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. A traumatic event (such as a fall onto the upper limb) can lead to rotator cuff tearing and a shoulder that becomes symptomatic and nonfunctional. Symptomatic massive irreparable rotator cuff tears present in one of four recognizable patterns depending on the muscular imbalance that occurs and the symptoms that are present: painful loss of active elevation, with conserved muscle balance; isolated loss of active elevation, with loss of vertical muscle balance; isolated loss of external rotation, with loss of horizontal muscle balance; and combined loss of elevation and external rotation, with loss of vertical and horizontal muscle balance. Assessing the plane of shoulder muscle imbalance is a key feature in the decision-making process. Classifying and understanding these tears allows surgeons to select the correct treatment (conservative measures, arthroscopic techniques, reverse shoulder arthroplasty, or tendon transfers) to restore shoulder balance and function.