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At least 595 records · Page 33Linked to original sources
PubMed2004

Surgical management of polyethylene wear and pelvic osteolysis with modular uncemented acetabular components.

Osteolysis, usually associated with polyethylene wear, has become one of the most prevalent complications associated with total hip arthroplasty inserted without cement. Management of osteolysis is challenging because the disorder tends to develop silently and surgical intervention can result in complications. In addition, long-term outcomes are unknown. We discuss the current knowledge and data available on polyethylene wear and pelvic osteolysis with modular uncemented acetabular components. We also outline an algorithm for evaluation and treatment of patients. In general, we see patients with well-fixed components every 2 years, and we base follow-up visits after 6 years on predicted polyethylene wear rates and the presence or absence of pelvic osteolysis.

Arthroplasty, Replacement, Hip↗
PubMed2004

Fracture of the polyethylene tibial post in a NexGen posterior-stabilized knee prosthesis.

We reported a case of fracture of a polyethylene tibial post in a 44-year-old woman after 3 years of NexGen posterior-stabilized total knee arthroplasty (Zimmer, Warsaw, IN). Burnishing and delamination of the polyethylene was found around the breakage site of the post, especially over the anterior aspect of the post base. It indicated that the possible failure mechanism was the repeated anterior impingement between the metal femoral cam and polyethylene tibial post. After replacement of the broken insert, the patient obtained complete relief of previous symptoms. To our knowledge, this is the first report of post breakage of a NexGen posterior-stabilized knee prosthesis.

Adult↗
PubMed2005

Polyethylene failure of the patellar component in New Jersey low-contact stress total knee arthroplasties.

In a postoperative 5- to 12-year follow-up study of 598 New Jersey low-contact stress total knee arthroplasties, 32 required revision. All retrieved patellar components were examined for polyethylene damage. These 32 cases had 3 types of failure: split rupture (7 cases), peripheral wear (21), and cantilevering breakage (4), respectively 75%, 64.3%, and 100% of which showed subluxation and/or tilting of the patellar component on the prerevision roentgenograms. Misalignment at the joint contact surfaces and rotational blockage of the mobile patellar component were considered the major causes of the failure. A design of a flatter metallic button (giving larger focal thickness of the polyethylene) and a dome-shaped polyethylene (reducing stress concentration at the pinnacle) may alleviate the failure driving mechanism should subluxation or tilting of the patellar component take place.

Arthroplasty, Replacement, Knee↗
PubMed2004

Cementless metal-on-metal hip arthroplasty in patients less than 50 years of age: comparison with a matched control group using ceramic-on-polyethylene after a minimum 5-year follow-up.

Thirty-nine cementless hip arthroplasties using metal-on-metal articulation were consecutively implanted in 30 patients less than 50 years of age and compared with a matched control group (by age, diagnosis, Devane activity, and Harris hip scores) of cementless arthroplasties using ceramic-on-polyethylene articulation. The Harris hip score at follow-up (minimum 5 years) for the metal-on-metal was 94.9 (range, 74-100). After the same follow-up, the results of the ceramic-on-polyethylene were significantly worse: 9 osteolyses and 7 surgical revisions related to wear (none in the metal-on-metal). Five-year survival rates were 97% +/-2% for the ceramic-on-polyethylene and 100% for the metal-on-metal. The metal-on-metal may be recommended to prevent wear problems in younger and more active patients; however, a longer follow-up is required to confirm this encouraging data.

Adult↗
PubMed2005

Polyethylene liner failure in second-generation Harris-Galante acetabular components.

Polyethylene liner failure of cementless acetabular components has been reported to be the most common complication of current modular cups. We performed a retrospective review of 128 consecutive primary total hip arthroplasties in 111 patients who had a second-generation Harris-Galante cup (Harris-Galante II, Zimmer, Warsaw, Ind). The mean length of the follow-up period was 8.0 years (range 5-12.9 years), with 26 cups (20.2%) having undergone revision by that time. Twenty-two hips (17.3%) had failure of the polyethylene liner. We found that polyethylene liner failure remains the main cause of revision of this modular cup. The main difference between our population of patients and other populations that have used this cup and liner is our population's cultural inclination toward squatting and leg crossing, body positions that increased the risk of impingement and eccentric wear.

