Similar to a Total Shoulder Arthroplasty, a reverse total shoulder arthroplasty involves replacing the natural surfaces of the arm bone (humerus) and cup side of the shoulder (glenoid). However, excessive wear of the bony surfaces or deficiency of the rotator cuff muscles can lead to a painful, dysfunctional shoulder that cannot be restored using components that restore natural anatomic position. In these cases, a reverse shoulder replacement can be used, placing a ball on the cup side of the joint and a cup on the ball side of the joint. See the video below to watch the surgical procedure.
The ball placed on the cup side requires far less bone to achieve adequate fixation than an anatomic shoulder replacement, so it can be used in cases of more severe bone loss or deformity of the glenoid. Reverse shoulder replacement also allows the shoulder to function using the deltoid instead of the rotator cuff, allowing patients with irreperable rotator cuff tears or rotator cuff atrophy to regain a considerable amount of motion.