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PubMed1999

Polyethylene terephthalate and polyurethane coatings for endovascular stents: preliminary results in canine experimental arteriovenous fistulas.

PURPOSE: To evaluate polyethylene terephthalate and polyurethane as coatings of vascular endoprostheses in the treatment of experimental arteriovenous fistulas (AVFs). MATERIALS AND METHODS: Nineteen bilateral carotid artery-to-external jugular vein AVFs were created in 10 adult dogs. Fourteen polyethylene terephthalate-coated and five polyurethane-coated self-expandable nitinol stents were placed with a transfemoral approach. Angiography was performed immediately after placement, after 1 and 3 weeks, and at months 3, 6, 9, and 12. All grafts were examined histopathologically. RESULTS: The AVF was successfully occluded with all but one of the polyethylene terephthalate-coated stents. Graft patency was seen with 12 polyethylene terephthalate-coated stents, while acute vessel occlusion was evident with two polyethylene terephthalate-coated stents following percutaneous transluminal angioplasty immediately after implantation. In the group with polyurethane-coated stents, three graft dislocations and two delayed vessel occlusions were observed. In both groups, histologic examination disclosed a mild foreign body reaction with a few macro-phages. No inflammatory reactions were seen. An unorganized fibrin layer was found adjacent to the polyurethane coating. CONCLUSION: Polyethylene terephthalate-coated nitinol stents showed good biocompatibility and a high rate of occlusion of experimental AVFs. The mechanical properties of the polyethylene terephthalate coating were similar to those of the nitinol stents, which facilitated handling. Polyurethane-coated stents showed frequent dislocation.

Alloys↗

PubMed1992

Polyethylene wear of metal-backed tibial components in total and unicompartmental knee prostheses.

We examined 86 polyethylene inserts, retrieved from total and unicompartmental knee prostheses after an average of 39.5 months in situ, grading them from 0 to 3 for seven modes of polyethylene degradation. Severe wear, with delamination or deformation, was observed in 51% of the implants, and was associated with time in situ, lack of congruency, thin polyethylene, third-body wear debris, and heat-pressed polyethylene. Significant under-surface cold flow was identified in some areas of unsupported polyethylene, and was associated with delamination in the load-bearing areas of thin inserts above screw holes in the underlying metal tray. We recommend the use of thicker polyethylene inserts, particularly in young, active patients and in designs with screw holes in the tibial baseplate. Thin polyethylene inserts which are at risk for accelerated wear and premature failure should be monitored radiographically at annual intervals.

Aged↗

PubMed1996

Wear of polyethylene cups in total hip arthroplasty. A study of specimens retrieved post mortem.

The wear of polyethylene components of total hip replacements has previously been studied radiographically and by analysis of retrieved components. The extent of wear, however, has largely been determined from components retrieved at reoperation and has therefore been based on a subset of patients in whom the prosthesis is more likely to show excessive wear. The study of cups retrieved post mortem provides a better indication of the extent of wear of well functioning components. Twenty-six polyethylene liners were retrieved at autopsy from nineteen patients, after a mean of ninety-one months (range, thirty-three to 206 months) in situ. Each component had articulated with a thirty-two-millimeter-diameter femoral head. The components were evaluated visually for evidence of polyethylene wear such as pitting, scratching, and burnishing. Additionally; a shadowgraph technique was used to examine molds of the inner surface of the liner to determine the direction and extent of wear. The mean extent of linear wear of the retrieved liners was 0.45 millimeter (range, 0.17 to 1.07 millimeters), and the mean rate of wear was 0.07 millimeter (range, 0.02 to 0.18 millimeter) per year. The mean volumetric wear was 245.3 cubic millimeters (range, 13.0 to 779.1 cubic millimeters), and the mean rate of volumetric wear was 39.8 cubic millimeters (range, 1.0 to 131.3 cubic millimeters) per year. The mean rate of wear for the twenty-six liners was 45 to 69 per cent less than the rates reported in the literature for polyethylene liners retrieved at reoperation. Examination of the articulating surface did not reveal gross evidence of surface failure such as delamination or fatigue cracks. In general, the surfaces were merely burnished and scratched. The rates of wear of press-fit, metal-backed liners were significantly higher than those of all-polyethylene cemented components (p < 0.05). Additionally, statistical analysis revealed no correlation between wear and the patient's age, weight, or gender; the duration of implantation; or the thickness of the polyethylene. These results indicate that wear of the polyethylene of well functioning hip replacements is not as excessive as reported previously.

