Shoulder Region, Shoulder Joint, Arm and Cubital Fossa

Question 1

Discuss Erb’s paralysis. Hint: (1) Nerve roots involved, (2) 9 muscles that are paralyzed, (3) describe the position of upper limb and hand, (4) sensory loss, (5) autonomic signs

Answer 1

(1) Nerve roots involved: C5 and C6

(2) Muscles paralyzed: Deltoid, supraspinatus, infraspinatus, biceps brachii, brachialis, brachioradialis, supinator and extensor carpi radialis longus

(3) Position of upper limb and hand:
Policeman’s tip, characterized by
- arm adduction
- medial rotation
- elbow extension
- pronation

(4) Sensory loss: along outer aspect of arm

(5) Autonomic signs: absent

[Diagram]

Question 2

Discuss Klumpke’s paralysis. Hint: (1) Nerve roots involved, (2) 9 muscles that are paralyzed, (3) describe the position of upper limb and hand, (4) sensory loss, (5) autonomic signs

Answer 2

a) Nerve roots involved: C8 and T1

b) Muscles paralyzed: all intrinsic hand muscles as well as some muscles of the forearm

c) Position of hand: claw hand
- paralysis of flexors of wrist and fingers
- paralysis of intrinsic hand muscles

d) Sensory loss: along medial border of forearm and hand

d) Autonomic signs: present (Horner’s syndrome)
[Diagram 1] [Diagram 2]

Question 3

Outline the surface landmarks of the shoulder region.

Answer 3

Clavicle
Suprasternal notch (jugular notch)
Sternal angle (of Louis)- useful landmark to identify 2nd rib
Infraclavicular fossa (palpate on yourself)
Coracoid process
Nipple

Question 4

Describe the sensory innervation of the shoulder region.

Answer 4

Upper half of the deltoid region is supplied by the supraclavicular nerves (C3, C4)

Lower half of the deltoid region is supplied by the superior lateral brachial cutaneous nerve (C5-C6), which is a cutaneous branch of the axillary nerve.

[Diagram]

Question 5

What joints constitute the shoulder joint complex?

Answer 5

1. Glenohumeral joint
2. Acromioclavicular joint
3. Sternoclavicular joint
4. Scapulothoracic articulation/scapulothoracic linkage (functional linkage between the scapula and thorax)

Question 6

What type of joint is the glenohumeral joint?
(Brief note: This joint is the primary articulation of the shoulder girdle and generally termed shoulder joint by clinicians.)

Answer 6

Ball-and-socket type of synovial joint

Question 7

Attachments of capsule of glenohumeral joint?

Answer 7

Medially: margins of the glenoid cavity beyond the glenoid labrum but it extends beyond the supraglenoid tubercle thus enclosing the long head of biceps brachii
Laterally: anatomical neck of humerus
Inferiorly: extends downwards 1.5 cm or more on the surgical neck of the humerus

[Diagram]

Question 8

Differentiate between Erb’s paralysis and Klumpke’s paralysis in terms of mode of injury.

Answer 8

Erb’s paralysis is caused by excessive increase in the angle between the neck and the shoulder (e.g. falling and landing on the shoulder, or traction of the arm during birth) whereas Klumpke’s paralysis is caused by hyperabduction of the arm (which may occur when one falls on an outstretched hand or an arm is pulled into machinery or during delivery).
[Diagram]

Question 9

List crucial ligaments of the glenohumeral joint and accessory ligaments of the joint as well.

Answer 9

Crucial ligaments:
1. Capsular ligament
2. Superior, middle and inferior glenohumeral ligaments
3. Coracohumeral ligament (from the base of the coracoid process to the anterior aspect of the greater tubercle of the humerus)
4. Transverse humeral ligament (this bridges the bicipital groove between the greater and lesser tubercle, converting the groove into a canal that provides passage to the tendon of long head of biceps brachii surrounded by a synovial sheath)

Accessory ligaments
1. Coracoacromial ligament - protects superior aspect of the joint
2. [Technically not a ligament, but just take note …] Coracoacromial arch formed by coracoid process, acromion process and coracoacromial ligament between them, forming a protective arch for the head of humerus and preventing its superior dislocation above the glenoid cavity
[Note: supraspinatus muscle passes under this arch and lies deep to the deltoid where its tendon blends with the joint capsule]

[Diagram 1] [Diagram 2]
[Cadaveric image]

Question 10

List bursae related to the shoulder joint.

