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Wear Testing of UHMWPE on Nanocrystalline Diamond Coated Ti-6AL-4V Alloy

Wear Testing of UHMWPE on Nanocrystalline Diamond Coated Ti-6AL-4V Alloy. Kristin B. Ferguson REU Physics Student Alan Eberhardt Associate Professor of Biomedical Engineering at the University of Alabama at Birmingham Yogesh K. Vohra

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Wear Testing of UHMWPE on Nanocrystalline Diamond Coated Ti-6AL-4V Alloy

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  1. Wear Testing of UHMWPE on Nanocrystalline Diamond Coated Ti-6AL-4V Alloy Kristin B. Ferguson REU Physics Student Alan Eberhardt Associate Professor of Biomedical Engineering at the University of Alabama at Birmingham Yogesh K. Vohra Professor of Physics & University Scholar at the University of Alabama at Birmingham

  2. Background Information • 1962 - John Charnley first total hip arthroplasty (THA) . • Original model success, average life 20 years, improvements possible[Ostlere S, 2003]. • Materials used over years - Ultra High Molecular Weight Polyethylene (UHMWPE), ceramics, alloys, etc.

  3. PROBLEMS UHMWPE-on- metal ,metal-on- metal, ceramic-on-ceramic, etc. release particles Osteolysis, aseptic loosening, metallosis: FAILURE[Keogh CF, et al, 2003][Wilkinson JM, et al, 2003][Ostlere S, 2003]. Coatings – nanocrystalline diamond (NCD) & hydroxyapatite-calcium titanate will not adhere to metal substrates[Catledge SA, et al, 2002].

  4. Proposed Alternative • Dr. Yogesh Vohra, UAB, functionally-graded nanostructured films [Catledge SA, et al., 2002]. • Nanocrystalline Diamond coat alloy pieces of implants [Catledge SA, et al., 2002]. • Coatings enhance hardness, toughness, bioactivity, reduce coefficient of friction [Catledge SA, et al., 2002].

  5. Goals • Test UHMWPE pins on disks ,simulate THA, figure eight • Program Ortho-POD, Report coefficients of friction, pin on plate • Report wear reduced or eliminated for coated Ti-6AL-4V www.globalspec.com/FeaturedProducts/Detail?ExhibitID=14708

  6. Hypothesis • Nanocrystalline Diamond coated Ti-alloy, when wear tested against UHMWPE, will produce less friction and less wear than uncoated Ti-alloy against UHMWPE.

  7. Procedure • UHMWPE pins 3/8” diameter • Soaked in calf Bovine serum, minimum 1 week • Weighed on 0.00001g scale • Run in Ortho-POD wear tester • 500,000 cycles; 125,000 cycles per day; 25,000 cycles for data.

  8. Procedure (cont’d) • Loads 10, 75, max 180N ~20MPa, figure eight. • Lubrication solution of 70% calf bovine serum 30% water. • Articulate against uncoated Ti-6AL-4V alloy disks & NCD coated Ti-6AL-4V alloy disks .

  9. The Ortho-POD Three load cells measure x, y, & z axis: coefficient of friction. www.amtiweb.com/transducerhome.htm Each station can load a maximum of 445N at one time. Six Station pin-on-plate wear tester machine. Figure 1: The Ortho-POD Wear Tester (http://www.amtiweb.com/images/Pod.jpg)

  10. RESULTS Weight lost/gained by pins on disks and controls

  11. Coefficient of Friction for NCD coated and Uncoated Ti-6AL-4v alloy disks 0.115 0.112

  12. SUMMARY • Not significant difference in coefficients of friction for uncoated Ti alloy and NCD coated Ti alloy. • No statistics done. • Weight lost for pins - uncoated Ti alloy appeared to be less than NCD coated Ti alloy. • Assume data to be insufficient due to lack of specimens tested (NCD=1).

  13. Discussion: • Polyethylene most common choice in THAs • Issues - Polyethylene wear, osteolysis, failure • NCD- reduce friction, enhance hardness & toughness • UHMWPE +Diamond= Good choice • Results do not support hypothesis

  14. Discussion (cont’d): • Only preliminary data. • Things overlooked – UHMWPE just one kind of poly, others may have better results.

  15. Further Testing… • NCD coated CoCr instead of Ti-alloy (more common) • Continue testing NCD against poly or new test with NCD on NCD • Test more specimens

  16. Acknowledgements • Dr. Alan Eberhardt for the opportuniy to work in his lab. • Brandon Etheridge, John Gliestein, and Witt Isreal for technical assistance. • Charita Cadenhead for coordinating events and with assistance. • Dr. Yogesh Vohra for the opportunity to participate in the Physics REU program.

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