What is the center of rotation (COR) of the humeral head defined as biomechanically?

The center of rotation (COR) of the humeral head, in biomechanical terms, is defined as a fixed point with zero velocity. This concept is essential in understanding how the shoulder joint functions during movement.

When the humerus rotates around the COR, it maintains a consistent pivot point that allows the arm to move smoothly with respect to the shoulder girdle. This fixed point ensures that the forces acting on the shoulder joint are managed effectively, facilitating controlled movement without generating excessive strain on the surrounding soft tissues, ligaments, and tendons.

Understanding that the COR is a fixed point with zero velocity helps clinicians and surgeons appreciate how a proper alignment during shoulder arthroplasty can positively impact the patient's range of motion and overall joint mechanics. If the COR shifts or does not maintain this characteristic during motion, it could lead to complications such as impingement or instability in the shoulder joint.

In this context, recognizing the importance of the COR is vital for successful surgical outcomes and rehabilitation protocols following total shoulder arthroplasty.