A standard total shoulder replacement depends upon muscles and tendons around the shoulder joint to be intact. These muscles and their tendons function to move the shoulder and are together called the rotator cuff. When these tendons become extensively torn so that they do not attach to the bone any longer, the shoulder often does not function normally. The loss of the rotator cuff can produce pain and also loss of motion. A normal shoulder replacement is designed to work only if those tendons are intact.
Reverse Shoulder Replacement (Arthroplasty) has emerged as a very attractive alternative for patients with cuff-tear arthropathy, selected proximal humerus fractures and nonunions. Its indications continue to expand, especially for revision surgery.
Without an intact rotator cuff, the ball can ride high in the socket and wear abnormally, creating abnormal contact forces across the joint. Over time this leads to 'cuff-tear arthropathy.' In the later stages of a cuff tear, the patient develops arthritis in the shoulder and the result is constant pain, weakness and lack of function. The pain is so severe that patients suffering from cuff-tear can't sleep at night; they can't do their activities of daily living. They get depressed about their shoulder and it's affecting everything about what they do and who they are.
Reverse or Inverse Total Shoulder Arthroplasty (RTSA) is designed specifically for the treatment of glenohumeral (GH) arthritis when it is associated with irreparable rotator cuff damage, complex fractures as well as for a revision of a previously failed conventional Total Shoulder Arthroplasty (TSA) in which the rotator cuff tendons are deficient.
Like standard shoulder replacement surgeries, the arthritic joint surfaces are replaced with a highly polished metal ball attached to a plastic socket. But in the reverse procedure, the socket and metal ball are switched. The reverse procedure constrains the ball in a cup that is inserted into the end of the humerus and the metal ball is attached to the shoulder bone. This allows the patient to use the healthier, stronger deltoid muscle instead of the torn rotator cuff to lift the arm.
Anyone who has a condition that predisposes them to an infection is a poor candidate for RTSA. That may include patients with diabetes, someone who is on an immunosuppressant, or someone with rheumatoid arthritis. And because of the need to affix the prosthesis to the shoulder, patients with poor bone quality are also poor candidates.
The prosthesis system used for Reverse Shoulder Replacement are the opposite of the system used in standard shoulder replacement. In this socket and metal ball are switched as shown in the image below.
