A fixation assembly 10 for securing parts of a sternum is provided. The assembly 10 comprises a first section 12 having a first attachment structure 22 for securing the first section 12 to a first sternum part, a second section 14 having a second attachment structure 26 for securing the second section 14 to a second sternum part, a mating arrangement 32 defining a mating direction and a predetermined relative position between the first and second sections 12, 14 in a plane perpendicular to the mating direction, and at least one holding member 16 for detachably holding the first and second sections 12, 14 in an abutting relationship in the predetermined relative position. This may be achieved in one variant by simultaneous engagement of the first and second sections 12, 14 substantially along the mating direction.