A New Test Rig for Human Joint and Prosthesis Characterization

In vitro experimental studies are of great importance in human joint biomechanics. Data from in vitro tests allow the study of kinematics, kinetostatics, and dynamics of human joints. Understanding the joint behavior is required for prosthesis and orthosis design as well as for model validation. Several in vitro test rigs are reported in the literature. Most devices currently in use are either specifically designed for a prescribed set of tests, thus limiting possible applications, or obtained by adapting industrial machines to biomechanics, which results in a poor fit to the intended application, e.g., limiting the flexion range achievable during tests. In general, the main issue for these rigs is to apply specific external loads variable in time with flexion, without introducing additional unwanted constraints to the relative motion of the main bones. In this study, a new test machine is presented as an evolution of a previous one. In particular, the new systems for load application, joint motion, and femur-to-rig fixation are shown, which make the use of the machine more quick and efficient and extend its possible applications to a wider range of loading conditions and joint motion.