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PubMed1982

[The usefulness of polyethylene for quickly measuring the rate of food passage through the digestive tract of ruminants].

In experiments with 5 rams it was investigated whether it is possible to use pulverised polyethylene for measuring the passage rate of the feed through the digestive tract. Polyethylene of a particle diameter of 0.4 mm and the specific weight of 0.924 represented 1.78 and 3.56% of the pelleted diet, which contained 41.8% meadow hay, 25.3% barley, 15.4% beech sawdust, 15% molasses, 1.3% urea, 1.2% mixture of vitamins and minerals. After the single polyethylene application to 3 sheep the quota of its recovery in faeces was 68.9-74.4-87.4%. During the continuous polyethylene application over 8 days 64.8% was rediscovered, after the end of the application 80.25% (12th day). The best results in the quota of recovery were achieved after the application of the continuous daily ration with 25 g polyethylene per fistula during the feeding of a ground feed ration with additionally long hay. In this case the quota of the recovery of polyethylene was between 93.2 and 98.9%. The low quota of the recovery of polyethylene was probably caused by retention in the rumen and the large intestine, which was corroborated by the pathologic-anatomic dissection one month after the end of the experiment. Possibly there is a different explanation for the low quotas of recovery both in the size and the shape of the polyethylene particles and in the method of determination and the method of application.

Animal Feed↗

PubMed2004

In vivo polyethylene bearing mobility is maintained in posterior stabilized total knee arthroplasty.

In vivo knee kinematics, including polyethylene bearing mobility, were determined in a group of nine patients implanted with a posterior stabilized, mobile-bearing total knee arthroplasty. Each patient, while under fluoroscopic surveillance, did a weightbearing deep knee bend and was analyzed using a 3-D computer model-fitting technique. Patients were evaluated at three and 15 months postoperatively. All nine patients had polyethylene bearing rotation relative to the tibial tray at both times, with the maximum amount of polyethylene bearing rotation at any flexion interval averaging 8.5 (range, 5.2-15.5) and 9.8 (range, 4.8-14.2) at 3 and 15 months, respectively. Minimal rotation of the polyethylene bearing relative to the femoral component was observed, averaging only 1.9 and 1.0 of rotation from full extension to maximum knee flexion at three and 15 months, respectively. This study determined that the polyethylene bearing is primarily rotating relative to the tibia rather than the femoral component. Therefore, as the femoral component axially rotates, the polyethylene bearing is rotating a similar magnitude in the same direction. This should result in reduced shear stresses on the superior aspect of the polyethylene bearing, lessening polyethylene wear.

Algorithms↗

PubMed2006

Revision of the polyethylene component for wear in TKA.

Given reports of failure in isolated polyethylene exchange in well-fixed TKA components, we asked whether isolated exchange could be successful either by replacing the polyethylene in implants whose locking mechanism accepts currently available polyethylene designs or by creating a new locking mechanism fabricated with a carbide bit and augmented with polymethylmethacrylate cement. We performed isolated liner exchange for wear in 46 patients (49 knees). The polyethylene locking mechanism in two total knee designs (13 knees) allowed polyethylene exchange without polymethylmethacrylate fixation. A locking mechanism was fabricated for three implant designs (36 knees). Clinical function after polyethylene component exchange was good in all but three knees. No knees with a fabricated locking mechanism failed. The mechanical strength of the fabricated locking mechanism was tested in the laboratory. The cement- fabricated locking mechanism in the unmodified tray notably outperformed the standard polyethylene locking mechanism. Isolated polyethylene component exchange was successful in this small clinical study. Fabricating a locking mechanism with a carbide bit and acrylic cement was effective in laboratory testing and clinical application.

