The invention relates to a device for linking a longitudinal support (11) with a bone or a bone fragment. The inventive device comprises the following elements: A) a bone fixation device (1) with a lower part (3) to be immobilized on a bone and an upper part (2) to be linked with a longitudinal support (11); and B) a locking ring (15) that can be coaxially displaced on the upper part (2) and that is provided with a center bore (22) having a diameter d; C) the upper part (2) comprises a channel (12) that is open at the upper end (13) of the upper part (2) and that has a channel axis (21) for receiving a longitudinal support (11) running at an angle to the longitudinal axis (5) and two tongues (19) that can be elastically deformed at an angle to the channel axis (21); D) the locking ring (15) can be displaced into a first position in which the two tongues (19) can be forced against the channel axis (21); and E) the upper part (2) comprises between its lower end (14) and the channel (12) a groove (8) having a core diameter DK1 and being concentric to the center axis (5), the core diameter DK1 of the groove (8) being smaller than the diameter d of the center bore (22) in the locking ring (15).