Answer 10

1. Subscapular bursa - lies between tendon of subscapularis and the neck of scapula and protects the tendon from friction against the neck of scapula
2. Subacromial bursa - lies between the coracoacromial arch and supraspinatus tendon and joint capsule. It continues downwards beneath the deltoid, where it is referred to as the subdeltoid bursa.
3. Infraspinatus bursa - lies between the tendon of infraspinatus and posterolateral aspect of the joint capsule.
4. [Diagram 1] [Diagram 2]

Question 11

What other stability factors are there besides what has been mentioned in the glenohumeral joint so far (the ligaments)? Briefly explain how they contribute to stability.

Answer 11

1. Rotator cuff (musculotendinous cuff) muscles - their medial pull holds the head of the humerus against the smaller and shallow glenoid cavity
2. Long head of biceps tendon - passes above the head of the humerus thus prevents its upwards dislocation
3. Glenoid labrum - deepens shallow glenoid cavity
4. Coracoacromial arch - forms the secondary socket of the glenohumeral joint and prevents upward dislocation of the head of the humerus

Question 12

Movements of the glenohumeral joint? (State the movement, its prime movers and its accessory muscles. There are 6 key movements.)

Answer 12

1. Flexion: Pectoralis major (clavicular part), deltoid (anterior fibres), short head of biceps brachii, coracobrachialis, pectoralis major (sternocostal head)
2. Extension: Deltoid (posterior fibres), latissimus dorsi, teres major, long head of triceps
3. Adduction: pectoralis major (sternocostal part), latissimus dorsi, teres major, coracobrachialis, short head of triceps, long head of triceps
4. Abduction: deltoid (lateral fibres) (15 to 90 degrees), supraspinatus (initiator from 0 to 15 degrees), serratus anterior, upper and lower fibres of trapezius
5. Medial rotation: subscapularis, pectoralis major, latissimus dorsi, deltoid (anterior fibres), teres major
6. Lateral rotation: deltoid (posterior fibres), infraspinatus, teres minor

Bold indicates prime movers.

Question 13

Describe the mechanism of arm abduction.

Answer 13

The total range of abduction is 180°. Abduction up to 90° occurs at the glenohumeral joint. Abduction from 90° to 120° can occur only if the humerus is rotated laterally.
Abduction from 120° to 180° can occur if the scapula rotates forwards on the chest wall.

The articular surface of the head of humerus permits elevation of arm only up to 90°, because when the upper end of humerus is elevated, to 90° its greater tubercle impinges upon the under surface of the acromion and can only be released by lateral rotation of the arm.

Therefore, the arm rotates laterally and carries abduction up to 120°.

Abduction above 120° can occur only if scapula rotates.
So that the scapula rotates forwards on the chest wall.

Question 14

Give the range of motions of the various arm movements.

Answer 14

• Flexion - 90°
• Extension - 45°
• Abduction - 180°
• Adduction - 45°
• Lateral rotation - 45°
• Medial rotation - 55°

Question 15

Why does dislocation of the shoulder joint mostly occur inferiorly?

Answer 15

Because the joint is least supported on this aspect. “There is no cuff inferiorly.” (from Last’s)

Question 16

Which nerve is often injured during dislocation of the shoulder joint?

Answer 16

The axillary nerve because of its close relation to the inferior part of the joint capsule.

Question 17

Clinically, dislocation of the shoulder joint is described as anterior or posterior dislocation indicating what?

Answer 17

Indicating whether the humeral head has descended anterior or posterior or to the infraglenoid tubercle of the scapula and long head of the triceps.

Question 18

What usually causes dislocation at the shoulder joint?

Answer 18

excessive extension and lateral rotation of the humerus

Question 19

How does dislocation of the shoulder joint clinically present itself?

Answer 19

(a) Hollow in rounded contour of the shoulder
(b) Prominence of shoulder tip
(c) [Diagram]

Question 20

Discuss frozen shoulder (adhesive capsulitis). (Hint: Symptoms, cause)

Answer 20

It is a clinical condition characterized by pain and uniform limitation of all movements of the shoulder joint, though there are no radiological changes in the joint. It occurs due to shrinkage of the joint capsule, hence the name adhesive capsulitis. This condition is generally seen in individuals with 40–60 years of age.

Question 21

Name two rotator cuff disorders.

Answer 21

1. calcific supraspinatus tendinitis [caused by deposition of calcium phosphate in the tendon of supraspinatus. Calcium deposition irritates the overlying subacromial bursa causing subacromial bursitis. Consequently, when the arm is abducted the inflamed bursa is caught between the tendon and coracoacromial arch, and this causes severe pain.]
2. subacromial impingement syndome

Question 22

What type of joint is the acromioclavicular joint?

