The onset of fretting at the head‐stem connection in hip arthroplasty is affected by head material and trunnion design under simulated corrosion conditions

Abstract

Mechanically assisted crevice corrosion (MACC) is a mechanism for trunnion damage in total hip arthroplasties (THAs). Retrieval studies have shown reduced MACC-related damage for ceramic heads compared with cobalt-chromium (CoCr) heads. We propose that ceramic heads demonstrate fretting at higher cyclic compressive loads than CoCr heads on titanium alloy trunnions in a simulated corrosion model. A closed electrochemical chamber was used to measure fretting current onset loads for two modern titanium alloy trunnions (Zimmer 12/14 and Stryker V-40) in which trunnion failure has been reported. Ceramic and CoCr alloy 36 + 0 mm heads were impacted on each trunnion and cyclically loaded at 3 Hz with increasing magnitude from 100 to 3,400 N for 540 cycles. Onset load was the cyclic compressive load at which the slope of the average fretting current increased significantly. A CoCr head with V40 trunnion demonstrated the lowest onset load (1,400 N), while the V40 trunnion with a ceramic head showed the highest onset load (2,200 N). Significant differences occurred in average fretting current between head materials for V40 trunnions (p < 0.001) at loads over 2,000 N. CoCr-12/14 and ceramic-12/14 couples demonstrated similar onset loads (2,000 N). All head-trunnion combinations showed cyclical fretting response to loading at 100 N. Head material composition was observed to increase fretting at the taper junction but the effect was taper geometry dependent. Using ceramic heads may reduce the phenomena of trunnion fretting and corrosion but the effect of both trunnion geometry and metallurgy warrants further investigation. Statement of clinical significance: Trunnion corrosion may occur with titanium alloy stems regardless of the head material used. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1630-1636, 2018.

Electrochemical Method of Fretting Corrosion Testing in Modular Hip Prostheses

“…The results of the electrochemical fretting corrosion test are important for understanding the effect of design changes, load application modes, and combination of components made from different materials. Recently, use of electrochemical tests by Rowan et al [4] evaluated the effect of two different designs (V40 and 12/14) of titanium alloy taper and two different head materials (Co-Cr and ceramic) on the fretting corrosion. They showed that the V40 taper with ceramic head presented the lowest propensity to fretting corrosion than the same taper with a Co-Cr head.…”

“…The modular type of hip prosthesis has become widely used, because it provides a better fit to the patient's anatomy, since it is possible to combine components of different sizes, types and materials [2], [3]. Surgeons may also perform femoral head replacement on already fixed stems, for a less aggressive revision procedure [4], [5]. The head-stem modular connection of the hip prosthesis usually consists of a metal-on-metal conical junction where the femoral stem has a conical tip and the femoral head has the tapered bore for fitting, as can be seen in Fig 1. Hip prostheses may vary from manufacturer to manufacturer, in terms of angle of the taper and bore of the head (one example can be seen in Fig.…”

“…These materials rely on the formation of a passive film that prevents the process of corrosion. The film consists of an oxide that forms spontaneously on the surface of the metal, avoiding the transport of ions and electrons [7]; however, when the components of this prosthesis are connected, they inevitably form a crevice in the connection, which can lead to so-called mechanically assisted crevice corrosion or fretting corrosion, a corrosion process that occurs due to the formation of crevices combined with the fretting in the interfaces that are submitted to small-scale relative motion [4], [6]. This corrosion is related to the combined action of the mechanical removal of the passive film due to fretting, and corrosion of the exposed metal surface with the consequent release of debris, as seen in the Fig.…”

“…This analysis is usually performed by means of a short-term test using an electrochemically simulated corrosion chamber. According to a recent study [4], there are still few data in the literature that were obtained using electrochemical chambers, with most of the information pertinent to fretting corrosion damages based on retrieval studies [4], [11]- [13].…”

“…It is possible to detect the corrosion not only in the interface of the head-taper, but also in other regions of the prosthesis that are subject to the relative movement. The great advantage of this method is the possibility of real-time evaluation of the effect of compressive loads on the current generated at the head-taper interface in a controlled environment [4].…”