Electrochemical evaluation of damage level to weight bearing surface of metal head joint prosthesis

Abstract

Pin on disk friction tests were carried out for three types of metals, 316L S.Steel, Co-28Cr-6Mo, and Ti-6Al-4V alloys in PBS(-) to estimate the range of loads that can be applied to the bearing surface of a joint prosthesis, based on the degree of damage to the passivation film. The results were as follows: (1) When two metals of the same type were rubbed against each other, the passivation film was almost completely destroyed immediately after the onset of friction, even when a very low normal load was applied. (2) In the metal to UHMWPE friction test, the passivation film was severely damaged immediately after the onset of friction. However, the passivation film recovered until the polarization potential reached a certain level, which was specific to each metal. (3) The allowable load on the bearing head was calculated, assuming that the degree of damage to the passivation film was 20% or 40%. When a metal acetabulum socket was used, damage to the passivation film on the head was severe, regardless of the type of metal used for both the acetabulum socket and the head. When a UHMWPE acetabulum socket was used, the allowable load ranged from 8.16x10 2 N to 1.31x10 5 N for 316L S.Steel, from 7.83x10 3 N to 1.31x10 5 N for Co-28Cr-6Mo alloy, and from 43N to 6.08x10 2 N for Ti-6Al-4 Valloy.