THE ROLE OF THE LONG HEAD OF THE BICEPS MUSCLE AND SUPERIOR GLENOID LABRUM IN ANTERIOR STABILITY OF THE SHOULDER

The authors conducted a study to determine if the long head of the bic eps muscle and its attachment at the superior glenoid labrum play a ro le in stability of the shoulder in an overhead position. Their study u sed a dynamic cadaveric shoulder model that simulated the forces of th e rotator cuff and long head of biceps muscles as the glenohumeral joi nt was abducted and externally rotated. Their data suggest that the lo ng head of the biceps muscle contributes to anterior stability of the glenohumeral joint by increasing the shoulder's resistance to torsiona l forces in the vulnerable abducted and externally rotated position. T he biceps muscle also helps to diminish the stress placed on the infer ior glenohumeral ligament. Detachment of the superior glenoid labrum i s detrimental to anterior shoulder stability as it decreases the shoul der's resistance to torsion and places a greater magnitude of strain o n the inferior glenohumeral ligament.