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PubMed2001

Chemically coupled hydroxyapatite-polyethylene composites: structure and properties.

Silanation of hydroxyapatite and acrylic acid grafting of polyethylene were employed to improve bonding between hydroxyapatite and polyethylene. The structure and properties of chemically coupled hydroxyapatite reinforced high-density polyethylene (HA/HDPE) composites were subsequently investigated using various techniques. It was shown that there existed a silicon-containing interphase between the hydroxyapatite particle and the polyethylene matrix. The silane coupling agent used promoted chemical adhesion between hydroxyapatite particles and the polymer. The use of the silane coupling agent also facilitated the penetration of polymer into cavities in individual ceramic particles, which resulted in enhanced mechanical interlocking at the matrix-reinforcement interface. With a strong bond (both mechanical and chemical) being formed between hydroxyapatite and polyethylene, chemically coupled HA/HDPE composites possessed improved mechanical properties and fracture behaviour.

Durapatite↗
PubMed2003

The effect of frictional heating and forced cooling on the serum lubricant and wear of UHMW polyethylene cups against cobalt-chromium and zirconia balls.

Hip simulator tests of femoral balls of cobalt-chromium alloy or zirconia against acetabular cups of UHMW polyethylene were run with and without a coolant circulated inside the femoral balls. Without cooling, the wear of polyethylene against zirconia was about 48% lower than with cobalt-chromium alloy, but the steady-state temperature of the zirconia ball was higher (55 degrees C vs. 41 degrees C), and there was more precipitation of protein from the serum, which sometimes formed an adherent layer on the surface of the zirconia. Circulating coolant at 1-20 degrees C markedly reduced the bearing temperatures and the protein precipitation. With coolant at 4 degrees C, wear of the polyethylene against cobalt-chromium alloy was about 26% lower than against zirconia, but the macroscopic and microscopic appearance of the worn polyethylene surfaces were unlike that typically generated in vivo. With or without coolant, the morphology of the polyethylene wear debris was comparable to that generated in vivo, but the ratio of fibrillar to granular debris was higher at the reduced temperature. These results suggested that circulating coolant at an appropriate temperature could avoid overheating (due to non-stop running of the simulator), preventing excessive protein precipitation while providing wear surfaces and wear debris with morphologies closely comparable to those generated in vivo.

Artifacts↗
PubMed2001

Immobilized salt-tolerant yeasts: application of a new polyethylene-oxide support in a continuous stirred-tank reactor for flavour production.

Immobilization of salt-tolerant yeasts considerably decreases the total time required for the flavour development in soy-sauce processes. For immobilization of cells, alginate gel is mostly used as support material. However, alginate is not very suitable for use in soy-sauce processes because alginate is sensitive to abrasion and chemically unstable towards the high salt content of the soy-sauce medium. In contrast, a newly developed polyethylene-oxide gel seems to be more suitable, but this gel has not been used so far for flavour production in a bioreactor with a high salt content. Therefore, this gel was applied with immobilized salt-tolerant yeasts in a continuous stirred-tank reactor, containing more than 12.5% (w/v) salt. In this reactor, the polyethylene-oxide gel particles did not show any abrasion for several days, while alginate gel beads were already destroyed within 1 day. In addition, the polyethylene-oxide gel particles with immobilized salt-tolerant yeasts Candida versatilis and Zygosaccharomyces rouxii showed a good flavour production. From this work, it was concluded that the application of polyethylene-oxide gel in long-term soy-sauce processes is attractive in the case the sticking together of polyethylene-oxide gel particles can be controlled.

Alginates↗
PubMed1992

Effects of isopropyl alcohol, ethanol, and polyethylene glycol/industrial methylated spirits in the treatment of acute phenol burns.

