Medical instrument for provisionally fastening a polyaxial pedicle screw

A medical instrument for provisionally fastening a polyaxial pedicle screw having a threaded shank having a shank head formed proximally thereon, on which shank head a holding sleeve is rotatably and/or pivotally arranged, a clamping plunger acting on the shank head being mounted in the holding sleeve, in such a way that the holding sleeve can be positionally fixed on the shank head by relative tensioning the holding sleeve and the clamping plunger, the instrument having a coupling unit for releasably engaging the holding sleeve and a pressure tappet for applying a pressing force to the clamping plunger in the distal direction, the coupling unit and the pressure tappet being movable relative to each other in an axial direction, wherein the instrument has a sleeve in which the coupling unit is arranged so as to be movable in the axial direction such that the coupling unit can be coupled to or uncoupled from the holding sleeve in a first axial position and is non-detachably fastened to the holding sleeve in a second axial position in order to implement a provisional fastening of the polyaxial pedicle screw with the pressure tappet,

• wherein the coupling unit has a radially inwardly projecting detent structure in a distal end region for coupling engagement with a mating detent structure of the holding sleeve provided therefor,
• wherein the coupling unit has at least one coupling arm extending in the axial direction, the distal end region of which can be positioned in a radial direction due to elastic deformation in the radial direction, and
• wherein the transition from the at least one coupling arm to the detent structure is formed such that a radially outer side of the detent structure projects radially outwards with respect to a radially outer side of the at least one coupling arm.