Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Polyethylene”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 415 records · Page 23Linked to original sources
PubMedDate not supplied

Revision rhinoplasty using porous high-density polyethylene implants to reestablish ethnic identity.

BACKGROUND: This study aimed to evaluate a surgical technique used for patients requiring revision rhinoplasty to reestablish their ethnic identity. METHODS: A retrospective review involved 29 patients who underwent revision rhinoplasty to reestablish their ethnic identity using residual septal cartilage and porous polyethylene implants. The follow-up period ranged from 6 month to 7 years. RESULTS: For all patients undergoing revision rhinoplasty, multiple porous polyethylene implants were used to reestablish ethnic identity and to restore nasal function. Implant extrusion developed in one (3.4%) of the 29 patients. There were no cases of postimplant infection. CONCLUSIONS: In our experience, patients who feel they have lost their ethnic identity after primary rhinoplasty tend to have overresected dorsal cartilage and bone and overresected tip cartilages. The use of multiple porous polyethylene implants in revision rhinoplasty to restore ethnic identity can provide the necessary grafting material needed for reconstruction. Many grafting options are available. According to our experience, porous polyethylene provides safe, effective, and reliable results.

Adult↗
PubMed2006

Increased polyethylene wear after cementless ABG I total hip arthroplasty.

INTRODUCTION: The cementless, hydroxyapatite-coated Anatomique Benoist Giraud-I (ABG-I) hip endoprosthesis represented a modern implant in the 1990s. The aim of the current retrospective study was to evaluate the clinical and radiological results of this prosthesis. In addition, an analysis of the complications and retrieved implants was conducted. MATERIALS/METHODS: The medium-term results (follow-up 5.23 years) of 193 hip joints are presented. Of 158 total cohorts, 81.9% was able to undergo follow-up performed with standardized clinical and radiological investigations. Physical characteristics of the patients and the underlying disease prompting the need for total hip arthroplasty, as well as a clinical score (Merle d'Aubigné) were recorded. At the time of follow-up, a radiologic examination of all patients with a standardized evaluation was performed. In addition, the migration of the acetabular cup and femoral head as well as polyethylene wear could be determined digitally in 118 cases (61.1%) using one-picture Roentgen analysis. RESULTS: Clinical results, as measured with a Merle d'Aubigné Score increase from 8.4 to 16.2, were very good. Radiographs demonstrated successful osseous integration of the anatomically molded shaft. Within the period of the investigation, no revision procedures of the femoral shaft were necessary. However, the rate of polyethylene abrasion of 0.23 mm/year was markedly high. 13.9% of hips (n = 27) required acetabular cup revision due to wear. This calculates to a prosthesis 7-year survival probability of 63%. Intraoperative findings during the revision cases showed extensive periacetabular osteolysis with foreign body granulation tissue. Analysis of data from the total patient cohort versus data from cases requiring revision showed a significantly increased frequency of high polyethylene wear in young active patients as well as in cases where an unfavorable acetabular cup to femoral head relation existed in correspondence with polyethylene thickness. There is evidence, however, that suggests that multifactorial causes for the increased wear are significant in regards to the principal material and technical features of the prosthesis. CONCLUSION: On the basis of these results, it is strongly recommended that all patients treated with an ABG-I hip endoprosthesis should receive close clinical and most importantly close radiologic follow-up.

Adult↗
PubMed1998

Detection of cracks in polyethylene components of retrieved knee joint prostheses.

Subsurface cracks that had formed in polyethylene artificial knee components were observed nondestructively with a new method, scanning acoustic tomography (SAT). Standardization of the SAT observation was done by in-vitro rolling fatigue testing on an unimplanted ultra high molecular weight polyethylene (UHMWPE) knee component. Retrieved knee components were of two types; KOM (Kyocera, Kyoto, Japan) sterilized with ethylene oxide gas, and MG (Zimmer, IN, USA) sterilized with gamma-irradiation. The SAT images revealed cracks in all the retrieved components, and these existed mainly 0. 3-1.0 mm from the surface. Comparison of crack formation in each portion of the contact area of the polyethylene components showed that the middle portion of the MG type had the highest concentration of cracks. When the distribution of compressive stress on the polyethylene components was assessed by mechanical testing, the strongest compressive stress was seen in the middle portion of MG type components.

