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At least 505 records · Page 28Linked to original sources
PubMed1999

Solubility changes in shelf-aged ultra-high molecular weight polyethylene acetabular liners.

Crosslinking of extruded, air-packaged, irradiated, shelf-aged (10 consecutive years) polyethylene acetabular liners was measured versus time and material location by using a hot xylene extraction protocol. Insolubility (crosslinking) of new polyethylene liners was 87%, but decreased to 45% after 10 years of shelf-aging. This degradation is similar to that observed from retrieved (aged in vivo) acetabular cups. Crosslinking varied with depth in the aged liners and with radial location in the unaged liners. Given that crosslinking improves polyethylene's wear resistance, crosslinking degradation of polyethylene orthopaedic components must be controlled to improve the long-term clinical performance of total joint implants.

Acetabulum↗
PubMed2000

Failure of the locking mechanism between the acetabular metal shell and the polyethylene liner after primary total hip arthroplasty--a case report.

The short and intermediate-term clinical and radiographic results associated with Harris-Galante II porous-coated acetabular modular cup without cementing have been excellent in most patients. Nevertheless, its modular design introduced the potential for failure of the locking mechanism. There are four pairs of locking ties on the rim of metal shell to fix the polyethylene liner within it. Failure of any locking tine would result in less rigid fixation between the metal shell and the polyethylene liner and potentially produce instability or even disassembling of the liner. Only nine cases have been reported previously about the fractures of the locking tine, but it has never been reported in literature in Taiwan. We report a case with fracture of one tine following minor trauma at five years after primary total hip arthroplasty. During reoperation, scratching injury on the outer surface of the polyethylene liner in contact with the inferior tines of the metal shell was noted. Although no disassembling of the liner was noted, the remaining locking mechanism was found to be less rigid when the liner was taken out of the shell. The locking mechanism of HG II cup may be mechanically weak and may fail without major trauma; therefore, its design ought to be improved in an attempt to prevent postoperative dissociation of the polyethylene liner.

Acetabulum↗
PubMed2000

[Experimental in vitro investigations of hardness changes in hip prosthesis polyethylene cups caused by x-rays and aging].

The aim of this paper was to determine the influence of X-rays and ageing on the mechanical properties of polyethylene cups of Weller type hip prostheses. Polyethylene cups produced in the period between 1987 and 1992 were investigated. Some of the cups were exposed to a radiation dose exceeding greatly the average dose used in a routine X-ray examination. Polyethylene cups produced in different years and those subjected to "artificial ageing" (long-term exposure to high temperature) were examined. Brinell's method was used to assess the hardness of polyethylene. The results of this study indicate that both exposure to X-rays and ageing lead to hardening of the cups. This may in turn cause cup fractures--a potential source of complications following hip replacement procedures.

Equipment Failure Analysis↗
PubMedDate not supplied

Efficacy and safety of oral sodium phosphate versus polyethylene glycol solution for bowel preparation for colonoscopy.

OBJECTIVE: To assess the acceptability, safety and effectiveness of an oral sodium phosphate solution (Exelyte) for colon preparation prior to colonoscopy, compared with a polyethylene glycol solution (Peglec). METHOD: A colonoscopist-blinded, prospective, randomized, observational clinical study. PATIENTS: One hundred patients undergoing colonoscopy for various indications were randomized (n = 50 each) to receive either 90 mL of oral sodium phosphate mixed with 300 mL clear liquid and then consume about 4-5 glasses of water, or 2 liters of polyethylene glycol solution. RESULT: Sodium phosphate showed a safety profile similar to that of polyethylene glycol. However, patients tolerated it better. The colonoscopist reported similar cleansing of bowel in both groups. CONCLUSION: Oral sodium phosphate is well tolerated, is safe and provides bowel cleansing similar to that with a polyethylene glycol solution.

Administration, Oral↗
PubMed2003

The modification of renal transplantation with the usage of own polyethylene receptacle.

In this study a method of elimination of the second warm ischemia is shown. The method is based on the application of a specially constructed polyethylene bag, in which the transplanted kidney is placed in the time course from a removal from ice to the reconstruction of vessel flow. The bag is built of polyethylene foil HDPE of low density produced under high pressure. Own construction of the bag (three spaces and polyethylene) enables the storage of a transplanted organ at the stable temperature +4 Celsius degrees. Thanks to the separation of containers for melting ice and for the kidney, possible becomes unrestrained performance of both venous and arterial anastomosis independently of existing operative conditions. Due to the applied method of the elimination of the second warm ischemia with the usage of own construction of polyethylene bag HDPE, one can expect better early renal function after transplantation--decrease in the number of cases and shortening of the time of acute tubular necrosis (ATN--Acute Tubular Necrosis).

