Chapter 7 - Importance of in vitro assessment of total hip arthroplasty using hip simulator and preliminary results

Abstract

Total hip replacement (THR) is a surgical revolution that replaces an arthritic or accidentally damaged joint with a prosthetic joint. In spite of 100 years of operative history, the performance of a THR is critically challenged by implant fracture, biotribocorrosion, or osteolysis and aseptic loosening, limiting its life to merely 15–20 years. This leads to a revision of the hip replacement, which is very painful and more complex and takes longer operational time to replace some or all the parts of the original prosthesis with new ones. In this scenario, it is essential to evaluate the life of the implant to be used in a total hip arthroplasty (THA) before any invasive procedure, keeping the efficacy and safety of the patient in mind. However, it is an immense challenge for researchers to reproduce the wear mechanism and bodily fluid environment that is substantially equivalent to what a patient experiences physiologically. Other than the bearing material combinations for total hip arthroplasty (THA)—metal-on-metal, ceramic-on-polymer, metal-on-polymer, and ceramic-on-ceramic—the design of the joint and many other parameters govern wear performance and life. To imitate the in vivo loading and angular displacements under biolubricant, typical devices, called hip joint wear simulators, are employed to apply a set of motions and loads under lubrication conditions, which create an in vitro tribological environment comparable to those experienced by a THA under in vivo conditions. The hip joint simulator plays a most important role in validating the newly developed implants before use. Currently used simulators basically differ in parameters like single- or multistation(s), loading cycle, ball–cup relative position, degree of freedom, lubricant chamber, etc. This chapter reviews the simulator test results under standard protocols and explicates the requirement of preclinical assessment of wear and tribocorrosion in new hip implants before using them for THR.