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1

The surface topography of a metallic femoral head and its influence on the wear mechanism of a polymeric acetabulum

Niemczewska-Wójcik M., Piekoszewski W.

Archives of Civil and Mechanical Engineering

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2017

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Vol. 17, no. 2

307--317

EN

The wear mechanisms of friction components depend on conditions of articulation, material properties and surface topography of the co-acting parts. Therefore, it is important to examine these determinants in order to improve the durability of a friction pair. With the view of securing the longer life of articulating surfaces, a metallic femoral head used in conjunction with a polymeric acetabulum was subject to research. The components of the friction pair were prepared in accordance with the standard specification ASTM F2033-12. From the precision machining process of metallic femoral heads, two different kinds of surface topography (defined by Ra parameter: Ra(A) < Ra(B)) were obtained. The tribological research was performed with a testing machine simulating the kinematic movements and the working conditions of a natural joint (friction pair: ball-and-socket) in the Ringer's solution. The measurements of the surface topography (machined and worn surfaces) were conducted using the following measuring devices: coordinate measuring machine, white light interference microscopy and scanning electron microscopy. Based on the analysis results, the influence of the surface topography of the metallic ball upon tribological characteristics was determined. The wear mechanisms of the polymeric socket resulted from a number of phenomena, including plastic deformation, abrasive wear, fatigue and adhesion.

2

Failure analysis of a femoral hip stem made of stainless steel after short time of exposure

Mierzejewska Ż. A., Oksiuta Z.

Acta Mechanica et Automatica

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2014

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Vol. 8, no. 3

146--150

EN

This paper describes a case study summarising the failure analysis of a stainless steel femoral stem, which failed prematurely within 36 months of exploitation in human body. In order to determine the mechanism of failure, a broken stem component were analyzed by means of macroscopic and microscopic obserwations and hardness measurements. Metallurgical obserwations revealed that the tested material does fulfill ASTM requirements. Scanning electron microscopy images revealed the presence of stress-induced cracking. The results of the hardness revealed significant nonuniformity from the surface towards the inner part of the stem. It is assumed that any discontinuity or defect on the fracture surface of the stem acted as preferential site for a crack nucleation and propagation by fatigue until the cross section of stem was not able to sustain a load generated by a patient.

3

Types of wear and tear of biomaterials used in orthopaedic surgery

Klimek L., Wołowiec E., Majkowska B.

Journal of Achievements in Materials and Manufacturing Engineering

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2013

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Vol. 56, nr 2

83--89

EN

Purpose: Purpose of this paper is presentation of observations on different kinds of wear and tear of biomaterials used in contemporary orthopaedic surgery. Design/methodology/approach: Types of prosthesis damage, encountered in medical practice, and their causes have been described. Results of many clinical studies were analysed to review prosthesis damage from the stage of implanting (such as intrusion of a foreign object between its components) to their natural wear and tear after many years of use (abrasive wear, biological corrosion). Findings: It has been shown that prostheses heads may also succumb to quick wear and tear despite being made of harder and more durable materials than sockets. Research limitations/implications: Clinical and laboratory of defective implants discover the reasons of damage, but they are time consuming. There are also difficulties in obtaining objects for research. Originality/value: The research has helped to systematise the knowledge on the mechanisms of wear and damage of endoprostheses, which is vital for improvement of their life cycle.

4

Analysis of wear of polyethylene hip joint cup related to its positioning in patient’s body

Rońda J., Wojnarowski P.

Acta of Bioengineering and Biomechanics

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2013

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Vol. 15, no. 1

77--86

EN

Polyethylene parts of endoprosthesis are the weakest parts of each medical implant. They can be worn out within several years. During this period, a patient can enjoy good physical efficiency until the wear of polyethylene part limits his/her mobility. Then the reoperation is necessary and positioning of all parts of endoprosthesis has an effect on future patient’s mobility and durability of implant. Elements of endoprosthesis during exploitation are heavily loaded both by normal and tangential forces and moments. In this paper, the dependence of wear of polyethylene cup on its positioning in pelvis is the major problem. Wear of the cup is determined by two measures: the depth and volume of a material rubbed off from the contact surface. The sensitivity of the depth of rubbing off is evaluated relative to two angles of anteversion and abduction, and radii of the cup. Numerical results are obtained by using Abaqus FE system with data related to patient’s activity identified on the basis of medical reports.

