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At least 667 records · Page 37Linked to original sources
PubMed2002

Polyethylene exchange only for prosthetic knee instability.

From 1987 to 1996, 47 revision total knee arthroplasties were done for tibiofemoral instability. Sixteen of these patients had polyethylene exchange only to treat their instability. Fourteen of these patients were available for review. The mean followup was 56 months. The mean Hospital for Special Surgery Knee Score increased from 50 points preoperatively to 73 points at the most recent followup. Clinically, stable knees were produced in 71% of patients (10 of 14). The results of the current study suggest that polyethylene exchange can be an effective, low morbidity procedure to treat certain types of prosthetic knee instability. A failure rate of 29% (four of 14) however, is concerning. Alternative methods of stabilization should be used, if there is any question concerning the stability of a construct where a polyethylene exchange only is used.

Adult↗
PubMed1992

Neutron response of a polyethylene-moderated superheated drop detector.

Monte Carlo neutron transport calculations were performed to obtain the neutron response functions of a superheated drop detector (SDD-100) that is surrounded by polyethylene of various thicknesses. The calculational results suggest that a SDD-100 surrounded by 2.54 cm of polyethylene gives the best dose-equivalent response in a free neutron field. Results were confirmed by a sequence of experiments using various neutron sources. This polyethylene-moderated SDD-100 is ideal for use as an area neutron dose monitor.

Equipment Design↗
PubMed2004

Polyethylene glycol for constipation in children younger than eighteen months old.

BACKGROUND: Polyethylene glycol (PEG) is a safe and effective treatment for constipation in children older than 18 months. Data on its safety and efficacy in infants are lacking. The goal of this study was to determine safety, efficacy, and optimal dose of polyethylene glycol powder for treatment of constipation in patients younger than 18 months. METHODS: The authors reviewed the charts of patients younger than 18 months treated with PEG 3350 for constipation. The initial dose, effective maintenance dose, response to therapy, duration of therapy, and side effects were recorded. RESULTS: Twenty-eight patients younger than 18 months of age treated with PEG were identified (3, age 0-5 months; 9, age 6-11 months; 16, age 12-17 months). Mean duration of therapy was 6.2 +/- 5 months (range, 3 weeks-21 months). Mean initial dose was 0.88 g/kg/day (range, 0.26-2.14 g/kg/day). Mean effective maintenance dose was 0.78 g/kg/day (range, 0.26-1.26 g/kg/day). PEG relieved constipation in 97.6% of patients. One infant experienced increased gas per rectum and four others experienced transient diarrhea that resolved after adjusting the dose. CONCLUSION: Oral powdered polyethylene glycol at a maintenance dose of 0.78 g/kg/day is safe and effective for patients younger than 18 months. Dose and safety profiles are similar for those reported in older children.

Cathartics↗
PubMed1993

Reconstruction of the burned external ear using a Medpor porous polyethylene pivoting helix framework.

This paper describes a new technique using a Medpor porous polyethylene pivoting helix framework for reconstruction of the burned auricle. The polyethylene framework is composed of two distinct components, a curved shape that represents the helical rim which pivots around a base component. This framework is covered with a temporoparietal fascia flap and a skin graft that is chosen to match the adjacent resurfaced facial burn. The porous framework then becomes rapidly vascularized with soft-tissue ingrowth and collagen deposition. The pivoting helix design can be used to create an auricle of almost any size or projection. The helix can move independently and can be compressed against the head in the event of external pressure on the ear. The resultant ear reconstruction is extremely durable and remains flexible over time. Twenty-six consecutive ear reconstructions were performed using this method over a 2-year period. Two exposures occurred which were managed without removal of the implant. All reconstructions successfully restored an ear that was both aesthetically pleasing and functional so as to provide support for a pair of eyeglasses. The Medpor porous polyethylene pivoting helix framework offers an excellent solution for a difficult reconstructive problem.

Adolescent↗
PubMed1996

Injectable cartilage using polyethylene oxide polymer substrates.

