Abstract
In this study, the movement of climbing a step is decomposed in 4 EOS images. A patient-dependent 3D model of the knee is then created from MRI, and several numerical simulations are carried out according to the experimental boundary conditions (force and flexion angle), so as to ensure the global knee mechanical equilibrium. To validate this patient-specific model, its bony structure is confronted with the EOS images once the mechanical equilibrium is reached. This model gave us an estimation of the stress in the ligaments for every flexion angle as well as a pressure map on the cartilages.
Introduction
Knee osteoarthritis is one of the major causes of disability in older adults. According to a study conducted in the United Kingdom and the Netherlands on a population of 55 y.o. and more, 25% declared having chronical and persistent knee pain (Peat et al. 2001). Osteoarthritis is the combined effect of degradation of the cartilage, thickening of the subchondral bone and new bone formation on the edges of the cartilages. The main clinical diagnosis tool for osteoarthritis is the radiography, with effects being apparent on X-ray images: joint space narrowing for the cartilage destruction, variation of the signal intensity for the thickening of the subchondral bone and the bone formation is directly seen.
Conclusion
In order to study on the question of knee degradation and pain when developing osteoarthritis, related to both the pressure on the cartilages and the knee stability, a knee joint model was created. We proposed a mixed approach, both using medical imaging (MRI, EOS X-ray system) and force platform in conjunction with a FE model. The goal was to obtain pressure maps on the cartilages of the knee and the stress sustained by its ligaments during a daily activity.
