CH 8: The Shoulder

Question 1

What are the main differences in the structures of the shoulder V the hip?

Answer 1

Hip:
- Built for dynamic stability
- predominately made of ligaments
- Less prone to injury

Shoulder:
- Built for dynamic mobility
- Predominately made of muscles
- More prone to injury, especially in sports that involve lots of overhead movement

Question 2

Most attachment sites for muscles and ligaments will run through the articulation of what 3 bones?

Answer 2

The Clavicle, the Humerus and the Scapula

Question 3

What are the main ligaments of the shoulder? (medial to lateral)

Answer 3

SC: Sternoclavicular Ligament
CC: Coracoclavicular Ligament
AC: Acromioclavicular Ligament
CA: Coracoacromial Ligament

Question 4

What are the main 4 joints within the shoulder and their articulations?

Answer 4

1) Glenohumeral
- Glenoid fossa of scapula + head of humerus
- Mobility > Stability
2) Acromioclavicular
- Acromion process of scapula + distal clavicle
- Stability > Mobility
3) Sternoclavicular
- Superior sternum + proximal clavicle
- Only attachment between shoulder complex and axial skeleton
4) Scapulothoracic
- Because muscle attaching to scapula permits motion with respect to the trunk, this is technically a joint between scapula and thoracic spine

Question 5

Muscles of the shoulder complex

Answer 5

Rotator Cuff:
1a) Supraspinatus
1b) Infraspinatus
1c) Subscapularis
1d) Teres Minor
2) Triceps Brachii
3) Biceps Brachii
4) Latissimus Dorsi
5) Pectoralis Maj.
6) Pectoralis Min.
7) Deltoid
8) Trapezius

Question 6

What are the 2 main actions of the rotator cuff?

Answer 6

Primary Action: To pull/keep the humerus in the Glenoid Fossa of the scapula
Secondary Action: Rotation of the shoulder blade

Question 7

What is Scapulohumeral rythym?

Answer 7

Important coordination of scapular and humeral movements to facilitate greater ROM at the shoulder.

For ever 1 degree of motion that the ST (scapulothoracic) joint creates, 2 degrees of motion occur at the GH (glenohumeral) joint.

Question 8

Characteristics & MOI of a sternoclavicular sprain

Answer 8

• Disruption will usually drive the SC joint, anteriorly, medially and superiorly
  Common MOI:
• FOOSH (Pushing)
• Traction force pulling abducted arm away from body (pulling)
• Blunt force trauma

Question 9

Characteristics & MOI of Clavicle fractures

Answer 9

Common MOI:
- FOOSH
- Blunt force trauma
- Falling on tip of shoulder

• Most common place to fracture is middle third where the shape and direction change, making it a structural weak point
• Clavicle may appear lower

Question 10

What is the main function of the Labrum?

Answer 10

Acts similarly to the menisci of the knee: deepens the glenoid cavity, creating a greater SA for the head of the humerus to articulate and minimizes the chances of unwanted humeral displacement.