This study demonstrates that polyethylene oxide gels, which are biocompatible and biodegradable synthetic polymers, can be utilized for the encapsulation of isolated chondrocytes and maintenance of three-dimensional spatial support for new tissue development. Chondrocytes isolated from the glenohumeral and humeroradioulnar joints of a calf were added to a 20% polyethylene oxide solution in Ham's F-12 medium to generate a final cellular density of 10 x 10(6)/mL. The polymer-chondrocyte constructs were injected through a 22-gauge needle in 500-microliters aliquots subcutaneously in 12 nude mice and incubated for 6 and 12 weeks in vivo. Histologic and biochemical analyses including deoxyribonucleic acid and glycosaminoglycan quantitative analyses confirmed the presence of actively proliferating chondrocytes with production of a well-formed cartilaginous matrix in the transplanted samples. Control specimens from eight implantation sites consisting of chondrocytes alone or polyethylene oxide substrates did not demonstrate any gross or histologic evidence of neocartilage formation. These findings demonstrate the potential use of an injectable and moldable polymer substrate that can support cell proliferation and matrix synthesis after subcutaneous transplantation for neocartilage generation. The use of functional biologic tissue substitutes may serve as an alternative solution to current methods of augmentation or reconstruction of structural craniofacial contour deformities.

Animals↗
PubMed2003

Migration of metal-on-metal versus ceramic-on-polyethylene hip prostheses.

In a prospective randomized study, 32 metal-on-metal prostheses and 29 ceramic-on-polyethylene prostheses of similar design were implanted in 59 patients. Radiolucency, cup migration, wear, and function were examined after a minimum of 2 years followup (followup rate, 87%). The purpose of the current study was to evaluate whether higher frictional torque of metal-on-metal will lead to a higher rate of early metal-on-metal cup loosening. A computer-assisted method was used for wear and migration measurements of the acetabular component. Metal-on-metal prostheses migrated in a craniocaudad direction significantly less than ceramic-on-polyethylene prostheses. The mean total migration for both types of prostheses exceeded 1.5 mm at 2 years. Clinically, no difference between the two prostheses regarding activity, pain, or range of motion was found at 2 years. As migration of metal-on-metal prostheses was not higher in comparison with ceramic-on-polyethylene prostheses, the expected higher frictional torque of metal-on-metal prostheses did not increase migration during short-term followup. The different debris produced by both bearings did not influence the short-term results of this study, but might cause different long-term results.

Aged↗
PubMed2004

Highly cross-linked, electron-beam-irradiated, melted polyethylene: some pros.

Extensive new evidence generated within the past the year provides strong support for the use of electron-beam highly cross-linked, subsequently melted ultra-high molecular weight polyethylene in total hip replacement arthroplasty. In terms of wear reduction, three studies involving three different demographic groups and two different measurement techniques have found that the femoral head penetration with this type of polyethylene after bedding in has finished taking place is less than 10 micra per year. This wear rate is similar to the wear rate of metal-on-metal and ceramic-on-ceramic articulations. Retrieval specimens up to 3 years after insertion confirmed the minimal wear by exhibiting persisting machine marks throughout the inside diameter of the liner. Extensive studies show no evidence of oxidation, confirming the absence of residual free radicals. No evidence of fatigue failure exists except three known cases out of 150,000, in which malposition of the acetabular component produced abnormally high contact stresses on unsupported polyethylene. The in vivo wear, oxidation resistance, and mechanical properties of this alternative bearing material are excellent, with in vivo durations now exceeding five years. The other major advantages over hard-on-hard bearings including familiarity, adaptability, forgiveness, and cost seem to be compelling.

Adult↗
PubMed2005

A review of current cross-linked polyethylenes used in total joint arthroplasty.

Major improvements have been made in new polyethylenes in regards to wear resistance and oxidation resistance. The background for and explanation of these improvements are presented in this study. The various manufacturing processes are described along with the possible features that the differences in manufacturing processes may have on wear, rate of particle generation, oxidation and mechanical properties. The role of some of the new polyethylenes in permitting the use of larger-diameter heads and the advantages of large-head diameters are discussed. Some of the advantages of metal-on-polyethylene versus hard-on-hard bearings also are described.

Arthroplasty, Replacement↗
PubMed2006

Large diameter femoral heads on highly cross-linked polyethylene: minimum 3-year results.

