The objective of the present study was to elucidate, in the framework of a biomechanical model, the biomechanical prerequisites for the development of osteodystrophic changes in stirrup bones in the case of their osteodystrophic fixation. The comparative analysis of the biomechanical models of mobile and ankylotic stapes demonstrated that the mild enough strain-stress state under the normal conditions turns into the rigid state in otosclerosis. The main dampher in case of load application to the adequately mobile stapes footplates is the round ligament. If the stapes footplates are fixed in the oval window of the labyrinth the conditions for the functioning of this bone change drastically. Variations of the strain-stress state of the ankylotic stapes footplates undergoing the acoustic impact promotes the development of dystrophic processes in the bone structures in response to the altered conditions of functioning and the appearance of supraphysiological strains and stresses.