There are two basic types of shoulder replacement. Both replace the ball at the top of your upper arm and provide a socket for your upper arm bone to fit into. The main difference between them is how they attach the ball to your arm bone (humerus). One type, a cemented shoulder replacement, has a metal stem that’s attached to your humerus bone with cement. The other type, which is called an uncemented or press-fit shoulder replacement, has a ball that fits into your upper arm bone without using cement.