Acetabulum↗

PubMed2003

The AGC all-polyethylene tibial component: a ten-year clinical evaluation.

BACKGROUND: While high success rates have been achieved in association with other all-polyethylene tibial components, an alarming number of failures have occurred at our institution in association with the use of an all-polyethylene version of the AGC tibial component. The purpose of the present study was to describe the survival of the AGC all-polyethylene tibial component. METHODS: Five hundred and thirty-six AGC all-polyethylene tibial components were implanted in 405 patients and were followed over a ten-year period. The average age of the patients at the time of surgery was 70.3 years, the average weight was 78 kg, and the most common diagnosis was osteoarthritis (prevalence, 92.9%). A clinical and radiographic analysis was performed, Knee Society knee and function scores were determined, and Kaplan-Meier survivorship analysis was conducted. Failure was defined as aseptic loosening as evidenced by progressive radiolucent lines and/or revision due to aseptic loosening or collapse. RESULTS: A high rate of failure was noted in the early postoperative period, with a survival rate of 90.04% (95% confidence interval, 87.35% to 92.72%) after three years. At ten years, the survival rate was 68.11% (95% confidence interval, 57.57% to 78.65%). Fifty-eight (73.4%) of seventy-nine failures occurred in association with loosening or collapse of the bone beneath the medial tibial plateau. CONCLUSION: While some all-polyethylene tibial designs have been successful, the low success rate among knees treated with the AGC all-polyethylene tibial component suggests that the results associated with all-polyethylene tibial components are design-sensitive. LEVEL OF EVIDENCE: Therapeutic study, Level IV (case series [no, or historical, control group]). See Instructions to Authors for a complete description of levels of evidence.

Adult↗

PubMed1993

An in vitro evaluation of cocaine hydrochloride adsorption by activated charcoal and desorption upon addition of polyethylene glycol electrolyte lavage solution.

Cocaine body-packers and body-stuffers have become a common medical problem. Significant morbidity and mortality result when cocaine is absorbed from the gastrointestinal tract due to cocaine package compromise. The clinical prevention of gastrointestinal absorption of cocaine includes oral activated charcoal and/or whole bowel irrigation with polyethylene glycol--electrolyte lavage solution. This in vitro study investigates the maximal adsorptive capacity of activated charcoal for cocaine at varying activated charcoal:cocaine ratios, at pH 1.2 and pH 7.0, and the effect of polyethylene glycol--electrolyte lavage solution upon this binding. The percent adsorption of cocaine to activated charcoal was significantly better at pH 7.0 for all ratios of activated charcoal:cocaine tested and the maximal adsorptive capacity was 29% greater at pH 7.0 (273 micrograms/mg) than at pH 1.2 (212 micrograms/mg) (p < 0.05). Addition of polyethylene glycol--electrolyte lavage solution to the cocaine-activated charcoal slurry caused significant desorption of cocaine from activated charcoal at all pHs and ratios tested (except the 1:1 ratio at pH 7.0) and was most pronounced at pH 1.2. The addition of polyethylene glycol--electrolyte lavage solution to activated charcoal prior to adding cocaine solution further decreased the adsorption of cocaine to activated charcoal. This difference was significant at both pHs and all ratios tested except the 1:1 ratio at pH 1.2. The maximal adsorptive capacity of activated charcoal for cocaine at pH 1.2 was reduced 75% by pretreatment with polyethylene glycol--electrolyte lavage solution from 212 to 54.2 micrograms/mg, while at pH 7.0 the maximal adsorptive capacity was reduced by 11%, from 273 to 243 micrograms/mg. Polyethylene glycol--electrolyte lavage solution significantly reduces the adsorption of cocaine to activated charcoal particularly if the two are combined at a low pH prior to the addition of cocaine. The in vitro effects suggest that activated charcoal mixed in water should be administered first, followed by the polyethylene glycol--electrolyte lavage solution.

Adsorption↗

PubMed1996

The effect of polyethylene glycol on the charcoal adsorption of chlorpromazine studied by ion selective electrode potentiometry.

