The Shoulder

Question 1

Name the stabilising elements of the shoulder (5)

Answer 1

Labrum
Joint capsule 
Ligaments 
Cartilage 
Rotator cuff

Question 2

MOA for shoulder dislocation?

Answer 2

Anteriorly directed force as the arm is externally rotated and abducted

Question 3

Factors that contribute to instability in the shoulder (3)

Answer 3

Ligamentous laxity
Loose capsule
Shallow glenoid

Question 4

Why might you get recurrent shoulder dislocation after the first incident? (2)

Answer 4

Labrum sheared off - physical bumper

Laxity in the capsule - afferents containing stretch information can no longer feedback to the brain - neurological bumper

Both the capsule and labrum are sheared off of the anterior portion of the glenoid –> Bankart lesion.

Question 5

What are the 3 aetiologies of shoulder dislocation? (3)

Answer 5

Traumatic (90%) (type 1)

Laxity (type 2)

Muscle patterning issue (type 3)

Question 6

What is type 3 shoulder instability and explain it (2)

Answer 6

Muscle patterning

There is no true structural reason for the instability. Poor co-ordination of muscle activation during movement leads to the humeral head not being centred in the glenoid. Pectoralis major (anterior pull) and Lat dosri (posterior pull) are thought to be the main culprits.

Some adverse muscle patterners are strong enough to completely dislocate their shoulders, but more often than not it just creates enough force to sublux or create sensations of instability in the shoulder.

Question 7

What scoring system is used to rate laxity?

Answer 7

Beighton

Score out of 9. More than 6 indicates hyper mobility.

Question 8

What % of people fall into all 3 types of shoulder dislocator?

Answer 8

1%

Question 9

What four muscles make up the rotator cuff?

Answer 9

Supraspinatus
Infraspinatus
Teres minor
Subscapularis

Question 10

What is the function of the rotator cuff?

Answer 10

To centre the humeral head, and allow the deltoid to produce movement

Question 11

How do you manage tears in the elderly? Describe in detail.

Answer 11

Reverse arthroplasty - humeral head is moved to the glenoid - changing the centre of rotation- taking the rotator cuff out of the equation.

Issues:
- Upward shearing force where the humeral head is fixed to the glenoid - screws will break

• Over stretching of the deltoid.

Question 12

How do you manage rotator cuff tears in the young?

Answer 12

Surgical repair of the tear itself.

Question 13

Imaging for shoulder dislocation? What is the specific sign on an x-ray called?

Answer 13

Depression in the top of the humerus upon repeated dislocation –> Hills-Sachs Lesion