Aged↗

PubMed2006

2006 Otto Aufranc Award Paper: significance of in vivo degradation for polyethylene in total hip arthroplasty.

Our research group developed an implant retrieval program to study in vivo degradation of polyethylene. We now have evidence to support our hypothesis that degradation of radiation-sterilized polyethylene occurs in the body for not only historical gamma air sterilized liners, but also for conventional gamma inert sterilized (ArCom) and annealed highly crosslinked polyethylene (Crossfire) liners as well. Our research has also led to the discovery that the most severe manifestations of in vivo oxidation typically occur in regions of the liner experiencing minimal wear, such as the rim of the component, where the body fluids (containing oxidizing species) have access to the polyethylene. Our data from historical, ArCom, and Crossfire retrievals all point to a similar scenario in which the femoral head limits the in vivo oxidation of polyethylene at the bearing surface. Consequently, provided rim impingement does not occur, and the polyethylene locking mechanisms remain relatively isolated from oxidizing fluid, in vivo oxidation does not seem to be clinically important in the first 10 years of implantation for conventional gamma sterilized polyethylene. We conclude that in vivo degradation should be included among the list of potential long-term failure modes for modular polyethylene components for total hip arthroplasty.

Arthroplasty, Replacement, Hip↗

PubMed2006

Intracellular calcium response and adhesiveness of chick embryonic retinal neurons to photoelectric dye-coupled polyethylene films as prototypes of retinal prostheses.

Photoelectric dyes, which absorb light and convert photon energy to electric potentials, were shown to stimulate retinal neurons in culture. One of these dyes coupled with polyethylene film surface, as a prototype of retinal prostheses, could induce intracellular calcium elevation in chick embryonic retinal tissues. In this study, we used retinal cells from chick embryos in which no photoreceptor outer segments yet developed, and assessed cell adhesiveness and response to the original and modified types of our retinal prostheses. Extruded-blown film of high density polyethylene was used as the original polyethylene film. Polyethylene film surface was modified either by coupling with type 1 collagen or by crystallization from the melt of the original polyethylene film. A photoelectric dye, 2-[2-[4-(dibutylamino)phenyl]ethenyl]-3-carboxymethylbenzothiazolium bromide, was coupled to these different types of polyethylene films through amide linkage. Retinal cells from chick embryos at the 12-day embryonic stage were cultured on the surface of dye-coupled films. The response of retinal cells to the dye-coupled films was observed by calcium imaging. Cell types, either neurons or glial cells, were detected by immunocytochemical staining and also observed by scanning electron microscopy (SEM). Intracellular calcium elevation was observed in cells, including both neurons and glial cells, on the surface of the original dye-coupled film, collagen-coated dye-coupled film, and dye-coupled recrystallized film, in contrast with no response of cells cultured on the dye-uncoupled plain film. Retinal neurons grew upon colonies of glial cells settling on the surface of all different types of the films. The number of retinal neurons on the collagen-coated dye-coupled film and dye-coupled recrystallized film was significantly larger than the number of neurons on the dye-uncoupled plain film (P = 0.0004, analysis of variance; P < 0.05, Tukey-Kramer test). With SEM, Muller cell-like large cells covered the original dye-coupled film and collagen-coated dye-coupled film, while neuron-like small cells settled directly on the dye-coupled recrystallized film and also formed large colonies on Muller-like cells. Retinal neurons and glial cells were cultured directly on the different types of dye-coupled polyethylene films. Photoelectric dye-coupled polyethylene films could be used as prototypes of retinal prostheses.

Aniline Compounds↗

PubMed1992

Brain and tissue distribution of polyethylene glycol-conjugated superoxide dismutase in rats.

BACKGROUND AND PURPOSE: The purpose of this study was to determine the distribution of polyethylene glycol-conjugated superoxide dismutase in the brain, cerebrospinal fluid, and various organs. METHODS: Distribution of iodine-125-labeled polyethylene glycol-conjugated superoxide dismutase was determined in three groups of male Sprague-Dawley rats: a normotensive sham control group (n = 9) and groups given 125I-labeled polyethylene glycol-conjugated superoxide dismutase either 30 minutes before (n = 10) or 30 minutes after (n = 7) norepinephrine-induced hypertensive injury. RESULTS: In the first 30 minutes after intravenous administration, polyethylene glycol-conjugated superoxide dismutase plasma activity declined to 70% of the initial value and then decreased negligibly between 30 and 90 minutes. Levels of 125I-labeled polyethylene glycol-conjugated superoxide dismutase in normotensive animals were low in the brain and cerebrospinal fluid and highest in kidney. Brain levels of polyethylene glycol-conjugated superoxide dismutase were elevated only in those rats that received it before hypertensive injury; however, cerebrospinal fluid levels were elevated in animals receiving the drug either before or after hypertensive injury. CONCLUSION: Our results suggest that the blood-brain barrier becomes more permeable to polyethylene glycol-conjugated superoxide dismutase only during the hypertensive period but that the blood-cerebrospinal fluid barrier sustains more permanent injury. We suggest that the therapeutic effectiveness of polyethylene glycol-conjugated superoxide dismutase in hypertensive brain injury is due to its action in the vascular wall or to its extracellular activity in the cerebrospinal fluid.

