The acromiohumeral and coracohumeral intervals are abnormal in rotator cuff tears with muscular fatty degeneration.

UNLABELLED: We sought to determine how various types of full-thickness rotator cuff tears, fatty degeneration of the rotator cuff muscles, duration of symptoms, and mechanism of injury affect the sizes of the acromiohumeral and coracohumeral intervals. We studied 206 shoulders with rotator cuff tears that had surgical treatment. The acromiohumeral interval (anteroposterior radiograph) and the coracohumeral interval (computed tomogram) were measured on preoperative imaging studies. An abnormal acromiohumeral interval was associated with multiple-tendon rotator cuff tears involving the infraspinatus, fatty degeneration of the supraspinatus or infraspinatus, and duration of symptoms longer than 5 years. An abnormal coracohumeral interval was associated with a combined tear of the supraspinatus and subscapularis and fatty degeneration of the infraspinatus or subscapularis. Fatty degeneration of the infraspinatus therefore was associated with an abnormal acromiohumeral interval and an abnormal coracohumeral interval. Evaluation of a patient who has a diminished acromiohumeral or coracohumeral interval should involve examination with computed tomography or magnetic resonance imaging of the rotator cuff tendons to determine the type of tear and of the rotator cuff muscles to determine the degree of fatty degeneration. LEVEL OF EVIDENCE: Diagnostic study, Level II-1 (development of diagnostic criteria on basis of consecutive patients--with universally applied reference "gold" standard). See the Guidelines for Authors for a complete description of levels of evidence.