This PhD dissertation examines the role of management devices in the evolution of organizational practices. The author relies on the case of a French public hospital, where a new managerial model has been implemented: medico-economic divisions were created, headed by a doctor, and associated with ad hoc management instruments (income statements and budget). The author recalls the ideological origins and the difficulties linked with the implementation of a new managerial model, in an organization such as a public hospital. Then she recalls how management tools have been studied throughout the management science literature. Finally, the author adopts a sociomaterial perspective as a theoretical framework for interpreting the role of instruments in organizations. From this perspective, instruments are deeply entangled and are co- constitutive of the physical and social context in which they are being performed. Building upon interviews and observation of practices, this work examines how these instruments are produced and used by the administrative managers, and by the doctors heads of the medico-economic divisions. In particular, three levels of instrument practices are confronted: the canonical practices as described in the management control literature; the official practices as enounced in the actors' interviews; and the observed practices, as can be inferred from the observation of everyday work. The author shows that instruments can be used in very different ways within the organization, depending on the sociomaterial assemblage upon which they are performed. And she wonders about the instrument's capacity of constraint, through the concept of affordances.