Animals↗

PubMed2003

Wear and deformation of ceramic-on-polyethylene total hip replacements with joint laxity and swing phase microseparation.

Wear of polyethylene and the resulting wear debris-induced osteolysis remains a major cause of long-term failure in artificial hip joints. There is interest in understanding engineering and clinical conditions that influence wear rates. Fluoroscopic studies have shown separation of the head and the cup during the swing phase of walking due to joint laxity. In ceramic-on-ceramic hips, joint laxity and microseparation, which leads to contact of the head on the superior rim of the cup, has led to localized damage and increased wear in vivo and in vitro. The aim of this study was to investigate the influence of joint laxity and microseparation on the wear of ceramic on polyethylene artificial hip joints in an in vitro simulator. Microseparation during the swing phase of the walking cycle produced contact of the ceramic head on the rim of the polyethylene acetabular cup that deformed the softer polyethylene cup. No damage to the alumina ceramic femoral head was found. Under standard simulator conditions the volume change of the moderately crosslinked polyethylene cups was 25.6 +/- 5.3 mm3/million cycles and this reduced to 5.6 +/- 4.2 mm3/million cycles under microseparation conditions. Testing under microseparation conditions caused the rim of the polyethylene cup to deform locally, possibly due to creep, and the volume change of the polyethylene cup when the head relocated was substantially reduced, possibly due to improved lubrication. Joint laxity may be caused by poor soft tissue tension or migration and subsidence of components. In ceramic-on-polyethylene acetabular cups wear was decreased with a small degree of joint laxity, while in contrast in hard-on-hard alumina bearings, microseparation accelerated wear. These findings may have significant implications for the choice of fixation systems to be used for different types of bearing couples.

Ceramics↗

PubMed2002

Analysis of polyethylene thickness of tibial components in total knee replacement.

BACKGROUND: Excessive wear of the polyethylene bearing surfaces of tibial components has become an important factor in early failure of total knee arthroplasty. Inadequate thickness of the polyethylene insert is one cause of excessive wear, and various minimum thicknesses have been recommended in order to reduce contact stresses within the polyethylene. However, the true thicknesses of modular polyethylene tibial inserts typically are not stated accurately by the manufacturers in their product information. The purpose of this study was to determine whether the information about the thickness of tibial inserts supplied by the manufacturers is adequate. METHODS: Five of the thinnest available polyethylene tibial inserts from five different manufacturers were selected. The minimum thickness of each was measured with use of a Sigma electronic micrometer comparator to an accuracy of +/-0.005 mm. RESULTS: The stated thicknesses of the polyethylene tibial inserts were 8, 9, and 10 mm, values that differed markedly from the actual minimum thicknesses, which ranged from 5.5722 to 6.2048 mm (mean values). CONCLUSION: The thickness of polyethylene tibial inserts has been implicated as a potential cause of excessive wear and early failure of total knee replacements. This paper highlights the fact that the information supplied by the manufacturers is inaccurate and potentially misleading; in one case, the true thickness was much less than the recommended minimum thickness. We recommend that the minimum thickness of the tibial components as well as the combined thickness of the polyethylene insert and the metal tibial tray be specified in the product information and on the packaged insert.

Arthroplasty, Replacement, Knee↗

PubMed2003

Comparison of the wear rates of twenty-eight and thirty-two-millimeter femoral heads on cross-linked polyethylene acetabular cups in a wear simulator.