Acoustics↗
PubMed2006

[Craniofacial augmentation with porous polyethylene implants (Medpor: first clinical results].

SUBJECT: Porous polyethylene (Medpor) is an alloplastic material commonly used in craniofacial reconstruction. We report about our first clinical experiences with Medpor for facial augmentation procedures. PATIENTS AND METHODS: We treated 27 patients between 2001 and 2005 (11 female, 16 male) with 48 Medpor-implants. The indications for application of porous polyethylene implants in our clinic were congenital malformations (15), post-traumatic defects (10), and reconstructions after tumor resection (2). The implants were used for nasal/paranasal augmentations (16), for zygomatico-orbital augmentations (18), and for augmentations of the chin and malar region (11). The procedures were performed in a standardized manner. We used prefabricated, self-contoured implants and fixed them subperiosteally with titanium osteosynthesis screws. All operations were performed under general anesthesia. We evaluated the aesthetic results and the ingrowth behavior clinically and histologically. RESULTS: We achieved good aesthetic results and the patients showed no signs of discomfort or rejection. Four patients required a second intervention. These revision surgeries included two cases of local infections and two for aesthetic contouring. The necessary reduction of the implants allowed the harvesting of tissue and implant samples for microscopy. CONCLUSION: Porous polyethylene implants showed a good fibrovascular integration without encapsulation under the light microscope. Giant cells were detected on the surface of the implants. Besides this there was evidence for resorption of the implant material. Fixation with titanium screws is very effective. No implant dislocation or implant fracture occurred. The implants showed high volume stability and were easily handled and contoured. It is not possible to visualize Medpor implants with current imaging techniques, because polyethylene shows no contrast.

Adolescent↗
PubMed1984

Precipitation of collagens by polyethylene glycols.

Types I, II, and III collagens are readily precipitated at neutral pH by polyethylene glycols (PEG). As the molecular weight fraction of the polyethylene glycols increases, they become more effective as precipitants on a weight basis. The amount of PEG required for precipitation depends on the pH, the ionic strength, and the nature of the buffer or salts present. In tissue culture media, low concentrations of collagens and procollagens may be quantitatively precipitated and readily collected by low-speed centrifugation. Polyethylene glycol precipitation can be used to obtain collagens and procollagens from tissue culture media at either analytical or preparative scale, and since the polyethylene glycols do not bind to collagens, the precipitates may be further analyzed directly by chromatographic or electrophoretic methods.

Cells, Cultured↗
PubMed1984

Polyethylene glycol interferes with protein molecular weight determinations by gel filtration.

Gel filtration studies on Sephadex G-75 demonstrate markedly increased elution volumes for proteins chromatographed with polyethylene glycol. As little as 5% (w/v) polyethylene glycol in the applied protein sample can reduce apparent molecular weight estimates by gel filtration as much as 55%. Furthermore, gel filtration columns equilibrated with polyethylene glycol are not size-separating columns. Consequently, caution must be exercised when performing and interpreting gel filtration studies of proteins previously treated or precipitated with polyethylene glycol.

Chromatography, Gel↗
PubMed1993

Soft tissue reaction to collagen-immobilized porous polyethylene: subcutaneous implantation in rats for 20 wk.

Collagen-immobilized porous polyethylene, in which the immobilization was through covalent bonding, and virgin porous polyethylene were implanted subcutaneously in rats from 1 to 20 wk. The results were the ingrowth of the connective tissue into collagen-immobilized porous polyethylene was rich and contained a low level of inflammatory cellular infiltration compared with that of virgin porous polyethylene. The material-tissue interface showed that the living body-originated collagen fibres were firmly anchored into the immobilized collagen layer. These results suggested that covalent immobilization of collagen on to the biomaterial surface is useful in promoting the ingrowth of soft tissue and the tissue adhesion.

