Massive irreparable rotator cuff tears: how to rebalance the cuff-deficient shoulder.

In its natural state, the shoulder is unbalanced in both the vertical and horizontal planes because the deltoid is stronger than the rotator cuff muscles and the internal rotator muscles are stronger than the external rotator muscles. With aging, this muscle imbalance can become worse, leading to tendon wear, irreversible fatty infiltration of the rotator cuff muscles, and upward migration of the humeral head. Most shoulders with tendon wear are functional and asymptomatic.