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

Background Information Background Information  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.

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].

 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]. Proposed Alternative

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 xhibitID=14708

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

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

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.

The Ortho-POD Figure 1: The Ortho-POD Wear Tester ( Six Station pin- on-plate wear tester machine. Each station can load a maximum of 445N at one time. Three load cells measure x, y, & z axis: coefficient of friction.

RESULTS Weight lost/gained by pins on disks and controls

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

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).

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

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

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

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