STUDY OBJECTIVE: To compare the effects of water rinse with those of isopropyl alcohol, polyethylene glycol with industrial methylated spirits, or ethanol on cutaneous phenol burns. DESIGN: Controlled trial with all animals receiving all treatments applied to different cutaneous phenol burn sites. TYPE OF PARTICIPANTS: Swine weighing 9 to 18 kg. INTERVENTIONS: In phase 1, each burn site was treated with water rinse for zero, one, or five minutes combined with either isopropyl alcohol, polyethylene glycol with industrial methylated spirits, ethanol, or no other treatment. Biopsies of treatment sites were done at 30 minutes and at 48 hours. In phase 2, a pilot study, the effect of isopropyl alcohol, polyethylene glycol with industrial methylated spirits, or water treatment on serum phenol levels was noted in animals with 5%, 10%, and 15% body surface area burns. MEASUREMENTS AND MAIN RESULTS: In phase 1, on histological examination of biopsy specimens, significant differences in tissue damage occurred among the groups (P < .05). Isopropyl alcohol and polyethylene glycol with industrial methylated spirits were the most efficacious treatments; the duration of water rinse had no significant effect. In phase 2, the systemic absorption of phenol may be greater with water treatment than with isopropyl alcohol treatment. CONCLUSION: Isopropyl alcohol and polyethylene glycol with industrial methylated spirits are equally effective in the amelioration of phenol burns of less than 5% total surface area. The wider availability of isopropyl alcohol makes it potentially the most useful treatment for these small burns. Further studies of its risks are needed.

1-Propanol↗
PubMed2001

Contact stress on polyethylene components of a new rotating hinge with a spherical contact surface.

OBJECTIVE: To assess the nonlinear contact stress of a new rotating hinge of our knee prosthesis at various rotation angles. DESIGN: The contact surface between the metal tibial bearing and the ultra-high-molecular weight polyethylene plate of a conventional rotating hinge is of cylindrical design. We have designed a new type of rotating hinge with a congruous spherical contact surface. BACKGROUND: The endoprosthesis for reconstruction of limb after wide resection of malignant tumor around knee usually incorporates a rotating hinge. Our new rotating hinge with a spherical contact surface incorporates the benefits of an increased contact surface and potentially increased rotational stability during axial loading. METHODS: We utilized the ABAQUS finite element program to assess the nonlinear contact stress of this new rotating hinge at rotation angles of 0 degrees, 4 degrees and 8 degrees, based on a contact force of about 2800 N. RESULTS: The results show that von Mises stress for the finite element model of the polyethylene component of this rotating hinge ranges from 4.90 x 10(-6) to 8.22 MPa at the aforementioned rotational angles. The von Mises stress is about 1.31--1.82 MPa on the major parts of the ultra-high-molecular weight polyethylene plate, including both flanks. There is a mild stress concentration on the outer edge of polyethylene component, especially at 4 degrees and 8 degrees of rotation. The maximum values of von Mises stress at the contact surface at 0 degrees, 4 degrees and 8 degrees of rotation are 5.92, 7.49 and 8.22 MPa, respectively. These contact stresses are within the safety range of the ultra-high-molecular weight polyethylene (compressive yield strength, 14 MPa). CONCLUSIONS: This new rotating hinge has an evenly distributed contact stress during axial load because of congruous contact design.

Finite Element Analysis↗
PubMed2003

Clinical performance of a highly cross-linked polyethylene at two years in total hip arthroplasty: a randomized prospective trial.

We report the 2-year results for a prospective randomized trial comparing highly cross-linked with standard polyethylene in total hip replacements. In our study, 46 hips were available for radiographic analysis at 2- and 3-year follow-up. Femoral bearings were 28-mm cobalt chrome with the polyethylene insert randomly selected at the time of implantation to be highly cross-linked polyethylene (Crossfire; Stryker Howmedica Osteonics, Allendale, NJ) or standard polyethylene (N(2)/Vac, Stryker Howmedica Osteonics). Polyethylene wear rates were measured based on anterior-posterior (AP) and lateral pelvis radiographs at 6 weeks and at yearly intervals using a validated computer-assisted edge-detection method. Wear rates between the 2 groups were compared using the nonparametric Mann-Whitney test at the 95% level. A significant reduction in 2- and 3-dimensional linear wear rates (42% and 50%) was found in the highly cross-linked group (P =.001 and P =.005).

