Fretting Corrosion Mechanisms at Modular Implant Interfaces

Abstract

Modular connections have been commonly and successfully utilized in orthopaedic implant systems for the last 15 or so years, particularly at the head/neck junction in total hip arthroplasty (THA). However, recent retrieval studies have shown that some of the tapered junctions between femoral heads and stems in total hip arthoplasty can be prone to fretting corrosion, and may be a cause for concern in the longevity of implants. Fretting corrosion, which may release metallic products (particulate debris and ions) into the joint space, is a complex phenomenon in which the interplay between mechanically induced interfacial micromotion (fretting) and electrochemical corrosive activity play an important role, along with materials selection and processes. This suggests that interfacial fretting corrosion at modular implant interfaces can be significantly affected by the design variables of the modular junction. The working hypothesis of this study was that different designs of the modular head/stem combination of femoral hip prostheses exhibit different release of fretting corrosion metal products during fatigue testing used to simulate ten years of in vivo service. Three designs of femoral head (Co-Cr-Mo alloy) and stem (Ti-6Al-4V alloy) combinations were investigated in this study. The study included detailed taper metrology followed by environmental fatigue testing of the tapered junctions. The results of this study showed that important taper design differences do exist in the three constructs tested, and these differences manifested in different fretting corrosion behavior.

A large taper mismatch is one of the key factors behind high wear rates and failure at the taper junction of total hip replacements: A finite element wear analysis

“…It is known that design variables such as head diameter, head offset, material combination and taper angles have a significant effect on taper debris generation in THRs (Bone et al, 2015;Jani et al, 1997;Langton et al, 2012;Schmidt et al, 1997). There is inevitable variability in the manufacturing tolerances for the taper and trunnion cone angles of these THRs.…”

“…Brock et al (2015) also showed high volumetric wear rates for the taper of explanted CoCr heads and hypothesised that a rougher taper surface could increase the wear rates at this taper junction. Jani et al (1997) showed that taper variations such as taper design and taper surface finish have a significant impact on the fretting behaviour at the THR taper junction. Femoral head offsets are also known to likely have an effect on the generation of wear debris at the taper junction (McGrory et al, 1995).…”

“…There is evidence that taper and trunnion tolerances are around eight-fold larger than those used in the machine tool industries (Bobyn et al, 1993;Jani et al, 1997). As published by the American Society for Testing and Materials (Marlowe et al, 1997), there are no specific standards for taper and trunnion tolerances for the orthopaedic industry and mainly manufacturers use their own.…”

Corrosion of Metallic Biomaterials: A Review

“…Nevertheless, fretting corrosion may occur also at backside contacts in joint prostheses, bone-implant contact regions, overlapping cardiovascular stent contact points and other locations where surface contact and small cyclic motion exist [40]. Hence, fretting corrosion of biomaterials and implants has been studied extensively in the lab as well as on retrieved implants [40,68,142,143,271,329,330,331,332,333,334,335,336,337,338,339,340,341,342,343,344,345,346,347,348]. ASTM F1875 [349] specifies fretting corrosion testing of hip femoral head/bore and cone taper interface in modular implants.…”

In vitro corrosion testing of modular hip tapers

“…Several in vitro studies have been conducted on cyclically loaded modular prostheses to investigate the effects of mechanical loading on fretting and corrosion 8–23. Many researchers concluded that fretting could lead to corrosion due to disruption of the surface oxide 10, 12, 19, 24, 25.…”