Following on from last week’s blog topic on the relationship between rotator cuff tears and sub acromial impingement syndrome, this week we are going to discuss shoulder dislocations.
Shoulder dislocations one of the most common traumatic sporting injuries and affect the passive structures (bones and ligaments) of the shoulder joint rather than the surrounding soft tissue (there will be secondary affects).
The shoulder is a ball and socket joint made up by the head of humerus and the glenoid fossa of the scapula, it is technically known as the glenohumeral joint (GHJ).
In a passive (unmoving) position the joint is inherently unstable, and needs to be to account for the large range of movement the shoulder allows.
As you can see in the picture the head of the humerus is much larger than the glenoid fossa. To increase the surface area for articulation there is a meniscus like structure, known as the labrum, that acts to ‘catch’ the head of the humerus and provide passive stability to the joint.
Further passive stability is provided by the 3 (superior, middle and inferior) glenohumeral ligaments and reinforced by the coracohumeral ligament, while dynamic or active stability is provided by the rotator cuff muscles (review last week’s blog).
The shoulder joint is the most mobile joint in the body. The small surface area for articulation allows it to move in 7 directions, through three planes:
With any joint in the body the more stable it is the less movement it allows. Given the shoulder is the most mobile joint in the body, stability is sacrificed for mobility and therefore prone to problems associated with hypermobility, subluxation and dislocation.
A shoulder dislocates when the joint is forced beyond its normal range of movement forcing the head of humerus to
move completely out of the glenoid fossa.
Partial movement of the humeral head is known as a subluxation.
The joint can dislocate into an anterior (front), posterior (back) or inferior (downward) position.
Anterior dislocations account for over 90% of dislocations and typically occur when the shoulder is forced into abduction and external rotation.
Quite often there is force applied from behind the shoulder that facilitates this dislocation, such as when footballers take overhead marks and are simultaneously hit from behind.
Posterior dislocations account for less than 5% and commonly occur with a fall on an outstretched arm with some degree of internal rotation and or adduction of the shoulder.
Issues that can arise secondary to a dislocation may include:
· Bankart lesion: damage to the front of the labrum
· SLAP lesion: damage to the top of the labrum
· Bony Bankart lesion: damage to the front of the labrum and joint which pulls part of the bone off
· Hill-Sachs lesion: compression fracture of the outer part of the humeral head.
A shoulder dislocation is associated with a sudden onset of acute shoulder pain and may be described as feeling the shoulder “pop out”. If the humerus has not relocated or reduced back into the glenoid fossa then the humeral head will be quite prominent with an obvious step deformity or hollow right below the acromion. Other symptoms following a dislocation include pain with movement, reduced range of motion, feelings of instability, swelling and or bruising.
A dislocated shoulder should be reduced as soon as possible, the longer the humerus is out of the joint, the more difficult it is to reduce. Following reduction dislocations should be routinely x-rayed to rule out any associated fracture or loose fragments.
The easiest procedure to relocate the humeral head back into the glenoid fossa is to bend over at the hip, turning your arm so your thumb is facing down (internal rotation) and either holding onto a small weight or using your other arm to apply a bit of traction (pulling the arm down towards the floor). If unsuccessful you should seek medical attention.
Once the shoulder has been relocated and any bony injuries ruled out, the joint needs to be stabilised to prevent recurrent dislocations. This is commonly done by placing the arm in a sling in an adducted and internally rotated (across the body) position. 2nd and 3rd dislocations are much more common in the first 48 hours and occur in 60-90% of young active individuals.
Once the shoulder has stabilised it’s time to see your physiotherapist, chiropractor or remedial massage therapist, to begin restoring movement, stability and strength to the joint. A good treatment plan should consist of releasing the spasm in the surrounding muscles of the shoulder joint, mobilisation of the shoulder, neck and thoracic spine to increase movement and decrease pain followed by a progressive strengthening program to provide more stability to the GHJ and minimise the rate of recurrence.
Shoulders dislocations are difficult to predict and hence difficult to prevent. They are most common in high velocity accidents (i.e. car crashes), contact sports and activities that involve or have a risk of falls. To help try and prevent an initial dislocation, or more importantly, a recurrent dislocation follow the guidelines below:
1. Try to avoid falls – wear good, supportive footwear and pay attention as you walk
2. If you do fall avoid falling onto an outstretched hand. Learning how to roll effectively can help with this
3. Wear protective padding or taping when playing contact sports
4. Engage in regular strength and flexibility exercises for your shoulders, the stronger they are the more force is required to create damage
5. To avoid a recurrence, follow a specific, progressive strength and stability program that has been prescribed by your health care practitioner.
So that’s a brief overview of how shoulder dislocations can occur, If you have questions or comments feel free to e-mail us at firstname.lastname@example.org and we will happily answer them for you.
If you are still suffering from pain and weakness following a shoulder dislocation and want lasting relief, then call us on (08) 9486 8653 and we will arrange an appointment for you.