Replacement Ceramic Hip Joints

Replacement Ceramic Hip Joints

1. Executive Summary

Rennib Advanced Ceramics ( RAC ) Ltd is an advanced ceramics fabricating company, which provides assorted ceramic merchandises covering a really broad country. Artificial hip articulation will be a really competitory ceramic merchandise for RAC during the following few old ages.

The clients of the merchandise are patients enduring assorted hip jobs. Artificial hip articulation offers patients a good opportunity to replace their original hip articulation with an unreal one.

RAC can supply different types of unreal hip articulations to run into the different demands of different clients. Sing the ages of the clients, different picks can be made. Most immature patients are suggested to take a merchandise with ceramic femoral caput which has a longer service life and higher cost than metal merchandises.

Normally, those high public presentation ceramic femoral caputs consist of aluminum oxide or zirconium oxide. A better pick is to oxidize the Zr surface with a metal femoral caput inside, which reaches a via media to supply both high wear opposition and low cost.

Presently, the processing techniques used in doing ceramic hip implants are hot isostatic pressure and colloidal processing. New fast sintering techniques, such as ‘Spark Plasma ‘ and ‘Microwave Sintering ‘ or even fast warming rate furnaces are now available. Since new techniques are non mature plenty, most of them remain in the research lab phase and assorted jobs still exist.

Based on the size of the current hip replacing market, there still exists really big market potency for the ground that the demands of the unreal hip articulations have been increasing stably since 2000. The anticipation is that the increasing tendency will still keep an upward impulse in the following few old ages.

RAC will be in an first-class place if the Board members of the company make up one’s mind to put more power on researching and developing new techniques to cut the cost of production without the disbursal of merchandise quality.

RAC ‘s selling scheme is to maintain concentrating on the merchandise quality. The patients, for case, will experience comfy to take our merchandise without vacillation for the ground of high merchandise quality. All RAC ‘s unreal hip articulations will be purely tested prior to selling.

2. Ceramic Replacement Hip Joints

British orthopedist Sir John Charnley is accredited by many as the first individual to finish a entire hip replacing in 1960, although developments in the practise had been good underway since the early 1900s [ 1 ] . Charnley ‘s articulation was made up of a metal femoral root and ball caput that attached to the bone utilizing PMMA and this so inserted into a replacing socket articulation made from extremist high molecular weight polythene, which was besides bonded to the bing hip utilizing PMMA [ 1 ] .

Since Charnley ‘s creative activity, many other stuffs have been tried and tested in the production and usage for replacing hip articulations. The metal on polymer construction of the articulation was used for many old ages but patients frequently needed repetition operations due to the life span of the metal on polymer articulation being excessively abruptly. The ceramics aluminum oxide and zirconium oxide were introduced as possible new stuffs in the early 1970s and 1980s severally [ 1 ] . This was because they were found to be far more wear immune and therfore, although more expensive to purchase and industry, they decreased the likely goon of patients necessitating multiple surgeries in their life-times.

Presently under consideration is the possible usage of non oxide ceramics to be used in replacing articulations. Examples of these are silicon carbide or Si nitride and they are under consideration because of their close unsusceptibility to the slow growing of clefts [ 2 ] . This belongings would farther increase the life span of a replacing articulation if either non oxide were to be used and would make a joint even more superior to one made from aluminum oxide or zirconium oxide. The high cleft opposition besides relates to a higher overall strength, hence an improved wear opposition of the merchandise over the ceramics presently used. However, due to these non oxide ceramics being harder and more wear resistant, they besides become more hard to treat therefore doing them more expensive to purchase and fabricate [ 2 ] .

3. Market Analysis

By and large, unreal hip articulations are utilized in the orthopedic surgical field. The concluding purchasers are patients enduring from assorted hip jobs including degenerative arthritis, arthritic arthritis, traumatic arthritis and avascular mortification [ 3 ] . Harmonizing to King [ 4 ] , the unreal articulations market is valued at approximately $ 12.2 billion in 2008, within which hip and articulatio genus replacings act as one of the cardinal sections. Considering of the big market demand, a market analysis is indispensable to measure the possible market potency.