Animals↗
PubMed1990

Biliary excretion of different sized polyethylene glycols in the cat.

Polyethylene glycol (PEG) 900 is excreted more extensively into bile than mannitol and erythritol. In this study, the biliary recovery of intravenously injected marker molecules was analysed in anaesthetised cats with ligated renal pedicles. It was demonstrated that among polyethylene glycols sized 292-1250 Da, the species sized 1074 Da was maximally excreted in the bile. After 5 h, about 12% of the injected amount of this molecular species was recovered in bile. Both larger and smaller polyethylene glycol molecules had a lower biliary excretion. The distribution of different sized PEGs in the range 766-1250 Da in serum was fairly constant and cannot explain the recovery profile in bile. 14C-Labelled mannitol was recovered in bile to the extent of 0.7% of the amount given i.v. after 5 h, a figure that corresponds to that obtained for polyethylene glycol with a size of 370 Da. Bile/plasma ratios during steady state conditions of labelled PEG 450, PEG 900, PEG 2500 and PEG 4000 were 10, 36, 3 and 4, respectively. The results may be tentatively explained by restricted passage of the larger PEG molecules into the canaliculi, and leakage of the smaller molecules from bile back to plasma.

Animals↗
PubMed1986

Effect of polyethylene glycol 400 on adriamycin induced histamine release.

The activity of polyethylene glycol 400, a widely used drug solvent, was tested on the release of histamine induced by adriamycin in vitro on peritoneal rat mast cells and in vivo in a mouse model. Preincubation of mast cells with high (10 and 5%) concentrations of polyethylene glycol 400 significantly inhibited the important histamine release induced by 100 micrograms/ml of adriamycin; furthermore, polyethylene glycol 400 (3.45 g/kg; 0.345 g/ml) pretreatment almost completely abolished the peritoneal and pericardial mast cell degranulation and the cardiac toxicity caused by an intraperitoneal injection of 15 mg/kg of adriamycin. This effect of polyethylene glycol 400 on adriamycin-induced histamine release could explain the protective action exhibited in vivo on adriamycin treated animals, therefore confirming that adriamycin cardiotoxicity could be related to the release of histamine and other vasoactive substances.

Animals↗
PubMed1982

Polyethylene glycol intoxication in burn patients.

Unexplained increases in the anion gaps and serum osmolalities were observed in 3 burn patients who died following treatment with a polyethylene glycol-based burn cream. Toxicity due to absorption of polyethylene glycol was suspected after other causes had been excluded. Ethylene glycol was found in the circulation and the 3 patients died in acute renal failure. All the patients were acidotic with increased anion and osmolal gaps. This syndrome was similar to the more common poisoning with ethylene glycol but also included an increased serum calcium with a concomitant decrease in the ionized calcium. The cause of this high 'calcium gap' appeared to be binding of calcium by dicarboxylic acid metabolites of polyethylene glycol. These findings were the same as those found in rabbits treated with polyethylene glycol.

Acute Kidney Injury↗
PubMed1992

New extraction procedure and high-performance liquid chromatographic method for analyzing polyethylene glycol-400 in urine.

We describe a new, highly efficient method for extracting polyethylene glycol-400 from urine and for its analysis by isocratic reversed-phase high-performance liquid chromatography. This method is an improvement over previously published methods in that it does not require the use of ion-exchange resins and lyophilization prior to extraction, nor does it require the separation and analysis of the individual polymers of polyethylene glycol. The procedure described in this report entails extraction with a salt-solvent combination of ammonium sulfate and dichloromethane and analysis by reversed-phase high-performance liquid chromatography. The lower limit of detection was approximately 0.25 g/l with a 2-ml urine sample. Analytical recoveries of polyethylene glycol-400 added to urine at 2.5 and 5.0 g/l averaged 97 and 96%, respectively (n = 10). Within- and between-day coefficients of variation were less than 5% at 2.5 and 5.0 g/l. Studies of various urine samples from patients receiving polyethylene glycol-400 revealed no interferences from other urine substances.

