Date of Award

12-2013

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Bioengineering

Advisor

DesJardins, John

Committee Member

Pace , Thomas

Committee Member

Kennedy , Marian

Abstract

The goal of total joint replacement (TJR) is to replace nonfunctioning joint components and relieve pain, improve quality of life, and to improve joint function. Although TJR is a successful procedure, more than 54,000 knee revisions occur each year due to factors, such as wear, loosening, infection, fracture, instability, and patient related factors (Ranawat, 2010). TJRs consist of components typically composed of polyethylene and a metallic counterface (Navarro, 2008). The sliding contact that occurs between the metal and polyethylene components has been well studied and is shown to produce both surface damage and wear of the implant components (Barbour, 1997; Fisher, 1991; Jin, 1995). Although extensive work has concentrated on the polyethylene surfaces, less effort has been placed on understanding wear of the metallic surface of these devices (Barbour, 2000, 1997; Firkins, 1998; Fisher, 1995). Metallic femoral components are exposed to scratches and roughening of the surfaces, which can limit the service lifetime of the metallic component (Jasty, 1994; Mcgrory 2012; Mirgahny, 2004). The goal of this study is to determine how scratch morphologies change when articulated against polyethylene. Previous studies have shown that scratches on retrieved femoral components form material pile up along the scratch with heights ranging from 0.1 to 1 μm high (Jasty 1994; Mcnie 1994). The work presented in this thesis includes the replication of scratches similar to those seen in retrieved metallic components on five fabricated F74 cobalt chrome (CoCr) (DJO Austin, TX) wear testing pins; scratch morphology was characterized utilizing a non-contact surface profilometer (WYKO ii NT2000, Veeco Corp., Tucson, AZ). These CoCr pins were exposed to tribologic conditions similar to a TKR environment replicated in an in-vitro pin-on-disk wear test; CoCr pins applied a normal load against machined UHMWPE disks on a multi- directional six station pin-on-disk machine wear tester (OrthopodTM, Advanced Mechanical Technology Inc, Waltham, MA). The wear test was conducted to 80 km of sliding to replicate approximately ~4 years of in-vivo function (Desjardins, 2008). The surfaces of the pins were analyzed for morphologic changes in scratch architecture during 10 km intervals. Results from this work provide data to interpret how different scratch severities evolve and their contribution to metal debris over time.

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