3.1. Current Market

In a Datamonitor study of hip and knee replacing market [ 5 ] , the part of the US is about 50 % of entire processs worldwide and the part of Europe is about 30 % . This statistics show that the US and Europe are the two largest markets for hip and articulatio genus implants on a planetary graduated table.

Harmonizing to the Datamonitor ‘s market informations [ 5 ] , “ the 2005 grosss for hip implants in the US were $ 2 billion and that for Europe was $ 1.4 billion ” . Taking the US market for illustration, the entire hip replacing processs ( including hip resurfacing ) figure was 368,660 in 2005 [ 5 ] .

Another illustration is the information of the Australian orthopedic market. Harmonizing to a planetary market research [ 6 ] , “ there were about 72,007 joint replacing operations performed ” .

3.2. Future Growth

A statistical information cited by The New York Times [ 7 ] shows that “ the figure of entire hip replacings has risen by about 80 % since 2000 ” .

The figure of entire US hip replacings have been turning stably since 2000. It is expected that this tendency will be a sustainable growing in the following few old ages.

3.3. International Rivals

The 10 biggest worldwide orthopedic device makers in 2007 were listed inTable 1as follow, harmonizing to a top companies report [ 8 ] .

WithinTable 1, 7 companies of the top 10 are now fabricating the unreal hip articulations and see this merchandise as one of their chief merchandises to do net incomes. They are Stryker Corp, DePuy, Zimmer Holdings, Smith & A ; Newphew, Biomet, DJO Incorporated and Wright Medical [ 8 ] .

Using 2005 US knee replacing market portion for mention ( the hip replacing market informations is hard to obtain ) [ 5 ] , the chief rivals are really obvious as follow.

4. MATERIALS CURRENTLY USED IN REPLACEMENT HIP JOINTS

The three constituents of an unreal hip articulation can each be manufactured from a figure of stuffs. To do a new liner for the hip socket, a cup can be made from polythene. However, polyethylene cups do non hold great wear opposition and the changeless friction of the harder ball inside the softer polymer cup can gnaw it and go forth dust in the joint that can foster increase eroding rate. This can ensue in the replacing articulation necessitating replacement and a patient holding to undergo more than one operation in their life-time. This means that metal or ceramic cups are frequently used because although more expensive to bring forth, they offer a longer life and cut down the opportunity of a repetition operation [ 9 ] . The root that attaches to the bing thighbone is today made from either Ti or Co or Cr based alloys. Finally, the femoral caput is normally made of either metal or a ceramic such as aluminum oxide or zirconium oxide [ 9 ] .

If a cobalt-chrome metal is used to do the femoral caput of an unreal hip implant, it can be manufactured by agencies of crunching and smoothing to accomplish an accurate spherical form at a comparatively low cost. The job with an alloy femoral caput, though, is that it does non hold such good wear opposition when paired with a polyethylene cup. The wear creates more dusts, which can do the surface of the caput rougher, therefore farther increasing wear and the likely goon of the patient necessitating another replacing articulation. The life of a replacing hip can be increased if a ceramic is used. A ceramic femoral caput can be produced utilizing the same grinding method but due to it being far harder than the metal, it is more expensive to fabricate but will offer superior wear opposition to that of the alloy femoral caput.

Above images show a machine similar to the 1 Smith and Nephew usage in the production of their femoral caputs and a close up of a femoral caput and cutting tool.