Contemporary highly cross-linked polyethylenes have become the most widely used alternative bearing surfaces in total hip replacement and may be paired with large diameter femoral heads (> 32 mm) in patients considered to be at high risk for dislocation. We report on a prospective series of 42 patients (45 hips) who had total hip replacement using large diameter cobalt-chrome femoral heads articulating with a highly cross linked polyethylene after a minimum of 3 years followup (mean 3.3 years). At final followup, the final patient cohort showed excellent clinical results with no radiographic failures or episodes of loosening. There was no evidence of pelvic or femoral osteolysis. One patient sustained a dislocation due to a grossly malpositioned acetabular component necessitating early isolated acetabular revision. The average yearly steady state wear rate was -0.06 +/- 0.41 mm/year. The results of our short-term prospective series indicated total hip replacement with large femoral heads articulating with a highly cross linked polyethylene showed excellent wear characteristics and clinical results and could be considered in patients at increased risk for dislocation.

Aged↗
PubMed2001

Development of fabric sintering/compaction process to produce porous UHMW polyethylene composites.

Implants based on solid (nonporous) Ultra High Molecular Weight (UHMW) polyethylene have serious disadvantages such as generation of fine polymer particles, because of the lack of internal natural lubricant inside the implant body. A novel family of porous multilayer composites based on Ultra High Molecular Weight (UHMW) polyethylene commercial fabrics has been developed. These composites are produced using a compaction/sintering process with a compression molding technique. The developed porous materials have much higher tensile strength than solid (nonporous) UHMW polyethylene materials.

Biocompatible Materials↗
PubMed2006

Reinforcement effect of polyethylene fibre in root-filled teeth: comparison of two restoration techniques.

AIM: To compare in vitro two different fibre placement techniques on reinforcement of root-filled molar teeth with mesio-occluso-distal (MOD) cavities. METHODOLOGY: Fifty sound extracted human mandibular molars were used (n = 10). Group 1 served as control. From group 2-5, endodontic access and standard MOD cavities were prepared. Following root canal treatment, group 2 was kept unrestored. In groups 3 and 4, the teeth were restored with composite resin (AP-X; Kuraray, Japan). A groove was prepared on occlusal surface of the finished restorations in group 4 from buccal to lingual direction. Polyethylene woven fibre (Ribbond; Seattle, WA, USA) was inserted in the groove in combination with flowable resin that was cured for 20 s and covered with composite resin. Cavity surfaces were covered with flowable resin in group 5, and polyethylene fibre was placed into the bed of resin in a buccal to lingual direction before the composite restoration was placed. All specimens were stored in 100% humidity at 37 degrees C for 24 h. Compressive loading of the teeth was performed by a universal testing machine at a crosshead speed of 0.5 mm min(-1) until failure. The data were recorded in Newton and submitted to anova and Tukey post hoc test. RESULTS: The mean load necessary to fracture the samples in each group was: G1: 1671.57 +/- 131.54(a); G2: 375.21 +/- 34.30(b); G3: 749.47 +/- 124.54(c); G4: 1224.36 +/- 132.17(d); G5: 926.88 +/- 118.28(e). Different superscript letters demonstrate significant difference between groups. CONCLUSIONS: Polyethylene fibre use over or under MOD composite restorations significantly increased fracture strength. However, when the fibre was placed on the occlusal surface of the restoration in buccal to lingual direction, significantly higher fracture resistance was observed.

Composite Resins↗
PubMed1990

The stimulation of postdermabrasion wound healing with stabilized aloe vera gel-polyethylene oxide dressing.

Full-face dermabrasion provided an ideal opportunity to document the effects of dressings on wound healing management. Following the procedure, the abraded face was divided in half. One side was treated with the standard polyethylene oxide gel wound dressings. The other side was treated with a polyethylene oxide gel dressing saturated with stabilized aloe vera. The polyethylene oxide dressing provided an excellent matrix for the release of aloe vera gel during the initial 5 days of wound healing. By 24-48 hours there was dramatic vasoconstriction and accompanying reduction in edema on the aloe-treated side. By the third to fourth day there was less exudate and crusting at the aloe site, and by the fifth to sixth day the reepithelialization at the aloe site was complete. Overall, wound healing was approximately 72 hours faster at the aloe site. This acceleration in wound healing is important to reduce bacterial contamination, subsequent keloid formation, and/or pigmentary changes. The exact mechanism of acceleration of wound healing by aloe vera is unknown.