5

Zastosowanie spiekanych biomateriałów ze stali 316L na węzły tarcia endoprotez stawu biodrowego

Grądzka-Dahlka M., Dąbrowski J. R., Deptuła P.

Tribologia

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2010

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nr 1

19-26

PL

Wśród zagadnień biotribologii jednym z najczęściej pojawiających się problemów jest wydłużenie trwałości endoprotez stawów. Konieczność zapewnienia korzystnych parametrów tarciowych przy zachowaniu wymogów biozgodności implantów wymusza poszukiwanie nowych rozwiązań. W pracy przedstawiono koncepcję węzła tarciowego endoprotezy stawu biodrowego opartego na pracy samosmarnego łożyska porowatego. Panewka z warstwą porowatą, wykonaną z porowatego spieku ze stali 316L, powinna zapewnić niskie współczynniki tarcia i małe zużycie elementów współpracujących. Badania przeprowadzono na symulatorze tarcia stawu biodrowego. W celach porównawczych wykonano także analogiczne testy dla tradycyjnych panewek polietylenowych. Ocenę zużycia panewek przeprowadzono zgodnie z normą ISO 14242-2. Badania eksperymentalne potwierdziły słuszność koncepcji porowatego łożyska endoprotezy stawu biodrowego.

EN

One of the most common among the biotribological issues is elongation of joint endoprosthesis durability. Necessity to ensure favourable friction parameters along with the implants biocompatibility requirements forces search for new solutions. The new conception of tribological system of hip joint endoprosthese, based on the idea of porous selflubricating bearing, was presented in this work. Hip joint cup with porous layer made of porous sintered 316L steel should ensure low friction coefficient as well as low wear of working elements. Research were undertaken on hip joint friction simulator. Similar tests were taken for traditional polyethylene cup for comparison. Wear assessment were led in accordance with ISO 14242-2. Experimental research confirmed legitimacy of the conception of porous hip joint bearing.

6

Biomechanical changes of hip joint following different types of corrective osteotomy - photoelastic studies

Iliescu N., Pastrama S. D., Gruionu L. Gh., Jiga G.

Acta of Bioengineering and Biomechanics

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2008

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Vol. 10, nr 3

65-71

EN

The paper presents the results of some comparative experimental studies that show the biomechanical changes which appear following different types of corrective osteotomy. The photoelastic technique was applied to plane models. The modifications in the stress distribution on the contour after the osteotomy in comparison with the situation before surgery were studied. Three types of osteotomy are considered: valgus osteotomy, varus osteotomy and Chiari pelvis osteotomy. Using the same experimental technique, the distribution of the contact pressure at the interface between the polyethylene cup and the femoral head is investigated, for a total hip prosthesis, as the extreme solution in the case of advanced hip arthroses. Both a normal situation and the malposition of prosthetic components were analyzed.

7

Analysis of the tribology processes on the artificial hip joint

Sovilj B., Igartua A., Zlokolica M., Grujic J., Djokic V., Sovilj-Nikic I., Radovanovic M.

Tribologia

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2002

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nr 6

1613-1622

EN

The problem of degenerative changes, that is, of diseases of the bone-joint systems in people is increasingly present in the contemporary medical practice, especially the changes in the hip joint in older people. Likewise, the number of serious injuries in which the hip joint is damaged is permanently increasing. In most cases only the surgical therapy is efficient, that is, the implementation of the artificial hip joint or the hip joint prosthesis. With the application of the artificial joint the long-standing aspiration of the medical thought to replace an afflicted or damaged part of the body has come true. The hip joint prosthesis is designed for enabling the user to carry on his normal life and work. Under the normal conditions the hip joint prosthesis should faultlessly function for the period of 15 years from the implementation to the revision, that is, it should withstand 12 million cycles. The basic task of the prosthesis head is to transmit the loading to the prosthesis body that, in its turn, should transmit it to the lower extremity; thus, coupled with the acetabulum cup its should provide for an easy mobility of the hip joint. It follows from this that the friction and wear conditions of these components of the artificial hip joint affect the working life of the hip joint prosthesis. The friction between the head and the acetabulum depends upon the quality of working of these elements starting from the microwear R and the macrowear - error in shape, upon the lubrication conditions and the mutual size of these elements as well as upon the overall load, that is, the body weight, the way of sterilizing the plastic acetabulum (gamma rays, ethylene oxide). By optimizing these parameters it is possible to optimize the conditions of friction and wear as well. The paper presents an analysis of the tribology processes on the artificial hip joint based on biomechanics of the hip joint and on the load zones.