BACKGROUND: This investigation was undertaken to study: a) the adsorption characteristics of chlorpromazine to activated charcoal and its formulations Carbomix powder and Ultracarbon tablets at gastric pH; b) the effect on chlorpromazine adsorption of polyethylene glycol and its combination with electrolyte lavage solution; c) the effect of the order of addition of polyethylene glycol-electrolyte lavage solution. METHOD: Ion selective electrode potentiometry, based on the selective, direct and continuous response of a chlorpromazine-ion selective electrode to the concentration of the free drug, was used. Successive additions of microvolumes of a chlorpromazine solution were made into a charcoal slurry in acidic medium of pH 1.2 with measurement of the chlorpromazine-ion selective electrode potential at equilibrium. RESULTS: The maximum adsorption capacity values of activated charcoal, Carbomix and Ultracarbon, were 297, 563, and 382 mg/g respectively, while the affinity constant values were 40.2, 70.4, and 40.5 L/g, respectively. The adsorption of chlorpromazine to each of the Ultracarbon and Carbomix components was compared to the total adsorption of the formulations. The addition of polyethylene glycol-electrolyte lavage solution causes a slight desorption of chlorpromazine from activated charcoal at gastric pH, more pronounced when polyethylene glycol-electrolyte lavage solution follows the addition of activated charcoal, suggesting the possibility of a nonspecific binding of chlorpromazine to polyethylene glycol. The amount of chlorpromazine absorbed to Carbomix and Ultracarbon was not significantly affected at gastric pH by the presence of polyethylene glycol or polyethylene glycol-electrolyte lavage solution added either concurrently or sequentially to these formulations.

Adsorption↗

PubMed1992

Polyethylene glycol-conjugated superoxide dismutase attenuates reperfusion injury when administered twenty-four hours before ischemia.

Covalent linkage of polyethylene glycol to superoxide dismutase prolongs the serum half-life of the enzyme and may facilitate intracellular access. We tested the myocardial protective effect of polyethylene glycol superoxide dismutase administered once, 24 hours before ischemia. Because hearts were studied ex vivo in a crystalloid perfused system, cardioprotection could be ascribed to intramyocardial or membrane-bound polyethylene glycol superoxide dismutase accumulation. Thirty isolated rabbit hearts from the four following groups were studied: (1) control: untreated rabbits (n = 7); (2) PEG-control: 24-hour intravenous preinfusion of methoxypolyethylene glycol 5000 (5 mg/kg) to examine the effect of polyethylene glycol alone, without conjugation to superoxide dismutase (n = 8); (3) PEG-SOD 10,000: 24-hour preinfusion of polyethylene glycol superoxide dismutase (10,000 U/kg) (n = 8); (4) PEG-SOD 30,000: 24-hour preinfusion of polyethylene glycol superoxide dismutase (30,000 U/kg) (n = 7). After measurement of baseline function with use of an intraventricular balloon, hearts were subjected to normothermic ischemia until a 4 mm Hg rise in intracavitary pressure was observed. Function was assessed at 15-minute intervals throughout reperfusion and expressed as percent return of developed pressure. After 60 minutes of reperfusion, recovery of function was greater for the PEG-SOD 30,000 group (85.6% +/- 2.6%) when compared with either the untreated or PEG-control group (68.9% +/- 2.3% and 71.4% +/- 2.0%, respectively). A similar difference was seen throughout reperfusion. Although an improved return of function was shown in the lower dose PEG-SOD 10,000 group, the margin of difference when compared with any of the control groups was determined to be insignificant at all times of reperfusion and at 60 minutes (75.9% +/- 3.2%). These data demonstrate that high, but not low, doses of polyethylene glycol superoxide dismutase significantly reduce reperfusion injury when administered 24 hours before initiation of global ischemia. Moreover, since the perfusate was superoxide dismutase free, this effect was most likely intramyocardial or membrane bound and therefore might be added to protection afforded by circulating superoxide dismutase.

Animals↗

PubMed1980

Solubility properties of IgG immune complexes. Comparison between the effects of low molecular weight solvents and polyethylene glycols.

