Fretting corrosion of fully cemented polished collarless tapered stems: The influence of PMMA bone cement

Abstract

a b s t r a c tIn order to investigate the effect PMMA bone cement chemistry has on the fretting corrosion of cemented femoral stems, a novel test setup with integrated electrochemistry was developed and conducted in part reference to ISO 7206-4:2010. Ultima TPS TM femoral stems were cemented into a specially prepared delrin moulds using a third generation cementing technique similar to the procedure used in-vivo. Three commercially available PMMA bone cements were tested in order to understand the role bone cement chemistry plays on the fretting-corrosion rates at the stem-cement interface. Each stem-cement component was then orientated and set in place using laboratory grade PMMA cement, immersed in 0.9% NaCl and subjected to 500,000 cycles of cyclic loading at 1 Hz. Intermittent Open Circuit Potential (OCP) and Linear Polarisation Resistance (LPR) measurements were conducted in order to assess the effect PMMA bone cement chemistry has on the localised dissolution of cemented femoral stems. Macroscopic observation and scanning electron microscopy with integrated energy dispersive X-ray analysis (SEM/EDX) was conducted in order to support the electrochemical findings.Crown

Characterisation of the surface topography, tomography and chemistry of fretting corrosion product found on retrieved polished femoral stems

“…This leaves the cobalt (Co 2+ ), known to be extremely soluble at the electrode potential and pH found at the interface, to migrate and leave the interface due to an electrical potential established across the interface due to the separation of anodic and cathodic areas. This has also been observed in experimental simulations complimenting clinical literature (Bryant et al, 2013a;Bryant et al, 2013b).…”

“…Figure 1 summarises the possible locations and mechanisms for tribocorrosion and tribochemical reactions to occur. To date the authors have presented experimental and preliminary clinical finding outlining the mechanisms, system variables influencing the degradation and the elemental chemistry of both laboratory simulated and retrieved CoCrMo femoral stems (Bryant et al, 2013a; …”

The role of surface pre-treatment on the microstructure, corrosion and fretting corrosion of cemented femoral stems

“…Full details of the experimental arrangement and electrochemical method have been reported elsewhere [16,15]. In brief, cemented femoral stems were orientated at 9 and 10˚ flexion and extension, respectively, and subjected to a compressive sinusoidal load (0.3-2.3 kN) at 1 Hz.…”

“…It is only of late that the tribocorrosion degradation, described as material loss owing to mechanical and electrochemical reactions, and the factors influencing this have been considered for cemented devices [8][9][10][11][12].…”

“…Currently only a few studies exist investigating the role of fretting-corrosion and the influence of system variables at the stem-cement interface [8,14,11,15]. Recently the authors have presented systematic work outlining the tribocorrosion mechanisms [15,13] and role of system variables such as cement type [16,17] and mixed metal couples [18] on the overall degradation of cemented femoral stems. This study goes further to examine the influence of surface processing on the fretting-corrosion characteristics, subsurface microstructure and surface chemistry of cemented femoral stems through the use of in-vitro tribocorrosion simulations and advanced surface analysis techniques.…”