The shoulder joint is a complex structure that allows for a wide range of arm motion and strength. It is the most mobile and flexible joint in the body. To allow this mobility the shoulder has a large humeral head (ball) which forms a joint with a small flat glenoid (socket), a bit like a golf ball on a tee. As a result, the shoulder is vulnerable to injury, particularly instability.
The head of the humerus is normally held firmly in place in the glenoid by ligaments that connect the humerus to the shoulder blade, rotator cuff tendons that connect the muscles of the shoulder blade to the humerus, and a rim of cartilage (labrum) that encircles the glenoid, increasing the depth of the socket.
Shoulder instability is a very common problem in the young athletic population. This results when the shoulder has come out of joint (dislocation) or tried to come out of joint (subluxation), usually following a traumatic injury. As a result, there is often damage that occurs to the supporting structures of the shoulder, most commonly the labrum and attached ligaments. This can then result in recurrent episodes of instability, which not only cause pain and disability, but can result in progressive damage to the shoulder joint.
Treatment Options for Shoulder Instability
Because the torn labrum and ligaments do not heal by themselves non-operative treatment is generally not successful in preventing recurrences, especially in the young athletic population. It aims to restore range of motion in the shoulder and strengthen the rotator cuff and scapula muscles (dynamic stabilisers) so that they can better assist with stability and control. Although this form of treatment may be effective in patients with low physical demands, it rarely results in long term stability for younger more active patients who require the support provided by the damaged structures (static stabilisers).
When conservative treatment options fail to relieve shoulder instability, your surgeon may recommend shoulder stabilization surgery. Shoulder stabilization surgery is performed to improve the stability and function of the shoulder joint and prevent recurrent dislocations.
The primary aim of surgery is to restore shoulder stability and function by repairing the damaged structures back to where they should be. This is done by using little absorbable ‘suture anchors’ which are inserted into the glenoid. The sutures from these anchors are then used to attach the ligaments and labrum back to the bone. The procedure normally takes from 60 to 90 minutes and is most commonly done through keyholes (arthroscopic). If there has been damage to the bone of the glenoid from multiple instability events, then occasionally a bone graft has to be performed to restore bone support. This is done through a small cut over the front of the shoulder.
Anterior shoulder instability, also known as anterior glenohumeral instability, is a condition in which the head of the humerus (upper arm bone) is able to dislocate or sublux from the glenoid fossa (socket), compromising the function of the shoulder. Dislocation is where the ball comes completely out of the socket and often needs to be reduced (manipulated) back into position. Subluxation is where the ball only partially comes out of the joint and then spontaneously reduces.
Instability may be described by the direction in which the humerus is subluxated or dislocated from the glenoid. When it occurs in several directions it is referred to as multidirectional instability. There may be one predominant direction of instability, but in this condition the ball can move in multiple planes. It is often associated with ligamentous laxity of the joint (loose ligaments around the shoulder).