Acetabulum↗
PubMed2005

Highly cross-linked polyethylene: the debate is over--in opposition.

Highly cross-linked polyethylene compared to conventional ultra high molecular weight polyethylene (UHMWPE) results in significantly decreased wear in hip simulators and early prospective randomized clinical studies. However, the contact stresses in a total knee bearing surface are much higher than in a total hip. As a result, fatigue wear mechanisms occur more typically in total knee compared with total hip arthroplasty. Cross-linking reduces the mechanical properties of UHMWPE including fatigue crack propagation resistance, which may limit its role in total knee arthroplasty. Although the in vitro and in vivo studies provide compelling evidence that highly cross-linked polyethylene may improve the longevity of total hip arthroplasty, it does not appear to offer similar benefits for total knee arthroplasty.

Arthroplasty, Replacement↗
PubMed2005

In vivo comparative wear study of traditional and highly cross-linked polyethylene in total hip arthroplasty.

In this study, we compare the in vivo wear performance of electron beam-irradiated, postirradiation-melted, highly cross-linked polyethylene (HXLPE) and traditional UHMWPE via the Martell method. Seventy hips with HXLPE performed at the Massachusetts General Hospital had 138 radiograph pairs for wear analysis and a 31.2-month average follow-up (range, 24-44 months). An age-matched, sex-matched, and body mass index-matched subgroup of 111 hips with 214 acceptable radiograph pairs and a 4-year follow-up from our previously published study on traditional polyethylene performed at Rush-Presbyterian-St. Luke's Medical Center served as a control group. Martell wear analysis was performed for each group. Overall and steady-state wear rates were compared via a specialized t test. The steady-state wear in the HXLPE arm was observed after 2.0 years, was 0.007 mm/y, and was significantly less than the steady-state wear in the traditional arm (0.174 mm/y) (P = .003). Highly cross-linked polyethylene penetration rate was not affected by sex, age, activity, or body mass index by Mann-Whitney analysis.

Arthroplasty, Replacement, Hip↗
PubMed2005

The effect of total hip arthroplasty cup design on polyethylene wear rate.

Using 743 total hip arthroplasties that included 6 hemispheric porous-coated cup designs, this study used a multiple linear regression to identify those factors that influenced polyethylene wear rates. Wear rates for each hip were based on serial head penetration measurement made with computer-assisted techniques. Implant factors associated with an increased wear rate included terminal sterilization with a non-cross-linking chemical surface treatment, a 4-mm lateralized liner, a cobalt-chrome femoral head, and a longer shelf life for liners gamma-irradiated in air. After accounting for these implant characteristics and patient factors, wear rates among the 6 cup designs were not significantly different (P = .89). Although polyethylene wear is frequently characterized for specific implant designs, this study demonstrated that there are several common factors that influence polyethylene wear rates.

Acetabulum↗
PubMed2006

Wear of highly cross-linked polyethylene acetabular cup in Japan.

The wear characteristics of ultra-high-molecular-weight polyethylene acetabular cups irradiated with 6.0 to 7.5 Gy of gamma-irradiation were studied in a hip simulator and in vivo in 70 hips for 6 to 39 months. The linear wear was 2.5% to 4.5% of the wear seen in conventional polyethylene cups. A biphasic wear pattern was observed over time with a relatively large wear in the first year and a subsequent leveling of the wear rate curve. The linear wear rate in the second phase (steady state) was 0.006 mm/y. The extent of decrease in clinical wear of 6.0-Mrad polyethylene (Aeonian, Kyocera Corp, Kyoto, Japan) cups is comparable with the decrease of the in vitro wear measured by the hip simulation test.

Acetabulum↗
PubMed2006

The correlation of RANK, RANKL and TNFalpha expression with bone loss volume and polyethylene wear debris around hip implants.

