The use of finite element modeling to improve biomechanical research on knee prosthesis

Biomechanical numerical models in orthopedic research are currently becoming more and more frequent, complex and comprehensive. In this context, finite element analysis of biomechanical models has consistently increased in the last decades. The growing trend in the use of such numerical technique is indeed strongly correlated with the increasing and the easiest access to computational resources and, parallel to this, with the development of more sophisticated data handling algorithms. In fact, looking to the past, the use of finite element analysis in the field of biomechanics was mainly limited to simplistic approaches, such as bi-dimensional models, considering mainly linear analyses, and investigation of single structures or tissue types only. Nowadays, fully three-dimensional, nonlinear, multi-structures and tissues, and even multi-joint systems, can be also easily implemented in the simulation. More specifically, for a knee with an implant (e.g. total knee arthroplasty (TKA), unicondilar knee arthroplasty (UKA) or patello-femoral joint), the model aims to replicate the behavior of three-dimensional biological structures, like bones, cartilage and ligaments, coupled with non-biological knee components made of different synthetic materials. An additional complexity in knee modeling is provided by the huge variability inherent to the field. This variability is due to the vast range of different kinematics and contact forces that could be induced by the variety of prosthesis designs, in different patients, and under specific motor tasks. Due to the multiplicity of these aspects, the use of finite element modeling is of foremost importance; in fact, it allows to obtain qualitative guesses and qualitative data that cannot be provided by any other method (such as in-vitro experimental tests or gait analysis) such as the stresses distribution for bone and prosthesis components under different conditions, and contact forces interactions, both for generic and patient-specific solutions. These outputs, coupled with clinical outputs, allow to relate, for example, stress changes, from the physiological to a knee with a prosthesis and to a bone mineral density changes in the patients, allowing to formulate possible answers to common unsolved clinical questions. An added value derived by the use of finite element analysis is the possibility to characterize performances of prosthesis designs in restoring knee functions and maintaining long-term mechanical integrity for different patients and in agreement with different surgeon requests. In more general terms, the use of finite element modeling in the understanding of knee prosthesis biomechanics is fundamental to answer clinical questions, to improve and predict clinical outputs, to provide more surgeon-friendly guidelines and, last but not least, to improve TKA. success and avoid critical situations. This modeling procedure can help bridging the gap between surgeons and engineers, aiming in the improving of the biomechanical research on knee prosthesis.SCOPUS: ch.b