A device for treating fractures of the femur and includes an intra-medullary pin (1) with a central longitudinal axis (2), a front piece (3), which is introduced into the medullary channel of the femur, a rear piece (4) and a hole (5) going through the rear piece (4) at an angle to the longitudinal axis (2) with a non-circular cross-section (6). A sliding sleeve (10) that is introduced through the hole (5) with non-circular cross-section, has a front end (11), a rear end (12), a central longitudinal drilling (13), an outer sleeve surface (14), an inner sleeve surface (15) and a longitudinal axis (16). A longitudinal bone fixation element (20) with a longitudinal axis (21), a head piece (22) with fixation element (23), which is brought into engagement with the femur head on use and a shaft (24), which is introduced co-axially into the sliding sleeve (10), whereby the outer sleeve surface (14) of the sliding sleeve (10) has a non-circular cross-section (17), at least in a partial region. The inner sleeve surface (5) of the sliding sleeve (10) has a round cross-section (18) and fixation elements (30) are provided for the selective blocking of the rotation of the longitudinal bone fixation element (20) in the sliding sleeve (10).