Equipment Design↗
PubMed1992

Separation of the polyethylene liner from acetabular cup metal backing. A report of three cases.

In three young patients with cementless Porous Coated Anatomic (PCA) total hip prostheses implanted two to four years previously, the polyethylene liner separated from metal backing. These cups were of the original PCA design, manufactured and packaged as single assembled components, rather than the more recent two-piece components packaged with interchangeable liners separate from the metal backing. Each case of separation was associated with the failure of the thin outer polyethylene rim and central polyethylene peg on the back of the liner that secures it to the metal backing. Cup liners should be securely attached to the metal backing. The possibility of polyethylene failure is considerable when cementless metal-backed acetabular cups are used in active young patients.

Acetabulum↗
PubMed1992

Wear of polyethylene in total joint replacements. Observations from retrieved PCA knee implants.

Observations of wear damage were performed on 12 retrieved porous coated anatomic (PCA) tibial components, all of which were removed because of excessive polyethylene wear. Density measurements of the remaining polyethylene were obtained as a function of depth from the surface of the components. Comparison to previous results from similar studies of total condylar type knee components and total hip acetabular components revealed distinct differences between the types and severity of damage, emphasizing the influence of design factors on the corresponding wear damage. These results confirm previous conclusions that nonconforming articulating surfaces on thin polyethylene components will be at higher risk of damage than more conforming surfaces on thicker components. It also appears that the high cyclic loads to which polyethylene implants are subjected in vivo are most responsible for the degradation in properties of the material near the articulating surface, although the heat pressing of the articulating surface of the PCA components may contribute to the problem.

Aged↗
PubMedDate not supplied

Porous polyethylene for tissue engineering applications in diabetic rats treated with calcitonin: histomorphometric analysis.

PURPOSE: The purpose of this work was to study the bone tissue reaction after porous polyethylene (Polipore) implantation into surgical defects in the parietal bones of rats with streptozotocin-induced diabetes, treated with salmon calcitonin. MATERIALS AND METHODS: Porous polyethylene implants were placed in bone defects created in 36 adult female rats. The rats were divided into 3 equal groups: diabetic treated with calcitonin (DCa), diabetic (D), and control (C). The animals of the DCa group received applications of salmon calcitonin on alternating days immediately after the surgery until sacrifice. The rats were sacrificed after 15, 30, 60, and 90 days, and the defects were examined histologically and statistically through histomorphometric analysis. RESULTS: Histomorphometric analysis showed that there was no statistically significant difference in the mean quantity of inflammatory cells among all study groups after 15 and 90 days. At 30 days, a statistically significant difference was observed between the D and C groups and the D and DCa groups. At 60 days, there was no statistically significant difference between the D and DCa groups. DISCUSSION: Porous polyethylene can be considered an option for implant material when there are investigations that prove its biocompatibility and stability in the host tissues. Salmon calcitonin positively aided the bone repair and attenuated the inflammatory response until 30 days after the surgery. CONCLUSION: Porous polyethylene was tolerated by the host tissues in all groups, and moderate chronic inflammatory reaction was observed up to the 90-day period. Salmon calcitonin attenuated the inflammatory response up until 30 days.

Animals↗
PubMed2005

Mechanical effects of high density polyethylene dynamic compression plate hole inserts on bone-plate constructs.

This study was conducted in order to investigate the mechanical effects of high density polyethylene screw hole inserts in 4.5 mm Dynamic Compression Plate (DCP)--synthetic bone constructs. A mid-shaft 'osteotomy' was created in synthetic bone cylinders. The bisecting 'osteotomy' was reduced using six-hole broad DCPs and 4.5 mm cortical bone screws. The screws adjacent to the 'osteotomy' were placed using a load-guide. The remaining screws were placed in neutral position. High density polyethylene DCP screw hole inserts were incorporated with each screw in neutral position, in the experimental group. The bone plate constructs were tested in four point cyclical bending with the plates loaded at 2,000 Newtons, for a total of 6,000 cycles. Osteotomy gap was measured at 3,000 and 6,000 cycles. Screw head deflection adjacent to the osteotomy was measured. Kruskal-Wallis non-parametric testing was used for statistical comparisons. There was significantly less gapping at the osteotomy site in the treatment group after 3,000 cycles (0.49 +/- 0.18 mm [control] vs. 0.06 +/- 0.14 mm [treated], P=0.02) and 6,000 cycles (0.6 +/- 0.18 mm [control] vs. 0.1 +/- 0.22 mm [treated], P=0.02). The screws adjacent to the gap were significantly more deformed in the control group than those in the treated constructs (3.63 +/- 1.81 [control] vs. 1.06 +/- 1.55 [treated], P=0.0002). The polyethylene inserts improved the interface between bone plate and screw head, resulting in decreased relative movement of the implant and bone. The polyethylene inserts also resulted in less bending of the loaded screws.