BACKGROUND: The use of larger femoral head sizes in total hip arthroplasty has been shown to reduce the rate of dislocation and to increase the range of motion; however, such components have been associated with unacceptably high polyethylene wear rates. Studies have shown dramatic differences in wear rates between nominally cross-linked polyethylene (i.e., polyethylene that is cross-linked during radiation sterilization) and elevated cross-linked polyethylene (i.e., polyethylene that is cross-linked to a higher degree than that obtained by radiation sterilization alone). The aim of this study was to test the effect of increased cross-linking and of increased head size on polyethylene wear rates. METHODS: Four groups of acetabular liners obtained from a single manufacturer, including 28-mm-diameter nominally cross-linked, 32-mm-diameter nominally cross-linked, 28-mm-diameter elevated cross-linked, and 32-mm-diameter elevated cross-linked polyethylene liners, were tested. Three implants from each group were tested in a twelve-station hip wear simulator with use of 90% bovine serum as a lubricant. The liners were articulated with the appropriately sized cobalt-chromium femoral head. Additional liners from each design were subjected only to the same load without motion to serve as load-soak controls to account for any weight gain due to fluid absorption. Gravimetric analysis was performed every 500,000 cycles for a total of five million cycles. RESULTS: Nominally cross-linked liners demonstrated mean wear rates of 14.97 and 16.92 mg per million cycles for the 28-mm and 32-mm head sizes, respectively. Both of the elevated cross-linked liners had significantly lower wear rates than the nominally cross-linked liners, with a mean of 1.51 and 2.57 mg per million cycles for the 28-mm and 32-mm head sizes, respectively (p < 0.001). CONCLUSION: The dramatic reduction in wear rates with polyethylene cross-linking, even with the larger head size, may increase the potential for use of 32-mm head components in total hip arthroplasty.

Acetabulum↗

PubMed2005

Clinical performance of a Durasul highly cross-linked polyethylene acetabular liner for total hip arthroplasty at five years.

BACKGROUND: Highly cross-linked polyethylene is currently the most common articulation surface used for total hip arthroplasty. The hypothesis of the present study was that the Durasul highly cross-linked polyethylene acetabular liner would have less wear at five years than would a conventional polyethylene liner used in association with the same total hip replacement system. METHODS: Forty-three consecutive patients (fifty hips) underwent total hip replacement with an uncemented titanium porous-coated metal cup and a Durasul liner that was mated with a 28-mm cobalt-chromium femoral head. Thirty-one patients (thirty-seven hips) were followed for at least five years. Thirty-five other patients (thirty-seven hips) underwent total hip arthroplasty with the same system but with a conventional polyethylene liner, and these patients also were followed for five years. Clinical assessment was performed with use of the Harris hip score and a patient self-assessment examination. Radiographic analysis included measurements of acetabular component position, fixation, and osteolysis. Femoral head penetration of the Durasul liners was compared with that of the conventional liners. RESULTS: The clinical results as determined on the basis of Harris hip scores and patient self-assessment examinations did not differ between the Durasul group and the control group. The mean bedding-in penetration was 0.054 +/- 0.07 mm for the Durasul group and 0.059 +/- 0.154 mm for the control group. The subsequent penetration, with elimination of the bedding-in wear, resulted in a linear wear rate of 0.029 +/- 0.02 mm per year for the Durasul group, compared with 0.065 +/- 0.03 mm per year for the control group (p < 0.005). The annual penetration at one and five years was 0.074 mm and 0.011 mm, respectively, for the Durasul group, compared with 0.151 mm and 0.04 mm, respectively, for the control group. CONCLUSIONS: While the qualitative wear pattern of the highly cross-linked polyethylene liner was the same as that of the conventional polyethylene liner, the annual linear wear rate was 45% of that seen with the conventional polyethylene liner. Therefore, we believe that these early data support the continued use of this highly cross-linked polyethylene liner for total hip arthroplasty.

Adult↗

PubMed1992

Polyethylene wear in unicondylar knee prostheses. 106 retrieved Marmor, PCA, and St Georg tibial components compared.

106 unicondylar knee replacement tibial components were retrieved and analyzed for the amount and type of polyethylene wear. Three different designs were retrieved which had essentially the same femorotibial conformity. Each design showed a characteristic failure pattern. The polyethylene of PCA tibial components showed serious delamination after only short durations, as a result of heat pressing. St Georg sledge prostheses showed some delamination after 4 years' duration due to sub-surface cracks which were initiated by fusion defects in the polyethylene; metal backing of the components did not affect delamination of this prosthesis. The Marmor designs showed the least wear, with shiny depressions and surface pitting; no delamination was observed in the Marmor prosthesis. Molecular weight determination by gel permeation chromatography and analysis of crystallinity using Fourier transformation infra-red spectroscopy demonstrated that St George polyethylene had higher molecular weight and crystallinity than Marmor polyethylene. In some of the components investigated, crystallinity and molecular weight of the polyethylene were reduced under the wear track when compared with the unworn polyethylene. Since fusion defects may cause delamination of polyethylene we urge manufacturers to reduce the number of such defects.