So, there is a quandary. Does one cut production costs by utilizing inferior stuffs, but increase the opportunity of the constituents have oning out? Or should superior stuffs, which increase the production cost but besides the merchandise life, be used? Smith and Nephew are a Memphis based house that maker and provide a scope of different joint replacings. They offer hep replacing systems with different femoral caputs ; cobalt-chrome metal, alumina or zirconium oxide. Research workers at Smith and Nephew discovered that Zr could be oxidised to ensue in a metal with a ceramic ( zirconium oxide ) surface.A This made them see, that if they could machine Zr to the coveted dimensions every bit easy as they could with the cobalt-chrome metal so they could oxidize it to give the best of both universes ; the cheaper production costs available utilizing a metal but with a hardened and more wear immune surface of a ceramic. [ 10 ]

5. Processing Paths In the Development in Ceramic Artificial Hip Joints

Ceramic hip articulations can usually be formed through production of a green compact which is so sintered/hot isostactically pressed utilizing Zirconia ( ZrO2 ) or more commonly Alumina ( Al2O3 ) pulverization. However in this modern twenty-four hours environment the hip articulation has many variables and many variable stuff combinations such as ceramic/ceramic wear twosome or ceramic/polyethene wear twosome [ 11 ] . Therefore the each constituent can be processed otherwise.

Ceramic stuffs are known to be brickle and susceptible to decelerate cleft growing. In medical usage when in the hip articulation, one of the chief jobs is that the ceramic ball undergoes wear and can so fracture. Modern ceramic bearings have much greater belongingss and dependability compared with old coevalss of the same stuff. Controling the get downing stuffs such as the pureness, and improved fabrication procedures have led to great betterments in both these countries. Current processs include tightly controlled ceramic processing methods for homogenous commixture and consolidation of the pulverizations, and treating environments such as clean-room installations to minimise inclusions and drosss. The first coevals of Al2O3 bearings was produced by sintering. Today, hot isostatic pressure is normally used to vouch the production of an about to the full heavy stuff with a all right grain size.

The procedure used by ‘Ceram Tec ‘ is used normally by other makers to make the femoral ball of the hip articulation: First a high pureness pulverization of Alumina is used as the merchandise needs to hold maximum mechanical belongingss therefore the pureness needs to be high or else the mechanical belongingss will drop. The pulverization so undergoes cold isostatic pressure where the pulverization is enclosed in a bag so submerged in H2O and pumped to high force per unit area to compress and determine the pulverization. This achieves a unvarying form and denseness to the mold. The mold is so shaped farther and so undergoes ‘pre-sintering ‘ where the mold is heated up to below concluding sintering temperature to do handling of it easier. The mold is so machine bored to do the hole for the root to be inserted into subsequently. After the ball has been bored it is so sintered where it is heated up and the mean grain size additions [ 12 ] . This leads to increased strength and mechanical belongingss. After the ball has been sintered it undergoes hot-isostatic pressure where a gas at high temperature ( higher than recystallization temperature of stuff ) and high force per unit area is used to pack the mold [ 13 ] . After the hot-isostatic processing the close finished merchandise is laser marked. This is because each single portion needs to be marked and recorded as there is such importance on the merchandise non neglecting, that if it does they can recognize which batch it came from and may hold to halt that batch from being used. Laser marker is a speedy procedure and has reduced surface abnormalities that can function as emphasis intensives. After the optical maser etching the merchandise goes into the concluding phase of the procedure where it land and polished so undergoes the concluding review. Other fluctuations of the procedure are used by other makers such as the ball can be pressed, and after compaction by sintering and hot isostatic pressure, the dullard can be machined. Laser marker can be performed before or after sintering [ 14 ] .

Another procedure used is the ‘collodial procedure technique ‘ The colloidal processing construct involves the use and control of the interparticle forces in pulverization suspensions. The drosss are removed from a stable suspension of the zirconium oxide toughened alumina pulverization by it being placed in absolute ethyl alcohol ( 99.97 % ) with diluted Zr alkoxide being dripped in. After drying under magnetic stirring at 70A°C, the pulverizations are thermally treated at 850A°C for twohours in order to take surplus. The pulverization is so abrasion milled, as a suspension in intoxicant, with 3mm aluminum oxides balls for one hr. The pulverizations is so dried and sieved to less than 45Aµm. They are so cold isostatically pressed to an initial form. They are so sintered in air at 1550A°C for two hours. This leads taking to 98 % theoretical denseness. The samples are cut and polished. The advantages of this technique are that it improves merchandise dependability and it is inexpensive [ 15 ] .

