A system for use in a wellbore, comprises a length of casing, a structure that is configured to deform with deformation of the casing, said structure being affixed to the length of casing at substantially the same radial position along the length of casing, and a sensing device that is configured to measure deformation of the structure, said device comprising a plurality of sensors that are distributed with respect to at least one of the length of said structure and the periphery of said structure.