I-RIM Conference 2019 October 18 - 20, Rome, Italy ISBN: 9788894580501 Experimental Robotic Systems for Design, Development and Testing of Orthopaedic Devices Nicola Sancisi Department of Industrial Engineering University of Bologna 40136 Bologna, Italy nicola.sancisi@unibo.it Michele Conconi Department of Industrial Engineering University of Bologna 40136 Bologna, Italy michele.conconi@unibo.it Vincenzo Parenti-Castelli Department of Industrial Engineering University of Bologna 40136 Bologna, Italy vincenzo.parenti@unibo.it Abstract—The paper presents new robotic systems for test- ing general medical devices. Two applications are presented that show the advantage of experimental tests and articular models in prosthesis optimization and design. Keywords—orthopaedic devices, prostheses, test, robotic rigs I. INTRODUCTION The main objective of orthopaedic devices such as articu- lar prostheses, prosthetic limbs, orthoses and exoskeletons is to replicate or recover the natural behaviour of a joint. This is obtained by a careful design of the mechanical constraints pro- vided by the device, imposing a wanted motion or behaviour of the limb including the device itself. For instance, articular prostheses aim at recovering the joint mobility and stability after substitution of the patient articular surfaces. Thus, pros- thetic components must replicate the natural joint behaviour, reproduce the function of articular structures removed during the implant, and respect the residual structures. To achieve these results, we believe that prosthesis design should be based on a rigorous process combining experi- mental analysis, joint modelling and prototype testing. Exper- imental motion analysis allow definition of the natural joint behaviour at different loading conditions, highlighting the role of each articular structure in constraining the joint motion [1]. Articular models replicate this role in a computational envi- ronment [1,2], where the articular constraints can be substi- tuted by mechanically equivalent counterparts that will con- stitute the basic features of the prosthesis (or the general de- vice). The result of the design process must be built and tested to verify if it satisfies the desired constraints [3,4]. Patient- specific features could be also introduced in the final solution, requiring personalised measures, design and production [4]. The first and the last step of this process consist in the ex- perimental analysis of the joint before and after implant. Be- fore proceeding with clinical studies on patients, these anal- yses can be performed by in-vitro tests on cadaveric speci- mens. Several in-vitro test rigs were proposed, which allow the study of the human joint dynamic behaviour. These de- vices can be divided into two groups: the human joint simula- tors, which aim at reproducing the behaviour of the joint in a physiological way [5], and the robot-based systems [6], which aim at reproducing the loading conditions at the joint by a ro- bot. The main objective of these rigs is to apply given dynamic external loads to the bones, without additional unwanted con- straints. Limitations of most devices currently in use are low flexion ranges, low dynamics and loads, reduced prescribed set of possible tests. The scope of this paper is to describe a family of new test- ing rigs that overcome the present limitations and that are cur- rently used for joint analyses by our group. Two examples and relevant results are included to show successful applications of a “testing and modelling” approach to prosthesis design and optimization. II. TESTING RIGS A. General Feature The testing rigs were designed and built by our labs and show common characteristics. They feature three main parts (Fig. 1, left): a frame (4), a loading system (2, 3, and 11), and a portal (9). The loading system is a six degrees-of-freedom (dof) robot. A first version was a cable-driven robot using six pneumatic actuators, with an inherent force control.