Coupling assembly for coupling a rod with an anchoring bone element, the coupling assembly comprising a receiving part (5, 5 ') having a first end (5a), a second end (5b) and a central axis (C) extending through the first end (5a) and the second end (5b), a recess (52) to accommodate a rod (100), the recess presenting a bottom, and an accommodation space (54, 54 ') for accommodating a head (3) of an anchoring element (1), the accommodation space having an opening (55, 55 ') at the second end (5b) sized to allow the insertion of the head (3) and a hole that extends from the accommodation space to the first end (5a), a retaining element (6, 6 ') configured to be placed at least partially in the accommodation space (54, 54') and sized to surround at least partially, a head (3) inserted； characterized in that the retaining element (6, 6 ') comprises at least one spring-shaped part (66a, 66b； 66') that can be compressed in an axial direction and extending in an axial direction at least to a position towards the first end (5a) of the receiving part that is higher than the bottom of the recess (52) for the rod.Conjunto de acoplamiento para acoplar una varilla con un elemento óseo de anclaje, comprendiendo el conjunto de acoplamiento una parte receptora (5, 5') que presenta un primer extremo (5a), un segundo extremo (5b) y un eje central (C) que se extiende a través del primer extremo (5a) y el segundo extremo (5b), un entrante (52) para alojar una varilla (100), presentando el entrante un fondo, y un espacio de acomodación (54, 54') para acomodar una cabeza (3) de un elemento de anclaje (1), teniendo el espacio de acomodación una abertura (55, 55') en el segundo extremo (5b) dimensionada para permitir la inserción de la cabeza (3) y un taladro que se extiende desde el espacio de acomodación hasta el primer extremo (5a), un elemento de retención (6, 6') configurado para ser colocado al menos parcialmente en el espacio de acomodación (54, 54') y dimensionado para rodear, al
