Final answer:
The center of rotation in a reverse total shoulder arthroplasty is moved medially and inferiorly, altering the shoulder mechanics and utilizing the deltoid muscle for improved arm elevation in cases of rotator cuff deficiencies.
Step-by-step explanation:
In a reverse total shoulder arthroplasty, the center of rotation is moved medially and inferiorly relative to a native shoulder. This adjustment changes the mechanics of the shoulder to allow for improved function in patients with rotator cuff deficiencies. By moving the center of rotation medially (towards the midline of the body), and inferiorly (downwards), the deltoid muscle becomes more effective in elevating the arm, as it compensates for the deficient rotator cuff.
The relocation of the center of rotation is a critical concept in reverse total shoulder arthroplasty that ensures the prosthesis can utilize different muscles to maintain shoulder function. This is unlike the natural anatomy where the rotator cuff muscles play a significant role in stabilizing the shoulder joint and facilitating movement.