Shoulder Instability

   

The shoulder has the greatest range of movement of any joint in the body, but at a cost. The shallow “ball and socket” shape of the joint allows a very free range of movement but stability is provided by the joint capsule (ligaments) and the muscles around the shoulder. The shoulder dislocates when the “ball” is forced out of the “socket”, causing ligaments to stretch and tear. Although there is a degree of healing of the ligaments, they often remain stretched and ineffective in controlling the stability of the shoulder joint, resulting in a risk of further dislocations. This situation is often referred to as “recurrent shoulder instability”.

The commonest cause of shoulder dislocation is trauma. Usually, the arm is forced into a position of hyperextension, causing the shoulder to dislocate anteriorly, tearing the ligaments on the front of the shoulder joint. Sometimes the joint will relocate immediately but often it remains in a dislocated position and has to be reduced. The shoulder will be sore for several days. Pain settles rapidly and range of movement recovers, encouraging a return to normal activities. This can be a problem in a sportsman. An early return to sport places that individual at a high risk of a further dislocation and then sets the scene for recurrent episodes of dislocation of the shoulder. This is a particularly common scenario in contact sports such as rugby.

Recurrent instability of the shoulder is particularly common in younger sportsmen and women (under 25) who play sport regularly, particularly contact /collision sport such as rugby and martial arts. The risk of recurrent dislocation is approximately 80%. If recurrent dislocation develops, surgery is the only effective treatment and this involves repairing and reattaching the ligaments on the front of the shoulder, which will restabilise the joint. Surgery usually involves a day visit to hospital and the operation is performed under a general anaesthetic. Both keyhole and open surgical techniques are used, depending on individual circumstances. The results are generally excellent, with more than 90% returning to their pre-injury level of activities, with a less than 10% risk of further episodes of dislocation.

There are other forms of instability that do not involve an injury. Athletes who use their arms above their head in their sports, such as swimmers and tennis players and where throwing is a regular part of their sport, such as in cricket and baseball, may develop instability due to stretching of the ligaments around the shoulder. This problem may present as pain and a sense of numbness in the shoulder, referred to as a “dead arm”. Careful assessment will confirm that the shoulder is unstable. Investigations such as an MRI arthrogram can be helpful to identify a deficiency in the ligaments. Initially, non-surgical treatment is used in these circumstances by strengthening the muscles around the shoulder and sometimes adjusting the athlete’s technique when throwing or serving. If these measures fail to improve the situation, surgery may be required. This type of instability is seen in individuals who are flexible (double jointed), where there ligaments are unusually elastic. This type of instability usually affects both shoulders and requires careful assessment and treatment by rehabilitation of the muscles around the shoulder. A physiotherapist who specialises in shoulder rehabilitation should be involved in this situation.

RWN’s view

Due to the high risk of recurrent dislocation in young sportsmen playing contact collision sport, early repair of the damaged shoulder ligaments after the first dislocation may be indicated. Studies have shown that these individuals (studies have been performed in American Army recruits), the incidence of recurrent dislocation can be reduced from 80% to less than 15% by repairing the ligaments after the first dislocation. This is still a relatively controversial subject but it is becoming increasingly accepted that high risk individuals who play sport regularly, usually professional sportsmen, should be offered early stabilisation of their shoulder after the first dislocation.

There is a debate about the best surgical technique for stabilisation of the shoulder. Arthroscopic (key hole) techniques have been developed over the last 10 years, which are effective but have a higher risk of redislocation than open surgical techniques, particularly in individuals who play contact sports. Most of my patients with recurrent shoulder dislocation are rugby players and I favour open stabilisation, which I feel provides them with the most reliable results.

After surgery, there is a temporary period of immobilisation in a sling for two weeks, after which the sling is gradually discarded and physiotherapy is started, concentrating on re-establishing shoulder movement and muscle strength. In most cases, a return to sport after approximately six months is possible.

Finally, with regard to atraumatic instability, that is shoulders that have become unstable without an episode of injury, careful assessment is required. Usually an MRI scan will be needed.Rehabilitation with an experienced shoulder physiotherapist is usually the first line of treatment but if this is unsuccessful, a keyhole examination of the shoulder is required. In this situation, keyhole surgery is very effective in repairing and reattaching damaged ligaments in the shoulder, followed by further rehabilitation and a return to sport in approximately six months.