This study investigates receptor activator NF-kappaB (RANK), RANK ligand (RANKL) and tumour necrosis factor (TNFalpha), key factors regulating bone turnover, present in the tissues near peri-prosthetic osteolysis. Tissue was obtained from zones of peri-prosthetic osteolysis from 11 patients undergoing revision of total hip prostheses, analysed preoperatively by high-resolution spiral multislice CT using a metal artefact suppression protocol. Synovial tissue from 10 patients with osteoarthritis undergoing primary hip replacement was used as control tissue. Immunohistochemical analysis of formalin fixed tissue sections demonstrated that RANK, RANKL and TNFalpha were strongly expressed by large multinucleated cells containing polyethylene wear debris in revision tissues. Control tissue stained weakly for RANK, RANKL and TNFalpha. A strong statistical correlation (p<0.02) was found between the five parameters, volume of bone loss, polyethylene wear debris, RANK, RANKL and TNFalpha expression. Importantly, in vitro studies revealed that RANKL and TNFalpha synergise to increase the volume of bone resorbed, by more than seven fold, when compared to the effect of either cytokine treatment alone. This suggests that the interaction of TNFalpha and RANKL promotes osteoclast activity associated with polyethylene wear and therapies targeting TNF activity may be useful to treat peri-implant osteolysis.

Arthroplasty, Replacement, Hip↗
PubMed2006

Polyethylene glycol solution as an oral contrast agent for MRI of the small bowel in a patient population.

AIM: To assess the efficacy of polyethylene glycol solution as an oral contrast agent in a patient population. MATERIAL AND METHODS: Patients were fasted from 12.00 am. Administration of the oral contrast medium commenced 15 min before imaging and comprised one sachet of Norgine (Klean-prep, Middlesex, UK) reconstituted in 1 l water of which the patient took between 500-750 ml. Norgine is a balanced mixture of polyethylene glycol and electrolytes, which when added to water produces a clear colourless, iso-osmotic solution. RESULTS: In total 38 candidates were identified retrospectively covering a 2-year period. Visualization of the jejunum, ileal loops and ileocaecal region was excellent or sufficient in 87, 95 and 89%, respectively. The time taken to obtain complete visualization of the small bowel, from the jejunum to the ileocecal region varied from 15-240 min with an average time of 65 min and 73.7% of patients necessitating delayed imaging. CONCLUSIONS: Polyethylene glycol was demonstrated to be an excellent oral contrast medium in distending the small bowel. However, small bowel transit times were significantly delayed and problematic necessitating repeated imaging within the patient population. As result of theses findings longer examination time should be expected within a patient population and this should be borne in mind when scheduling patients.

Administration, Oral↗
PubMed2006

Stabilization of solid dispersions of nimodipine and polyethylene glycol 2000.

Previous investigations revealed that solid dispersions consisting of 20% (m/m) nimodipine and 80% (m/m) polyethylene glycol 2000 prepared by the melting method, represent supersaturated solid solutions of nimodipine recrystallizing upon storage at +25 degrees C. The objective of this study was the improvement of the storage stability by preventing recrystallization. The first approach in order to prevent recrystallization was the development of thermodynamically stable solid solutions by using solvents aiming to enhance the solubility of nimodipine in the carrier material. As potential solubility enhancing additives, polyethylene glycol 300, poly(ethylene/propylene glycol) copolymer, polypropylene glycol 1020, propylene glycol, glycerol and ethyl acetate were evaluated. The second approach enhancing storage stability was the addition of recrystallization inhibitors to supersaturated solid solutions, thereby delaying the transformation of the metastable supersaturated system to the thermodynamically stable state. Macrogol cetostearyl ether, macrogol glycerol monostearate, polysorbate 60, cetostearyl alcohol, glycerol monostearate and sodium lauryl sulphate as well as hydroxypropylcellulose, butylmethacrylat-(2-dimethylaminoethyl)methacrylat-methylmethacrylat-copolymer, polyacrylic acid, polyvinyl alcohol and povidone K17 were included in the study. It could be shown that povidone K17 effectively prevents recrystallization in solid solutions containing 20% (m/m) of nimodipine during storage at +25 degrees C over silica gel thereby ensuring a substantial increase in the dissolution rate and degree of supersaturation in water. On the contrary, stabilization by solubility enhancement was only successful at drug loadings not exceeding 1% (m/m) using polyethylene glycol 300 as solubility enhancing additive.

