How Does It Work?

The shoulder is the most mobile joint in the body. The shoulder joint is similar to a ball-and-socket joint but more closely resembles a golf ball on a tee. The rotator cuff provides the stability – keeping the golf ball on the tee.

The shoulder joint is comprised of three main bones: the collarbone (clavicle), the shoulder blade (scapula) and the upper arm bone (humerus). The glenoid (part of the scapula) and humeral head (part of the humerus) are normally the parts of the shoulder that have to be replaced because they rub together when you move your arm. In a healthy shoulder, these portions of bone are covered with cartilage, which allows for painless motion—lifting, pushing and pulling. But arthritis can damage this protective cartilage, which makes these motions painful.

Arthritis is one of the most common conditions that causes wear and tear to your joint cartilage and develops after years of constant motion and pressure on the joints. If non-surgical treatment options such as medication, physical therapy or lifestyle changes fail to provide relief, your surgeon may recommend shoulder replacement surgery.

Primary Shoulder Replacement

Shoulder replacement surgery replaces the damaged part of your shoulder to recreate the natural contours of the bones in a healthy shoulder. Sometimes, only the ball is replaced (hemiarthroplasty), while other times, both the ball and socket are replaced (total shoulder arthroplasty). The ball is usually metal and the socket is usually plastic.

During surgery, an incision is made in the front of the shoulder. Once your surgeon exposes your shoulder joint, the surgeon will remove the damaged bone and cartilage. The head of the humerus is then removed and a metal stem is placed into the humeral canal. This provides a stabilizing anchor for the head.

Reverse Shoulder Replacement

If you have a massive, irreparable rotator cuff tear and arthritis, your surgeon may opt to perform a reverse shoulder replacement. The rotator cuff is a group of muscles and tendons that surround the shoulder in order to keep the humerus centered while performing shoulder-related tasks such as lifting the arm. When a rotator cuff tears, the muscles lose their ability to keep the humerus centered on the glenoid, causing your humerus to move upward and out of the socket. This instability, combined with arthritis or a previous shoulder injury, can cause severe pain and loss of function.

In this procedure, the anatomy of the shoulder is reversed by attaching a metal ball (glenosphere) to the glenoid and the plastic socket (humeral liner) to the upper humerus.