Which statement best differentiates anatomic total shoulder arthroplasty from reverse total shoulder arthroplasty?

• A. RTSA uses native glenoid cavity and rotator cuff.
• B. Anatomic relies on native glenoid cavity and intact rotator cuff; RTSA uses reversed ball-and-socket to rely on deltoid; indicated for cuff tear arthropathy; changes center of rotation and deltoid mechanics.
• C. RTSA is indicated for intact rotator cuffs.
• D. Anatomic uses reversed ball-and-socket design.

Answer: (B)

The main idea is how the two implants achieve shoulder function with different joint geometry and soft-tissue reliance. In anatomic total shoulder arthroplasty, the native glenoid is preserved and a conventional ball-and-socket joint is used. The success of this setup hinges on a healthy rotator cuff to center the humeral head and control movement, so having an intact rotator cuff is essential.

In contrast, a reverse total shoulder arthroplasty swaps the ball and socket: a glenosphere on the glenoid side and a humeral cup on the humerus side. This reversed configuration shifts the center of rotation medially and inferiorly, which changes the mechanics of the joint and makes the deltoid the primary driver of elevation, rather than the rotator cuff. This design is especially useful when the rotator cuff is torn or irreparable, such as cuff tear arthropathy.

So the statement that best differentiates them aligns with the idea that anatomic relies on the native glenoid and an intact rotator cuff, while reverse uses a reversed ball-and-socket to rely on the deltoid, is indicated for cuff tear arthropathy, and alters the center of rotation and deltoid mechanics.