A cup and a temporary insert are respectively configured to be tightly press fitted into each other along their periphery. The temporary insert includes a through hole communicating outside with a free space between the outer surface of the temporary insert and the inner surface of the cup. In the through hole can be engaged the threaded end of an impactor, for manipulating the cup when it is being set. A syringe can be engaged, enabling a liquid under pressure to be injected into the free space, thus separating the temporary insert from the cup without any risk of damaging the inner surface of the cup. Thus, the cup can be securely manipulated when it is being set without any risk of damaging the inner surface of the cup.