Arthroplasty, Replacement, Hip↗
PubMed1995

Use of cemented all-polyethylene and metal-backed acetabular components in total hip arthroplasty. A comparative study.

The results of 115 primary total hip arthroplasties (97 patients) performed using the Charnley system and contemporary cementing techniques were reviewed. Fifty-five all-polyethylene cups and 60 metal-backed cups were used. The mean follow-up period was 84 months. No statistically significant difference was noted between groups for radiographic loosening and no cup has been revised to date. Survival analysis did not reveal a statistically significant difference between groups. Although all-polyethylene cups had significantly greater polyethylene thickness, no difference was noted for rate of wear. Increased loosening of the metal-backed cups was not observed. Polyethylene thickness is increased by the use of 22-mm heads and this may have accounted for the lack of difference in loosening rates of the all-polyethylene and metal-backed cups.

Acetabulum↗
PubMed1993

Comparison of metal-backed and all-polyethylene tibial components in cruciate condylar total knee arthroplasty.

An evaluation of 78 knees in 63 patients using the cruciate-sparing total condylar prosthesis was performed. At a mean of 10 years following the arthroplasty there were 86% good or excellent results in knees with an all-polyethylene tibial component compared to 95% with a metal-backed tibial component (NS). Survivorship at 10 years using an endpoint of revision was 96% (NS) in both groups; using an endpoint of revision or poor knee score was 85% (NS) in the metal-backed compared to 92% (NS) in the all-polyethylene groups; using an endpoint of revision, poor knee score, or complete radiolucent line was 85% in the metal-backed compared to 90% (NS) in the all-polyethylene groups. There were no significant differences in the frequency of radiolucent lines at the last evaluation. Two percent of the tibial components in the metal-backed group had complete radiolucent lines compared to none in the all-polyethylene group. The cruciate-sparing total condylar prosthesis provides satisfactory results with no significant differences between the metal-backed or all-polyethylene tibial components at 10 years.

Adult↗
PubMed2004

Bowel preparation for colonoscopy: a randomized controlled trial comparing polyethylene glycol solution, one dose and two doses of oral sodium phosphate solution.

OBJECTIVES: To compare three bowel preparation regimens for colonoscopy in terms of the quality of preparation, the side effects and patient acceptance. METHODS: A total of 299 patients who underwent colonoscopy were randomized to three bowel preparation regimens: polyethylene glycol solution (n = 106), or a single dose (n = 92) or two doses (n = 101) of sodium phosphate solution. The colonoscopists who recorded the quality of bowel preparation were blind to the preparation regimens. The discomforts associated with bowel preparation and patient acceptance of the preparation were also recorded. RESULTS: Two doses of sodium phosphate solution achieved significantly better bowel preparation than polyethylene solution or a single dose of sodium phosphate solution (p < 0.05). Although two doses of sodium phosphate solution was associated with more dizziness and anal irritation, patients preferred preparation with sodium phosphate solution than with polyethylene glycol solution. Of the 69 patients in the sodium phosphate solution groups who had prior experience of bowel preparation using polyethylene glycol solution, 55 patients (80%) stated that they preferred sodium phosphate solution. CONCLUSION: Two doses of sodium phosphate solution achieved better bowel preparation than polyethylene glycol solution and was more acceptable to patients. A single dose of sodium phosphate did not achieve similar bowel preparation to two doses of the solution.

Adult↗
PubMed2000

Anatomical repair of nerve membranes in crushed mammalian spinal cord with polyethylene glycol.

