In shoulder replacement surgery, the damaged parts of the shoulder are removed and replaced with artificial components, called a prosthesis. 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).
Your shoulder is a ball and socket-type joint made up of two main parts: the glenoid (socket) and the humerus (upper arm bone, which makes up the ball). It is therefore known as the glenoid-humeral joint. When arthritis affects the shoulder it causes the lining of these joint surfaces to wear, causing pain and stiffness. During a total shoulder replacement, both the head of the humerus and the socket are replaced with artificial surfaces (metal and plastic).
Replacing the worn surfaces with replacement surfaces (prostheses) will reduce your pain and increase the range of movement available from your shoulder joint.