have been related to minimal toxicity of the test substance but was probably secondary to the dosing procedures. Signs of slight cutaneous irritation were observed in many treated animals of both species but only a few rabbits had confirmatory microscopic diagnoses while none of the rats had microscopic changes in the skin. Slight decreases in the mean absolute weight of the testes, spleen and thymus were observed in rats treated with 5 g undiluted MPEG-350/kg/day for 14 days. Similar changes were not observed in rats following 28 days of treatment. There were no microscopic changes in any of these organs except for one rat that had moderate to high aspermatogenesis and multinucleated spermatids. There were no microscopic changes observed in the testes of any other animals (including rats treated for 28 days with 5 g undiluted MPEG-350/kg/day). Therefore, a relationship of the testicular changes observed in this one animal to treatment with MPEG-350 was considered to be improbable. While a mechanism for the production of toxic metabolites from systemically absorbed MPEG-350 was considered to be possible, there was no indication from these and other cutaneous studies of significant cutaneous absorption of the compound. Therefore, repeated cutaneous exposure to MPEG-350 was not expected to result in significant toxicological effects.

Administration, Cutaneous↗
PubMed1997

Usefulness of polyethylene glycol for cryopreservation by vitrification of in vitro-derived bovine blastocysts.

A series of five experiments measured the high survival of bovine blastocysts produced in vitro after cryopreservation by vitrification. The vitrification solution (designated VS) contained 40% (v/v) ethylene glycol, 6% (w/v) polyethylene glycol and 0.5 M sucrose in phosphate-buffered saline. Embryos developed in vitro at Days 7 and 8 (Day 0 = insemination day) were exposed in one step to VS for 1 min or two steps with 10% ethylene glycol for 5 min and then VS for 1 min. In both cases, the embryos were finally cryopreserved in liquid nitrogen. After the embryos were warmed rapidly and the VS solution diluted, the survival rates were assessed by monitoring hatching rate in vitro. They were 13.0% for the one-step and 72.7% for the two-step procedures (P < 0.001). When embryos were exposed to individual solutions containing 6% (w/v) of each of 4 macromolecules (polyethylene glycol, BSA, polyvinylpyrrolidone or Ficoll) in the two-step protocol and then cryopreserved, the survival rates were 79.3, 34.8, 41.4 and 57.1%, respectively. After embryos had been exposed to the VS in two steps and then cryopreserved, there were no significant differences in survival rates when the solutions were diluted with or without sucrose. These results indicated that a vitrification solution containing polyethylene glycol can be used for cryopreservation of bovine blastocysts produced in vitro, and that a two-step addition of VS improved the in vitro survival of post-warming embryos. It was also shown to be possible to dilute post-warming embryos directly without the use of sucrose solution.

Animals↗
PubMed2001

On-line deproteinization by adsorption of proteins on a polyethylene powder pre-column for the determination of Na, K, Mg and Ca in human serum by high-performance liquid chromatography.

Deproteinization of human serum was carried out on-line using a polyethylene powder cartridge as pre-column. The serum sample, after dilution, was injected into the chromatograph, and when passing through the cartridge the proteins were adsorbed by the polyethylene. A protein-free eluate was carried to the analytical column while the pre-column was washed with methanol and water to elute the adsorbed proteins by changing the pump channels. After washing, the pre-column was conditioned with the eluent to receive the next sample. Deproteinization was evaluated off- and on-line using pooled serum, and testing the protein residue after passing through a polyethylene cartridge with the Comassie Brilliant Blue reaction. Parameters such as serum volume, eluent and washing solution were investigated. Sodium, potassium, magnesium and calcium determinations were performed by high-performance liquid chromatography with conductimetric detection. The proposed method is suitable for the determination of these cations in serum samples without further treatments. The total analysis time was about 20 min and a linear range from 0.3 to 1.2 mg/l for sodium, potassium, magnesium and calcium was observed. The method was characterized by a precision of about 95% and recoveries from spiked samples were between 96 and 102%. The results for serum samples analysed by the proposed method were compared with photometry and atomic absorption spectrometry.

Adsorption↗
PubMed2003

Comparative study of the lubricant performance of Compritol HD5 ATO and Compritol 888 ATO: effect of polyethylene glycol behenate on lubricant capacity.

