Instability (dislocation)

The shoulder is a joint which has a huge range of motion but this means that it is inherently unstable and relies on the surrounding structures (muscles and ligaments) to stop it dislocating. If any of these structures is damaged the shoulder can become unstable. The shoulder can be unstable in any direction. I will only consider the anterior variations (the most common) here.

There are several different types of instability

  • Traumatic
  • Atraumatic
  • Muscular Imbalance

It is possible to move from one type of instability to another with time and there is a spectrum in-between these points.

Traumatic

Bankart Lesion
Bankart Lesion
Xray of a normal shoulder
Xray of a dislocated shoulder

This is the most common form and usually occurs as a result of a fall in which the arm is twisted up and away from the body (as in preparing to throw a ball). The tissues at the front of the shoulder (the "labrum") can be damaged, tearing them away from their attachment.

What are the signs and symptoms?

Acute dislocation causes severe pain in the arm which is commonly held by the side. Usually the patient is unwilling to allow anyone to touch the arm. Sometimes it is possible to see a swelling in the front of the shoulder.

How is the diagnosis made?

Acute dislocation is usually easy to diagnose based on the history and Xrays.

If the patient is seen at a later time (when the shoulder has been reduced) the history of the dislocation(s) will be taken and the shoulder examined. There are usually certain positions in which the shoulder feels as if it is going to dislocate.

Investigations include:

  • Xray
  • MRI
  • CT scan

What is the initial treatment?

The first priority is to reduce the shoulder (put it back into the joint). Many people have been taught how to do this on the side of the pitch. If not then the patient will be requesting to be taken to hospital.

In hospital a combination of a painkiller and muscle relaxant is given and the shoulder manipulated back into the joint. The position will be checked with an X-Ray although the instant relief of pain is a good indication of success. Rarely it is not possible to put the shoulder back into the joint like this and a full anaesthetic is required.

The arm will be placed in a sling for 3 weeks followed by physiotherapy to strengthen the muscles.

If initial treatment doesn't work, what's next?

After a first dislocation there is a chance of dislocating the shoulder again with far less trauma because of the internal damage to the joint. The chance is higher if the patient is younger or is involved in contact sports. In some cases the chances can be as high as 80%.

If the shoulder keeps dislocating or if the patientis highly likely to suffer recurrent dislocation it may be necessary to operate to stabilize the shoulder.

Shoulder Stabilisation (Bankart repair)

On occasion the bone of the glenoid becomes damaged and a soft tissue repair is unlikely to work. If this is the case then the surgeon may recommend that the bone be rebuilt by moving a small adjacent bone - this is known as the Latarjet Procedure.

Figure 1
Latarjet procedure - Fig 1
Figure 2
Latarjet procedure - Fig 2
Figure 3
Latarjet procedure - Fig 3
Figure 4
Latarjet procedure - Fig 4

How can further injury be prevented?

Unfortunately once the shoulder has dislocated the damage has been done to the inside of the joint. This does not mean that arthritis will follow but means that further dislocation is more likely again unless all movements which may dislocate the shoulder are avoided. Physiotherapy can help to strenghten the muscles and correct any imbalances. Avoidance of the cause (i.e. stopping the sport) may also reduce the risk of recurrence.

Atraumatic Dislocation

This form of shoulder dislocation is less common and arises either as a result of an abnormality of the tissues stabilizing the shoulder or as a result of "repetitive microtrauma". This is experienced by gymnasts, swimmers and people who repeatedly stress the shoulder through a wide range of motion.

What are the signs and symptoms?

The symptoms may be the same as for a Traumatic dislocation or there may be an ache in the shoulder and a feeling of looseness. Often sportsmen complain of a "dead arm" during sports.

How is the diagnosis made?

As with the traumatic type of dislocation the history of the events will be taken and the shoulder examined. Investigations are performed as for the traumatic type

What is the initial treatment?

If the shoulder is dislocated then the acute treatment is the same. If the symptoms are more vague then a period of physiotherapy is required. The aim of this is to improve the balance of the shoulder muscles and to "stabilize the scapula". The scapula (shoulderblade) is the structure of which the whole arm hangs and it moves around the chest wall as the arm moves. If it does not move properly then the shoulder will not move properly.

If initial treatment doesn't work, what's next?

In many cases the shoulder will settle with physiotherapy. If there is a significant structural problem within the shoulder it may be necessary to operate to repair this and to recreate the internal stabilising structures.

Shoulder Stabilisation (Capsular shift)

Muscular Imbalance

This is the least common form of instability and occurs when the coordination between the muscles of the shoulder is lost. The shoulder is inherently unstable and relies on the fine balance between the muscles to keep it from dislocating. For example: the muscle of the chest wall (pectoralis major) are usually quiet when the arm is lifted up from the side. If this muscle starts to contract at the same time as the arm is being lifted up it will try to pull the top of the arm (the shoulder) forwards and can lead to dislocation.

There is usually nothing wrong inside the shoulder itself and physiotherapy can have very good results although it is a long slow process.