Abstract
Modular hip joint implants were introduced in arthroplasty medical procedures because they facilitate the tailoring of patients’ anatomy, the use of different materials in one single configuration, as well as medical revision. However, in certain cases, such prostheses may undergo deterioration at the head–neck junctions with negative clinical consequences. Crevice-corrosion is commonly invoked as one of the degradation mechanisms acting at those junctions despite biomedical alloys such as Ti6Al4V and CoCr being considered generally resistant to this form of corrosion. To verify the occurrence of crevice corrosion in modular hip joint junctions, laboratory crevice-corrosion tests were conducted in this work under hip joint-relevant conditions, i.e., using similar convergent crevice geometries, materials (Ti6Al4V and CoCr alloys vs. ceramic), surface finish, NaCl solution pHs (5.6 and 2.3), and electrochemical conditions. A theoretical model was also developed to describe crevice-corrosion considering relevant geometrical and electrochemical parameters. To verify the model, a FeCr alloy, known to be sensitive to this phenomenon, was subjected to the crevice-corrosion test in sulfuric acid. The experiments and the model predictions clearly showed that, in principle, crevice corrosion of Ti6Al4V or CoCr is not supposed to occur in typical crevices formed at the stem-neck junction of hip implants.
Highlights
Hip joint prostheses are implants used to replace failed natural joints
These complications were attributed to the material degradation in the trunnion-bore contact by mechanisms such as fretting-corrosion and crevice corrosion [3,5,6,7,8,9]
The goal of this paper is to evaluate whether crevice corrosion of biomedical-grade titanium and cobalt-chromium can occur in typical trunnion-bore hip implant contacts
Summary
Hip joint prostheses are implants used to replace failed natural joints. Modern modular hip joints typically consist of a ball inserted on a stem through a conical junction with the trunnion on the top of the stem and the corresponding cone bore on the ball. The ball is made out of ceramics or CoCrMo alloys while titanium or other metals (stainless steels, CoCrMo alloys) are used for the stem [2] Both metals exhibit the necessary corrosion resistance to withstand the contact with the synovial fluid, essentially a water solution containing organic molecules and ions such as chlorides with a pH around 7. Despite these advantages, modular hip joints have been associated with health complications such as adverse tissue reactions and highmetallic-ion levels in the blood [1,3,4]. These complications were attributed to the material degradation in the trunnion-bore contact by mechanisms such as fretting-corrosion and crevice corrosion [3,5,6,7,8,9]
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