Dislocated Shoulder & Shoulder Instability
by Dr Marcus Chia - Shoulder and Elbow Surgeon
The shoulder is one of the most mobile joints in the human body. It is made up of three bones: the humerus (arm bone), the scapula (shoulder blade) and the clavicle (collar bone). The joint made by the humeral head (top of the arm bone) and the glenoid (part of the shoulder blade) is typically referred to as the shoulder joint or the glenohumeral joint. It is considered a ball and socket joint and allows for a large degree of mobility.
The tremendous mobility of the shoulder joint means that it is less stable than other joints in the body. Mobility comes at the expense of stability. Hence, the shoulder relies on many soft tissue structures to provide stability (glenohumeral ligaments, capsule, labrum) rather than relying on how the bones fit together. The ligaments and capsule blend together and attach to a rim of cartilage that surrounds the glenoid (socket) called the labrum. The labrum increases the depth of the socket and helps to keep the humeral head (ball) in the proper position.
When the shoulder is dislocated, the ball and socket of the shoulder joint become separated. The shoulder can dislocate forwards, backwards or downwards. Some individuals have what is referred to as multidirectional instability (or MDI) which is often seen in people that are ‘loose-jointed’. The force of the event typically causes a tear in the labrum, ligaments and capsule of the shoulder joint. In some cases, the dislocation can cause damage to the bone of the glenoid (called a Bony Bankart lesion) or the humeral head (called a Hill-Sachs lesion). When the normal stabilisers of the shoulder joint are disrupted, the result is an unstable joint.
Most people dislocate their shoulder during a contact sport such as rugby, or in a sports-related accident. In older people the cause is usually falling onto an outstretched hand and can be associated with rotator cuff tears. Shoulder dislocations can occur more easily in people who are flexible, such as those with joint hypermobility (loose joints) and connective tissue disorders.
The risk of recurrent shoulder dislocations or symptoms of shoulder instability is extremely high in young adults. The risk of repeat dislocations is less in people who are older and in those that are less active.
The symptoms associated with a shoulder dislocation include a ‘popping’ sensation, pain, numbness and tingling in the fingers or a ‘dead arm’ feeling, difficulty or inability to move the arm and deformity or abnormal appearance of the shoulder.
If a shoulder dislocation is suspected, emergency care should be sought immediately. It is important that the shoulder be reduced (put back in place) as soon as possible. In some cases the shoulder will reduce spontaneously but in others it will need to be manually manipulated to put the ball back into the socket. This usually results in immediate relief of pain.
Once the dislocation has been reduced, Dr Chia will assess the injury, examine the shoulder and confirm that the shoulder is reduced with an xray. In certain cases an MRI or CT scan may be ordered to further assess the damage to the shoulder and guide treatment.
Initial treatment consists of rest, ice, immobilisation in a sling and physiotherapy. In certain patients or when non-surgical treatment is not effective at preventing recurrent shoulder dislocations, Dr Chia may recommend surgery. In most cases, key-hole (arthroscopic) surgery is able to be performed to repair the damaged labrum and ligaments.
In cases of multiple dislocations where bone loss from the socket (glenoid) or ball (humeral head) has occurred, Dr Chia may recommend a Latarjet procedure. This is a specialised procedure that involves the transfer of a piece of bone (coracoid process) with its attached muscles into the bony defect over the front of the socket (glenoid). This replaces the missing bone and the transferred muscle also acts as a ‘sling’ to prevent dislocation. It has proven to be an effective procedure with excellent results.
Post-operatively the shoulder will be placed in a sling. A rehabilitation program will be prescribed based on the surgery performed. Physiotherapy after surgery is as important as the repair itself.
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