What distinguishes an anatomic TSA from a reverse TSA?

An anatomic total shoulder arthroplasty (TSA) is designed to closely mimic the natural anatomy of the shoulder joint. In this procedure, both the humeral head and the glenoid are preserved, meaning that the original components of the joint are maintained as much as possible. This preservation allows the anatomic TSA to provide a more normal range of motion and functioning that aligns with the body's natural mechanics.

In contrast, reverse TSA involves altering the configuration of the shoulder joint. This procedure typically removes the native humeral head and replaces it with a prosthetic component that is positioned in a manner to improve stability and function, particularly in cases where the rotator cuff is compromised.

Thus, the distinguishing feature of anatomic TSA is that it maintains the native components of the shoulder, allowing for a more natural operation, which is why the answer highlights that it preserves the native glenoid and humeral head. This differentiation is fundamental in understanding how each type of shoulder replacement addresses specific anatomical and functional needs based on the patient's condition.