The aim of this paper is to study the lubricant capacity of Compritol HD5 ATO, a glyceryl and polyethylene glycol dibehenate, obtained by atomization. This material is compared to Compritol 888 ATO, constituted only by glyceryl dibehenate. First, this study verifies that Compritol HD5 ATO and Compritol 888 ATO present the same granular characteristics and that their mixes with Lactopress present no structural differences. Secondly, in term of compressibility and cohesiveness, the use of Compritol 888 ATO or Compritol HD5 ATO with Lactopress does not involve any significant modification. Finally, the minor difference of lubricant capacity between Compritol HD5 ATO and Compritol 888 ATO has no consequence in compression practice. The presence of polyethylene glycol behenate does not decrease the glyceryl dibehenate compression functionality. This study concludes that Compritol HD5 ATO could be a very interesting excipient because it associates the glyceryl dibehenate lubricant capacity with the polyethylene glycol behenate-specific capacity in terms of dissolution enhancement.

Chemistry, Pharmaceutical↗
PubMed1998

Determination of the enantiomeric purity of (-) terbutaline by capillary electrophoresis using cyclodextrins as chiral selectors in a polyethylene glycol gel.

A method was developed for determination of the enantiomeric purity of the therapeutic-pharmacological active (-)-enantiomer of terbutaline using cyclodextrins as a chiral selector dissolved in a removable liquid polyethylene glycol gel by use of capillary electrophoresis. The effect of temperature, type and concentration of polyethylene glycol and cyclodextrins was studied on the resolution between the two enantiomers. Best results were obtained with 10 mM hydroxyethyl-beta-cyclodextrin dissolved in a 10% polyethylene glycol-2000 solution at 15 degrees C. Under these conditions, an impurity of 0.1% (distomer/eutomer) can be readily detected.

Chemistry Techniques, Analytical↗
PubMed1991

[Comparison of thrombogenic risk between teflon and polyethylene in prolonged catheterization of the radial artery].

This prospective study was designed to compare the rates of radial artery thrombosis after long-term cannulation with two different types of catheters with similar size. It included 101 patients, randomly assigned to group A (n = 51, 61 +/- 17 years, 80% males), and group B (n = 50, 55.8 +/- 18 years, 54% males). Patients in group A were cannulated with a polyethylene catheter (Leader Cath. 115-09), and those in group B with a Teflon catheter (Plastimed Seldicath). The diagnosis of arterial occlusion was made by way of a bedside angiography performed before catheter removal. An X-ray was taken after injection of 10 to 15 ml Hexabrix through the catheter. The two groups were similar with regard to anthropometric parameters (except for the sex ratio), cannulation technique, used drugs, duration of cannulation, pathological events during the stay in intensive care. The rate of complete arterial thrombosis in the two groups was similar (10%). There were no differences in the rates of partial thrombosis (51 vs. 36%, n.s.) and of absence of thrombosis (39 vs. 54%, n.s.). The rate of arterial thrombosis did not vary with the duration of cannulation, nor with age, sex, systemic heparinization, vascular collapse, cannulation technique. However, 4 polyethylene catheters were infected on removal (coagulase negative Staphylococcus, Pseudomonas aeruginosa) versus only one Teflon catheter (Staphylococcus epidermidis). In conclusion, the biocompatibility of Teflon and polyethylene catheters was found to be similar.

Adult↗
PubMed2000

Reduction of polyethylene wear by concave dimples on the frictional surface in artificial hip joints.

For the purpose of reduction of polyethylene wear generated in artificial hip joints, concave dimples were formed on the surface of the metal femoral head by electrical discharge etching with the constant diameter of 0.5 mm, pitch of 1.2 mm, and depth of 0.1 mm. Using a hip joint simulator, the total amount of polyethylene wear was 7.2 mg in the concave-patterned condition and 23.1 mg in the nonpatterned condition. The reasons for the reduction of polyethylene wear by the concave pattern may be i) a reduction of abrasive wear by providing escape dimples for wear particles and ii) an improvement in the lubricity on the frictional surface by the supply of lubricant that is stored in dimples.

Friction↗
PubMed1995

Fracture of the femoral head after ceramic-on-polyethylene total hip arthroplasty.