Chromatography, High Pressure Liquid↗
PubMed2006

Study on the pyrolysis of polyethylene in the presence of iron and copper chlorides.

Pyrolysis experiments were conducted to elucidate the effects of metal chlorides on the thermal degradation of low-density polyethylene on a continuous pyrolysis temperature range of 600 degrees C to 1100 degrees C. The present work focusses on the ratio of aromatics generated on increasing the pyrolysis temperature in the presence of metal salts, iron(II), iron(III) and copper(II) chlorides. It was observed that beside alpha,omega-dienes, alpha-olefins and n-alkanes which are usually observed during the thermal decomposition of polyethylene, the level of aromatics noticeably increases with the addition of metal salts. At high temperatures, the formation of these aromatics took place in such a way that they become the major products when polyethylene is pyrolyzed in presence of FeCl(3) and CuCl(2). Quantification of the effect of metal salts has been tempted comparing the variation of the ratio of aromatics with pyrolysis temperatures. Mechanisms responsible for the formation of these aromatics in presence of metal salts have been tentatively investigated. They are proposed to result from cyclization/dehydrogenation reactions similar to those observed during the thermal decomposition of polyethylene, but with an increased efficiency due to the metal salts.

Chlorides↗
PubMed2005

Activation of NF-kappaB signalling and TNFalpha-expression in THP-1 macrophages by TiAlV- and polyethylene-wear particles.

Wear particles are believed to induce periprosthetic inflammation which contributes to periprosthetic osteolysis. TNFalpha plays a pivotal role in the pathogenesis of this process. The molecular mechanisms leading to the development of periprosthetic inflammation with upregulated TNFalpha expression in monocytic cells in response to different wear particles have yet to be defined. In this study we evaluated the effects of polyethylene- and TiAlV-particles on activation of NF-kappaB signalling pathways and TNFalpha biosynthesis and release in monocytic cells with respect to periprosthetic osteoclastogenesis. THP-1 monocytic cells were differentiated to macrophage-like cells and exposed to LPS-detoxified polyethylene and prosthesis-derived TiAlV-particles. TNFalpha release was analyzed in culture supernatant by ELISA. NF-kappaB activation was examined by electrophoretic mobility shift assay (EMSA), and NF-kappaB target promoter activities including transactivation of the TNFalpha promoter were determined by luciferase reporter gene assays. Differentiated THP-1 macrophages were exposed to increasing numbers of particles for 0, 60, 180 and 360 min. Both, polyethylene- and TiAlV-particles induced a significant activation of both NF-kappaB and TNFalpha promoters at 180 min. A significant TNFalpha release was detected after 360 min exposure to polyethylene- and TiAlV-particles in a dose dependent manner. In comparison, LPS induced a much greater activation of NF-kappaB and TNFalpha promoters, and TNFalpha secretion into the supernatant was strongly induced. These results provide evidence that induction of the NF-kappaB signal transduction pathway in macrophages plays a major role in initiating and mediating the inflammatory response leading to periprosthetic osteolysis.

Alloys↗
PubMed1998

Meta-analysis and cost comparison of polyethylene glycol lavage versus sodium phosphate for colonoscopy preparation.

BACKGROUND: Although polyethylene glycol lavage solutions are widely used for colonoscopy preparation, evidence suggests that sodium phosphate is better tolerated and has similar efficacy. The purpose of this study was to compare compliance with and efficacy of polyethylene glycol and sodium phosphate using meta-analysis and to compare the cost of colonoscopy with both methods. METHODS: We used Medline to identify all randomized controlled trials comparing the two preparations. Study methods were evaluated, and quantitative data were abstracted independently, including inability to complete the preparation and preparation quality, rated as adequate or excellent. A random effects model was used to calculate the pooled relative risk. Direct costs and literature-based probability estimates were used to compare costs. RESULTS: Among 1286 subjects from eight colonoscopist-blinded trials, the pooled relative risk of inability to complete the preparation was 0.23 (95% CI [0.18-0.28]) in favor of sodium phosphate. Although the best estimate of the relative risk for an adequate quality preparation revealed therapeutic equivalence (relative risk = 1.06: 95% CI [0.95-1.19]), an excellent quality preparation was more likely with sodium phosphate (relative risk = 1.72: 95% CI [1.16-2.53]). Assuming reexamination rates from published literature of 3% and 8% for sodium phosphate and polyethylene glycol, respectively, direct costs of colonic examination were $465 and $503. There were no clinically important adverse effects with either method. CONCLUSION: The results suggest that sodium phosphate is as effective and less costly, with a more easily completed preparation, compared with polyethylene glycol and is the preferred method of preparation for colonoscopy for certain patient subgroups.