Acute damage to axons is manifested as a breach in their membranes, ion exchange across the compromised region, local depolarization, and sometimes conduction block. This condition can worsen leading to axotomy. Using a novel recording chamber, we demonstrate immediate arrest of this process by application of polyethylene glycol (PEG) to a severe compression of guinea pig spinal cord. Variable magnitudes of compound actions potentials (CAPs) were rapidly restored in 100% of the PEG-treated spinal cords. Using a dye exclusion test, in which horseradish peroxidase is imbibed by damaged axons, we have shown that the physiological recovery produced by polyethylene glycol was associated with sealing of compromised axolemmas. Injured axons readily imbibe horseradish peroxidase-but not following sealing of their membranes. The density of nerve fibers taking up the marker is significantly reduced following polyethylene glycol treatment compared to a control group. We further show that all axons-independent of their caliber-are equally susceptible to the compression injury and equally susceptible to polyethylene glycol mediated repair. Thus, polyethylene glycol-induced reversal of permeabilization by rapid membrane sealing is likely the basis for physiological recovery in crushed spinal cords. We discuss the clinical importance of these findings.

Action Potentials↗
PubMed1999

Allergic contact dermatitis to polyethylene glycol and nitrofurazone.

We report a case of worsening dermatitis after the application of an antibiotic ointment (Furacin) containing furazone and polyethylene glycol. Patch tests to nickel sulfate, potassium dischromate, chloride cobalt, Furacin, nitrofurazone 1% petrolatum, polyethylene glycol mix 4% petrolatum, polyethylene glycol (PEG) 300 4% petrolatum, and PEG 400 as is (ai) were positive. The use of topical agents containing nitrofurazone or polyethylene glycol on damaged skin may predispose to contact allergy. We discuss the sensitizing properties of nitrofurazone and polyethylene glycol.

Anti-Infective Agents, Local↗
PubMed2007

[Screening of modified polyethylene surfaces for tissue engineering of chondrocytes].

BACKGROUND: Reconstructive surgery needs high requirements of substitutes for cartilages. The availability of autologous material is limited. The use of implants can cause inflammatory reactions. Therefore the biocompatibility of porous polyethylene should be improved by masking the synthetic surface with autologous cells. The polyethylene surface was functionalized by collagen, in order to enhance the contact between polyethylene and the surrounding cells. METHODS: The modified surfaces were characterized and tested by an in vitro screening with primary human chondrocytes. RESULTS: The modification of polyethylene surfaces by collagen coating increased the life time of chondrocytes growing at this surface. The effect was independent of the former functionalization. CONCLUSIONS: It is possible to cultivate chondrocytes on polyethylene surfaces. The results have to be proven in a long-term animal experimental study.

Biocompatible Materials↗
PubMed1998

A prospective randomized trial of Teflon versus polyethylene stents for distal malignant biliary obstruction.

BACKGROUND AND STUDY AIMS: Clogging of biliary stents continues to be a major clinical problem. Different polymer materials may have different effects on clogging. In vitro studies have shown a direct relation between the frictional coefficient of a polymer and the amount of encrusted material. Teflon appeared to be the best polymer for biliary stents. Two different types of stents made of Teflon have been tested in clinical practice and showed favourable patency rates. However, a randomized trial has never been performed. We compared the patency of an Amsterdam-type polyethylene stent with a Teflon stent in a prospective randomized trial. PATIENTS AND METHODS: Between September 1995 and November 1996, 42 patients received a Teflon stent and 42 patients a polyethylene stent. All patients had a distal malignant biliary stricture without a previous drainage procedure. Diagnoses included carcinoma of the pancreas (n = 76), papilla (n = 1), bile duct (n = 5) and metastases (n = 2). The internal and external diameter (10 Fr), length (9 cm) and stent design (a straight stent with two side flaps and one side hole at each end) were similar for both stents. RESULTS: A reduction in bilirubin of more than 20% within one week was seen in 91% of the patients. Early complication rates were similar in both groups (10%). The median follow-up was 142 days. Stent dysfunction occurred in 28 Teflon and 29 polyethylene stents. The thirty-day mortality was 14% in both groups. Patient survival did not differ significantly between the groups (median survival: Teflon 165 days, polyethylene 140 days). The median stent patency was 83 days for Teflon and 80 days for polyethylene stents, and was not significantly different either. CONCLUSION: Teflon material did not improve patency in biliary stents with an Amsterdam-type design.