A systematic study of the influence of organic solvents on the interaction between human IgG and rabbit anti-human IgG IgG++ has been conducted, using difference turbidity and sucrose gradient centrifugation methods. It was found that very small alcohols like methanol and ethanol increased the turbidity signal, whereas larger alcohols (propanol, isopropanol, propanediol and ethylene glycol) had no influence on the signal. Sucrose, dioxane, dimethylformamide and dimethylsulphoxide decreased the difference turbidity signal. Sucrose gradient centrifugation did not show any influence. Polyethylene glycols were investigated with regard to molecular weights as well as concentrations. In contrast to the low molecular weight solvents, polyethylene glycols with molecular weights from 600 up to 20,000 gave a clearly expressed increase in the development of turbidity as well as in the size of the final turbidity signal. By sucrose gradient centrifugation, it was found that polyethylene glycols of molecular weights from 1000 to 10,000 had a profound effect on the solubility of immune complexes. The influence depended on the molecular weight as well as on the concentration. By use of [14C]-labelled polyethylene glycol it was found that polyethylene glycols did not form stable complexes with immune complexes. Furthermore, it was found that the zoning phenomenon was retained in the presence of small concentrations of polyethylene glycols, but higher concentrations of polyethylene glycols caused even antigen-excess complexes to show turbidity.

Alcohols↗

PubMed1996

An ultrasound method to evaluate polyethylene component wear in total knee replacement arthroplasty.

Evaluation of a painful total knee replacement has been limited to physical examination, aspiration, plain radiographs, and radionuclide studies. Visualization of the polyethylene tibial-bearing component without surgery has not been possible. Polyethylene wear is a well-recognized cause of total knee replacement failure. We have developed an ultrasound method to evaluate polyethylene insert shape and thickness with the ability to clearly demonstrate structural loss of plastic. Before clinical trials, a total knee replacement was cemented into a fresh cadaver knee. Ultrasound imaging of the polyethylene insert was performed in the longitudinal plane using a 10 MHz linear transducer. A characteristic bone/metal/polyethylene interface enabled recognition of the insert material from which its dimension was estimated. The entire perimeter of the liner, the metal tray, and the bone-metal interface was visualized. Five consecutive measurements at each location were performed on each of the 8-, 10-, and 12-mm polyethylene liners with the ultrasonographer blind to the insert thickness. Once removed, measurements were made directly on the liners adjacent to the marked points with an electronic caliper. Coefficient of variation (r2) ranged from 1.6% to 8.3% for the ultrasound measurements, and 0.26% to 1.5% for the caliper measurements. A plot of ultrasound versus caliper measurements allowed calculation of a linear equation, with r2 = 0.98, demonstrating high correlation between the two measurements. Our ultrasound measurements are accurate to 0.5 mm with a 95% confidence interval. Ultrasound is an accurate way to measure the dimensions of the polyethylene liner in total knee replacement arthroplasty. Early experiences with ultrasound evaluation prior to revision have been very encouraging for the evaluation of polyethylene wear, defects, and of prosthetic loosening.

Anthropometry↗

PubMed1971

Evaluation of water stress control with polyethylene glycols by analysis of guttation.

The water relations of pepper plants (Capsicum frutescens L.) under conditions conducive to guttation were studied to evaluate the control of plant water stress with polyethylene glycols. The addition of polyethylene glycol 6000 to the nutrient solution resulted in water relations similar to those expected in soil at the same water potentials. Specifically, xylem pressure potential in the root and leaf became more negative during a 24-hour treatment period, while osmotic potential of the root xylem sap remained constant. The decrease in pressure potential was closely correlated with the decrease in osmotic potential of the nutrient solution. In contrast, the addition of polyethylene glycol 400 to the nutrient medium resulted in a reduction of osmotic potential in the root xylem sap; this osmotic adjustment in the xylem was large enough to establish an osmotic gradient for entry of water and cause guttation at a nutrient solution osmotic potential of -4.8 bars. Pressure potential in the root and leaf xylem became negative only at nutrient solution osmotic potentials lower than -4.8 bars. About half of the xylem osmotic adjustment in the presence of polyethylene glycol 400 was caused by increased accumulation of K(+), Na(+), Ca(2+), and Mg(2+) in the root xylem. These studies indicate that larger polyethylene glycol molecules such as polyethylene glycol 6000 are more useful for simulating soil water stress than smaller molecules such as polyethylene glycol 400.

Journal Article↗

PubMed1975

Oxygen availability in polyethylene glycol solutions and its implications in plant-water relations.

