Centering the humerus in the glenoid
The glenoid suction cup stabilization mechanism is easily demonstrated in young cadaver shoulders in which the articular cartilage glenoid labrum and joint capsule are compliant. The magnitude of this stabilizing effect has not been measured.
Like stabilization from adhesion-cohesion the glenoid suction cup centers the head of the humerus in the glenoid without muscle action and is effective in midrange positions in which the capsule and ligaments are not under tension. The suction cup mechanism is disrupted in situations where the socket cannot seal to the surface of the humeral head such as an avulsion of the glenoid labrum or glenoid fracture.
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Glenoid-labrum suction cup and adhesion-cohesion forces  |
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