An extractable device is used to insert a medicinal filling into a spinal disc. The device comprises a filling member and a flowable medicine. The filling member is made of a flexible and permeable wall and is provided with a holding portion and an injection port via which the flowable medicine is injected into the holding portion after the filling member is inserted into the spinal disc. The holding portion is provided with an opening which is releasably lashed by one end of one or more threads so as to make the opening leakproof. Upon completion of solidification of the flowable medicine in the holding portion of the filling member, other end of the thread is pulled to unlash the opening of the holding portion, thereby enabling the filling member to be extracted from the spinal disc so as to leave only the medicine in the spinal disc.