Shoulder

Question 1

Functional articulations of the shoulder

Answer 1

1. sternoclavicular joint- articulation between the sternum and the clavicle (synovial saddle joint)
2. acromioclavicular joint- articulation between the acromion and clavicle (synovial plane joint)
3. scapula-thoracic joint
4. GH
5. supra-humeral ‘sub acromial’
6. Long head of biceps and bicipital groove

Question 2

Scapulo-humeral rhythm

Answer 2

The scapulohumeral rhythm is the ratio between glenohumeral and scapulothoracic movement in the elevation (abduction) of the arm

the first 30 degrees of the motion come purely from the glenohumeral joint, after 30 degrees the scapula starts to upwardly rotate
– the ratio after 30 degrees, is 2:1 for every 2 degrees of GH movement, there is 1 degree of scapula movement

so 90 degrees will mean 60 GH and 30 scap

there are 3 phases of arm abduction:
- phase 1:
—- 30 degrees GH abduction
—- minimal scapula movement
—- 0-5 degrees of clavicle elevation

• phase 2:
  —- 40 degrees abduction of humerus (up to 90 degrees now)
  —- 20 degrees scapula (2:1 ratio of GH to scap)
  —- 15 degrees of elevation of clavicle
• phase 3:
  —- 60 degrees abduction and 90 degrees external rotation (helps with abduction)
  —- 30-40 degrees of scapula lateral rotation (2:1 ratio)
  —- 30-50 degrees of posterior rotation of clavicle and 15 degrees of elevation

Question 3

Role of the long head and short heads of biceps

Answer 3

– Provides anterior stability to the GH, the long head connects to the supragelenoid tubercle.
– therefore, failure of the stabilisation of the long head can have damaging effects on the GH and the rotator cuff function

• Achieved through compression of the humeral head against the glenoid fossa
  – Observations have been seen that the tendon of the long head hypertrophies in patients that have rotator cuff tears, so this confirms that it has a role in the stability of the GH

– it is actually the short head acting in unison with the long head that also ensures that the humerus stays away from the sub acromial space

Question 4

Force coupling of the shoulder

Answer 4

Force coupling is forces rotating around a pivot
There can be multiple forces acting at once
they can be equal or unequal depending on what activity is being performed

Different muscles like:
- rhomboids elevate scapula
- serratus anterior, evelates and upwardly rotates pulling from the anterior surface of the upper border of the scapula
– trapezius
– lev scap pulls from the superior angle

Question 5

Roll and slide of clavicle

Answer 5

Clavicle is the only axial attachment for the entire upper extremity

Movements of the clavicle:
– elevation, depression, rotation, protraction and retraction
– all these movements are passive accessory movements

– all clavicular movements are essential to position the scapular in the optimal position to accept the head of the humerus

Question 6

Roll and slide of the GH

Answer 6

Convex on concave (rolls and slides in the opposite directions):
– humerus convex (active)
– scapula concave (passive)

Abduction:
– humerus rolls superiorly
– humerus slides inferiorly as well

– this is beneficial so the huermus doesn’t decrease the sub acromial space too much so this can prevent impingement

Question 7

Roll and slide of SC

Answer 7

Convex on concave (roll and slide in opposite directions):
– this is a biproduct of the roll and slide joint in the glenohumral joint between the humerus and the scapula

Manubrium is concave

Proximal clavicle is convex

Clavicle will roll superiorly due to its elevation when the arm is abducted
– it will also slide inferiorly

Question 8

Importance of the sub acromial space

Answer 8

Structures packed into the space:
– the tendon of the long head of the biceps muscle
– subacromial bursa
– rotator cuff (supraspinatus tendon)

Closing the gap:
– lifting the arm into abduction (due to the pull of the supraspinatus muscle will close the gap)
– lifting the arm in general
—- this can lead to shoulder impingement

Abnormal arthrokinematics:
– flat (17% of cases)
– curved (43%)
– hooked (39%)
—- about 70% of rotator cuff tears are associated with a hooked acromion
—- may be the result of the ossification of the coracoacromial ligament

– convex ‘upturned’ (1%)

ROLE:
– plays a significant role in normal function and movement of the shoulder joint
– it is a passage for the tendons stated above
– it helps with rotator cuff function due to it allowing the supraspinatus tendon to go through
– prevents impingement syndrome
– shoulder health and injury prevention

Question 9

Movers and stabilisers in the shoulder

Answer 9

Movers:
– deltoid (anterior, medial and posterior)
– supraspinatus
– biceps brachii
– brachioradialis
– pectoralis major

Joint stabilising tissues:
– capsule
– ligaments
– articular disc (AC/SC)

Stabilising muscles:
– subscapularis
– serratus anterior
– latissimus dorsi (when people have an anterior dislocation, important to get the pt working on these 3 muscles

– coracobrachialis
– pectoralis major

Coracoacromial ligaments

Coracohumeral ligaments

Glenohumeral ligaments

Question 10

Painful and weak shoulder

Answer 10

Rotator cuff related shoulder pain
– subacromial impingement syndrome
– SLAP lesion

Question 11

Painful and stiff shoulder

Answer 11

Adhesive capsulitis

OA of GH and AC (GH is less common, very rare)

Question 12

Painful and unstable

Answer 12

Dislocations

Repeated dislocations

Subluxation