Regional mechanical properties of the long head of the biceps tendon

Long head of the biceps tenodesis reliably relieves pain, and restores strength, stability, and normal appearance of the upper extremity in the event of biceps tendinopathies. Regional differences in tendon mechanics may provide surgeons with valuable guidance in the placement of the tenodesis repair construct. The purpose of this study was to compare the mechanical properties of the long head of the biceps tendon in three functional regions of the tendon: intra-articular (proximal), suprapectoral (middle), and subpectoral (distal).

Uniaxial tensile tests were performed on the long head of the biceps tendon segments to quantify the material and structural properties of the tendon. Material properties were obtained using dogbone-shaped specimens while structural properties were obtained using intact specimens where the clamp boundary conditions simulated the common "gold standard" tenodesis, the interference screw.

Elastic modulus for the supra- and subpectoral regions were significantly greater than the intra-articular region (P≤0.048). The tensile strength of the subpectoral region tended to be lower compared to all other functional regions (P=0.051). The failure mechanism for intact specimens was similar to that seen for interference screw fixation where tissue failure occurs due to tearing at the bone/tendon/screw interface.

The higher tensile strength of the suprapectoral region compared to the subpectoral region may make this a more desirable location for tenodesis placement based on tissue strength. Similar elastic moduli and structural stiffness between the supra- and subpectoral regions indicate that the construct type may play a bigger role in functional outcomes in relation to construct deformation.