Aloe↗
PubMed1968

Respiratory inhibition in Chlorella produced by "purified" polyethylene glycol 1540.

Polyethylene glycol 1540, added to culture solution in amounts sufficient to reduce the water potential to -10 atmospheres, inhibited respiration in Chlorella much more than mannitol solutions at -10 atmospheres. This occurred despite the purification of the polyethylene glycol by passage through exchange columns. The toxic properties, which developed some time after purification, increased with time of storage of solutions of polyethylene glycol 1540 at room temperature.

Depression, Chemical↗
PubMed1970

Microbiological aspects of ethylene oxide sterilization. IV. Influence of thickness of polyethylene film on the sporicidal activity of ethylene oxide.

Spores of Bacillus subtilis var. niger, dried on nonhygroscopic and hygroscopic surfaces, were enclosed in one of four thicknesses of low-density polyethylene film (2, 4, 6, and 20 mils). The surfaces were then placed in a specially designed thermochemical death rate apparatus and exposed to an ethylene oxide concentration of 600 mg/liter (at 54.4 C) and 50% relative humidity. Survival data, including both spore survivor curves and decimal reduction values (expressed as D values at 54.4 C-600 mg of ethylene oxide per liter), demonstrated similar survivor patterns when the B. subtilis var. niger spores were enclosed in low-density polyethylene films 2, 4, and 6 mils thick. A comparison of these patterns with those of spores enclosed in glassine and subjected to identical exposure conditions revealed only slight variations. The use of 20-mil polyethylene film greatly increased the time required to kill B. subtilis var. niger spores under the exposure conditions.

Bacillus subtilis↗
PubMed2004

Autogenous temporalis fascia patch graft for porous polyethylene (Medpor) sphere orbital implant exposure.

BACKGROUND: Temporalis fascia has been recommended for hydroxyapatite sphere exposure. The aim of this study was to identify potential risk factors for exposure of porous polyethylene (Medpor) sphere implants and evaluate the use of autogenous temporalis fascia as a patch graft for exposure. METHODS: A retrospective review of consecutive cases of porous polyethylene sphere orbital implant exposure. RESULTS: Five cases presented between May 2000 and October 2001 (three males, two females; mean age 44.5 years). Three had enucleation (two with primary implants) and two had evisceration (one with primary implant). Exposure occurred in one primary, two secondary, and two replacement implants. Orbital implant diameter was 20 mm in four cases and 16 mm in one case (contracted socket). The mean time from implantation to exposure was 23 months (range 0.7-42.6). Three patients had secondary motility peg placement before exposure. The average time from last procedure (sphere implant or peg insertion) to exposure was 3 months (range 0.7-12.6). Four patients required surgical intervention, of which three needed more than one procedure. Autogenous temporalis fascia grafting successfully closed the defect without re-exposure in three of these four patients. The grafts were left bare in three patients, with a mean time to conjunctivalise of 2.4 months (range 1.6-3.2). CONCLUSIONS: Exposed porous polyethylene sphere implants were treated successfully with autogenous temporalis fascia graft in three of four patients. This technique is useful, the graft easy to harvest, and did not lead to prolonged socket inflammation, infection, or extrusion.

Adult↗
PubMed2002

Percutaneous self-expanding metal stents versus endoscopic polyethylene endoprostheses for treating malignant biliary obstruction: randomized clinical trial.