Four of 184 ceramic femoral heads that the authors used in total hip arthroplasty fractured from 5 to 9 months after surgery. A polyethylene-lined acetabular component was used in all cases. The fracture rate, 2.2%, was much higher than previously reported for ceramic head fractures when used with a polyethylene cup. The fractures occurred during normal daily activities. Possible causes included manufacturing defects, neck length (short in all cases), bearing diameter (28 mm in all cases), cone-trunnion mismatch, excess hoop stresses from impaction, or material deterioration. All patients were treated by removal of debris, wide excision of capsular tissue containing tiny abrasive fragments, exchange of the modular polyethylene liner, and implantation of a cobalt-chrome femoral head. The trunnion had been somewhat damaged by relatively brief exposure to the ceramic particles in every case. The authors' experience suggests that ceramic femoral heads be used with caution.

Adult↗
PubMed1996

Impact of gamma sterilization on clinical performance of polyethylene in the knee.

Damage and rapid wear of the ultrahigh-molecular-weight polyethylene bearings of knee components continue to be major sources of failure of knee prostheses. Despite considerable research into the roles of design, polyethylene thickness and quality, and component alignment, the source of the rapid wear failures has remained a mystery. This study documents elevated oxidation resulting from the use of gamma sterilization in air, the most common sterilization technique used by the orthopaedic implant industry. This oxidation reduces static strength and elongation properties and significantly decreases the resistance of polyethylene bearings to fatigue, a frequent source of early damage of many of these devices.

Gamma Rays↗
PubMed1997

Large amounts of polyethylene debris in the interface tissue surrounding bipolar endoprostheses. Comparison to total hip prostheses.

A histologic and biochemical comparison of interface membranes around femoral components of bipolar endoprostheses (n = 17) and total hip prostheses (n = 17) inserted without cement was conducted. The patients' profiles were similar in both groups with respect to age, sex, primary diagnosis, weight, and the interval between primary and revision arthroplasty. Macroscopically, marked circumferential abrasion of the polyethylene insert in the retrieved bipolar cups was noted. Histologic analysis revealed significantly larger amounts of polyethylene debris in the bipolar group. The membranes from the bipolar group also produced significantly greater amounts of prostaglandin E2 (P < .05). The inflammatory membranes associated with large amounts of polyethylene debris may have contributed to aseptic loosening and osteolysis in patients with a bipolar hip prosthesis.

Collagenases↗
PubMed1997

Wear of retrieved cemented polyethylene acetabula with alumina femoral heads.

Four yttrium-stabilized alumina ceramic-on-polyethylene articulations obtained from patients who were undergoing revision surgery for sepsis (3) or recurrent dislocation (I) between 34 and 73 months were evaluated to assess their in vivo wear performance. The annual volumetric wear of the acetabular components determined directly by a fluid displacement method ranged from 58 to 140 mm3/y. Scanning electron microscope examination of these four ceramic heads revealed similar surface damage in all cases from a variety of causes. These included differential granular wear (alumina grains and yttrium-stabilized alumina grains at different depths), multidirectional scratches with heaped up boundaries, and incompletely sintered grains, as well as the formation of craters and separation of grain boundaries. The femoral heads in this small series of revision cases show that yttrium-stabilized alumina ceramic heads may develop surface irregularities from either manufacturing processes or in vivo use. The wear rates of this type of alumina-on-polyethylene articulation up to the time of revision were not substantially different from those found in other metal-on-polyethylene articulations retrieved at revision surgery.

Acetabulum↗
PubMed1999

Fracture of the femoral component associated with polyethylene wear and osteolysis after total knee arthroplasty.

Fracture of the femoral component associated with polyethylene wear and osteolysis after total knee arthroplasty (TKA) has not been well reported before. A 63-year-old man with osteoarthritis of the right knee underwent TKA with a New Jersey LCS Knee, with cementing on the tibia and patella but not on the femoral component. After 42 months, in addition to wearing of polyethylene of the tibia and patella, severe osteonecrosis of the medial femoral condyle was noted. Osteonecrosis caused loss of osseous support of the medial flange of the femoral component, and the bone ingrowth of the central and lateral flange to the distal femur was so good that it overcame the yield stress of the metal of the femoral component and caused fracture of the femoral component. The osteolytic area was filled with autogenous iliac bone, and a new femoral component was inserted and cemented. The patient's condition became satisfactory with relief of pain. Although uncommon, fracture of the femoral component does occur associated with polyethylene wear and osteolysis.

