Tribology of hip joint prostheses

The implantation of a hip joint prosthesis has become a common orthopedic surgical procedure, with a high success rate. Worldwide, the number of hip replacements implanted each year now runs into the hundreds of thousands, if not millions. Successful hip replacement surgery requires both mechanically and chemically stable prostheses and appropriate clinical procedures. From an engineering point of view, the challenge is highly complex, involving the production of prostheses whose shape is adapted to the human anatomy, and which fulfil both their structural and load-distributing role, as well as joint functionality. The materials used must meet a series of specifications: absence of toxicity, good biocompatibility, mechanical strength, good fatigue endurance, shock resistance, resistance to corrosion by body fluids. For articular and bone-anchoring parts, there is also the need for appropriate tribological behavior. In this article, the topic of hip prostheses will be considered solely from a tribological point of view, with the intention of illustrating the application, in implant engineering, of basic concepts relating to friction, lubrication and wear. The article will focus on the tribology of the articular joint and, for reasons of space, will not deal with the subject of anchoring the prosthesis in the bone and static contact points in modular prostheses.

Following this introduction, the article includes a section outlining the main materials used in prostheses, followed by a section describing the tribological aspects of the natural synovial joint. The concepts, advantages and limitations of low-friction, low-wear prostheses are then presented. The article concludes with a brief review and an outline of development prospects.