Shoulder Instability.
Shoulder instability occurs when the structures surrounding the shoulder joint do not effectively keep the humeral head (ball) tightly within the glenoid (socket). There is a wide variation in the degree of shoulder instability, from subluxation (joint slipping) to a complete dissociation of the joint surfaces (dislocation) where you may not be able to ‘put it back in joint’ yourself.
The socket of the shoulder is very flat which allows the shoulder to lift and rotate as well as reaching above the head. Unfortunately the flat socket also means that the shoulder is the most unstable large joint, which means that it is prone to dislocation.
Shoulder stability relies on a combination of intact boney anatomy, stabilizing soft tissues and muscle strength.
Patients with shoulder instability may notice an uncomfortable sensation that their shoulder may be about to slip out of joint – this is what is known as “apprehension.”
Sometimes the first symptoms of instability can be shoulder pain or an ache during or after certain activities. Patients will often report loss of power or weakness during overhead activities as well as clicking, clunking or popping sensations.
What causes shoulder instability?
It is crucial that the exact cause for your shoulder instability is determined prior to surgery being considered. There are three main causes of instability, which can often co-exist:
Traumatic (Type 1) instability is where there has been a distinct injury to the shoulder causing a dislocation or subluxation. This causes internal damage to the stabilising structures of the shoulder.
Atraumatic (Type 2) instability occurs in patients who are naturally prone to subluxations or dislocations without the need for significant trauma. These patients usually have very lax joints and may be referred to as ‘double jointed’.
Muscle patterning (Type 3) instability is rare, it occurs when the muscles that usually stabilise the shoulder act in an incorrect pattern and cause dislocation or subluxation. Both shoulders are often affected and it is more common in young females. Surgery is very rarely indicated for this type of instability and highly specialised rehabilitation is often needed.
How is shoulder instability diagnosed?
Usually your surgeon can diagnose instability with a combination of clinical examination and a careful assessment of your symptoms.
Further diagnostic tests are used for confirmation and to plan treatment.
X-rays are usually obtained on the day of your consultation and may demonstrate damage to the ball and socket of the shoulder.
MRI is almost always required to assess the extent to soft tissue damage to the shoulder. Most commonly the glenoid labrum is torn along with a portion of the joint capsule. If this is extensive and your symptoms are occurring frequently then surgery may be indicated.
CT scans are usually obtained if there is suspicion of extensive damage to the bone surfaces of the humeral head (ball) and glenoid (socket).
Treatment options
Your surgeon will tailor your treatment specifically to the underlying cause of your symptoms whilst taking into account your expectations and medical history.
Non-operative Management
Non-operative treatment should always be exhausted before considering any form of surgery. Possible non-operative options include:
A focused physiotherapy program to strengthen the muscles around the shoulder can prevent stiffness, help regain stability and improve range of motion. This will prove beneficial even of surgery is eventually indicated. Patients with instability as a result of underlying ligamentous laxity (Type 2) or muscle patterning (Type 3) are usually best managed with specialist physiotherapy and surgery is only rarely indicated.
Rest, activity modification. It is usually unadvised to stop moving or using your shoulder altogether as this can lead to stiffness. However avoiding overhead or aggravating activities can help to reduce the irritation of your shoulder. Following your first dislocation it may help to protect the soft tissues to allow healing and reduce inflammation, but it is important to balance this with the need to avoid unwanted stiffness.
Surgical Management
If you are under 20 years old when you first dislocate your shoulder, as a result of trauma rather than due to underlying ligamentous laxity, then there is an approximately an 80% chance of further dislocations. The risk of further dislocations decreases with age at the time of the first dislocation, but surgery may still be indicated of you are having recurrent symptoms despite an adequate course of physiotherapy.
Shoulder arthroscopy
If your MRI scan does not demonstrate significant damage to the bony surfaces of the shoulder then it is likely that arthroscopic repair of the soft tissues will be enough to provide stability. The operation is called ‘Arthroscopic Stabilisation’ and is a 'key hole' procedure to reattach the labrum to the glenoid (rim of the socket) and tighten the capsule and ligaments. A typical technique is demonstrated below.
Open bone-transport procedure
This procedure is performed when there is some bone loss from the front of the glenoid (socket) and simply repairing the soft tissues would not be enough to provide stability. The procedure is referred to as ‘bone-transport’ as bone is removed from one part of the body (typically the hip of coracoid bone) and transferred to the rim of your glenoid to deepen the socket. There are multiple variations of this procedure and Mr Moverley will discuss the options with you prior to surgery.