Answer 22

It is a plane type of the synovial joint between the lateral end of the clavicle and acromion process of the scapula.

Question 23

What are the two ligaments of the acromioclavicular joint?

Answer 23

1. Acromioclavicular ligament: It is a fibrous band that extends from acromion to the clavicle. It strengthens the acromioclavicular joint superiorly.
2. Coracoclavicular ligament: It lies a little away from the joint itself but play an important role in maintaining the integrity of the joint.
   The coracoclavicular ligament consists of two parts:
   (a) conoid and (b) trapezoid, which are united posteriorly and often separated by a bursa.
   The conoid ligament is an inverted cone-shaped fibrous band. The apex is attached to the root of the coracoid process just lateral to the scapular notch and base is attached to the conoid tubercle on the inferior surface of the clavicle.
   The trapezoid ligament is a horizontal fibrous band that stretches from upper surface of the coracoid process to the trapezoid line on the inferior surface of lateral end of the clavicle.
   [Diagram: Acromioclavicular Joint with the Ligaments]
   N.B. The coracoclavicular ligament is largely responsible for suspending the weight of the scapula and upper limb from clavicle.
   The coracoclavicular ligament is the strongest ligament of the upper limb.

Question 24

What type of joint is the sternoclavicular joint?

Answer 24

Saddle type of the synovial joint.

Question 25

What are the articular surfaces of the sternoclavicular joint?

Answer 25

1. Rounded sternal end of clavicle
2. Shallow socket at the superolateral angle of the manubrium sterni and adjacent part of the 1st costal cartilage
3. [Diagram: sternoclavicular joint]

The medial end of clavicle rises higher than the manubrium, hence it poorly fits into its shallow socket. But a strong thick articular disc of fibrocartilage attached superiorly to the clavicle and 1st costal cartilage inferiorly prevents the displacement of the medial end of the clavicle.

Question 26

What ligaments provide stability to sternoclavicular joint?

Answer 26

1. Anterior and posterior sternoclavicular ligaments:
   They reinforce the joint capsule anteriorly and posteriorly. The posterior ligament is weaker than the anterior ligament.
2. Interclavicular ligament: It is T-shaped and connects the sternal ends of two clavicles and strengthens the joint capsule superiorly. In between, it is attached to the superior border of the suprasternal notch.
3. Costoclavicular ligament: It anchors the inferior surface of the sternal end of clavicle to the first rib and adjoining part of its cartilage.

Question 27

Discuss the scapulothoracic linkage.

Answer 27

The scapulothoracic articulation is not a true articulation but a functional linkage between the ventral aspect of the scapula and lateral aspect of the thoracic wall. The linkage is provided by serratus anterior muscle. The movements of scapula around the chest wall are facilitated by the presence of loose areolar tissue between the serratus anterior and subscapularis muscles.

Question 28

What are the movements at the scapulothoracic joint? (6)

Answer 28

elevation
depression
abduction (protraction)
adduction (retraction)
upward rotation (happens when you raise your hand above your head)
downward rotation

Question 29

List the scapular sling muscles (they are scapulothoracic muscles that are like flexible straps used to support or raise the upper limb).

Answer 29

Trapezius
Levator scapulae
Rhomboid major
Rhomboid minor
Serratus anterior
Pectoralis minor (not a very significant scapular sling muscle)
Subclavius (not a very significant scapular sling muscle)

Question 30

State the dermatomes of the following:
Nipple
Tip of the shoulder
Lateral side of the arm
Lateral side of the forearm
Thumb
Hand and middle 3 digits
Little finger
Medial side of the forearm
Medial side of the arm
Axilla

Answer 30

Area Segment
Nipple T4
Tip of the shoulder C4
Lateral side of the arm C5
Lateral side of the forearm C6
Thumb C6
Hand and middle 3 digits C7
Little finger C8
Medial side of the forearm C8
Medial side of the arm T1
Axilla T2

Question 31

What does the primary neurovascular bundle of the medial side of the arm contain (5 structures)?

Answer 31

Brachial artery
Basilic vein
Radial nerve
Median nerve
Ulnar nerve

Question 32

List the surface landmarks of the arm.

Answer 32

1. Greater tubercle of the humerus
2. Shaft of the humerus
3. Medial epicondyle of the humerus
4. Lateral epicondyle of the humerus
5. Deltoid muscle
6. Biceps muscle
7. Brachial artery pulsations
8. Ulnar nerve
9. Superficial veins in front of elbow (i.e., cephalic, basilic, and median cubital veins)
10. Head of radius
11. Olecranon process of ulna

Question 33

What divides the arm into its anterior and posterior compartments?

