The Role of the Long Head of the Biceps Muscle and Superior Glenoid Labrum in Anterior Stability of the Shoulder

TLDR

The study examined whether the long head of the biceps and its superior glenoid labrum attachment contribute to shoulder stability during overhead motion. A dynamic cadaveric shoulder model simulated rotator cuff and long head of biceps forces during abduction and external rotation. The long head of the biceps enhances anterior shoulder stability by resisting torsion during abduction and external rotation and reducing strain on the inferior glenoid ligament, whereas detachment of the superior glenoid labrum weakens this stability and increases ligament strain.

Abstract

The authors conducted a study to determine if the long head of the biceps muscle and its attachment at the superior glenoid labrum play a role in stability of the shoulder in an overhead position. Their study used a dynamic cadaveric shoulder model that simulated the forces of the rotator cuff and long head of biceps muscles as the glenohumeral joint was abducted and externally rotated. Their data suggest that the long head of the biceps muscle contributes to anterior stability of the glenohumeral joint by increasing the shoulder's re sistance to torsional forces in the vulnerable abducted and externally rotated position. The biceps muscle also helps to diminish the stress placed on the inferior gle nohumeral ligament. Detachment of the superior gle noid labrum is detrimental to anterior shoulder stability as it decreases the shoulder's resistance to torsion and places a greater magnitude of strain on the inferior gle nohumeral ligament.