Abstract
Osteoporosis is a disease characterized by a loss of bone density and an altered bone architecture. These modifications lead to an increased risk factor for bone fracture, particularly of the femoral neck. This disease can be explained by a disorder in the bone remodeling process which is triggered by the apparition of micro-cracks within the bone. According to Frost’s theory [1], these micro-cracks appear for a specific local strain threshold. Thus, the knowledge of the microarchitecture and quality of trabecular bone is essential to determine this local strain threshold. This paper studied the mechanical trabecular bone behavior of 43 patients diagnosed as osteoporotic whose femoral heads were replaced by hip prosthesis. From each patient, a cylinder-shaped of trabecular bone samples was cored. Each sample was scanned by X-ray micro-tomography before a compression test in order to reconstruct a reliable Finite-Element (FE) model of the bone architecture in Abaqus. The force-displacement curves were recorded for all the samples and calibrated by the experimental responses. The force-displacement numerical curves were adjusted to the experimental ones, by modifying the tissue microscopic mechanical behavior. This process leads to the determination of the local strain threshold responsible for triggering the bone remodeling process.
Highlights
Osteoporosis is a disease of bone metabolism which decreases the bone density and alters the architecture of the trabecular bone
Three objectives were achieved: (i) developing a numerical FE model based on the microarchitecture of the trabecular bone to reproduce the experimental compression test performed on the real trabecular bone sample (ii) using an identification procedure to determine a reliable and personalized microscopic Young’s modulus (iii) finding a local deformation threshold εloc responsible for triggering the bone remodeling
All the mechanical parameters identified by this process were compared to the bone porosity and the age of patient
Summary
Osteoporosis is a disease of bone metabolism which decreases the bone density and alters the architecture of the trabecular bone. The determination of the mechanisms involved in osteoporosis is an essential point to better predict the fracture risk. In this context, a biomechanical approach is strongly relevant to determine the link between the mechanical properties and the microarchitecture of the trabecular bone. Knowledge of the bone remodeling process is of importance to gain understanding about the origin of osteoporosis. This process is equilibrium between destruction of the “old bone” by osteoclasts and formation of a “new one” by osteoblasts. Patients submitted to 400 μ def or less (i.e. under the minimum in vivo strain) are considered “under-stimulated” and patients submitted to over 3000 μ def (i.e. over the maximum in vivo strain) are considered “over-stimulated”
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