Shoulder Dislocation and Recurrent Instability
Dislocation of the shoulder joint involves the ball (humerus) coming out of the socket (glenoid). The dislocation may persist, requiring the shoulder to be ‘relocated’ by a clinician, however at times the shoulder goes back into its position after momentarily slipping out. A partial dislocation can also occur, termed a ‘subluxation’ which returns to its normal position soon after. For many people, the first episode of dislocation is quite a traumatic event, although if it continues to occur, the dislocations can occur with even trivial movements.
Shoulder dislocation: What is it?
The shoulder is a ball and socket joint. It has a large ball and a shallow socket, allowing the shoulder to be the most mobile joint in the body but at the cost of stability. The bony socket (glenoid) is made deeper and larger by a fibrocartilaginous rim (the labrum) surrounding the socket. Stability to the joint is helped by thickenings in the capsule surrounding the shoulder (ligaments) and the muscles spanning the joint (the rotator cuff).
After the first episode of dislocation, a number of injuries can occur to the structures within the shoulder. Most commonly, especially in younger patients, the labrum tears from the front of the socket, which usually does not heal back to its original position. In addition to this, an impression into the back of the ball of the joint can be caused by the impact of the dislocation (hill-sachs lesion). As people get older, the initial dislocating event has a higher chance of causing rotator cuff rupture, which usually requires repair.
Recurrent shoulder instability
Due to the damage that has occurred to the stabilising structures within the shoulder joint, many patients who experience a dislocation will then begin to experience further dislocations or subluxation. These tend to occur with progressively less force than the previous dislocation due to increasing laxity inside the shoulder joint. The younger a patient is when they suffer their first dislocation, the more likely they are to have repeated dislocating episodes. When people suffer their first dislocation as a teenager, their risk of having repeated dislocating episodes is as high as 90% without surgical treatment. As an older adult, this risk decreases significantly, and recurrent instability is often not a problem.
Shoulder instability: Diagnosis
The initial diagnosis of a shoulder dislocation may be obvious in a traumatic episode, however it may be more difficult to accurately diagnose when the shoulder self-relocates. Frequently, patients will feel their shoulder was ‘out of joint’ and painful thereafter. Careful history and a thorough examination will reveal the instability and at times this can be uncomfortable. Many patients feel apprehensive about their shoulder when the arm is placed out to the side (abduction and external rotation).
After an initial incident, an X-ray is recommended to exclude any associated fractures around the shoulder. Thereafter, an MRI is the investigation of choice which allows us to accurately diagnose the torn structures within the shoulder and discuss treatment options with you.
Shoulder instability: Treatment
Shoulder instability can be treated surgically or non-surgically. Non-surgical treatment involves physiotherapy and exercises to strengthen the muscles surrounding the joint. This can be successful for some people, or they may choose to modify their sporting activities. However, for many people, physiotherapy and strengthening is not successful and surgery is recommended.
In general, there are two options for surgical stabilisation of the shoulder joint.
Arthroscopic labral repair
Arthroscopic labral repair involves keyhole surgery where the torn labrum and ligaments are reattached to the front of the socket using suture anchors. This has a high chance of success and usually involves only 2 or 3 small 1-1.5cm incisions around the shoulder resulting in less scarring.
A Latarjet procedure is another type of shoulder stabilisation procedure where a piece of bone (the coracoid process) and its attached muscles are shifted to the front of the shoulder socket. I do this as an ‘open’ procedure, involving a 5-6cm incision over the front of the shoulder. For patients with bone loss or who participate in tackling sports, this procedure is often recommended as it has a lower risk of re-dislocation.
If you are experiencing a stiff and sore shoulder, please make an appointment to discuss your treatment options.