A new shoulder prosthesis is providing relief to patients who suffer from pain and limited function of their shoulder from arthritis, a rotator cuff injury or a previous shoulder replacement. Called a reverse shoulder prosthesis (RSP) or a "reverse ball and socket," the device works by reversing the usual positions of the ball and socket in the shoulder. Emory University is one of the few places in the Southeast performing this procedure, which can allow many patients to return to normal daily activities without the pain.
The shoulder is made up of a ball and socket joint, similar to a baseball glove holding a baseball. The ball consists of the head of the upper arm, while the socket consists of an indented area in the shoulder blade. In a typical total shoulder replacement surgery, a plastic liner or socket is attached to the shoulder blade and a metal ball replaces the head of the upper arm bone. Doctors then stabilize the new parts into the shoulder. While this procedure works well for many people, other alternatives are needed for more challenging injuries and cases.
Like its name implies, the reverse shoulder surgery reverses the position of the traditional shoulder prosthesis. "In this new procedure, we literally switch the locations of the ball and the socket," says Spero Karas, MD, assistant professor of orthopaedics, Emory University School of Medicine. "In the operating room, we replace the normal socket with a prosthetic sphere and the upper arm is replaced with an implant that has a socket in which the ball rests. This reverse positioning prevents the joint from dislocating, while improving the function of the surrounding muscles."
In all of these cases, the normal joint cartilage is worn away from arthritis, trauma or overuse. This cartilage erosion causes bone-on-bone contact, which results in significant pain.
Besides the ball and socket joint, the shoulder consists of the rotator cuff, which is made up of a small group of muscles and tendons that surround the shoulder joint. The rotator cuff helps lift and rotate the arm. It also helps to stabilize the ball of the shoulder in the socket. When the rotator cuff tears loose from the bone, range of motion and arm stability are severely affected and many patients experience intense pain.
"Some of the best candidates for the reverse shoulder surgery are people who have had a rotator cuff injury that has resulted in arthritis. Patients with a previous, failed shoulder replacement may also be candidates for the procedure," says Dr. Karas. "In particular, the reverse shoulder surgery helps the artificial joint to function when there is significant bone loss or when there is no working rotator cuff."
Dr. Karas goes on to say, "This is one of the most dramatic surgeries in the orthopaedics field today and an excellent alternative for many. Before surgery, these people often have pain scores of eight, nine or 10, with 10 being the most intense pain. After surgery, those pain scores drop to zero, one or two. Furthermore, it is common for patients who have not been able to lift their arm to get marked improvements in functional motion."
Patients who have the procedure usually spend one night in the hospital, followed by six weeks with their arm in a sling. Then patients go though six weeks of physical therapy. The FDA has recently approved the device. It has been used successfully in Europe for over 10 years.
Dr. Karas, a shoulder reconstructive specialist, is on the design team for the reverse shoulder prosthesis (a registered trademark by Encore Medical Corporation out of Austin, Texas). In addition to assisting with the implant design, he has done extensive clinical research on the device and currently teaches the surgical technique to physicians throughout the U.S. Dr. Karas also serves as a paid consultant to the company.