an implantable medical device comprising an implant body intended to be attached to a bone of a subject and at least one reflector coupled to the implant body, said reflector being configured to reflect an electromagnetic signal, and being embedded in a surrounding tissue of the subject when the implant body is attached to the bone of the subject,

a parameter representative of the structure of the bone of the subject is computed from a reflected signal corresponding to a reflection, on the reflector embedded in the surrounding tissue of the subject, of an excitation signal comprising at least one frequency in a characteristic frequency range of the reflector,

wherein said reflected signal is correlated either directly or indirectly to at least one electrical property variation of the surrounding tissue,

wherein the reflector is positioned along an internal face of an internal recess of the implant body,

wherein the implant body is an intervertebral implant positioned between two adjacent vertebral bodies.