5.1 Future Procedures

Hot isostatic pressure of Al2O3 ceramics is the most familiar for usage in the processing of the many bing ceramics stuffs [ 33 ] Manabe Y, Fujikawa T, Ueda M, Inoue Y. Effect of O2-HIP for oxide ceramics. In: First European ceramic society conference held at Maastricht, Netherlands, 18-23 June 1989.. This technique is still being improved to run into optimum agendas such that the coveted mechanical belongingss and decreased processing costs

New fast sintering techniques, such as ‘Spark Plasma ‘ and ‘Microwave Sintering ‘ or even fast warming rate furnaces are now available which give the chance into processing of ultrafine, to the full heavy ceramic stuffs offering options to Y-TZP ( Yttria Tetragonal Zirconia Polycrystal ) which is a stuff which offers great scratchs opposition ) . As these are new techniques and are non in full usage some paradigm of Alumina have been made from these procedures but unluckily they suffered hapless cleft opposition. [ 16 ]

Improved processing, such as the usage of colloidal methods for bring forthing more homogenous green microstructures, leads to an addition in KI0 ( stress strength factor ) and KIC ( fracture stamina ) . The two ways of bettering the strength of ceramics are: to diminish the presence and or the size of an dross, by careful processing and quality control. Second, by increasing KIC by debasing or by transforming the ceramic into a composite. Using colloidal processing and consolidation techniques along with optimal sintering and hot isostatic pressure processs, will bring forth massive ceramics with a homogenous, heavy, powdered microstructures which will heighten break strength and dependability. Machining is required to bring forth the smooth surfaces to take strength-limiting defects [ 14 ] .

6.Recommended Ceramic Process Route

The desirable features for stuffs used as the jointing surfaces in hip replacing are: high strength so that it does n’t interrupt under the strains and stresses the human organic structure will set it under, high elastic modulus, high break stamina ( to avoid fracturing and needing to be replaced which will intend further invasive surgery ) and high weariness opposition for mechanical dependability and to defy distortion when subjected to the tonss in the organic structure. It needs to hold high corrosion opposition as it will be traveling about in the socket under a burden for many old ages for several hours at a clip, high hardness and good surface coating for long-run wear [ 17 ] .

I would urge that the procedure used by ‘ceram investigator ‘ be used but to get down with the colloidal technique to take all defects in the pulverization to cut down hazard of failure in the concluding merchandise. By utilizing the ‘ceram investigator ‘ procedure it means that the merchandise is worked utilizing hot isostatic pressure, and it is besides sintered. The procedure is good respected and normally used across the universe at the minute doing it dependable. I would urge utilizing zirconia toughened alumina ( ZTA ) as oppose to alumina or zirconia on their ain are prone to fracture whereas if you use ZTA it increases the stamina. Some alumina-zirconia complexs are already being used or developed by companies which have shown betterment in aging opposition as compared to Y-TZP, and first-class cleft opposition [ 18 ] .A This will cut down the hazard of ‘subcritical cleft growing ‘ which is when clefts easy appear when under strain which is under the threshold of stamina [ 19 ] . To do the pulverization have optimum quality it should undergo the colloidal procedure as this will intend that the pulverization pureness is highly high bettering mechanical belongingss and besides it will do the pulverization optimum size for sintering.

When a merchandise is sintered in certain conditions, clefts will turn easy until it fails and fractures catastrophically. The sintering nevertheless does increase denseness and grain growing which lead to the desired features for the concluding merchandise [ 20 ] .

The merchandise will be hot isostatically pressed, which heats the merchandise up above the recrystallisation temperature and compressed once more which will take some of these little clefts hence taking the hazard of failure [ 21 ] . It besides makes the stuff more dense which makes the merchandise stronger and tougher [ 22 ] .

By optical maser etching the merchandise, it will salvage clip and cut down surface abnormalities that can function as emphasis intensives [ 19 ] .A Besides by taging each constituent it besides means the company is apt for a merchandise if it fails and can so replace the broken merchandise and can so instantly place any others which may endure similar destiny by recognizing which batch it came from.

