Shoulder series part 2

What is a subluxation and what is a dislocation?

The difference between a shoulder subluxation and a shoulder dislocation is defined by the amount of joint surface contact between the humeral head and the glenoid fossa of the scapula (the ball and socket joint respectively).

In a subluxation, there remains some joint surface contact after the incident. This is sometimes termed a ‘partial dislocation’. A 50% subluxation indicates that the normally opposing articular joint surfaces have lost halve of their contact and the joint capsule is either stretched or torn.

A 100% subluxation is the same as a dislocation, where the joint articular surfaces have lost ALL their contact.

How and why do they occur?

As outlined above, a shoulder subluxation occurs when the head of the humerus slides out and away from the glenoid fossa but then slides back. A dislocation results in the humeral head losing complete contact with the glenoid fossa and not sliding back in.

These can both occur in a number of ways including:

·       Forced combined movements of glenohumeral abduction plus external rotation

·       Violent trauma to the back of the humerus

·       A heavy fall on an outstretched arm

·       A collision with another person

The glenoid fossa of the scapula forms a very shallow socket for the larger head of the humerus to fit within – a great analogy of this is to consider the size difference of a golf ball (the humeral head) sitting on a golf tee (the glenoid fossa). To help reinforce the socket, there is a thin layer of cartilage (the labrum) which makes it slightly deeper, a tightly woven ‘bubble sheath’ created by the capsular ligaments and then a further encasing provided by the rotator cuff tendons discussed in the previous article. However the multi-axial movement and shallow socket still make this joint the most vulnerable in the body to subluxation / dislocation. The most common direction of injury is to the anterior / inferior part of the capsule (95% of all injuries), where lies the least amount of soft tissue protection.

What happens within the shoulder?

The degree of subluxation determines how much of the surrounding soft tissue is damaged and subsequently dictates how long the recovery will take. A dislocation is often far more traumatic. Both injuries can lead to:

·       Torn ligaments

·       Torn labrum (cartilage)

·       Weakened rotator cuff

·       Nerve impingements – pins & needles / numbness

Injury to the joint capsule from subluxation or primary dislocation weakens the capsular ligaments and increases the chances of a dislocation or repeat episode.

What are the symptoms?

In most cases, the client will present with:

·       Excruciating pain

·       A protruding humeral head, anterior to the glenohumeral join

·       Elevated collarbone

·       Numbness of the arm

·       Loss of arm movement

Treatment for a subluxation / dislocation using Pilates

If the client suffers a subluxation then the humeral head would have spontaneously reduced and ‘gone back in’. A dislocation renders the client unable to move their arm and / or relocate the humeral head without assistance. Therefore, a visit to A&E is required so that the shoulder can be passively reduced by suitably qualified medical personnel. Several methods of ‘closed’ reduction exist, but primarily the goal is the same – manipulate the humeral head to reposition it within the glenoid fossa. After the shoulder is relocated it is important that the client remain in a sling for at least 1 week to allow the capsule to heal and tighten up again.

If the client recently suffered dislocation or repeatedly subluxes, then they may require surgery to repair the labrum, tightening of the capsule and/or capsular ligaments / rotator cuff.

Following surgery or straight from the most recent episode, the post-injury rehab remains the same. Full functional movement is required first before a specific strengthening programme is employed.

The use of Pilates in strengthening the shoulder is a brilliant way to increase its stability but also reduce the risk of further episodes.

A well structured, gradually progressive exercise programme could be incorporating the use of a Reformer or other Pilates equipment. Client’ can significantly reduce the chance of a repeat episode by maintaining a strong base of support through the shoulder, targeting the rotator cuff and capsular ligaments. When working with a client who has sustained such an injury, it is imperative that you consider the entire medical history, make a note of their posture and observe their entire spinal movement. A good Pilates routine will pay particular attention to the deep rotators of the shoulder, postural stabilisers of the spine and overall movement education.