Journal of Bioengineering & Biomedical Science

Four Station Knee Simulator Wear Testing Comparing Titanium Niobium Nitride with Cobalt Chrome

Abstract

Malikian R Maruthainar K Stammers J Wilding CP and Blunn GW

A new non-destructive method was applied in order to assess bone integrity. The method is based on measurement of bHypersensitivity to an orthopaedic implant was first published in 1966 and since then, in sensitive patients, is known to cause serious problems in joint replacement surgery. Titanium niobium nitride (TiNbN) can act as a surface coat for knee arthroplasty to “hide” the cobalt chrome (CoCr) femoral component beneath, therefore affording an immunoprivileged state. The aim of this study is to determine the wear properties of titanium niobium nitride against Ultra High Molecular Weight Polyethylene (UHMWPE) compared to cobalt chrome and to examine the metallic alloy surface of knee prostheses after loading cycles using a knee simulator. Three TiNbN coated and one CoCr Vanguard total knee femoral components were articulated against standard UHMWPE grade tibial inserts in the Stanmore-Instron knee simulator. Surface roughness, UHMWPE mass, lowest point, surface profiles and volumetric change were measured every one million cycles up to five million cycles. After five million cycles the average roughness of the cobalt chrome medial and lateral femoral condyles was over three times that of the TiNbN coated femoral condyles. There was no obvious difference in weight loss, volume loss or progression of lowest points of the tibial inserts articulating with the TiNbN coated and the cobalt chrome femoral component. Despite a clear reduction in roughness progression over the course of this in vitro test, there was no demonstrable improvement in UHMWPE wear measured gravimetrically or by surface profiling. The TiNbN implant tested may still be of great benefit to patients who are metal sensitive, but the coat offers no benefit in UHMWPE wear.