Calcium Channel Blockers↗
PubMed2004

Polyethylene wear in a non-congruous unicompartmental knee replacement: a retrieval analysis.

Polyethylene wear is considered a threat to the long-term survival of unicompartmental knee replacement (UKR). This study aims to determine the linear penetration and volumetric wear associated with a non-congruent commonly used UKR, the St Georg Sled. This prosthesis has a biconvex femoral component which articulates with a flat polyethylene tibial component resulting in point contact. Components were retrieved from the knees of 19 patients undergoing revision for a failed UKR after primary replacement. Linear penetration and volumetric wear was measured using a coordinate measuring machine. Using an un-used implant, a three-dimensional computer model of the surface was generated and compared to the explanted specimen. Most patients had revisions because of disease progression to other compartments rather than specific wear related pathology. The mean linear wear for the sample was 0.89 mm (S.D. 0.59 mm) over an average period of 5.6 years giving the mean linear penetration rate of 0.15 mm/year. The mean volumetric wear was 99.7 mm3 (S.D. 79.3 mm3) over the same period giving a mean annual volumetric wear rate of 17.3 mm3/year. The results in this study indicate that clinically significant wear is not necessarily a feature of this fixed bearing unicompartmental knee replacement. The pattern of wear is consistent with clinical findings and indicates excavation of the polyethylene after implantation but at a slower rate than would be anticipated.

Arthroplasty, Replacement, Knee↗
PubMed2005

Repair of exposed porous polyethylene implants utilizing flaps from the implant capsule.

PURPOSE: To determine the feasibility of the use of flaps from the capsule surrounding porous polyethylene implants in repairing large or recurrent implant exposures. DESIGN: Retrospective, noncomparative, interventional case series. PARTICIPANTS: Sixteen patients with exposed porous polyethylene implants. METHODS: Vertical and horizontal flaps were created from the implant capsule. These flaps were used to create a double layer of closure to seal the exposure. All patients had a minimum follow-up of at least 12 months. MAIN OUTCOME MEASURES: Repair of the exposure without recurrence during the follow-up interval, and assessment of complications. RESULTS: At the last follow-up visit, the socket was completely healed in all but 2 patients. In 1 of them, the implant was subsequently exchanged. Other complications included motility loss, conjunctival cyst, and granuloma formation. CONCLUSIONS: The use of the implant capsule to salvage exposed porous polyethylene implants is an effective technique; it is associated with some complications that can be minimized by careful case selection.

Adolescent↗
PubMed2005

Polyethylene wear rate and osteolysis: critical threshold versus continuous dose-response relationship.

We studied the relationship between polyethylene wear and osteolysis in 230 subjects after cemented Charnley total hip arthroplasty in order to examine the validity of the wear rate threshold concept. Polyethylene wear measured using image analysis (EBRA) software was compared in 115 subjects with osteolysis versus 115 control subjects that were individually matched for age, sex, and follow up period. Subjects with osteolysis had almost twice the mean annual wear rate versus the controls. The incidence of osteolysis increased in a linear manner with each quintile increase in wear rate throughout the range 0.01-0.54 mm/year. The odds-ratio for osteolysis approximately doubled with each quintile increase in wear rate above the middle quintile (wear rate 0.08-0.11 mm/year), and decreased at a similar rate with each quintile decrease in wear rate below the middle quintile. Our data suggests that the association of osteolysis with polyethylene wear rate represents a continuous dose-response relationship and does not support the concept of a discrete critical wear rate threshold above which the risk of osteolysis is disproportionately increased.