7. Reason TO PROCEED

Sing the patents of the unreal hip articulations, the analysis of the major rivals and the market factors, the RAC has a comparatively good opportunity to acquire into the hip replacements market.

There are many patents which can be found in unreal hip articulations field. Some of them are buyable. Obviously, most rivals have their ain patents. Large companies, like Zimmer Holdings [ 23 ] and Smith & A ; Nephew [ 24 ] , normally own a research & A ; development system which is the beginning of researching and developing the patents. To a certain extent, the rational belongingss determine the height of the merchandises.

Most rivals gain less than 5 % market portion harmonizing to a maker ‘s appraisal [ 25 ] , though a few large rivals, like Depuy ( & gt ; 20 % ) , Biomet ( 5-20 % ) and Zimmer ( 5-20 % ) , gain more. The market portion informations may be undependable because most companies are non willing to give their exact market informations, but it still can be gained from some other beginnings, which should hold mention value. From the information it is clearly that no monopoly exists in the unreal hip joint field. Therefore, to RAC, there still be opportunities to acquire into the market and to portion it.

The published consequences [ 25 ] show that the rate of most alteration operations, which cost more and normally have worse maps than the original hip replacings, is approx 10 % at ten old ages. Therefore, long service life and dependable implants are going more and more of import. If RAC wants to accomplish sustainable competitory advantages, the company must get down to develop its ain engineering. Harmonizing to Murray, Carr and Bulstrode [ 25 ] , about no newer implants can exceed the established designs. This is a good opportunity to RAC because if the company can put more power on researching while selling the regular merchandises, there could be a opportunity to set up the company trade name over the hip replacing market via presenting newer and better merchandises.

As mentioned antecedently ( seeMarket Analysis) , the entire demands of hip replacings have been increasing stably ( seeFigure 1) . I believe the future growing of the market will besides be in a stable increasing. Therefore, RAC does hold a good opportunity to continue, and which should be taken into consideration by the Board members.

8.References

[ 1 ] Rahaman, M.N. , Yao, A. , Bal, B.S. , Garino, J.P, Ries, M.D. , 2007. Ceramicss for Prosthetic Hip and Knee Joint Replacement.Journal of the American Ceramic Society[ Online ] . 90 ( 7 ) .

. 42 ( 6 ) , Available at: hypertext transfer protocol: //www3.interscience.wiley.com/cgi-bin/fulltext/117955704/HTMLSTART

[ 2 ] A Chevalier, J. , Gremillard, L. ( 2009 ) . Ceramicss for medical applications: A image for the following 20 old ages.Journal of the European Ceramic Society. 29 ( 7 ) , p1245-1255. Available at: hypertext transfer protocol: //www.sciencedirect.com/science? _ob=ArticleURL & A ; _udi=B6TX0-4TMRK07-1 & A ; _user=122878 & A ; _coverDate=04 % 2F30 % 2F2009 & A ; _rdoc=1 & A ; _fmt=high & A ; _orig=search & A ; _sort=d & A ; _docanchor= & A ; view=c & A ; _searchStrId=1197320255 & A ; _rerunOrigin=google & A ; _acct=C000010119 & A ; _version=1 & A ; _urlVersion=0 & A ; _userid=122878 & A ; md5=770d8d5a0d09bae8ae2d23fa83274f04 # tbl1

[ 3 ]Slowik, G. erectile dysfunction. 2009.Hip Replacement[ online ] . [ Accessed 17 January 2010 ] . Available from: hypertext transfer protocol: //www.ehealthmd.com/library/totalhipreplacement/THR_needed.html.

[ 4 ]King, M. 2009.The Future of the Orthopaedic Devices Market to 2012[ online ] . [ Accessed 17 January 2010 ] . Available from: hypertext transfer protocol: //www.hipresurfacingnews.com/archives/265-The-Future-of-the-Orthopedic-Devices-Market-to-2012.html.

