7 - Alumina bearings in orthopedics: Present and future

Abstract

The story of the hip replacement in the 21st century is the story of zirconia toughened alumina (ZTA). ZTA hip bearings are equally the most important new technological development in alumina technology in the 21st century, along with the 1000+ channel-number bionic eye alumina/titanium/platinum bionic micro-feedthrough featured in Chapter 10. ZTA alumina bearings, which were commercialized in 2003, are a primary reason for alumina bearings achieving market dominance in the global hip replacement industry in the year 2015. Today 55% of the 1.3 million hip replacements implanted annually use ZTA alumina bearings, with metal-on-polyethylene bearings diminishing in market share as a consequence. There have been four main technology drivers underpinning the success of the alumina orthopaedic bearing:•Zirconia toughening (the technology underlying ZTA) which greatly enhanced the strength and toughness of alumina bearings.•Greatly reduced rates of wear compared to non-alumina bearings: two-to-three orders of magnitude less alumina wear particle numbers generated (alumina-alumina bearings) compared to polyethylene wear particle numbers (CobaltChrome (CoCr)-polyethylene bearings).•The benign nature of alumina wear particles compared to CoCr particles•The elimination of CoCr galvanic corrosion and CoCr fretting wear at taper joints, a problem of potential cobalt and chromium toxicity. The primary focus of this chapter is ZTA, which has changed the world of orthopedic bearings, and is well on the way to totally supplanting metal-on-polyethylene bearings from the market. Topics explored include: tribology of alumina and ZTA hip bearings; the significance of alumina hip bearings in eliminating the major problems of fretting wear and galvanic corrosion; wear particles and osteolysis; squeak in alumina hip bearings; the manufacturing engineering of ZTA hip bearings by global pioneer and market leader CeramTec; global market trends in hip replacements.