Arthroplasty IOT Training Practice Test

The main distinction lies in how the joint mechanics are restored. A reverse total shoulder reverses the ball-and-socket geometry so the glenoid side bears a ball and the humeral side has a socket. This configuration medializes and lowers the center of rotation, which makes the deltoid the primary driver of arm elevation and provides stability when the rotator cuff is deficient. Anatomic total shoulder preserves the native ball-and-socket anatomy and relies on a functional rotator cuff to center the humeral head on the glenoid; without a working rotator cuff, the anatomic design cannot compensate as RTSA can. So the best statement captures that RTSA depends on the deltoid and changes the center of rotation, while anatomic TSA relies on the native rotator cuff.