WHY DOES DISLOCATION OCCUR?

Dislocation can be either traumatic (due to an injury) or atraumatic (no injury). If someone dislocates their shoulder due to a fall or accident, the structures that normally act to hold the head of the humerus on the socket get torn or fracture and are unlikely to recover normal function again. If a young (<30 years) person dislocates their shoulder during an injury, they have a very high chance of having future dislocations and the trauma required to dislocate the joint will be less each time.

Atraumatic dislocations occur due to a number of factors including joint laxity (stretchiness or being double-jointed) and loss of the normal synchronised pattern of movement of the muscles around the shoulder joint. People that have 'lax' joints, can often hyper-extend their knees and elbows and can get the palms of both hands onto the floor with their legs straight with ease. Whilst this joint laxity is normal for these people and something they have always had, the instability often arises when there is a change in how the muscles around the shoulder are interacting with each other or a change in posture/ position of the arm. The main treatment for this is physiotherapy although the physiotherapist will need to be specialists in treating patients with this condition. The physiotherapist will look at the way in which the muscles and shoulder joint are moving as well as the patient’s posture. The physiotherapist will aim to train the patient to re-sequence the muscles in order to prevent further dislocations. The patient has to be highly motivated and willing to undergo this treatment which takes many, many months of perseverance. The treatment can be very frustrating in the early stages as it takes lots of patience and application to reactivate these muscles which may have been ‘dormant’ for many months or even years.

WHAT ARE THE SYMPTOMS?

An acute shoulder dislocation due to an injury is very painful. The shoulder will look abnormal. The patient may also experience abnormal sensations in the hand which is due to pressure on the nerves in the area. Sometimes the shoulder will go back into the socket of its own accord but more commonly the patient would come to hospital to have medical assistance in reducing the shoulder back into position. Usually when the shoulder is back in position, the pain is much improved. Usually a sling is provided by the hospital for comfort but should only be worn for as long as the shoulder is painful and then dicarded, usually about a week. If the shoulder continues to come out of joint the patient will sense that their shoulder feels ‘loose’ and they are nervous about their shoulder being in certain positions (called apprehension).

WHAT IS THE TREATMENT?

Nonsurgical Treatment:

After an acute dislocation or episode the important thing is to control your pain and rest the joint. In the chronic situation, physiotherapy can help to strengthen the muscles which help to keep the joint in a normal position. If you are not involved in manual work, particularly over-head height and not involved in collision sports, you may only need physiotherapy to avoid further problems.

Surgical treatment:

If you have physiotherapy or your activity means that future dislocation is likely, you may be offered surgery. The type of operation depends on which direction (out the front or out the back), and the reason why your shoulder is dislocating. If the primary cause is damage to the ligaments and labrum (cartilage) at the front of the joint, the commonest operation is called a Bankart repair, which aims to reattach these structures back onto the bone. Traditionally this operation was done through an incision (a cut) on the front of the shoulder and required alot of normal tissue to be dissected (disturbed) in order for the damaged tissue to be repaired. Nowadays it is more common for the operation to be performed arthroscopically (via key-hole surgery). It is often a day-case operation, not even requiring a nights stay in hospital. The camera (about the size of a thin pen) is inserted into the back of the shoulder and instruments are passed into the front of the shoulder. Small anchors (screws with stitches on the end) are placed on the front of the joint and the soft tissue is stitched down to hold it in place whilst it heals. You will need sling for approximately 4 weeks after the surgery in order to rest the shoulder and allow the healing to start. This may well be sufficient to keep your shoulder stable.

Sometimes not only is the tissue on the front of the joint damaged but there is also some damage to the bone at the front of the socket. This is called a 'bony-Bankart' lesion. As the humeral head comes to lie on the front of the socket in a dislocation, the back of the head presses firmly on the front of the socket.

This damages both the head (called a Hill-Sachs depression fracture) and the socket. Both of these lesions mean that future dislocations are more likely to happen as the shoulder tends to get to a position where it can ‘lever itself’ out of joint. If there is significant damage to the socket, you may be advised that a Latarjet procedure is most appropriate. This is an operation first described in France in the 1950s but popularised more recently. It involves a small knuckle of bone, normally present at the front of the shoulder (the coracoid process), being moved to the front of the socket. This makes the socket larger so the head needs to travel further before a dislocation happens. Attached to the coracoid process are two muscles. These muscles are left in place after the transfer and then have two functions. Firstly, they act as a sling in front of the joint to hold the head on the socket (quite possibly the main method by which this operation works). Secondly, muscles give bone a blood supply so enable the newly transferred knuckle of bone to heal onto the front of the socket to make the socket larger. The screws are then redundant but can be left in place. The procedure generally works very well and is particularly indicated for overhead / collision athletes or heavy manual workers. Since the bone is attached by screws (rather than stitches in a Bankart repair), the shoulder can normally be moved earlier in the recovery process so the patient needs less time in a sling, usually just 2 weeks.