Animals↗
PubMed1991

[Polyurethane versus polyethylene: in vivo randomized study of infectious complications of central catheterization].

Polyurethane (PU) and polyethylene (PE) catheters were distributed by randomization among adult ICU patients to evaluate the impact of the catheter polymer on the rate of catheter-related sepsis (CRS). The two catheters were otherwise strictly identical. Three hundred central venous catheters were randomized and inserted in the subclavian or internal jugular vein, at the discretion of the clinician. Mean duration of insertion was 9.2 (+/- 3) days for both catheter types and mean number of line openings was 159 (+/- 60). A bacteriologic culture using a variant of Maki's technique was performed on the 205 catheters removed before patient discharge. No significant differences were found between the two catheters. Total number of tip infections was 33 and polyurethane and polyethylene prevalence ratio was 0.7. A clinical evaluation was performed for the 183 catheters inserted for a least 48 hours (in 142 patients). Patients were divided into four clinical categories according to previously reported definitions (Brun-Buisson et al., 1987). Clinical tip-infection rate was 4.4% and polyurethane and polyethylene ratio was 0.7. For three additional catheters (1.6%), only the Luer-lock was infected. These three catheters were made of polyethylene and were inserted into the internal jugular vein. The Luer-lock was made of polypropylene.

Bacterial Infections↗
PubMed1991

Improved adhesion and proliferation of human endothelial cells on polyethylene precoated with monoclonal antibodies directed against cell membrane antigens and extracellular matrix proteins.

Endothelial cell seeding may improve the patency of synthetic vascular grafts provided that platelet reactivity of nonendothelialized sites is not increased. We have investigated if surface-adsorbed monoclonal antibodies directed against endothelial cell membrane proteins and against extracellular matrix proteins promote the adhesion and proliferation of cultured human endothelial cells, without causing platelet deposition at non-endothelialized sites. Adhesion of endothelial cells onto polyethylene coated with monoclonal antibodies directed against endothelial cell-specific membrane antigens, integrin receptors and glycoprotein CD31 was equal to or higher than adhesion onto fibronectin-coated polyethylene. Endothelial cells did not proliferate on these surface-adsorbed antibodies. However, pre-coating of polyethylene with mixtures of endothelial cell-specific monoclonal antibodies and monoclonal antibodies directed against fibronectin or von Willebrand factor, resulted in relatively high adhesion and optimal proliferation. Platelet reactivity of the polyethylene surface was found to significantly increase after adsorption of fibronectin, endothelial cell-specific monoclonal antibody or its Fc fragments. In contrast, adsorption of F(ab')2 fragments of endothelial cell-specific monoclonal antibody did not promote platelet deposition. Therefore, it is concluded that coating of vascular graft materials with mixtures of F(ab')2 fragments of monoclonal antibodies specifically directed against endothelial cells and against extracellular matrix proteins may be an effective way to both promote the growth of seeded endothelial cells and limit platelet-graft interaction.

Adsorption↗
PubMed1991

Analysis of the failure of 122 polyethylene inserts from uncemented tibial knee components.

The extent of wear of retrieved, polyethylene tibial components appears to be related to design. To test this observation, 122 tibial inserts were graded for wear, and new components of several designs were tested for contact stress using Fuji film. Finite element analysis provided insight into subsurface stresses. Significant wear was seen in 61.5% of the tibial inserts examined. The presence of unconsolidated polymer powder was seen in 44% of the tibial inserts and was found to be statistically correlated with severe wear of the articulating surface. Contact stress in several noncongruent designs was found to exceed the yield strength of polyethylene. There was a positive correlation between the intensity of wear and the level of contact stress, with noncongruent designs having greater wear than fully congruent geometries. In the noncongruent designs, the thinner polyethylene components showed greater wear than thicker polyethylene inserts of the same design.

Corrosion↗
PubMed1990

An all-polyethylene cementless tibial component. A five- to nine-year follow-up study.

An all-polyethylene cementless tibial component was used in 221 total knee arthroplasties. With one exception, failures did not occur before three years. Failure was characterized by medial subsidence of the tibial component. There was abrasion of the polyethylene on the undersurface of all components that failed. Survivorship was seven to nine years (87.1%). This study demonstrated that a flexible cementless component can function well when used with any type of bone. However, abrasion of the polyethylene that occurs from shearing forces is a concern. Polyethylene components need adequate provisions to prevent shearing or need surface treatment to prevent abrasion.

Adult↗
PubMed1990

Preparation of the bowel before elective surgery using a polyethylene glycol solution at home and in hospital compared with conventional preparation using magnesium sulphate.

