Increase of Functional Durability of Hip Prostheses by the Use of High-Tech Technologies
INCREASE OF FUNCTIONAL DURABILITY OF HIP PROSTHESES BY THE USE OF HIGH-TECH TECHNOLOGIES Drd.Ing. Gornoava Valentin 1,2, a,Prof.Univ.Dr.Ing Gheorghe I. Gheorghe1,2, b 1 Institutul Naţional de Cercetare Dezvoltare pentru Mecatronică şi Tehnica Măsurării Bucureşti, România 6-8 Şos. Pantelimon, sector 2, Bucureşti, România 2Conducător Doctorate Ştiinţifice – Şcoala Doctorală Inginerie Mecanică, U.V.Târgovişte; Prof. Asociat la U.T.M.Bucureşti, U.P.Bucureşti şi U.V.Târgovişte; Membru Corespondent al Academiei de Ştiinţe Tehnice din România a
[email protected], b
[email protected];
[email protected] Abstract - Using hip prostheses can make problems caused by fracturing and cementing, physiological reactions of the body rejecting the most important - wear material, which requires improving the tribological performance through design changes and even operating principle. Strain relief can be achieved by increasing the durability of the materials they are made of prosthetic components, a different surface chemistry to reduce friction and coating of the adhesive components by the thin film technology. This paper presents morphological studies of nanoparticle layers deposited on the surface of a hip prosthesis, by SEM and AFM microscopy. Keywords: nanotechnology, high tech technological flow.
1.
Introduction
Hip joint is a ball joint with three degrees of freedom (characterizing rotations around the three axes of a Cartesian system) that can be controlled theoretically only by six muscles. In fact, the mobility of this joint is controlled by 22 muscles, most of them having multiple functions. This joint is located at the junction of the trunk and lower limb freely, who are participating and ensures the optimum performance in orthostatism and locomotion. It performs transmission of the body weight from the pelvis to the femur in the phase of mono- or bipod support and the swing phase of limb required for moving. Normal function of the joints may be disturbed because of some illness, as well as the negative influence of many other factors who determine the mode of human life and professional activity. In the final stages most diseases causing disability joints and pain sensations become very pronounced. In such cases, drug therapy does not give positive results, so the only way to alleviate pain, restore limb length and joint mobility is the implantation of the pseudo-joints. Arthroplasty Surgery is a modern method of treatment for advanced stages of disease of the joints, who gives to the patient the opportunity to avoid serious disability and return to an active life.
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The surgery consists in regeneration with the aid of pseudimplants fragment in the joints damaged by disease. Arthroplasty is correctly performed if the movements after the products are less painltly and the surface friction torque works with a low friction coefficient for minimizing the wear. Total hip prosthesis implantation is currently conducted worldwide, with a total of approx. 1,000 prostheses per day is estimated that 80% of these are replacements of primary total hip prosthesis (THR). It is estimated that total hip prostheses have a lifespan of between 15 and 20 years. An endoprosthetic hip is efficient only if evidence of a survival rate of 95% after 10 years of operation. This quality is considered polifactorial due of the result of the influence of material properties from which is manufactured prosthesis design components, anchoring strategyand the surgical techniques accuracy To restore the natural movement of the hip, the total hip prosthesis consists of three main elements: the rod or tail, which is secured in the femur and provides fixation prosthesis head or ball that replaces the femoral head and acetabular cup that replaces cavity (Figure 1). In addition there is a metal shell located outside the acetabular component.
The Romanian Review Precision Mechanics, Optics & Mechatronics, 2014, No. 46
Increase of Functional Durability of Hip Prostheses by the Use of High-Tech Technologies
Figure 1 Hip prosthesis components Destruction of the structure of a hip prosthesis depends on the size of the particle volume and the total volume thereof or the type of material. Basically, there is a material perfectly smooth without any roughness. These rough preexisting natural systems add wear, giving rise to bone or prosthetic surfaces with high roughness. Depending upon the composition (ceramic, metal), such systems can be used for various periods of time. Articular surfaces are deteriorating mainly due to high surface pressures produced by mechanical movements of the body. The same happens in the case of hip prostheses. Wear a hip prosthesis depends on the number of cycles of friction which is subject and not for how much time the patient stays in the body. The rate of wear of dentures varies greatly from one patient to another because their work is very different. An individual with average activity, steps make about 1 million / year. Most Active reach 3.2 million cycles / year. The elderly, less active, are 0.2-0.5 million cycles / year. Men younger than 60 years walk by 40% more than those over 60 years. Men walk up to 28% more than women. In this case, wear can occur in the following areas of a hip prosthesis: - Outside and inside the shell - Femoral head - Stem prosthesis. 2.
