A lexicon for wear of metal-on-metal hip prostheses

Abstract

Research on metal-on-metal (MoM) hip bearings has generated an extensive vocabulary to describe the wear processes and resultant surface damage. However, a lack of consistency and some redundancy exist in the current terminology. To facilitate the understanding of MoM tribology and to enhance communication of results among researchers and clinicians, we propose four categories of wear terminology: wear modes refer to the in vivo conditions under which the wear occurred; wear mechanisms refer to fundamental wear processes (adhesion, abrasion, fatigue, and tribochemical reactions); wear damage refers to the resultant changes in the morphology and/or composition of the surfaces; and wear features refer to the specific wear phenomena that are described in terms of the relevant modes, mechanisms, and damage. Clarifying examples are presented, but it is expected that terms will be added to the lexicon as new mechanisms and types of damage are identified. Corrosion refers to electrochemical processes that can remove or add material and thus also generate damage. Corrosion can act alone or may interact with mechanical wear. Examples of corrosion damage are also presented. However, an in-depth discussion of the many types of corrosion and their effects is beyond the scope of the present wear lexicon. ß

Origins of material loss in highly worn acetabular cups of metal‐on‐metal total hip replacements

“…In the present study, the distributions of wear volume of the 42 cups showed that the excessive wear was generated not only at the edge but also at areas well inside the sockets. These results were consistent with the wear modes of MoM hip implants characterized in previous retrieval studies, 17,21 which also indicated in vivo wear occurs at edge and socket areas simultaneously. International standards (ISO14242-1 & 3) have specified a "standard" wear mode for hip simulator wear tests, that is, no edge contact.…”

Metallic Biomaterials: Current Challenges and Opportunities

“…Fatigue wear often takes place when repetitive, cyclic loading on the implant weakens the surface to produce cracks, eventually leading to fragmentation and pitting. Additional wear damage caused by these mechanisms include gouges, etches, surface discolouration, surface deposits and third-body particulate generation [ 153 ]. The fourth mechanism is tribochemical, an interplay of mechanical and corrosive wear, caused by mechanical activation of the body’s surrounding fluids [ 153 ].…”

“…Additional wear damage caused by these mechanisms include gouges, etches, surface discolouration, surface deposits and third-body particulate generation [ 153 ]. The fourth mechanism is tribochemical, an interplay of mechanical and corrosive wear, caused by mechanical activation of the body’s surrounding fluids [ 153 ]. A study into Ti-6Al-4V hip prosthetics showed 90% of surface fractures were caused by both cyclic stresses and corrosion [ 4 ].…”

“…Degradation by mechanical and chemical processes weakens the implants structural integrity and thus its ability to function. The four wear mechanisms of the MoM implants, namely scratching, etching, pitting and weakening the structure, increases the surface roughness which in turn increases wear rate [ 153 ]. Surface/subsurface corrosion of Mg alloys in particular releases hydrogen gas which induces SCC into the metal.…”

Diagnostic guidelines for the histological particle algorithm in the periprosthetic neo-synovial tissue

“…ceramic particles after a fracture of a ceramic femoral head or liner) [ 2 ]. Particulate material can also be generated by tribochemical wear (tribocorrosion) mechanism and by other modality at the head-neck tapers such mechanically assisted crevice/fretting corrosion, pitting and intergranular corrosion, and etching which depend on the material, material couple, and alloy microstructure [ 3 , 4 ].…”