PURPOSE: To compare percutaneous self-expanding metal stents with conventional endoscopic polyethylene endoprostheses for treatment of malignant biliary obstruction by means of a prospective randomized clinical trial. MATERIALS AND METHODS: Patients with biliary obstruction due to inoperable primary carcinoma of the pancreas, gallbladder, or bile ducts or regional lymph node metastases were included. Evaluated outcomes included technical and therapeutic success rates, morbidity and 30-day mortality rates, hospital stay length and readmission, biliary reobstruction, and overall survival rates. Data were analyzed according to both the intention-to-treat principle and the treatment actually administered. Univariate (Kaplan-Meier method) and multivariate (Cox model) analyses were performed. RESULTS: After randomization, 28 patients were assigned to receive a percutaneous self-expanding metal stent and 26 patients to receive a 12-F endoscopic polyethylene prosthesis. The technical success rates of both implantation procedures were similar (percutaneous, 75% [21 of 28 patients]; endoscopic, 58% [15 of 26 patients]; P =.29), whereas therapeutic success was higher in the percutaneous group (71% [20 of 28 patients] vs 42% [11 of 26 patients]; P =.03). However, major complications were more common in the percutaneous group (61% [17 of 28 patients] vs 35% [nine of 26 patients]; P =.09) but did not account for differences in 30-day mortality rates (percutaneous, 36% [10 of 28 patients]; endoscopic, 42% [11 of 26 patients]; P =.83). Overall median survival was significantly higher in the percutaneous group than in the endoscopic group (3.7 vs 2.0 months; P =.02). Cox regression analysis enabled identification of placement of the percutaneous self-expanding metal stent as the only independent predictor of survival (relative risk, 2.19; 95% CI: 1.11, 4.31; P =.02). CONCLUSION: Placement of a percutaneous self-expanding metal stent is an alternative to placement of an endoscopic polyethylene endoprosthesis in patients with malignant biliary obstruction.

Aged↗
PubMed1992

Titanium-induced arthropathy associated with polyethylene-metal separation after total joint replacement.

Complications of total joint replacements are not infrequent. The authors describe five patients with displacement of the polyethylene component in two knee (metal-backed patellar component) and three hip joint replacements. Clinical, radiographic, surgical, and pathologic findings were reviewed in all cases. Conventional radiographs revealed abnormal position of the metal components in all patients and opaque curvilinear periarticular deposits in four. Arthropathy caused by deposition of small titanium particles from metal friction (in the absence of interposed polyethylene) was pathologically proved to correspond to the periarticular opacity. The subtle radiolucent polyethylene component was identified in all patients; adequate visualization in some cases may necessitate imaging with additional methods such as magnification, phosphor plate, and soft-tissue radiographic techniques; conventional tomography; and arthrography. Early recognition of these abnormalities in patients with painful joint replacements may allow less extensive surgical revision and prevent development of titanium-induced arthropathy.

Aged↗
PubMed1997

Malignant esophageal obstruction and esophagorespiratory fistula: palliation with a polyethylene-covered Z-stent.

PURPOSE: To prospectively evaluate the clinical efficacy of polyethylene-covered metallic Z-stents in treatment of dysphagia secondary to malignant esophageal obstruction and esophagorespiratory fistula. MATERIALS AND METHODS: Thirty-five patients with dysphagia due to malignant esophageal obstruction (n = 32) and esophagorespiratory fistula (n = 3) were treated with polyethylene-covered Gianturco-Rösch Z-stents. RESULTS: Thirty-nine stents were placed in 35 patients. Stent placement was technically successful in all patients. Improvement in dysphagia was achieved in 34 of 35 patients. The average dysphagia score decreased from 3.1 (dysphagia to liquids) to 0.6 (essentially normal diet). An esophagorespiratory fistula was completely sealed in two of three patients. All 35 patients were followed up clinically at 1 day and 1 week and at 3-month intervals (range, 1 week to 18 1/2 months; mean, 4.8 months). Recurrent dysphagia or aspiration occurred in only three of 34 (9%) patients whose disease was initially palliated and was easily treated in all cases. Nine complications occurred in eight patients (23%) and included chest pain that required analgesia (n = 3), food impaction (n = 1), stent migration (n = 2), and upper gastrointestinal tract hemorrhage (n = 3). CONCLUSION: Polyethylene-covered stents are a relatively safe and effective means of long-term palliation in patients with severe malignant esophageal obstruction and esophagorespiratory fistula. These stents are easily deployed, and the rate of stent migration is relatively low.

Aged↗