Methods to reduce the wear
Untill now it doesn’t succeeded the completely removing of the problems associated with the use of hip prostheses: a fracture and loosening, rejecting physiological reactions of the body and most important wear material. It was tried to improve the tribological performance through design changes and even operating principle. Surface engineering provides an alternative possibility to reduce wear, wear particle production and
release of metal ions into metal-metal couplings. The factors that could contribute to this reduction are: increase of the sustainability of the components a different surface chemistry able to reduce friction adhesive. coated components who remain undamaged. 3. Coatings Deposition of thin insulating layers is used in the manufacture of the semiconductor layers, metal layers, and the like. In the case of hip prostheses the sliding surfaces must typically be hard to keep wear to a minimum. Pronounced decreases with increasing wear resistance to cracking surfaces (hard material). Need to have dentures resistant, anti-corrosive composition and improved mechanical properties have led to the application of thin films of materials with superior properties prosthetic surface. There have been studies and progress through the use of very hard alloys and biocompatible materials. There are experiments conducted with amorphous carbon. 4. Methods used for hedging The thin films are deposited on the prostheses by using various techniques. The most common technique for depositing a coating are physical and chemical techniques: physical vapor deposition, chemical vapor deposition, thermal coverage through the application of plasma sprayed, vacuum plasma covering, plasma electrolytic oxidation, deposition laser pulses, the method for polymer replication. 5. The thickness of the coating According to other researchers, the thickness of the coating layer plays an important role in connection hardness obtained. A layer of spheres with three folds (pleats) for a CoCr coatings produce higher values than a simple layer, while a fully porous layer leads to a decrease in shear force. The bone is not able to grow
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Increase of Functional Durability of Hip Prostheses by the Use of High-Tech Technologies arbitrary porous coatings. Was obtained at the interface force greater coverage compared to 0.5 mm thick coatings of 1 and 1.5 mm thick. Thus, it was concluded that higher coating thickness of 0.5 mm provides no mechanical advantage. Turner and his colleagues conducted a comparison of
the efficiency of different coatings on porous titanium spheres, fibers and powders. In measurements of bone contact was observed that the differences between different types of coatings are not significant even after one month or after 6 months (Table 1).
Table 1. Percentage of bone contact of different porous coatings for prostheses after 1 month and 6 months in animal experiments (Turner) 1 month 6 months 21.8 ± 2.5% 43.2 ± 4.5%
Titanium Coating Metal fiber Spheres siterizate Plasma spraying
34.0 ± 4.2% 32.5 ± 3.8%
33.3 ± 2.9% 41.9 ± 5.2%
Bone resorption observed in the proximal if the an increase in the material will occur if the rod was coated over the entire length. The most material is inert and if there is no movement at important conclusion of these experiments was why it is the location of the implant; better if the femoral stem is not fully covered (remote) pore size should possess a minimum of 50 μm to counteract osteoporosis protection force. There is also and 400 μm to ensure maximum fixed and rapid the possibility that excessive rigidity of the prosthesis to stabilization of the implant; be responsible for this phenomenon. based implant should be slightly smaller than Hahn and Palich made sustainability shear the implant adjusted to ensure primary stability measurements on samples of titanium plasma sprayed and produce direct contact between bone and with different pore diameters. There was an increase in porous surface; shear strength by a factor of 100 a reduction in the load should be observed for at Other measurements made with stainless steel least 3 weeks to ensure bone growth into the and titanium porous (Nilles) and alumina led to the pores, and thus promote rapid fixing side; conclusion that the modulus of elasticity of the The prosthesis stem should be covered only connection between the porous material and the bone is about the transfer of force in order to adapt to close to the natural value of bone. The elasticity of the physiological conditions, and to prevent osteoporosis material itself and the porosity affect the modulus of protection force in that region. For a complete elasticity in its entirety. characterization of TiN layers deposited with a certain Experimental observations in porous coatings of number of pulses was used the atomic force cementless prosthetic components were the following microscopy. link: Characterization of TiN layers by the atomic force microscopy A