PL

W praktyce medycznej coraz częściej spotykany jest problem zmian degeneracyjnych systemu kość-staw (spowodowanych chorobami) w ciele ludzkim. Szczególny problem stanowią zmiany w stawach biodrowych starszych ludzi. Tudzież liczba wypadków, w których uszkodzeniu ulega staw biodrowy wciąż rośnie. W większości przypadków skuteczny jest jedynie zabieg chirurgiczny, tzn. wszczepienie sztucznego stawu biodrowego lub jego protezy. Protezy stawów biodrowych są tak konstruowane, aby umożliwić pacjentowi prowadzenie normalnego życia i pracy. W typowych warunkach proteza bezawaryjnie funkcjonuje przez 15 lat od wszczepienia. Wobec czego powinna wytrzymać około 12 milionów cykli pracy. Podstawowym zadaniem główki protezy jest przenoszenie obciążeń do obudowy protezy - w taki sposób, aby łagodzić nagłe ich zmiany - oraz współpraca z panewką, by umożliwić swobodny ruch. Warunki tarcia i zużywania elementów protezy stawu biodrowego mają zasadniczy wpływ na jej trwałość. Tarcie pomiędzy główką a panewką zależy od jakości obróbki, poczynając od mikrozużywania R aż do makrozużywania - błędów kształtu, od warunków smarowania, rozmiarów, całkowitego obciążenia (wagi ciała), sterylizacji panewki (promieniami gamma, tlenkiem etylu). Przez optymalizację tych czynników można optymalizować również tarcie i zużycie. W artykule zaprezentowano analizę procesów tribologicznych w sztucznym stawie biodrowym bazując na biomechanice stawu biodrowego oraz strefach obciążeń.

8

Lubrication analysis of metal-on-metal hip joint prostheses in a free pendulum machine

Udofia I. J., Jin Z. M.

International Journal of Applied Mechanics and Engineering

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2002

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Vol. 7, no 3

1015-1024

EN

Total joint arthroplasty is probably the most effective treatment for severe degenerative bone diseases such as osteo-arthritis. There has been renewed interest in the use of hard bearings, particularly the metal-on-metal combination for hip joint replacements due to the osteolysis problem associated with current metal-on-polyethylene prostheses. The potential for full fluid film lubrication has been shown to exist during part of the walking cycle in these hard bearing joints. In this study, theoretical and numerical analyses were carried out to characterise the loading and velocity and the corresponding lubrication regime in a typical metal-on-metal hip joint replacement tested in a free pendulum machine. It was shown that the loading in the joint remains relatively constant throughout the duration of swing. The maximum angular velocity achieved under frictionless conditions with an initial angular displacement of 5o, was found to be about 0.387 rad/s, corresponding to a sliding velocity of 5.412 mm/s for a femoral head radius of 14mm. The lubricating film thickness due to the entraining action is only 0.011 micro m, which implies at best a mixed lubrication regime is experienced for the metal-on-metal hip joint tested in a pendulum machine with an average surface roughness of about 0.01 micro m. Under squeeze-film motion, the lubricating film thickness decreases to only about 0.01 micro m after the first few swings, assuming an initial separation between the head and the cup by the radial clearance. The theoretical predictions are consistent with experimental observations reported in literature. The lubrication regime under more realistic walking conditions cannot be deduced in the pendulum machine, largely due to the inappropriate loading and velocity conditions experienced in the pendulum.