Aged↗
PubMed2003

A randomized single-blind trial of whole versus split-dose polyethylene glycol-electrolyte solution for colonoscopy preparation.

BACKGROUND: Colonoscopy preparation regimens are often poorly tolerated because they require use of large-volume bowel preparation solution and diet restrictions for adequate cleansing. This study evaluated the efficacy and tolerability of a split-dose polyethylene glycol-electrolyte solution plus bisacodyl and a regular diet. METHODS: A total of 187 patients (104 men, 83 women; age range 18-91 years) were randomly assigned to receive either 3 L of polyethylene glycol-electrolyte solution (n = 96; Group A) with a liquid diet on the day before colonoscopy, or 2 L of polyethylene glycol-electrolyte solution, one tablet of bisacodyl, and a minimally restricted diet on the day before colonoscopy, and then 1 L of the same solution on the day of colonoscopy (n = 91; Group B). Acceptability, adverse events, and willingness to retake the preparation were assessed by questionnaire. The quality of the preparation was graded by an endoscopist, blinded to the type of preparation, by using a previously described scale (excellent to poor). RESULTS: There were 96 patients in Group A and 91 in Group B. Colon cleansing was significantly better in Group B with regard to the overall quality of the preparation (p lt; 0.05). Compliance was significantly higher in Group B as evidenced by the lower number of patients who discontinued the preparation (4 vs. 15; p = 0.02) because of side effects such as nausea or vomiting. The degree of discomfort, adverse events, and willingness to retake the preparation were not significantly different between the groups. CONCLUSIONS: Colonic preparation with split-dose polyethylene glycol-electrolyte provided better quality colon cleansing and higher compliance, with less dietary restrictions, than preparation with whole-dose polyethylene glycol-electrolyte.

Adolescent↗
PubMed2001

Alarming wear of the first-generation polyethylene liner of the cementless porous-coated Biomet Universal cup: 107 hips followed for mean 6 years.

Wear of the socket liner and resulting osteolysis are the major causes of failure in cementless hip arthroplasties. We report alarming wear of the first-generation polyethylene liner of the cementless porous-coated Biomet Universal cup. Radiographs of 107 primary hip arthroplasties were analyzed retrospectively. The mean follow-up time was 74 (47-91) months. The linear wear of the polyethylene liners was assessed using a modification of the Livermore method. The median linear wear was 1.0 (0-6.2) and the median linear wear rate was 0.17 mm/year. There was a statistically significant difference between the 28 mm and 32 mm femoral head groups both in the volumetric wear and in the volumetric wear rate. The median linear wear was 0.28 mm/year and 0.14 mm/year for the 32 mm and 28 mm heads, respectively. So far, 14 revisions have been performed or have been scheduled because of excessive wear of the polyethylene liner. In regression analysis, the factors related to the wear rate were the 32 mm size of the femoral head and screw fixation of acetabular shell. We found that the cases with calcar rounding were associated with significantly greater wear. Possible reasons for increased wear of the Hexloc liner may be the cylindrical design, thin polyethylene, and poor quality of the polyethylene. Regular clinical and radiographic follow-ups are recommended especially for hips with 32 mm femoral heads or with screw fixation. If progressive wear of the liner is observed, revision must be considered.

Adult↗
PubMed2004

Effects of polyethylene and TiAlV wear particles on expression of RANK, RANKL and OPG mRNA.

