THEORETICAL AND NUMERICAL INVESTIGATION IN BIOMECHANICS AND BIOTRIBOLOGY: FROM THE MUSCULOSKELETAL MULTIBODY MODELLING TO THE IN SILICO WEAR ASSESSMENT OF HUMAN SYNOVIAL REPLACEMENTS

THIS PHD WORK IS BASED ON THE INVESTIGATION OF THE PHENOMENA INVOLVED IN THE BIO-TRIBOLOGY OF THE SYNOVIAL REPLACEMENTS. THE SYNOVIAL JOINTS ARE THE NATURAL ARTICULATIONS OF THE HUMAN BODY LINKING TWO BONES, PROVIDING MINIMUM FRICTION AND ENSURING A HIGH RANGE OF MOTION BETWEEN THEM. WHEN THE NATURAL JOINT SUFFERS FROM ARTICULAR DISEASES, A SURGICAL PROCEDURE OF REPLACEMENT IS OFTEN REQUIRED: THE ARTIFICIAL IMPLANT REALIZED WITH BIOMATERIALS THAT IS GOING TO SUBSTITUTE THE UNHEALTHY JOINT HAS TO GUARANTEE THE SAME FUNCTIONALITY OF THE REPLACED ONE WHILE ENSURING THE MAXIMUM DURATION AND THEN THE MINIMUM IMPLANT WEAR. HENCE, AN ACCURATE TRIBOLOGICAL CHARACTERIZATION OF THE PROSTHESIS IS NEEDED: THE SCIENTIFIC COMMUNITY IS GOING TO MOVE FROM THE EXPERIMENTAL CHARACTERIZATION (IN VITRO) TO A NUMERICAL SIMULATIVE ONE (IN SILICO), IN ORDER TO HAVE FAST AND CHEAP COMPUTATIONAL TOOLS DURING THE DESIGN AND THE WEAR PREDICTION PHASE: THIS ASPECT REQUIRES A DEEP KNOWLEDGE OF THE PHYSICAL/MATHEMATICAL DESCRIPTION OF THE PROBLEM. WITH THESE FOUNDATIONS, THIS PHD WORK IS MOVING FOLLOWING TWO PARALLEL INVESTIGATIONS REGARDING IN PARTICULAR THE TOTAL HIP REPLACEMENT: - THE ASSEMBLING OF A MULTIBODY MODEL CAPABLE OF SIMULATE THE INVERSE KINEMATICS AND THE INVERSE DYNAMICS OF MUSCULOSKELETAL SYSTEMS, IN ORDER TO HAVE A GENERATOR OF TRIBOLOGICAL CONFIGURATIONS (LOAD AND RELATIVE MOTION) FOR THE ANALYZED JOINT DUE TO A SELECTED MUSCULOSKELETAL MOTION; - THE REALIZATION OF A TRIBOLOGICAL MODEL ABLE TO SIMULATE THE LUBRICATION/CONTACT REGIME OF THE ANALYSED TRIBO-SYSTEM IN TERMS OF LUBRICANT/CONTACT PRESSURE, SURFACES’ DEFORMATION AND SEPARATION, WEAR DEPTH, LOAD AND FRICTION TORQUE DUE TO A CERTAIN RELATIVE MOTION BETWEEN THE ARTICULATED SURFACES. THE DEVELOPED NUMERICAL MODELS RELATED TO BOTH THE INVESTIGATIONS ARE CONCEIVED IN MATLAB COMPUTATIONAL ENVIRONMENT AND HAVE TO BE COMMUNICATE IN ORDER TO OBTAIN A GLOBAL TOOL THAT CHARACTERIZES THE BIOTRIBOLOGICAL PERFORMANCE OF A SYNOVIAL REPLACEMENT DUE TO AN OVERALL MUSCULOSKELETAL PHYSICAL ACTIVITY. THE MAIN GOAL IS TO PROVIDE THE BASIS OF THE NUMERICAL MODELLING IN THIS FRAMEWORK AND TO MAKE THE REALIZED CODES MORE AND MORE ACCURATE BY ADOPTING ADVANCED NUMERICAL TECHNIQUES (FINITE DIFFERENCE METHOD, FINITE ELEMENT METHOD, BOUNDARY ELEMENT METHOD, RANDOM FRACTALS GENERATOR, DIFFERENTIAL ALGEBRAIC EQUATIONS, ETC.) AND BY THE VALIDATION WITH RESPECT TO EXPERIMENTAL/IN VIVO MEASUREMENTS OR EMPIRICAL BENCHMARKS.