[ 5 ]Datamonitor, 2006.Hip and Knee Replacement Market ( sample pages )[ online ] . [ Accessed 18 January 2010 ] . Available from: A hypertext transfer protocol: //www.datamonitor.com/store/Download/Brochure/ ? productId=DMHC2264.

[ 6 ]A & A ; M Mind Power Solutions, 2010.Global Orthopaedic Market – Focus on Hip and Knee replacing ( Description )[ online ] . [ Accessed 18 January 2010 ] . Available from: hypertext transfer protocol: //www.researchandmarkets.com/reportinfo.asp? report_id=1193932.

[ 7 ]Feder, B.J. 2008.That Must Be Bob. I Hear His New Hip Squeaking[ online ] . [ Accessed 18 January 2010 ] . Available from: hypertext transfer protocol: //www.nytimes.com/2008/05/11/business/11hip.html.

[ 8 ]Orthopaedic Design & A ; Technology. 2008.Top Companies Report: A Comprehensive Expression at the Biggest Worldwide Orthopaedic Manufacturers[ online ] . [ Accessed 18 January 2010 ] . Available from: hypertext transfer protocol: //www.thefreelibrary.com/Top+companies+report: +a+comprehensive+look+at+the+biggest+worldwide… -a0183984285.

[ 9 ]OrthopedicConnection: Hip Implants,www.orthoinfo.aaos.org

[ 10 ]Artificial Hip Joints: Applying Weapons Expertise to Medical Technology, LLNL ( Lawrence Livermore National Laboratory ) 1994

[ 11 ]hypertext transfer protocol: //www.ceramtec.com/04235,0125,0406,4132.php

[ 12 ] Kang, S-J.K ( 2005 ) .Sintering: compaction, grain growing, and microstructure. Oxford: Elsevier Butterworth-Heinaman.

[ 13 ] Koizumi, M. , Nishihara, M ( 1991 ) .Isostaticpressure: engineering and applications. New York: Elsevier Science Publishing Co. 120.

[ 14 ] Rahaman, M.N. , Yao, A. , Bal, B.S. , Garino, J.P, Ries, M.D. , 2007. Ceramicss for Prosthetic Hip and Knee Joint Replacement.Journal of the American Ceramic Society[ Online ] . 90 ( 7 ) .

. 42 ( 6 ) , Available at: hypertext transfer protocol: //www3.interscience.wiley.com/cgi-bin/fulltext/117955704/HTMLSTART

[ 15 ] De Aza, A. H. , Chevalier, J. , Fantozzi, G. , Schehl, M. , Torrecillas, R. ( 2002 ) . Crack growing opposition of aluminum oxide, zirconium oxide and zirconium oxide toughened alumina ceramics for joint prosthetic devices.Biomaterials [ Online ]. 23 ( 3 ) , p937-945. Available at: hypertext transfer protocol: //www.sciencedirect.com/science? _ob=ArticleURL & A ; _udi=B6TWB-44GDH8F-1B & A ; _user=122878 & A ; _coverDate=02 % 2F28 % 2F2002 & A ; _rdoc=1 & A ; _fmt=high & A ; _orig=search & A ; _sort=d & A ; _docanchor= & A ; view=c & A ; _searchStrId=1198558259 & A ; _rerunOrigin=scholar.google & A ; _acct=C000010119 & A ; _version=1 & A ; _urlVersion=0 & A ; _userid=122878 & A ; md5=00e6ef3c2d41e6b3b1ec11b3b359a36d # fig6

[ 16 ]Chevalier, J. , Gremillard, L. ( 2009 ) . Ceramicss for medical applications: A image for the following 20 old ages.Journal of the European Ceramic Society. 29 ( 7 ) , p1245-1255. Available at: hypertext transfer protocol: //www.sciencedirect.com/science? _ob=ArticleURL & A ; _udi=B6TX0-4TMRK07-1 & A ; _user=122878 & A ; _coverDate=04 % 2F30 % 2F2009 & A ; _rdoc=1 & A ; _fmt=high & A ; _orig=search & A ; _sort=d & A ; _docanchor= & A ; view=c & A ; _searchStrId=1197320255 & A ; _rerunOrigin=google & A ; _acct=C000010119 & A ; _version=1 & A ; _urlVersion=0 & A ; _userid=122878 & A ; md5=770d8d5a0d09bae8ae2d23fa83274f04 # tbl1

[ 17 ] Rahaman, M.N. , Yao, A. , Bal, B.S. , Garino, J.P, Ries, M.D. , 2007. Ceramicss for Prosthetic Hip and Knee Joint Replacement.Journal of the American Ceramic Society[ Online ] . 90 ( 7 ) .