Aged↗
PubMed2001

Gas chromatographic study of the volatile products from co-pyrolysis of coal and polyethylene wastes.

The aim of this study was to determine the volatile products distribution of co-processing of coal with two plastic wastes, low-density polyethylene from agriculture greenhouses and high-density polyethylene from domestic uses, in order to explain the observed decrease in coal fluidity caused by polyethylene waste addition. Polymeric materials, although they are not volatile themselves, may be analysed by gas chromatography through the use of pyrolysis experiments. In this way, a series of pyrolysis tests were performed at 400 and 500 degrees C in a Gray-King oven with each of the two plastic wastes, one high-volatile bituminous coal and blends made up of coal and plastic waste (9:1, w/w, ratio). The pyrolysis temperatures, 400 and 500 degrees C, were selected on the basis of the beginning and the end of the coal plastic stage. The organic products evolved from the oven were collected, dissolved in pyridine and analysed by capillary gas chromatography using a flame ionization detector. The analysis of the primary tars indicated that the amount of n-alkanes is always higher than that of n-alkenes and the formation of the alkenes is favoured by increasing the pyrolysis temperature. However, this effect may be influenced by the size of the hydrocarbon. Thus, the fraction C17-C31 showed a higher increase of n-alkenes/n-alkanes ratio than other fractions. On the other hand, the difference between the experimental and estimated values from tars produced from single components was positive for n-alkanes and n-alkenes, indicating that co-pyrolysis of the two materials enhanced the chemical reactivity during pyrolysis and produced a higher conversion than that from individual components.

Alkanes↗
PubMed2001

Wear simulation of total hip prostheses with polyethylene against CoCr, alumina and diamond-like carbon.

The wear of ultra-high molecular weight polyethylene acetabular cups was studied with a new biaxial hip wear simulator using diluted calf serum as a lubricant. The cups had been packed and gamma-irradiated in argon. The cups were articulated against two established types of femoral head, alumina and CoCr, and one experimental type, CoCr coated with diamond-like carbon (DLC). The diameter of the heads was 28 mm. Polyethylene against alumina and against CoCr were studied because their clinical wear behaviour is relatively well known. The new simulator was validated with these established materials. The wear mechanisms, including the size and shape of the wear particles, agreed well with those seen in clinical studies. The average wear rates of the cups against alumina and CoCr heads were 48 and 56 mg per 1 million cycles, respectively. The order is in agreement with clinical observations. The average wear rate against DLC was 58 mg per 1 million cycles. As a counterface for polyethylene, DLC did not markedly differ from alumina and CoCr.

Aluminum Oxide↗
PubMed2002

Platelet adhesion and activation on a shielded plasma gradient prepared on polyethylene.

Contact of blood with foreign materials evokes thrombogenic effects to an extent determined partly by the wettability of the biomaterials surface. Tools to study blood response towards a variation in materials wettability with minimal variation in chemistry are "gradient surfaces". However, most gradients have been prepared by diffusion or density immersion techniques, which results in a limited gradient range. Through glow discharge with partial shielding, gradients on polymers were prepared over a length of 5 cm, which facilitated studies to platelet adhesion on separate gradient sections. On polyethylene, advancing water contact angles varied from 90 degrees to 40 degrees, with a hysteresis of 30 degrees. ESCA indicated an increasing incorporation of oxygen towards the hydrophilic end. To examine the role of materials wettability on the activation of adhering platelets, sections of shielded plasma gradients were incubated in anticoagulated whole human blood. Fewer platelets adhered to the hydrophobic end, but those platelets were more activated than those on the hydrophilic end, as judged from their morphology and exposure of GpIIb-IIIa complex. However, partly related to the increased binding of platelets, the clotting activation after platelet deposition was highest on the hydrophilic end. Concluding, this new technique results in a large gradient range, which facilitates studies of formed blood elements in relation to the wettability. Platelets are more activated on hydrophobic polyethylene, while on moderate hydrophilic polyethylene more platelet adhesion and activation of the clotting system occurs.

Biocompatible Materials↗