What Factors Drive Taper Corrosion?

Abstract

Adverse local tissue reactions to corrosion products can lead to total hip arthroplasty failure. Although this problem has been well known for more than 25 years, it has seemingly increased in frequency over the recent years. The occurrence of corrosion is multifactorial-depending on implant, patient, and surgeon factors. As of now, there is no "one-size-fits-all" solution to prevent corrosion in total hip arthroplasty devices. Thus, it is imperative to fully understand the exact mechanisms of modular junction corrosion to prevent premature implant failure. This review highlights a few key concepts that need to be explored to minimize the impact of corrosion. The key concepts include (1) the prevention of micromotion, (2) the role of implant alloy metallurgy in the corrosion process, (3) the in vivo generation of a corrosive environment, and (4) potential unanticipated problems.

Keywords: adverse tissue reactions; corrosion; fretting; modular junction; taper; total hip arthroplasty.

Figure 1

Scanning electron micrographs (SEM) of column damage. A) Column-like troughs are running parallel to the taper axis, and perpendicular to the initial machining lines. B) At a higher magnification, it can be seen that the troughs are characterized by etching marks along with fine pitting at some locations.

Figure 2

Typical SEM image of an imprinted femoral head taper surface. In the lower half of the image the original head taper topography can still be seen. In the upper half of the image an imprint of the typically wider stem taper topography is visible. The imprinted surface appears fairly smooth, but some residual fretting marks remain (arrows). Thus, it appears likely that imprinting is a fretting driven process.