Atraumatic Shoulder Instability

When the first (and following) shoulder dislocation required no (or little) trauma and if you are able to dislocate your shoulder yourself, then the term broadly used is 'Atraumatic shoulder instability'. This excludes shoulder dislocations following an injury (e.g. rugby player), which is known as 'Traumatic Instability'.

Atraumatic shoulder instability is generally treated with rehabilitation in the first instance. Surgery is only very rarely required.

Current use of the term ‘atraumatic instability’ is confusing it can include the ‘loose shoulder’, voluntary dislocation and habitual dislocation.

Management of the two main groups is detailed below:

1. Atraumatic Structural Instability

This is acquired instability - either through repetitive microtrauma, which has placed undue stress upon the soft tissues; or rapid, forceful movements that contribute to the overall laxity of the joint.

This is a recognised problem in athletes, particularly throwers and swimmers, where they develop symptoms of instability due to overload and fatigue in the stabilising muscles of the shoulder.

Rehabilitation is focused on restoring muscle imbalance, soft tissue flexibility, proprioception and muscular control.

Surgery is occasionally required in the form of Capsular Shrinkage or Capsular Plication

2. Muscle Patterning (Positional) Instability

The stability of the shoulder joint throughout its large range of motion comes partly from precise synchronised muscle contractions and relaxations during movement. Each of the 30 muscles moving and stabilising the shoulder need to be activated at specific times. If this pattern is altered instability can occur.

Muscle patterning instability usually occurs in younger patients who can voluntarily slip the shoulder out of joint as a trick movement, but may then go on to dislocate repeatedly uncontrolled (involuntary). It is an instability that is caused by an abnormality of shoulder muscle patterning.

Without treatment, they may progress to the stage where the patient may be aware their shoulder is moving in an abnormal manner but will perceive it to be normal to them. Stress, cough, sneeze may all initiate the shoulder to spontaneously sublux/dislocate out of the patient’s control. Pain is not often an issue but can be when the shoulder remains subluxed for a period of time due to the surrounding shoulder muscles being in continuous action. The patient may not be taken seriously or blamed for causing their shoulder to sublux/dislocate.

The prime aim of treatment is to regain normal neuromuscular control and patterning. This can be difficult, may take time and requires a full team approach to treatment. The team comprises a specialist shoulder physiotherapist, shoulder surgeon and sometimes an occupational therapist and psychologist.

The aim of the rehabilitation should allow full return to work and try not to encourage an avoidance culture.

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