Your shoulder is made up of three bones:
your upper arm bone (humerus), your shoulder blade (scapula), and your
collarbone (clavicle). The shoulder is a ball-and-socket joint: The ball, or
head, of your upper arm bone fits into a shallow socket in your shoulder blade.
This socket is called the glenoid.
In shoulder replacement surgery, the damaged parts of the
shoulder are removed and replaced with artificial components.
The
treatment options are either replacement of just the head of the humerus bone
(ball), or replacement of both the ball and the socket (glenoid).