// Common injuries: Shoulder dislocation

by Paul Wright

Dislocation of the shoulder (or glenohumeral joint) is one of the most common traumatic joint related injuries seen by physiotherapists and sports physicians. In the majority of shoulder dislocations the humerus slips into a position in front of the scapula (an anterior dislocation). It is possible, however, for the humerus to end up behind the scapula (a posterior dislocation).

Anatomy and physiology

The glenohumeral joint (the joint between the humerus and the glenoid fossa of the scapula) is a multi axial ball and socket joint that allows an amazing degree of movement.

However, this freedom has only been achieved at the expense of stability and security. In comparison to the ball and socket joint of the hip, which is rarely dislocated, the glenohumeral joint has often been described as a ‘ball and saucer joint’ in reference to the lack of depth to the actual socket of the scapula. Another way to describe the lack of stability provided to the glenohumeral joint is to imagine the movement of a beach ball sitting on the nose of a seal – while this is a slight exaggeration, it does allow us to recognise the potentially unstable relationship that exists in this joint.

Due to the relatively shallow socket provided by the scapula, the glenohumeral joint requires support and assistance from other structures to improve stability - these support structures include the glenohumeral ligaments, glenohumeral joint capsule and a thin rim of fibro cartilage around the glenoid called the glenoid labrum. Although they don’t prevent dislocation, these support structures assist in keeping the humeral head in contact with the glenoid fossa during movement of the shoulder joint.

Signs and symptoms

The patient with a shoulder dislocation is usually in significant pain and describes a feeling of the shoulder having ‘popped out’ and now being difficult to move. The majority of dislocations come about due to events such as rugby tackles or landing on an outstretched hand, but it is possible for the injury to occur when reaching behind you while driving a car, or even when rolling over in bed. In the gym setting any exercise or stretch where the shoulder is externally rotated and abducted can place the shoulder joint at risk of dislocation. These include the press behind neck and rear pulldowns, as well as aggressive pectoral stretching.

The dislocated shoulder is characterised by the loss of the normal shape and outline of the shoulder and a hollowing out below the acromion, with the patient supporting the affected arm in a position of slight abduction. Neurological symptoms, such as a loss of sensation or pins and needles, can indicate damage to the axillary nerve and need to be monitored.

Management

It is essential the client is examined as soon as possible by a physiotherapist or sports physician who will determine an accurate diagnosis and chart the most appropriate management strategy. In the majority of cases, the dislocated shoulder should be X-rayed prior to being reduced (relocated) to rule out fractures. However, provided a suitably trained practitioner is available, the sooner the shoulder is reduced the better, as increasing spasm over time will make the reduction more difficult.

Following the reduction of the dislocation, the shoulder should be placed in a sling for up to three weeks to allow the shoulder to regain some ligamentous stability, but the exact post injury rehabilitation program will be determined by the medical professionals involved in the case. Intensive isometric exercises are commenced to help the muscular system regain support of the shoulder; initially only internal rotation is permitted, followed by external rotation exercises. It is important that the dislocating position of external rotation and abduction is avoided for at least six weeks post injury.

Unfortunately, even allowing for early reduction and comprehensive rehabilitation, a significant number of first time dislocators go on to dislocate again. Some reports indicate that there is an eighty per cent chance of dislocating again if the initial dislocation occurred when the patient was twenty years old or younger. This likelihood drops to just over a fifty per cent chance of re-dislocation in the twenty to forty age group. In these cases a surgical repair may be the best way to guarantee a stable shoulder.

The apprehension test

This test is commonly used by physiotherapists and sports physicians to determine the extent of shoulder instability. The patient lies supine with the shoulder at ninety degree of abduction. The therapist then gently externally rotates the humerus looking for any apprehension on the part of the patient – a positive test occurs if the patient stops the test as they fear a dislocation is imminent. Note: this test is not to be performed by trainers without appropriate medical training; however, the test is mentioned in this article to reinforce the problems of combined external rotation and abduction in the patient with a history of dislocation. 

Partner stretching - a word of warning

Trainers must be aware that some shoulders become unstable in the position of abduction and external rotation. Some partner stretches such as this partner pectoral stretch can be dangerous and should be avoided in patients with a history of shoulder instability. Check with your treating physiotherapist or sports physician before using these stretches in affected patients.

Isometric External Rotation

Isometric External Rotation exercises are an important component of the early stage rehabilitation following shoulder dislocation. Trainers should work closely with the treating medical team to co-ordinate the appropriate sets, reps and loads.

The Press Behind Neck

The Press Behind Neck is not recommended due to the extremes of external rotation and abduction. A safer alternative is to press to the front of the neck (Military Press) as this exercise reduces the amount of external rotation required, thus reducing the chance of dislocation in ‘at risk’ clients.

Paul Wright, BAppSc (Physio) DipEd (PE)
Australian Fitness Network’s Author of the Year 2006, Paul is the director of Get Active Physiotherapy Health Centres which has clinics inside Fitness First clubs at Carlingford, Castle Hill, Dee Why and St Leonards (Sydney, NSW). Get Active’s free GAPREP program keeps personal trainers up to date with the latest in injury prevention. Free membership provides physio tips, regular newsletters, free seminars and discounts on Get Active services and educational DVDs. To join the GAPREP program e-mail your details to gapreps@getactivephysio.com.au. For more information on Get Active Physiotherapy Health Centres visit getactivephysio.com.au or call (02) 9966 9464.



NETWORK • SPRING 2006
• PP65-67