BACKGROUND: Wear debris has been associated with periprosthetic osteolysis and loosening of total joint arthroplasties. RANKL (receptor activator of NF-kappaB ligand), RANK (receptor activator of NF-kappaB) and OPG (osteoprotegerin) are three key molecules which regulate differentiation, survival, fusion, and activation of osteoclasts. MATERIAL AND METHODS: We evaluated the effect of TiAIV and polyethylene particles on expression of RANK, RANKL and OPG mRNA. We used a human monocytic leukemic cell line (THP-1) in this in vitro study. THP-1 monocytes were differentiated into macrophage-like cells and exposed to polyethylene particles and prosthesis-derived TiAIV particles. The supernantant was used for measurement of TNFalpha protein and total RNA was extracted from the cells. Expression of the genes coding for OPG, RANKL and RANK was analysed at the mRNA level using a semiquantitative RT-PCR method. RESULTS: Both polyethylene and TiAIV particles induced a significant release of TNFalpha after 6 h of exposure and a significant upregulation of RANK mRNA. OPG mRNA expression was transiently upregulated after exposure to polyethylene and TiAIV particles. These effects were dependent on particle dose. RANKL mRNA was not detectable in our THP-1 model. In contrast, LPS exhibited a different pattern of RANK/ RANKL/OPG mRNA expression. INTERPRETATION: Our findings provide evidence that both polyethylene and TiAIV particles induce upregulation of RANK expression in cells of the monocytic lineage, which may be important for periprosthetic osteoclastogenesis.

Alloys↗
PubMed2002

Anaerobic treatment of polyethylene glycol of different molecular weights.

Biodegradation of high molecular weight polyethylene glycol has been found difficult under aerobic conditions. The use of a chemical treatment prior to the aerobic one was necessary to remove high molecular weight of polyethylene glycol. Anaerobic treatment of polyethylene glycol may present an alternative to integrated chemical and biological treatment for the elimination of this compound. Anaerobic biodegradation of polyethylene glycol from 200 to 10,000 molecular weight was studied. It showed that, unlike aerobic treatment, the size of the molecule up to 10,000 does not affect the process efficiency. The critical retention time and the optimum retention time were estimated and ranged from 10 to 14 and from 16 to 19 days, respectively. Under these operational conditions percentage of removal ranged from 85 to 90%. Thus, anaerobic degradation of polyethylene glycol presents removal percentages and hydraulic retention times compounds similar to those of biodegradable tested at the same operational conditions.

Bacteria, Anaerobic↗
PubMed1995

Quantitation of employee exposure to emission products generated by commercial-scale processing of polyethylene.

Although considerable research has been performed on the thermal degradation products of polyethylene, no data that can be compared to occupational exposure limits have been reported on the exposure of workers in commercial polyethylene extrusion operations. In this study, the actual airborne concentrations of previously identified analytes were measured during the commercial-scale processing of polyethylene resins. Nine polyethylene resins, spanning LDPE, LLDPE, and HDPE product slates were processed under commercial-scale conditions appropriate to their application: blown film, extrusion coating, blow molding, pipe extrusion, and rotational molding. Air samples were taken from operator breathing zones and of representative workplace air and contained air (inside film bubbles and molded parts) using recognized occupational health and safety protocols. The compounds selected for monitoring consisted of aldehydes (formaldehyde, acetaldehyde, acrolein, butyraldehyde, crotonaldehyde, and benzaldehyde), aromatics (benzene, toluene, xylenes, and styrene), formic and acetic acids, furan and tetrahydrofuran, and acetone. Airborne particulates also were measured. Of the 450 concentration measured from workplace air and operator breathing zones, 440 were below detection limits. Nine of the remaining ten concentrations were < 10% of the established exposure limits, while one particulate measurement was < 50% of the established exposure limit. As well, 180 contained-air samples were taken. Off-gases trapped inside film bubbles and molded parts accumulated to concentrations above those measured in the ambient air. It was concluded that polyethylene extrusion presents minimal inhalation hazards in a moderately ventilated environment.

Air Pollutants, Occupational↗