The invention relates to an automatic device for the insertion of a stylet and cannula to a predefined depth α within a bone, said depth α being irrespective of the thickness of the tissue above the bone, which comprises: (a) a trigger unit for activating the device (b) a barrel (c) a probe unit within said barrel which is driven by a secondary spring, said probe unit comprises one or more probing needles at a distal end, and an anvil at a proximal end for defining an end of movement location for a hammer unit (d) a hammer unit which is driven by a main spring, said hammer unit comprises a stylet at its distal end, a core at its proximal end, and a piston in between said core and stylet, wherein said stylet is inserted to within a cannula, and wherein when said hammer unit is positioned at said end of movement location, a tip of the stylet which is longer than said one or more probing needles is located a distance α farther to the distal direction from the respective ends of said probing needles and (e) one or more grasping units wherein activation of said trigger unit follows by, (f) release of said second spring which in turn pushes said probing needles of said probe unit toward the patients bone, up to a point of contact with the bone surface (g) grasp of the anvil of said probe unit by said grasping units, when said contact of the probing needles with the patients bone occurs and (h) release of said main spring, which in turn pushes said hammer unit up to said end of movement location, thereby inserting said cannula to a depth of α within the patients bone.