Corrosion↗

PubMed1998

An analysis of hylamer and polyethylene bearings from retrieved acetabular components.

Hylamer and conventional polyethylene acetabular liners of the same design, revised for a variety of reasons, were examined and compared to assess the performance of Hylamer as a bearing material. Clinical damage modes, linear wear rates, oxidation levels, and mechanical properties were measured. In both series, many liners were retrieved for dislocation. Wear/osteolysis was the most common reason for retrieval in the Hylamer series, while none of the conventional polyethylene liners were retrieved for this reason. Nearly all liners exhibited abrasion, burnishing, scratching, and creep. The Hylamer liners had more cracking, delamination, and pitting. The Hylamer liners had an average linear wear rate of 0.32 mm/year, while the conventional polyethylene liners had an average wear rate of 0.20 mm/year. Due to sample size, no statistical difference in wear rate was noted between the two groups. In general, both the Hylamer and conventional polyethylene showed oxidation peaks subsurface, resulting from their exposure to gamma radiation in air. Liners with elevated oxidation had decreased ultimate tensile strength, elongation, and toughness. For given oxidation levels, the corresponding mechanical properties of Hylamer appeared lower than those of conventional polyethylene. The ultimate tensile strength values ranged from 14 to 33 MPa for Hylamer and 19 to 32 MPa for conventional polyethylene. Elongation ranges were 19% to 350% (Hylamer) and 80% to 375% (conventional). The Hylamer retrievals in this study gave initial indications of performance; Hylamer appeared to behave similarly, but not superiorly, to conventional polyethylene, in the early functional period with respect to clinical wear and clinical performance. Both Hylamer and conventional polyethylene liners were degraded by gamma sterilization in air, with Hylamer liners demonstrating greater property changes.

Chemistry, Pharmaceutical↗

PubMed2005

Axial pattern composite prefabrication of high-density porous polyethylene: experimental and clinical research.

Currently, various alloplastic materials are being used for reconstruction of three-dimensional structures, and high-density porous polyethylene is so far the best and the most commonly used material. Various indications for high-density porous polyethylene have been defined for closure of craniofacial defects, correction of congenital anomalies, and aesthetic augmentations. A common property of various studies published so far is that after being fixed to the bone or underlying structures, high-density porous polyethylene has been covered primarily or by skin flaps. For reconstruction of complex three-dimensional structures such as the ear and nose, the success of current methods is limited by the thinness and pliability of the skin flap. In this study, the authors' aim was to investigate the graftability of high-density porous polyethylene after prefabrication with an axial pedicle and to explore possible clinical applications in light of the new data obtained. In the experimental study, three-dimensional implants (rectangular prism) carved from high-density porous polyethylene were prefabricated using bilateral superficial epigastric arteries and veins of 25 New Zealand rabbits. After a waiting period of 2 to 6 weeks in five groups, control samples were obtained and the prefabricated implants that had been left in place were directly grafted. The results showed that high-density porous polyethylene was vascularized 75 percent after 4 weeks and 90 percent after 5 weeks, and 95 percent of the grafts had survived after 8 weeks. In the clinical study, three nose defects, three ear defects, and one hard palate defect in seven patients ranging in age from 21 to 72 years were reconstructed using the same method. High-density porous polyethylene has been prefabricated and directly grafted for the very first time on a clinical basis. No serious complications have been observed, except for minimal graft loss in two patients. It is obvious that full-thickness skin grafts that are thinner than flaps will adapt better to the fine details of high-density porous polyethylene and will highly increase the detail obtained in the reconstruction of three-dimensional defects.

Abdomen↗

PubMed2005

[The effect of ultra high molecular weight polyethylene particle on the tissues of joint prosthesis].