The solubility of O(2) in polyethylene glycol 4000 and 6000 solutions of varying concentrations was determined iodimetrically (titrimetrically) and electrochemically using a rotating glassy carbon electrode and a PAR Model 174 Polarograph. The titrimetric determination resulted in the formation of an unexpected precipitate at 2% (w/v) polyethylene glycol corresponding to the approximate critical micelle concentration of the two polyethylene glycol homologs. Beyond 5% polyethylene glycol, O(2) concentration was inversely proportional to polyethylene glycol concentration, and was higher in polyethylene glycol 4000 solutions than in polyethylene glycol 6000. The electrochemical data are a direct measure of O(2) transport to the electrode surface, rather than O(2) activity or concentration. Results indicate that even at relatively high H(2)O potentials, the transport of O(2) to the root surface might be insufficient to meet the plant's respiratory requirements.

Journal Article↗

PubMed2005

Polyethylene wear particle generation in vivo in an alumina medial pivot total knee prosthesis.

Polyethylene wear particle generation is one of the most important factors affecting mid- to long-term results of total knee arthroplasties. It has been reported that the medial pivot total knee prosthesis (MP) design and alumina ceramic femoral component reduce polyethylene wear. The aim of this study is to evaluate in vivo polyethylene wear particle generation in the newly introduced alumina MP, in comparison with a metal MP. Synovial fluid was obtained from 11 knees with alumina MP and 15 knees with metal MP at nine months after the operation. Polyethylene particles were isolated, and examined using scanning electron microscope and image analyzer. Total number of particles in each knee was 7.10+/-2.86x10(6) in alumina (mean+/-standard error), and 5.70+/-2.82x10(7) in metal MP (p=0.048). Particle size (equivalent circle diameter) was 0.78+/-0.04 microm in alumina, and 0.66+/-0.06 microm in metal MP (p=0.120). Particle shape (aspect ratio) was 1.52+/-0.05 in alumina, and 1.88+/-0.11 in metal MP (p=0.014). Apart from the femoral component, the material and manufacturing method of polyethylene insert differed between the two groups, although the sterilization method was the same. Alumina MP generated fewer and rounder polyethylene wear particles than metal MP in early clinical stage, and could potentially reduce prevalence of osteolysis and aseptic loosening.

Aged↗

PubMed2004

Influences of sterilising techniques on polyethylene wear.

Over the last 10 years there has been increasing concern over wear of polyethylene and osteolytic potential in the knee. During this period there have been considerable developments in both the design, materials and sterilisation techniques used for polyethylene in the knee. This paper reviews wear performance of polyethylene sterilised by different techniques, under a range of kinematics conditions in a single knee joint simulator system. Reducations in polyethylene wear were found with both stabilised polyethylene and cross-linked polyethylene, and with rotating platform mobile bearing designs.

Biomechanical Phenomena↗

PubMed2004

Oxidized zirconium femoral components reduce polyethylene wear in a knee wear simulator.

Polyethylene wear remains a major problem that can jeopardize the long-term durability of prostheses used in total knee arthroplasty. Oxidized zirconium is a material that combines the strength of a metal with the wear properties of a ceramic. This study evaluated the wear rates of polyethylene inserts against oxidized zirconium femoral components. Three oxidized zirconium femoral components and three Co-Cr femoral components of identical geometry used in total knee arthroplasty were articulated against standard tibial components with modular tibial inserts made of noncross-linked ultra-high molecular weight polyethylene. Gravimetric and volumetric polyethylene wear rates were calculated after 5 million gait cycles on an AMTI knee wear simulator. Oxidized zirconium reduced polyethylene wear by 42% compared with Co-Cr alloy. This study shows that oxidized zirconium can reduce polyethylene wear substantially when used for fixed-bearing total knee arthroplasty.

Biocompatible Materials↗

PubMed2000

Possible explanation for the white band artifact seen in clinically retrieved polyethylene tibial components.

