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Friday, March 2, 2001

OxZr may help reduce wear-related complications

Wear-related complications in total knee arthroplasty (TKA) remain a concern. Oxidized zirconium (OxZr) alloy was developed to improve on the resistance to abrasion, friction and biocompatibility of CoCr femoral components, to reduce wear of the UHMWPE and to provide an alternative for nickel-sensitive patients.

A study in scientific exhibit 34 compared the wear performance of these two types of femoral components and found that OxZr component may contribute to reducing wear-related complications in TKA.

The investigators tested Zr-2.5Nb and CoCr alloy medium-sized, cruciate retaining, femoral components. The former was oxidized by thermal diffusion to create a zirconia ceramic surface about 5 micrometers thick. A six-station physiological knee simulator was used to conduct wear testing to 6.1 million cycles on three of each femoral-tibial assembly using a 90 percent gait, 10 percent stair-climbing, activity cycle. Measurements included: tibial component weight; wear particle number, size, and volume; and femoral surface roughness.

Even though abrasive wear conditions were not intentionally created, the CoCr femorals developed numerous scratches, some deep, early in the wear test. The OxZr femorals remained virtually pristine throughout the test. The aggregate UHMWPE wear rate for the OxZr femoral group was less by 85 percent (p<0.05), and the number and total wear particle volume in each size range was also less.

The study authors say greater lubricity and abrasion resistance of OxZr likely explain the reduction in UHMWPE wear. In the more abrasive in vivo environment, this improvement is expected to be magnified.

The coauthors are Myron Spector, PhD, department of orthopaedic surgery, Brigham & Women's Hospital, Boston; Michael Ries, MD, University of California, San Francisco; Robert Bourne, MD, London, Ont.; and Will Sauer MS; Marc Long, PhD, and Gordon Hunter, PhD, all of Smith & Nephew, Inc. Funding for the study was provided by Smith & Nephew, Inc.

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Last modified 15/February/2001 by IS