An extractable device is used to insert a flowable material into a vertebral body. The device comprises a filling member and a flowable material. The filling member is made of a flexible wall which includes a holding portion and an injection port via which the flowable material is injected into the holding portion after insertion into the vertebral body. The holding portion is provided with an opening which is releasably closed by a closure device so as to make the opening substantially resistant to the passage of material there through. Once the flowable material in the holding portion increases in viscosity, the closure device is released, thereby enabling the filling member to be extracted from the vertebral body so as to leave only the material in the vertebral body. The flowable material should be a material capable of setting to a hardened condition.