. 42 ( 6 ) , Available at: hypertext transfer protocol: //www3.interscience.wiley.com/cgi-bin/fulltext/117955704/HTMLSTART

[ 18 ] A Chevalier, J. , Gremillard, L. ( 2009 ) . Ceramicss for medical applications: A image for the following 20 old ages.Journal of the European Ceramic Society. 29 ( 7 ) , p1245-1255. Available at: hypertext transfer protocol: //www.sciencedirect.com/science? _ob=ArticleURL & A ; _udi=B6TX0-4TMRK07-1 & A ; _user=122878 & A ; _coverDate=04 % 2F30 % 2F2009 & A ; _rdoc=1 & A ; _fmt=high & A ; _orig=search & A ; _sort=d & A ; _docanchor= & A ; view=c & A ; _searchStrId=1197320255 & A ; _rerunOrigin=google & A ; _acct=C000010119 & A ; _version=1 & A ; _urlVersion=0 & A ; _userid=122878 & A ; md5=770d8d5a0d09bae8ae2d23fa83274f04 # tbl1

[ 19 ]De Aza, A. H. , Chevalier, J. , Fantozzi, G. , Schehl, M. , Torrecillas, R. ( 2002 ) . Crack growing opposition of aluminum oxide, zirconium oxide and zirconium oxide toughened alumina ceramics for joint prosthetic devices.Biomaterials [ Online ]. 23 ( 3 ) , p937-945. Available at: hypertext transfer protocol: //www.sciencedirect.com/science? _ob=ArticleURL & A ; _udi=B6TWB-44GDH8F-1B & A ; _user=122878 & A ; _coverDate=02 % 2F28 % 2F2002 & A ; _rdoc=1 & A ; _fmt=high & A ; _orig=search & A ; _sort=d & A ; _docanchor= & A ; view=c & A ; _searchStrId=1198558259 & A ; _rerunOrigin=scholar.google & A ; _acct=C000010119 & A ; _version=1 & A ; _urlVersion=0 & A ; _userid=122878 & A ; md5=00e6ef3c2d41e6b3b1ec11b3b359a36d # fig6

[ 20]Kang, S-J.K ( 2005 ) .Sintering: compaction, grain growing, and microstructure. Oxford: Elsevier Butterworth-Heinaman.

[ 21 ]Richerson, D.W ( 2006 ) .Modern ceramic technology: belongingss, processing, and usage in design. United statess: Taylor and Francis Group. 504.

[ 22 ]Wen, M.Y. , Mueller, H.J. , Chai, J. , Wozniak, W.T. ( 1999 ) . Comparative mechanical belongings word picture of 3 all-ceramic nucleus materials..The International Journal ofProsthodonticss. 12 ( 6 ) , 534-41.

[ 23 ]Zimmer Corporate and Careers*ZZ, 2004.Zimmer Granted Method Patent on MIS Hip Procedure[ online ] . [ Accessed 6 February 2010 ] . Available from: hypertext transfer protocol: //www.zimmer.com/z/ctl/op/global/action/1/id/7530/template/CP.

[24]Smith & A ; Nephew, 2009. Factory Consolidation for BIRMINGHAN HIP Resurfacing System [ online ] . [ Accessed 6 February 2010 ] . Available from:

hypertext transfer protocol: //global.smith-nephew.com/master/30271.htm.

[25]Murray, D.M. , Carr, A.J. and Bulstrode, C.J. 1994. Which Primary Total Hip Replacement.The Journal of Bone and Joint Surgery. pp.520-527.