A total shoulder replacement (total shoulder arthroplasty) treats severe shoulder pain and dysfunction, typically caused by arthritis or major injury. The surgery replaces the damaged ball and socket joint with artificial components made of metal and plastic. Because the shoulder is surrounded by a complex network of muscles, the surgical process must carefully manage these tissues to gain access to the joint while preserving movement and strength.
Understanding the Standard Surgical Viewpoint
The standard approach for an anatomic total shoulder replacement, used when rotator cuff tendons are healthy, is the Deltopectoral approach. This method is preferred because it utilizes a natural cleavage plane between two large muscles, minimizing the need to cut major power-generating tissues. The approach identifies the interval between the deltoid muscle (the rounded contour of the shoulder) and the pectoralis major muscle (the large chest muscle). Surgeons retract these muscles—the deltoid laterally and the pectoralis major medially—to gain reliable access to the front of the shoulder joint.
The Primary Muscle Incised During Replacement
To reach the joint capsule and replace the ball and socket, the surgeon must address one of the four rotator cuff muscles. The primary muscle released during a standard total shoulder replacement is the Subscapularis. This large, fan-shaped muscle originates on the shoulder blade and attaches to the front of the humerus. The Subscapularis functions as the shoulder’s main internal rotator, responsible for movements like reaching across the body.
To gain the necessary exposure, the surgeon must release the Subscapularis tendon from its attachment point on the humerus, known as the lesser tuberosity. This release is performed either through a controlled cut in the tendon (tenotomy) or by peeling the tendon off the bone (subscapularis peel).
Once the replacement components are secured, a meticulous repair of the Subscapularis tendon is performed to reattach it to the bone. Successful healing of this repaired tendon is important for achieving good long-term function and stability of the new joint. While the Subscapularis is temporarily detached, the Deltoid and Pectoralis Major muscles are typically only retracted and not cut.
Muscle Handling in Reverse Shoulder Surgery
Reverse total shoulder replacement is used when the rotator cuff is irreparably torn or dysfunctional. In this procedure, the ball and socket components are reversed, shifting the shoulder’s biomechanics. This reversal allows the Deltoid muscle to take over the primary function of lifting the arm, compensating for the damaged rotator cuff.
While the Deltopectoral interval may still be used, the focus shifts away from Subscapularis repair. Since the procedure relies on the Deltoid muscle for movement, the Subscapularis is often simply released or managed differently. The hardware placement effectively doubles the lever arm of the Deltoid, allowing it to become the main elevator and positioner of the arm.
Restoring Strength Through Rehabilitation
Following total shoulder replacement, the success of the procedure depends heavily on allowing the surgically handled muscles and tendons time to heal. For a standard replacement, the repaired Subscapularis tendon requires a period of protected healing, which typically involves wearing a sling for several weeks. During this initial phase, the patient is restricted to passive range of motion exercises. This means the arm is moved by a therapist or the non-operative hand, preventing the newly repaired tendon from being strained.
The next phases of rehabilitation gradually introduce active range of motion, where the patient begins to move the arm using their own muscles. Strengthening exercises, usually beginning around three months post-surgery, are then introduced to restore the power of the deltoid and other surrounding muscles. This structured, multi-phase physical therapy is designed to ensure the Subscapularis heals securely before it is subjected to significant load.