Adult↗
PubMed1984

Affinity partitioning of proteins in aqueous two-phase systems containing polymer-bound fatty acids. I. Effect of polyethylene glycol palmitate on the partition of human serum albumin and alpha-lactalbumin.

The partition of serum albumin between the two aqueous phases of a polyethylene glycol-dextran-water two-phase system is strongly influenced by replacing a small fraction of the polyethylene glycol by its palmitate ester. The partition of albumin is compared with the partition of polymer-bound palmitate using polyethylene glycol [1-14C]palmitate. The data indicate that a maximum ("saturation") effect on the partition of albumin corresponds to a binding of fewer than two palmitate groups per albumin molecule. The effect on alpha-lactalbumin corresponds to the maximum binding of 0.5 palmitate group per protein molecule. These data do not fit the most favoured available model for affinity partitioning. The deviation can be attributed to the observation that the palmitate groups probably form micelle-type aggregates in the polyethylene glycol-rich phase at the concentrations used for albumin extraction.

Chromatography, Affinity↗
PubMed2005

[Reliability of porous coating metal-backed cups: advantages and adverse effect of a posterior elevated rim polyethylene liner].

PURPOSE OF THE STUDY: We analyzed primary implantation of the Duraloc cup associated with a self-locking Muller stem at 9.6 +/- 1.6 years (8.6-11.4). Because of its particular 3/5 semi-spherical shape, the Duraloc cup has been associated with a high rate of dislocation. The objective of this study was to evaluate the efficacy of an anti-dislocation posterior elevated rim polyethylene liner on long-term dislocation rate and wear. MATERIAL AND METHODS: The series included 89 arthroplasties implanted between 1991 and 1993 in 82 patients, mean age 56.8 +/- 12.6 years (17.2-87). The Postel-Merle-d'Aubligné (PMA) score and subjective evaluation with a visual analog scale were used for the clinical assessment. Changes in the bone-cup interface, cup migration, and polyethylene wear were assessed radiographically. RESULTS: At last follow-up, the PMA function score was 16.2 +/- 1.9 points (10-18) (81% good, very good and excellent results). The postoperative x-rays showed a low incidence of lucent lines and osteolysis, respectively 8% and 4%. Mean annual linear polyethylene wear was 0.11 +/- 0.066 mm (0.03-0.57) and only 4% of the cups showed wear greater than 0.2 mm/year. Wear was correlated with the presence of acetabular osteolysis and high activity level. Two cups migrated (3-4 cm medialization). Three cups were revised, one for deep infection, one for recurrent dislocation, and one for dislocation associated with major wear. The rate of dislocation was 2.2% (two cases). Overall survival was 97.3% at 9.6 years (95%CI 0.93-1.0). DISCUSSION: Compared with other series in the literature using this implant, the presence of a posterior elevated rim polyethylene liner reduced the rate of instability and did not increase wear. The Duraloc cup is recognized as a reliable implant exhibiting excellent osteointegration and a low rate of migration. The presence of a posterior rim is associated with a lower rate of dislocation and does not increase wear. It can thus be proposed for primary implantation. The posterosuperior position for the liner is recommended.

Adolescent↗
PubMed2005

[Early femoral osteolysis following Charnley-Kerboull total hip arthroplasty combining a 22-mm zirconia head on polyethylene].

