"Evaluation du micro-endommagement osseux par spectroscopie ultrasonore non-lin\u00E9aire, vers une mesure quantitative" . . "Acoustique non lin\u00E9aire" . "Evaluation du micro-endommagement osseux par spectroscopie ultrasonore non-lin\u00E9aire, vers une mesure quantitative" . "Histomorphom\u00E9trie" . . . . "Text" . "Bone microdamage characterization as well as its involvement in bone metabolism or bone fragility remains a challenge, especially because no existing techniques are well suited to its measurement. Non invasive techniques for detecting and monitoring bone microcracks accumulation and propagation are thus highly desirable. The objective of this thesis was to evaluate the sensitivity of nonlinear resonant ultrasound spectroscopy (NRUS) measurements to the accumulation of damage in cortical bone by fatigue or by controlled crack propagation. First, NRUS method was optimized to achieve highly sensitive and reproducible bone nonlinearity measurements. Then, two groups of human cortical bone specimens were machined from the femoral mid-diaphysis. The first group was taken through a progressive fatigue protocol consisting of four steps of cyclic four-point bending. The second group was taken through a toughness protocol consisting of initiation and controlled propagation of a stable crack induced by 4-point bending mechanical loading. Our results evidenced a progressive increase of the nonlinear elastic parameter during fatigue testing or during toughness experiments. Moreover, the relative variation of nonlinear elasticity of the fatigued specimens was significantly related to the relative variation of the number density of small cracks assessed with micro-computed tomography, whereas in crack propagation experiments a significant relationship was found between the level of nonlinearity and total crack length. These results strongly suggest that NRUS measurements are sensitive to damage accumulation and bone non-linearity can be used as a marker of bone damage." . "Th\u00E8ses et \u00E9crits acad\u00E9miques" . "La caract\u00E9risation du micro-endommagement et la compr\u00E9hension de son r\u00F4le dans le m\u00E9tabolisme ou dans la fragilisation osseuse restent des challenges, tout particuli\u00E8rement en raison de l\u2019absence de techniques de mesures bien adapt\u00E9es \u00E0 son \u00E9tude. Il appara\u00EEt donc n\u00E9cessaire de d\u00E9velopper de nouvelles techniques non-invasives pour d\u00E9tecter et suivre l\u2019accumulation de micro-endommagement osseux, en particulier celui qui se manifeste par la pr\u00E9sence de microfissures. L\u2019objectif de la th\u00E8se est d\u2019\u00E9valuer la sensibilit\u00E9 de la spectroscopie ultrasonore non-lin\u00E9aire (NRUS) \u00E0 l\u2019accumulation du micro-endommagement osseux. La sensibilit\u00E9 et la reproductibilit\u00E9 de la technique NRUS ont tout d\u2019abord \u00E9t\u00E9 optimis\u00E9es. Puis, deux groupes d\u2019\u00E9chantillons d\u2019os cortical ont \u00E9t\u00E9 pr\u00E9lev\u00E9s sur des diaphyses f\u00E9morales humaines. Les sp\u00E9cimens du premier groupe ont \u00E9t\u00E9 endommag\u00E9s progressivement par fatigue en flexion 4-points. Le second groupe a subi un test de t\u00E9nacit\u00E9 pour initier et propager de mani\u00E8re contr\u00F4l\u00E9e une fissure unique. Nos r\u00E9sultats montrent que la non-lin\u00E9arit\u00E9 mesur\u00E9e des \u00E9chantillons fatigu\u00E9s et fissur\u00E9s augmente de mani\u00E8re significative apr\u00E8s les \u00E9tapes de fatigue ou le test de t\u00E9nacit\u00E9. De plus, nous observons une corr\u00E9lation significative entre la variation relative du param\u00E8tre non-lin\u00E9aire et l\u2019augmentation de la densit\u00E9 de petites fissures (\u00E9valu\u00E9e par microtomographie par rayonnement synchrotron). Enfin, le niveau de non-lin\u00E9arit\u00E9 des sp\u00E9cimens fissur\u00E9s est significativement corr\u00E9l\u00E9 \u00E0 la longueur totale de la fissure. Ces r\u00E9sultats sugg\u00E8rent que la technique NRUS optimis\u00E9e est sensible \u00E0 l\u2019accumulation du micro-endommagement osseux." . . "Contr\u00F4le non destructif" . . . . . . . . "Microtomographie" . "Biom\u00E9canique" . "Os" . "Bone microdamage monitoring by nonlinear resonant ultrasound spectroscopy, towards quantitative measurements" . "2012" . . . .