Anchoring device polyaxial bone, which includes: an anchoring element (1) provided with a stem (2) to be anchored in the bone and a head (3), the head having a part spherical outer surface including a maximum outside diameter (E) a receiver (5) member having an upper end (5a) and a lower end (5b), a channel (12) for receiving a rod therein, a bore (51) extending from the upper end (5a) towards the lower end (5b), the bore having an axis (C), and a seat (52) to receive the head at the lower end, said seat (52) spherical a pressure element (6) disposed within the bore of the head, with the pressure element (6) a surface portion of head contact (62, 63) which contacts the outer surface part spherical head (3), including the surface portion of head contact at least two circumferentially distinct projections (63) extending along an area of the head including the maximum outer diameter (E) in the axial direction rotatable head (3) relative to the receiving part (5) and can be fixed at a specified pressure on it through the pressure element (6), characterized in that, before putting it on the head (3) , the pressure element (6) has a smaller size relative to the head (3) only in an area of the projections (63) including a spherical section (63b) with an inner diameter (D2) which is smaller than the maximum diameter (E) of the head, and in which at least one spherical portion (63b) extends over the area with the maximum diameter (E) of the head (3) so that when the pressure element is placed on the head, it is held by friction between the spherical outer surface portion and the projections, and the projections extending at least partly within an accommodation space (55) provided in the receiving part.Dispositivo de anclaje de hueso poliaxial, que incluye lo siguiente: un elemento de anclaje (1) provisto de un vástago (2) para anclarlo en el hueso y de una cabeza (3), presentando la cabeza una parte de superficie exterior esférica que incluya un diámetro exterior máximo