Bowel preparation by conventional methods is time-consuming and unpleasant for both patient and staff. In addition, it requires admission to hospital several days before surgery. Preparation using oral polyethylene glycol solution is more acceptable and can easily be adapted so that the patient can perform the procedure at home before admission to hospital. In a prospective series we have compared the efficacy of preparation at home using polyethylene glycol with similar preparation in hospital and with a standard bowel preparation based on magnesium sulphate. Preparation was better after polyethylene glycol and this was significant when performed at home (P less than 0.01). There was no effect on either electrolytes or haematological parameters, but polyethylene glycol did result in a rise in the number of colonic Streptococcus faecalis seen. This rise was not seen with magnesium sulphate (P less than 0.001).

Administration, Oral↗
PubMed1986

The effect of polyethylene glycol on the growth and dissolution rates of a crystalline protein at high salt concentration. Phosphoglucomutase.

Although low concentrations of polyethylene glycol (1-5%, w/v) are essential for growing crystals of phosphoglucomutase from ammonium sulfate solutions (at close to 50% of saturation), the observed rate constant for short-term crystal growth on a defined, microcrystalline surface is essentially independent of polyethylene glycol concentration under these conditions. But this cosolute produces a substantial increase in the observed rate constant for the dissolution process and thus a corresponding increase in the solubility of the crystalline phase. These observations can be rationalized in terms of a decrease in the thermodynamic activity of the soluble form of phosphoglucomutase at high salt due to favorable interactions with polyethylene glycol (PEG) at the protein surface, coupled with a difference in accessibility of protein surfaces in the crystalline and solution states. Surfaces with a differential exposure in these two phases likely include both groups that interact favorably with polyethylene glycol relative to water (nonpolar groups) as well as those that interact unfavorably (ionic groups), but favorable PEG-protein interactions produced on dissolution must outweigh unfavorable ones. A PEG-induced increase in protein solubility at high salt concentration is likely to be general; PEG also may affect the growth of other protein crystals at high salt concentrations as it affects phosphoglucomutase.

Animals↗
PubMed1986

The problem of surface damage in polyethylene total knee components.

Observations of surface damage on retrieved total knee polyethylene components have been combined with experimental and analytical studies of the contact problem to identify important clinical and design factors. The amount and severity of damage occurring on the articulating surfaces of knee components increases significantly with patient weight and with the length of time the component is implanted. The design variables that affect the amount of damage are component thickness, the conformity of the articulating surfaces, and the type of polyethylene material used. Surface damage will be more severe in thin (less than 4-6 mm) components and in components with relatively flat tibial articulating surfaces. Surface damage is also expected to be more extreme for carbon-reinforced polyethylene components than for components made from plain polyethylene.

Body Weight↗
PubMed1995

Measurement of polyethylene wear in metal-backed acetabular cups. I. Three-dimensional technique.

A new technique, the 3-dimensional technique, has been developed. Using a digitzer, points taken from anteroposterior and lateral radiographs are input into a personal computer. A 3-dimensional solid model of the prosthesis is created using custom software. Tilt and anteversion of the acetabular cup are measured, and the model is rotated to a standard frontal view, allowing measurement of femoral head displacement from the center of the acetabular cup. Comparing serial radiographs of the same patient gives the direction and distance of femoral head displacement over time, and this value is used to calculate the minimum volume of polyethylene debris generated. The 3-dimensional technique has been validated by construction of a precision acrylic phantom, and milling of a metal-backed acetabular cup to simulate polyethylene wear. Three-dimensional measurement of femoral head displacement using this technique has an accuracy of +/- 0.15 mm, and volume calculations are within 8% of the true amount of polyethylene removed from the cup. The 3-dimensional technique gives previously unavailable information, and can be used for clinical evaluation of polyethylene wear and evaluation of new prosthetic designs and bearing surfaces.

Acetabulum↗
PubMed1994

The natural history of ultra high molecular weight polyethylene.

Degradative changes occurring during the lifetime of ultra high molecular weight polyethylene total joint components made from 2 different starting resins were determined from retrieved tibial inserts. The inserts were manufactured in the Department of Biomechanics of the authors' institution, for intrahospital use by the hospital's surgical staff, allowing the ultra high molecular weight polyethylene properties to be traced from production, to sterilization, to shelf life, and to subsequent retrieval. Changes were found in the density and the infrared spectra. Density was greater after sterilization and at retrieval, when compared with the density of the virgin ultra high molecular weight polyethylene material, with a greater increase near the surfaces than within the bulk of the inserts. The inserts that had the longest life-times demonstrated the greatest increase in density. Density increases are important because they reflect increases in the elastic modulus of the ultra high molecular weight polyethylene. Such increases near the articulating surface of a total joint component would cause significant increases in the stresses associated with wear damage occurring on and near these surfaces. The infrared spectra were consistent with oxidative degradation.

Aged↗