3.3 Shoulder complex

Question 0

What are the joints of the shoulder?

Answer 0

3 true bi-articular synovial joints

• sternoclavicular
• acromioclavicular
• glenohumeral

2 physiological/functional joints

• subdeltoid
• scapulothoracic

Ligaments for joint stability
Muscles
Nerves, blood supply (Hilton’s Law: the blood and n’ supply near a joint will supply that joint)

Question 1

What movements is the shoulder complex capable of?

Answer 1

F/E
Adduction/abduction
medial rotation/lateral rotation
circumduction

Question 2

Sternoclavicular (SC) joint

Answer 2

• Connects upper limb with thorax
• Saddle joint (like thumb)
• Articular disc (complete articular disc divides into 2 separate compartments that allow separate movements)
• 3 ligaments (sternoclavicular, interclavicular, costoclavicular)
• dislocation uncommon
• blood supply (internal thoracic, suprascapular)
• nerve supply (N. to subclavius)
• movements: elevation/depression, protraction/retraction, circumduction

Question 3

What causes sternoclavicular subluxation?

Answer 3

Usually direct trauma to front of chest.
The vessels at the root of the neck are susceptible to injury

Anterior subluxation of clavicle - fixed by immobilising joint
Posterior - much more dangerous, brachial plexus & subclavian artery travel behind

Question 4

What are the features of the acromioclavicular (AC) joint?

Answer 4

• Connects acromial end of clavicle with scapula
• Plane joint
• Partial articular disc
• Intrinsic ligament: acromioclavicular ligament
• Extrinsic ligament: coracoclavicular ligament (conoid, trapezoid)
• Shoulder separation in contact sports

Question 5

What is the blood and nerve supply to the AC joint?

Answer 5

Blood: suprascapular & thoracoacromial

Nerve: suprascapular, lateral pectoral, axillary (from posterior cord of brachial plexus)

Question 6

What is the function of the conoid and trapezoid ligaments?

Answer 6

Both are extrinsic ligaments of the AC joint, which hold joint together, deciding degree of shoulder separation.

Conoid: stops clavicle from elevating too far
-triangle, lies medially & in sagittal (vertically) plane

Trapezoid: prevents excessive rotation
-square, lies laterally & horizontally

Question 7

What are the clavicular movements at the SC and AC joints?

Answer 7

[look up]

Question 8

What are the grades of AC dislocation?

Answer 8

1. AC ligaments stretched but not torn. CC ligaments intact.
2. AC ligaments torn & disrupted. CC ligaments remain intact.
3. AC & CC ligaments ruptured. Wide separation of joint.
   * typically requires surgery to put joint back into position

Question 9

What are the features of the glenohumeral (GH) joint?

Answer 9

• Between glenoid cavity and head of humerus
• Synovial ball-and-socket joint (multi-axial joint)
• Poor congruence b/w articular surfaces
• Glenoid labrum deepens socket (fibrocartilaginous ring)
• connective tissue yields more than bone - less nerve endings/pain
• Tendon of LH of biceps has intracapsular origin

Question 10

What is the blood and nerve supply of the GH joint?

Answer 10

Blood supply: circumflex humeral arteries (anterior and posterior)

Nerve: suprascapular, axillary, lateral pectoral

Question 11

What are the ligaments of the GH joint and what deficiencies are there in the articular capsule?

Answer 11

Intrinsic ligaments:

• coracohumeral
• glenohumeral (superior, middle, inferior)

Extrinsic:

• coracoacromial
• transverse humeral

Rotator cuff muscles act as dynamic ligaments providing posterior support.

Deficiencies in articular capsule:

• anterior GH ligaments
• inferior articular capsule
• anterolateral LH of biceps

Question 12

What are the bursae at GH joint?

Answer 12

Subscapular, subacromial bursae

Question 13

What mobility is there at GH joint?

Answer 13

• High mobility, reduced stability
• Rotator cuff muscles act as fixator ligaments: SITS
• Greatest stability when the 2 articular surfaces make maximal contact, which is during abduction and external rotation.
• Paradoxically, this is also position for dislocation.

Question 14

What muscles act on shoulder joint anteriorly?

Answer 14

Deltoid
Pectoralis major
Coracobrachialis
Biceps brachii
Brachialis

Anterior deep:
Subscapularis
Coracobrachialis
Brachialis

Question 15

What muscles act on the shoulder joint posteriorly?

Answer 15

Suprasinatus
Infraspinatus
Teres major and minor
Triceps brachii (lateral and long head)
Latissimus dorsi

Question 16

What movements occur at the shoulder joint and what muscles are involved?

Answer 16

Flexion adduction and medial rotation by:
Pectoralis major, deltoid, biceps, coracobrachialis, teres major, latissimus dorsi, subscapularis

Extension, abduction and lateral rotation by:
Deltoid, teres major, latissimus dorsi, triceps, supraspinatus, infraspinatus, teres minor

*deltoid and supraspinatus are functionally and clinically important for abduction

Question 17

What physiological joints are there at the shoulder?

Answer 17

Subdeltoid:

• between supraspinatus and GH joint
• subacromial bursa minimises friction
• painful arc syndrome

Scapulothoracic:

• between serratus and thorax
• between serratus and scapula
• glenohumeral rhythm: scapula and humerus 1:2 ratio

Question 18

Where is the subacromial bursa?

Answer 18

• located under acromion process of scapula

- susceptible to irritation during shoulder abduction

Question 19

In what direction does dislocation of GH joint occur?

Answer 19

Anterior (inferior) - most common due to force applied to abducted & externally rotated arm

Posterior - less common due to electric shock/seizures, arm in adducted & internally rotated position