Studies have focused attention on the appearance of a subsurface white band in clinically retrieved polyethylene components and the possible contribution of this phenomenon to early polyethylene delamination. Unconsolidated polyethylene particles and oxidation have been suggested as possible reasons for the appearance of the white band. Calcium stearate and other additives used in processing ultra-high molecular weight polyethylene may also contribute to formation of the white band. A quantitative investigation was conducted on 11 retrieved tibial components that exhibited a subsurface white band to determine whether the amount of calcium stearate particles and additives were greater in the white band region when compared with the mid-portion of the same section of polyethylene. Calcium stearate particles and other additives were quantified using backscattered electron imaging with correlated elemental analysis. The particles were identified based on morphology and elemental patterns similar to reference calcium stearate particles and known additives. Significantly more (p < 0. 0001) calcium stearate particles and additives were present in the white band region (4578 +/- 418 particles/mm(2); mean +/- standard error) than the mid-portion region (1250 +/- 147 particles/mm(2)) of the sectioned tibial inserts. The percent area occupied by calcium stearate particles and additives was five times higher (p < 0.0001) within the white band region (0.81 +/- 0.10%) than the mid-portion region (0.16 +/- 0.03%). The increased presence of calcium stearate and other additives in the white band region suggests that they may play a role in the formation of the white band. In future investigations it may be important to consider how calcium stearate and other additives in polyethylene resins affect white band formation and the possible contribution to crazing, early delamination, and osteolysis in total joint replacement.

Adult↗

PubMed2001

The inhibitory mechanism of gap junctional intercellular communication induced by polyethylene and the restorative effects by surface modification with various proteins.

Gap junctional intercellular communication (GJIC) is a function that plays an important role in maintaining cell and tissue homeostasis and in regulating cell growth, development, and differentiation. Change in this function of V79 fibroblasts cultured on polyethylene films modified with albumin or collagen was estimated using fluorescence redistribution after photobleaching (FRAP) analysis. The GJIC function of V79 cells on nontreated polyethylene was strongly inhibited in comparison with those on a glass coverslip. When the cells were culture on collagen-immobilized polyethylene film, this function was recovered to about 70% of the cells cultured on the coverslip. However, albumin immobilization did not recover the function as much as collagen immobilization. Western blotting analysis and immunostaining of connexin 43, which is a major protein constituting gap junctional channel of these cells, revealed its abnormal expression and distribution in the cells on nontreated polyethylene, whereas its almost normal distribution was observed in the cells on collagen-immobilized polyethylene. This abnormal expression and distribution of connexin 43 induced by the surface of polyethylene may be ascribed to a strong inhibition of GJIC of V79 fibroblasts.

Albumins↗

PubMed2006

Three-dimensional printing of porous polyethylene structure using water-based binders.

This study demonstrated a freeform fabrication of porous hydrophobic polyethylene parts by three-dimensional printing technique, using water-based binder. This involved initially making a green structure by printing a binder onto the mixture of polyethylene and water soluble adhesive powder bed. The green structure was thermal treated to melt polyethylene fraction to achieve a well-connected structure within the part. Adhesive components were then leached out in water, leaving only porous structure of polyethylene. Specimens with ratios of polyethylene to adhesive from 80:20 to 20:80 were fabricated and characterized. It was found that increasing polyethylene content increased density, modulus, and strength while decreased porosity. Preliminary in vitro toxicity test of porous parts using L929 cells showed that the cells that were in contact with samples were healthy. No inhibition zone was observed.

Biocompatible Materials↗

PubMed2006

Influence of polyethylene creep behavior on wear in total hip arthroplasty.

After total hip arthroplasty (THA), polyethylene acetabular liner creep occurs quickly and serves to increases head-liner contact area and decrease contact pressures. What effect these early changes in contact mechanics will have on the wear behavior of the articulation remains unclear, and hence, selection or modification of polyethylene materials for optimal creep and wear performance is impossible. The objective of this study was to determine the influence of polyethylene creep behavior on volumetric wear and linear creep and wear penetration during simulated gait loading conditions. A finite element model of THA articulation was developed, and simultaneous numerical creep and wear simulation was performed to 10 million gait cycles with three levels of polyethylene creep behavior. Long-term volumetric wear and penetration were surprisingly unaffected by the polyethylene creep behavior due to the competing decrease in contact pressures coupled with increased contact area. In addition, variation in contact mechanics with the creep levels studied was only noteworthy in the initial postoperative period; after 1 million gait cycles, peak contact pressures and areas were within 13% regardless of the creep material behavior selected. Femoral head size had considerable impact on wear and penetration, while liner thickness primarily affected only early penetration. These results suggest that polyethylene creep behavior plays a major role in early penetration, but has little influence on the more important long-term volumetric wear.

Arthroplasty, Replacement, Hip↗