Abstract: The present invention concerns a guiding, positioning and boring sensor, comprising a flexible shaft mounted in rotation and axially displaceable in a flexible sheath presenting an external diameter substantially smaller than the minimum diameter of the transverse cross section of the cavity defined in the intramedullary nail, the flexible shaft bearing at a distal end a boring head and at its proximal end a connecting device to a rotary motor whereas the sheath is integral through its distal end to a guiding and positioning unit provided with an internal passage that is connected to the bore of the sheath and presents a transverse cross-section identical to that of the bore.