Arthroplasty, Replacement, Knee↗
PubMed1999

Severe polyethylene wear in uncemented acetabular cup system components: a report of 5 cases.

We report 5 cases of severe failure of the polyethylene liner at 4 to 7.4 years after uncemented anatomic medullary locking (AML) total hip arthroplasty, using the acetabular cup system (ACS). The mode of failure was by a combination of wear-through to the metal backing and liner fracture. Four of the 5 cases were associated with a 32-mm head. The ACS design is flawed because of a lack of hemispherical geometry resulting in rim loading on a region of the liner that has the thinnest polyethylene. All patients with this type of implant should be monitored for evidence of excessive polyethylene wear.

Acetabulum↗
PubMed1999

Polyethylene wear and synovitis in total hip arthroplasty: a sonographic study of 48 hips.

Forty-six patients (48 hips), operated on with cemented total hip arthroplasty (THA) because of arthrosis, were examined radiographically and sonographically at 10-year follow-up. Polyethylene wear of acetabular cups was measured on conventional non-weight-bearing pelvic radiographs, and the volume of polyethylene debris was calculated. Radiographic signs of loosening were identified. The capsular distance (ie, thickness of the synovium or synovial contents) was measured sonographically. We found a significant correlation between increased volumetric wear and increased capsular distance. Hips with radiographically loose acetabular components had significantly greater volumetric wear and capsular distance than those without signs of acetabular loosening. This relationship was not observed in hips with radiographically loose femoral components. In cemented THA, the volume of polyethylene wear debris and the thickness of the synovium and the synovial contents are related. In the event of radiographic loosening of the acetabular component, they are both increased.

Aged↗
PubMed2002

[Use of a polyethylene bag: a way to improve the thermal environment of the premature newborn at the delivery room].

BACKGROUND: Early interventions, such as occlusive wrapping of very low birth weight infants at delivery reduce postnatal temperature fall. This new intervention was implemented in our hospital on January 2000. The aim of this study was to investigate retrospectively the effect of polyethylene wrap, applied immediately at birth, on thermoregulation. PATIENTS AND METHODS: Matched pair analysis was conducted for 60 infants delivered inborn at less than 33 weeks' gestation and 60 premature infants who were born during the second half of 1999 fulfilling the same criteria. The only difference in the management (medical and environmental) was wrapping with a polyethylene bag in the delivery room. Rectal temperature and other vital parameters were taken, after removal of wraps, on admission to NICU. RESULTS: The perinatal characteristics of both groups were comparable. Use of wrapping resulted in a significantly higher admission rectal temperature (difference in means = 0.8 degree C, p < 0.0001), this difference was also significant in infants < 30 weeks. The incidence of hypothermia (< 35.5 degrees C) was less frequent in infants enclosed in plastic bags (8.3% vs 55%). No side effects (skin burns, infection or hyperthermia) were attributable to the intervention. The heart rate was higher in the wrapping group (163 +/- 16 vs 150 +/- 17 b/min, p < 0.01), as well as the capillary glycemia (62 +/- 26 vs 45 +/- 30 mg/dl, p < 0.01). There was no significant difference on arterial pressure. CONCLUSION: Occlusive wrapping with a polyethylene bag at birth prevented low rectal temperature in premature infants in the immediate postnatal period. This method is easy, practical and effective, and does not interfere with current practice for resuscitation.

Bedding and Linens↗
PubMed1998

Optimization of an effervescent tablet formulation containing spray dried L-leucine and polyethylene glycol 6000 as lubricants using a central composite design.

A rotatable central composite design is used to evaluate the effects of lubricants and compression force on the physical characteristics of effervescent tablets. Effervescent tablets lubricated with a combination of spray dried L-leucine and polyethylene glycol 6000 are prepared by direct compression and examined. Residual force, crushing strength and disintegration time are considered as response variables and related to the L-leucine and polyethylene glycol concentrations and to the compression force. The calculated models are used to assess the influence of the production factors on tablet properties. As increasing amounts of L-leucine, showing good lubricating properties, reduce the crushing strength and prolong tablet disintegration, the L-leucine concentration is kept at a low level. An optimum tablet formulation contains 2% L-leucine and 3% polyethylene glycol 6000. The tablets have a tensile strength of 0.47 MPa and disintegrate in less than 2 min. Predicted and experimental results are in agreement within a 95% CI.

Chemistry, Pharmaceutical↗