A coupling assembly for connecting a rod to a bone fixation element, a polyaxial bone fixation device, a modular polyaxial bone fixation device, and a modular stabilization device
A coupling assembly is provided comprising a receiving part (6) having a first end (6a), a second end (6b)and a central axis (C) extending through the first end and second end, a recess (62) for receiving a rod (100,101), and an accommodation space (61a,61b) for accommodating a head (3) of an anchoring element (1), the accommodation space having an opening (72) at the second end (6b) for inserting the head (3), a pressure element (7,7') configured to be positioned at least partly in the accommodation space, the pressure element having a first end (7a) and a second end (7b), wherein the second end (7b) is configured to be positioned closer towards the second end (6b) of the receiving part than the first end (7a), and a flexible portion (74,75,76,77) to clamp an inserted head (3)； wherein the flexible portion (74,75,76,77) comprises a hollow interior chamber (71) for accommodating a head of a bone anchoring element therein； a rod receiving element (8,8') that is a separate part comprising a groove (81) for supporting an inserted rod (100,101)； characterized in that the pressure element (7,7') further comprises at least one spring portion (79a,79b), the spring portion extending over a length in circumferential direction around the central axis (C) and being compressible in a radial direction； wherein the spring portion (79a, 79b) is configured to engage an engagement structure (65,66,67) at an inner wall of the receiving part (6) to be prevent movement of the pressure element towards the first end of the receiving part.
