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Computational simulation analysis for torus radius of edge contact in hip prostheses

Li F., Chen H, Mao K.

Acta of Bioengineering and Biomechanics

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2015

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Vol. 17, no. 3

67--73

EN

Stripe wear occurs when the components of hip prostheses move a sufficient distance laterally to contact the edge of the acetabular cup, causing abnormally high contact stresses. In this research, edge loading contact of prosthetic hip is analyzed in the most commonly used material pairs. The contact dimensions and maximal contact pressure are investigated in mutative normal edge loading with 3 different inclination angles (15°, 20°, 25°) and in alterable edge torus radius with edge loading of 2500 N and inclination of 20°. A computational case was conducted for a 14 mm radius alumina ceramic bearing with a radial clearance of 0.1 mm using a normal edge loading ranged from 0 N to 3000 N. Additionally, the Hertzian theory successfully captures principal curvature trends of the edge torus on the influence of maximal contact pressure and obtains the appropriate edge radius range for lower maximal contact pressure. This work elucidates the methods of applying classical contact theory to design the edge radius of hip bearings to better resist severe edge loading contact stresses and reduce the stripe wear.

2

Materiały ceramiczne w węzłach ciernych protez stawów biodrowych i kolanowych

Neyman A.

Tribologia

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2004

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nr 3

283-292

PL

Prace zmierzające do zwiększenia trwałości protez stawów biodrowych i kolanowych prowadzone są w trzech kierunkach: optymalizacji konstrukcji ich elementów, optymalizacji sposobu mocowania protez w kościach kończyn oraz doboru najlepszych skojarzeń materiałowych. Cztery typy skojarzeń są obecnie uważane za najlepsze: panewka z wysokocząsteczkowego polietylenu z główką ze stali nierdzewnej, stopu tytanu lub tlenku aluminium oraz zarówno panewka jak główka stawu z tlenku aluminium. W wielu ośrodkach prowadzone są obecnie badania nad zastosowaniem powłok ceramicznych w protezach. Najbardziej obiecujące wyniki uzyskiwane są w przypadku DLC i CNx.

EN

To day used hip and knee prostheses are not sufficiently durable. Efforts to increase durability of the prostheses are undertaken in three areas: optimization of prostheses construction, optimization of prosthesis elements fixation to bones, looking for the best choice of materials for prostheses elements. Investigations to choose the best materials available are being performed from 1890. Four types of articulated materials are considered to day as the optimal choice: ultra high molecular weight polyethylene (UHMWPE) cup with stainless steel head, UHMWPE cup with titanium alloy head, UHMWPE cup with aluminum oxide head or aluminum oxide cup with aluminum oxide head. All ceramic friction elements of prostheses are of much higher costs due to expensive machining of ceramic elements. Big advantage of "all ceramic" prostheses is much lower amount of wear particles. The presence of wear particles is serious problem in prostheses with polyethylene cup as loosening of prostheses elements joints is caused by the tissue response to polyethylene wear particles. Many investigations are performed in plain tribometers and prostheses simulators to develop bulk ceramics for prostheses elements and to look for possibility to use ceramic coatings in prostheses elements. Among many investigated materials modified aluminum oxide, silicon carbide and two coatings DLC and CNx are now considered as he most promising.

3

Different reactions of macrophages cultured with the samples from new and old polyethylene cups of the hip prosthesis

Czajkowska B., Otfinowski J., Ptak M., Pawelec A., Lekki J.

Inżynieria Biomateriałów

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2000

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R. 3, nr 11

8--10

EN

We estimated release of cytokines IL-6 and TNFα and tested viability of macrophages cultured with the samples of polyethylene obtained from new acetabular cup of the hip prostheses and from the cups retrieved 4-6 years after implantation. The macrophages cultured with old polyethylene showed decreased viability and released more IL-6 and TNFα.