Wear Testing of UHMWPE on Nanocrystalline Diamond Coated Ti6AL4V Alloy

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, 2003Wilkinson JM, et
  al, 2003Ostlere 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?Exhibit
ID14708
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 (contd)

• 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 (NCD1).

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 (contd)

• 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.