OBJECTIVE: To study the effect of the high molecular weight polyethylene on the periprosthetic tissue in vivo as to give some reference to treatment of loosening hip arthroplasty. METHODS: Every lower limb of 20 New Zealand white rabbits was implanted a Co-Cr-Mo plug in femur by intercondylar notch. 15 mg polyethylene particles, dispersed in 1.5 ml normal saline solution, were injected into one knee joint. The other knee joint was injected 1.5 ml normal saline solution as control. This procedure was repeated 2,4,6,8 and 10 weeks after the implantation. Both of two lower limbs were given a X-ray examination 10 weeks to assess if there were periprosthetic osteolysis and loosening of the plugs. All animals were killed 2 weeks afer the last injection. The distribution of polyethylene in the knee joint capsule was examined to understand if there were loosening of implants or tissue change around implants. Knee joint capsule tissues and periprosthetic tissues were examined by optical microscope. RESULTS: Nine cases formed fibrous membrane and four cases formed new bone around prostheses in experiment group. Eleven cases formed new bone and two cases formed fibrous membrane in control group (P < 0.05) The X-ray results indicated that the plugs were in distal medulla of femur. There was no sign of periprosthetic osteolysis, implants loosening or new bone formation. Optical microscope study indicated that there were a lot of polyethylene particles inside the capsule. The polyethylene particles were surrounded by multinucleated foreign-body giant cells and fibroblast. In some cases, there were fibroblasts and fibrous tissue around plug. There were no polyethylene particles and multinucleated foreign-body giant cells around plug in the marrow. There were a lot of polyethylene particles on the joint surface. The bone surface that contacted multinucleated foreign-body giant cells was coarse. CONCLUSION: Maximizing ultra high molecular weight polyethylene can restrain rabbit periprosthetic bone formation.

Animals↗

PubMed1995

Polyethylene wear in total hip arthroplasty.

Polyethylene wear increasingly has been blamed for osteolysis and granuloma formation after total joint arthroplasty. The authors evaluated the wear difference between bearing surfaces of stainless steel, cobalt chrome, and titanium alloy. They also compared cemented all-polyethylene molded cups with cemented metal-backed molded acetabular cups. These were compared with molded and machined polyethylene cups. Two patient groups were matched individually for gender, age, weight, and length of followup. Analyses were done using the technique of Livermore et al. The bearing surface evaluation consisted of 3 groups after matching, leaving 77 patients per group. Results showed linear wear rates of 0.06 mm per year, 0.05 mm per year, and 0.08 mm per year for stainless steel, cobalt chrome, and titanium alloy, respectively. The comparison between cemented molded metal-backed and nonmetal-backed acetabular components was not matched, with 134 metal-backed and 99 nonmetal-backed components. Results showed linear wear rates of 0.011 mm per year in the metal-backed group and 0.08 mm per year in the nonmetal-backed group. Results were statistically significant. These results indicate that the metal composition of the femoral bearing surface has minimal, if any, effect on the linear polyethylene wear rate. The method of polyethylene fabrication and the use of metal backing had a significant effect on the polyethylene wear rate in these patient groups. These results suggest that the compression-molded all-polyethylene acetabular component may be optimal for reducing polyethylene wear in total hip arthroplasty.

Aged↗

PubMed1994

Quantitative and qualitative analysis of polyethylene wear particles in synovial fluid of patients with total knee arthroplasty. A preliminary report.

Synovial fluid from 13 knees undergoing revision total knee arthroplasty was subjected to chemical digestion and ultrafiltration. Scanning electron microscopy was used to visualize high-density polyethylene particles filtered from the fluid, and the images were analyzed using digital imaging software. This data were correlated with polyethylene wear patterns seen at the time of revision surgery. Patients' prostheses with gross polyethylene wear were differentiated from those with surface deformation and burnishing. The knees had been in situ for periods ranging from 3 to 112 months, and included 6 different prosthetic designs. The average area of the polyethylene particles measured ranged from 41 to 701 mu 2, and the total number of particles identified for each sample ranged from 38 to 279 mu 2. The largest particle identified had a surface area of 17,500 mu 2. Using the fluid volume analyzed, the particle area per milliliter of synovial fluid examined was calculated, and values ranged from 6.22 x 10(4) to 2.06 x 10(6) mu 2/ml. Visualization of high-density polyethylene using scanning electron microscopy allows greater resolution of morphologic detail than is possible with routine histologic examination using light microscopy. There were trends toward increasing particle size and total particle area in patients with gross polyethylene wear. The area of high-density polyethylene per milliliter of fluid in patients with gross wear was found to be statistically greater than that of patients without gross wear (p = 0.047). This technique offers a potentially valuable method of evaluating the status of high-density-polyethylene bearing surfaces in situ using a noninvasive technique.

