An assembly for connecting a support element to a bone. The assembly comprises: a bone screw having a head at one end of a threaded shaft; and a clamp comprising: a base at a first end of the clamp delimiting an opening for receiving the head of the bone screw; and at least two side members extending from the base towards a second end of the clamp. The head of the bone screw and the clamp are configured to allow the head of the bone screw to be inserted into the base from the direction of the first end at a first orientation of the base to the bone screw, and to retain an inserted bone screw within the base at a second orientation of the base relative to the bone screw.This allows the screw to be inserted into the bone without requiring prior assembly of the screw and clamp. It also allows later revision whereby the clamp can be removed from the screw without requiring an implanted screw to be removed from the bone.