Biceps Mechanical Properties Are Not Altered in the Presence of Asymptomatic Rotator Cuff Tendon Tears

Introduction The long head of the biceps (LHB) tendon has different loading patterns in its intraand extra-articular regions. The intra-articular region is exposed to complex loads including tension, compression, shear, and frictional forces, while the extra-articular portion is subjected primarily to tensional loads. Previous studies have also shown that the intra-articular region has a more disorganized collagen organization and higher proteoglycan content than the extra-articular region, and may be more prone to increased pathology with decreased healing potential. However, the mechanical properties in each of these regions have not been evaluated. In addition, degenerative changes in the LHB often occur secondary to rotator cuff tendon pathology and the incidence of LHB pathology is correlated with the size and severity of rotator cuff tendon tears. However, the effect of rotator cuff tear size on the mechanical properties of the human biceps tendon is not known. Therefore, the objectives of this study were to: 1) characterize the mechanical properties along the length of the human LHB tendon and 2) investigate the changes on the LHB tendon in the presence of an isolated supraspinatus (supra only) and combined supraspinatus-infraspinatus (suprainfra) rotator cuff tears. We hypothesized that: H1) in normal shoulders, the properties of the LHB tendon will vary along the length due to different environments and H2) in the presence of rotator cuff tears, the LHB tendon will have inferior mechanical properties, with greater damage seen with increasing rotator cuff tear severity.