PURPOSE OF THE STUDY: New bearings have been developed to reduce polyethylene wear. Zirconia ceramic is one proposal with attractive tribologic properties. The purpose of this prospective study was to evaluate the clinical and radiological results at least two years after implantation in a continuous series of total hip arthroplasties combining a zirconia head with polyethylene socket. MATERIAL AND METHODS: The series included 56total hip arthroplasties performed in 51 patients (30 females and 21 males), mean age 52.2 +/- 12 years (25-76 years). Prostheses were implanted for primary degenerative disease (43%) and dysplasia (27%). The femoral component was a stainless steel stem with a Morse cone measuring 11degrees 25' for 27 hips and 5 degrees 40' for 28 hips. A 22-mm stabilized yttrium tetragonal polycrystalline zirconia head (Y-TZP) was used. The transtrochanteric approach was used for all arthroplaties with implantation of a cemented Charnley-Kerboull prosthesis. Clinical outcome was assessed with the Postel-Merle-d'Aubligné (PMA) score. Acetabular cup wear and periprosthetic osteolysis were measured on successive AP x-rays of the pelvis. RESULTS: Mean follow-up was 32 months (24-48). None of the patients were lost to follow-up. Mean function score at last follow-up was 17.8 +/- 0.2 (16-18) versus 12.2 +/- 2.6 preoperatively (Wilcoxon, p < 0.0001). There were no cases of implant migration (femoral or acetabular). An endosteal defect by femoral osteolysis in the calcar femoral was observed in 19 of 55 cases. It appeared early between first and second post-operative year and did not progress later. Its surface remained less than 1 cm2 in all cases. We were unable to identify any factor predictive of these osteolytic lesions. DISCUSSION: The short-term clinical results with this type of arthroplasty was comparable with earlier results described with classical Charnely-Kerboull implants using a metal-polyethylene bearing. The Merkel osteolysis observed in this series occurred early for one-third of the hips with no measurable polyethylene wear. We suggest surgeons should be cautious about using the zirconia head. We are continuing our surveillance of these patients.

Adult↗
PubMed2006

[The cemented Müller straight stem total hip prosthesis with polyethylene cup and 28 mm head: ten-year results].

PURPOSE OF THE STUDY: The purpose of this study was to evaluate the 10-year results of the cemented Müller straight stem total hip prosthesis with polyethylene cup and 28 mm head. MATERIAL AND METHOD: From May 1988 to May 1990, 187 cemented prostheses (second-generation technique) were implanted via a transgluteal approach for degenerative hip disease. A Protasul 10 straight stem with a 28 mm modular head and a gamma ray sterilized polyethylene cup was used in all cases. At ten years, the follow-up of the 187 implants was: 60 implants in deceased patients, 24 implants in patients contacted by telephone (all with implants in place), 90 implants in 82 patients seen for review. The series thus included 40 women and 42 men, mean age 65 years. The clinical outcome was assessed with the Postel Merle d'Aubigné (PMA) score. Radiographic assessment noted lucent lines, granulomas, implant migration, polyethylene wear, and ossifications. Survival curves were established with the actuarial method. RESULTS: Among the 187 implants, two patients required revision: one for sepsis and the other for posttraumatic dislocation. Among the 82 patients reviewed at 10 year, the PMA score was 16.8 (92% good and very good results). Radiographically, assessment of the acetabular component demonstrated three probable and one certain loosening, four cases of polyethylene wear greater than 2 mm. At the femoral level, osteolysis was noted in zones 1, 3, and 7 and rarified bone in zone 7 in four patients. Linear penetration of the stem into the cup was 0.09 mm/yr, corresponding to a volumetric wear of 55, 35 mm3/year. Brooker grade 3 ossification was observed in 27% of men and 14% of women. DISCUSSION: The clinical results were comparable to other series of cemented prostheses. At ten years, acetabular loosening was more frequent with active radiolucent lines present from the fifth year. It would thus appear that better results could be achieved by optimizing the bearing. Furthermore, there was no parallelism between the clinical and anatomic observations, cup loosening and femoral osteolysis were well tolerated. The prevention of ossification appears to be an important point, particularly in men.

Aged↗