Intratendinous strain fields of the supraspinatus tendon: effect of a surgically created articular-surface rotator cuff tear.

Articular-surface partial-thickness rotator cuff tears play a significant role in shoulder pathology, but the role of the articular-surface tissue is poorly understood. This investigation assessed the effect of an articular-surface partial-thickness rotator cuff tear on intratendinous strain fields. A magnetic resonance imaging-based technique quantified intratendinous strains in healthy cadaveric shoulders at 15 degrees, 30 degrees, 45 degrees, and 60 degrees of glenohumeral abduction. A second set of magnetic resonance images was acquired after an articular-surface partial-thickness tear was created arthroscopically. Measures of strain were grouped into 3 tendon regions. A 3-factor analysis of variance assessed the effects of joint position, tendon region, and tendon tear. Intratendinous strains were influenced significantly by joint position, but few differences existed between tendon regions. The articular-surface partial-thickness tear increased intratendinous strain for all joint positions except 15 degrees. The results lend insight into the mechanical behavior of the normal and pathologic rotator cuff.