Aged↗

PubMed1998

Polyethylene wear after total hip arthroplasty: the effect of a modular femoral head with an extended flange-reinforced neck.

The use of modular components in total hip arthroplasty has been thought to contribute to accelerated polyethylene wear. Specifically, a modular femoral head with a flange extension and a longer neck may cause increased wear. The purpose of the current study was to evaluate the effect of a flange extension on polyethylene wear. Ninety-one patients who had had a total of 100 primary total hip arthroplasties were evaluated after an intermediate duration of follow-up. All of the acetabular components consisted of a hemispherical titanium-alloy fiber-mesh porous-coated shell with a nonelevated modular polyethylene liner; they were inserted without cement and with use of supplemental screws through the dome after so-called line-to-line reaming. All of the femoral components consisted of a modular head with a diameter of twenty-eight millimeters and either a long neck (with a flange extension) or a short or medium neck (without a flange extension). The study group comprised sixty-two patients (sixty-six hips) who had had radiographic evaluation that was adequate to allow the valid measurement of polyethylene wear. Thirty-two hips were in men, and thirty-four were in women. The mean age of the patients was fifty-six years, the mean weight was seventy-three kilograms, and the mean duration of follow-up was 6.1 years (range, four to eight years). The rate of polyethylene wear in the eleven hips in which the femoral component had a flange extension was significantly greater than that in the fifty-five in which the femoral component did not have a flange extension (mean, 0.17 compared with 0.11 millimeter per year; p = 0.009). Multivariate analysis showed that the presence of a flange extension was associated with increased polyethylene wear to a greater degree (F = 2.86) than were all other variables that were measured, including a younger age (F = 1.72), a more vertical angle of the acetabular component (F = 0.49), a heavier weight (F = 0.14), male gender (F = 0.11), and a smaller initial thickness of the polyethylene (F = 0.02). These data support an association between the presence of a modular femoral head with a flange extension and an accelerated rate of polyethylene wear. The presumed mechanism is an increase in peripheral, or so-called rim, impingement of the flange-reinforced neck on the acetabulum due to a decrease in the ratio between the diameters of the femoral head and neck.

Adult↗

PubMed1999

Fungal deterioration of melon seeds stored in jute sacks and polyethylene bags in Ago-Iwoye, southwestern Nigeria.

Laboratory studies were carried out in the Department of Biological Sciences, Ogun State University, Ago-Iwoye, southwestern Nigeria, to determine the extent of fungal deterioration of melon seeds stored in two types of storage bags viz; jute and polyethylene bags. Melon seeds of varieties Tc139 and V2 were stored in jute and polyethylene bags under ambient conditions using the 2 x 2 factorial design (variety vs type of bag) for 12 months. The moisture content (mc), incidence of visible mouldiness (ivm) and germinability of the stored seeds were determined monthly. The mc of Tc139 ranged from 6.1 to 6.7% in jute and 6.2 to 6.5% in polyethylene bags. The ivm which was initially 2.1% increased to 10.7% and 5.5% in jute and polyethylene bags respectively, after 12 months in storage. The germination percentage decreased from 96.3% to 28.7% and 45.3% in jute and polyethylene bags, respectively. The mc of V2 stored in jute and polyethylene bags varied from 5.9 to 6.4%, and 5.8 to 6.2%, respectively. The ivm increased from 1.8% before storage to 8.9% and 4.8% in jute and polyethylene bags, respectively, after 12 months. The percentage seed germination declined from 98.0% to 37.3% in jute and 48.7% in polyethylene bags after 12 months. Decreased incidence of field fungi namely: Alternaria,Botryodiplodia theobromae, Cladosporium, Fusarium and Macrophomina phaseolina was accompanied by simultaneous increase in storage fungi viz: Aspergillus, Penicillium, and Rhizopus with prolonged storage.

Journal Article↗