B
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Increase of Functional Durability of Hip Prostheses by the Use of High-Tech Technologies C
Characterization by AFM and values of the topographic of surface TiN layer deposited at (a) 5000, (b) and 10000 (c) 20000 pulsuriStratul of TiN deposited at 5000 pulses has a lower surface uniformity, which could made the result more pronounced unevenness of the substrate. These results can be seen in the figure, after scanning 2D and 3D transform this image. Relatively little surface roughness values differ from one area to another, so the TiN layer deposited at 5000 pulses average value of roughness results from these measurements is 40.013 nm. 32 The surface layer of TiN deposited at 10,000 pulses has a higher uniformity of the deposited layer compared with 5000 pulses. These results can be seen in Figure 5.17b, after scanning 2D and 3D transform this image. It can be seen in these images and small surface defects, but their size is reduced. Mean surface roughness of TiN layer is deposited 26,334 to 10,000 nm pulses. Surface TiN layer is deposited to 20000 pulses uniformity largest of the three tests performed (5000 pulses, pulses 10000 and 20000 pulses). This can be seen from the scanning AFM 2D images and transform this image in 3D. The mean roughness of the deposited layer is 2527 nm at 20,000 pulses. It is the lowest value of average roughness layer of these samples demonstrated uniformity and surface coverage visible from AFM scans. Acknowledgements This paper has been financially supported within the project entitled „SOCERT. Knowledge society, dynamism through research”, contract number POSDRU/159/1.5/S/132406. This project is co-financed by European Social Fund through Sectoral Operational Programme for Human Resources Development 20072013. Investing in people!” 6. Conclusions The theoretical studies have highlighted the need for an resistant prosthesis , with an anticorrosion composition and high mechanical properties. In order to improve the mechanical properties of the prosthesis, they were made by an different materials who have been prepared or coated with materials that have superior properties.
TiN coating improved medium-term fixation of cementless femoral implants, while others showed that is no clinical or radiographic advantage. The survival rate of the cup ranges from 65% up to 99% for 10 years. An important step forward is coating of the components surfaces with nanostructures hip prosthesis using various techniques,. 7. Bibliography 1. G. Gheorghe, L. Badita, A. Cirstoiu, S. Istriteanu, V. Despa and S. Ganatsios, "Mechatronics Galaxy", a New Concept for Developing Education in Engineering," Applied Mechanics and Materials, vol. 371, pp. 754-758, 2013. 2. Micro si nanotehnologii avansate in mecatronica, 2009, autor: Prof. Univ. Euring. Dr. Ing. Gheorghe Ion Gheorghe, Drd. Fiz. Liliana Badita, 2009; 3. W. Crone, “A Brief Introduction to MEMS and NEMS,” in Springer Handbook of Experimental Solid Mechanics, W.N. Sharpe, Editor, SpringerVerlag, New York; 4. Dragoş-Viorel BREZOI, PROCEDEE SPECIALE DE DEPUNERE PE SUPRAFEŢE, ISBN 978-9730-05380-7, Târgovişte, 2007; 5. G. K. Fedder, et al, Sensors & Actuators A, v. 57, no. 2, 1997, pp.103-110; 6. H. Sato, , et al., Proceedings of the IEEE MEMS Conference, Japan, 2003, pp. 223-226; 7. F. Laermer and A. Schilp, “Method for anisotropic plasma etching of substrates,” U.S. Patent 5,498,312, Nov. 15, 1996; 8. S. A. McAuley, et al., J. Phys.D: Appl. Phys., v. 34, 2001, pp. 2769-2774; 9. T. D. Stowe et al., , Appl. Phys. Lett. 71, 288 ,1997; 10. J.H.Park, IEICE Electronics Expres, vol. 4, nr. 10, 2007; 11. C.-L. Dai, et al., Tamkang Journal of Science and Engineering, vol. 8, nr. 3, 2004. 12. Norio Taniguchi Nanotehnologie, Sisteme de procesare integrată pentru produse ultrafine şi de ultraprecizie, E.T., 2000; 13. Florin Ciontu, Liliana Badita Victor K.uncer NANOSPRINT Endyclopedia of Nanotechnology 2007.
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