Every year, thousands of conventional total shoulder replacements are successfully
done in the United States for patients with shoulder arthritis. This type of surgery,
however, is not as beneficial for patients with large rotator cuff tears who have
developed a complex type of shoulder arthritis called "cuff tear arthropathy." For these
patients, conventional total shoulder replacement may result in pain and limited
motion, and reverse total shoulder replacement is a better option.
Description
A conventional shoulder replacement device mimics the normal anatomy of the
shoulder: a plastic "cup" is fitted into the shoulder socket (glenoid), and a metal "ball" is
attached to the top of the upper arm bone (humerus). In a reverse total shoulder
replacement, the socket and metal ball are switched. The metal ball is fixed to the
socket and the plastic cup is fixed to the upper end of the humerus.
In a healthy shoulder, the "ball" of the humerus is held in the shoulder socket by several
muscles and tendons, including the rotator cuff tendon.
A reverse total shoulder replacement works better for people with cuff tear arthropathy
because it relies on different muscles to move the arm. In a healthy shoulder, the
rotator cuff muscles help position and power the arm during range of motion. A
conventional replacement device also uses the rotator cuff muscles to function
properly. In a patient with a large rotator cuff tear and cuff tear arthropathy, these
muscles no longer function. The reverse total shoulder replacement relies on the deltoid
muscle, instead of the rotator cuff, to power and position the arm.