Answer 33

Fascial septa (medial and lateral)
Fascial sleeve

Question 34

Which structures pierce the intermuscular septa of the arm to move from one compartment to another?

Answer 34

• Ulnar nerve and superior ulnar collateral artery pierce the medial intermuscular septum to enter the posterior compartment.
• Radial nerve and radial collateral artery pierce the lateral intermuscular septum to enter the anterior compartment.
• [Diagram]

Question 35

State the contents of the anterior compartment of the arm.

Answer 35

Biceps brachii
Coracobrachialis
Brachialis
Musculocutaneous nerve
Brachial artery

In addition to these, the following nerves also pass through this compartment:
Radial nerve
Median nerve
Ulnar nerve

Question 36

State the following under biceps brachii muscle:
1. Origin
2. Insertion
3. Nerve supply
4. Actions

Answer 36

1. Origin: (a) Long head - supraglenoid tubercle of the scapula, (b) Short head- Tip of the coracoid process of the scapula (along with coracobrachialis)
2. Insertion: posterior rough part of radial tuberosity, the deep fascia on the medial aspect of forearm by its aponeurosis (bicipital aponeurosis)
3. Nerve supply: musculocutaneous nerve (C5, 6, 7)
4. Actions: (a) Supination of forearm when elbow is flexed, (b) Flexion of forearm when elbow is extended

Question 37

State the following under coracobrachialis muscle:
1. Origin
2. Insertion
3. Nerve supply
4. Actions

Answer 37

1. Origin: tip of coracoid process of the scapula
2. Insertion: middle of the medial border of the shaft of the humerus
3. Nerve supply: Musculocutaneous nerve
4. Actions: weak flexor and adductor of the arm
5. [Diagram: Coracobrachialis]

Question 38

State the following under the brachialis muscle:
1. Origin
2. Insertion
3. Nerve supply
4. Actions

Answer 38

1. Origin: front of lower shaft of humerus
2. Insertion: anterior surface of coronoid process of ulna including ulnar tuberosity
3. Nerve supply: Dual innervation;
   Medial 2/3 - musculocutaneous nerve
   Lateral 1/3 - radial nerve
4. Actions: flexor of the forearm in all positions

Question 39

What features make the brachialis muscle unique as a flexor of the elbow?

Answer 39

(a) it only flexes the elbow
(b) it is the only flexor of the elbow which inserts into the ulnar bone
(c) in some instances it has dual innervation from musculocutaneous [main] and radial nerves
(d) it is supplied by two arteries: the brachial artery and the radial recurrent artery

Further notes:
Other flexors of the elbow, such as the biceps brachii and brachoradialis, receive blood supply proximally from the ulnar collateral artery, radial collateral artery, and middle collateral artery, and distally from the radial recurrent artery and the ulnar recurrent artery. Thus the brachialis has a more extensive and diverse blood supply compared to other elbow flexors.

Question 40

What are the contents in the posterior compartment of the arm?

Answer 40

Triceps brachii
Radial nerve
Profunda brachii artery

Note that ulnar nerve and ulnar collateral arteries pass through this compartment.

Question 41

State the following under the triceps brachii muscle:
1. Origin
2. Insertion
3. Nerve supply
4. Actions

Answer 41

1. Origin:
   Long head: Infraglenoid tubercle of scapula
   Lateral head: Oblique ridge above the spiral groove on the upper part of the posterior surface of shaft of humerus
   Medial head: Posterior surface of lower half of humeral shaft below the spiral groove
2. Insertion: Posterior part of the superior surfaces of olecranon process
3. Nerve supply: Radial nerve
4. Actions:
   - powerful extensor of elbow joint
   - long head supports humeral head during hyperabduction of arm

Question 42

State the boundaries of the cubital fossa (6 boundaries, which include floor and roof)
(Hint: it is a triangular space, and inverted for that matter)

Answer 42

Lateral: medial border of brachioradialis
Medial: Lateral border of pronator teres muscle
Base: an imaginary horizontal line joining the front of two epicondyles of the humerus
Apex: meeting point of lateral and medial boundaries. Here brachioradialis crosses over pronator teres
Floor: brachialis in the upper part, supinator in the lower part
Roof (from superficial to deep):
-Skin
-Superficial fascia containing medial cubital vein connecting cephalic and basilic veins and medial and lateral cutaneous nerves of the forearm
-Deep fascia strengthened by bicipital aponeurosis

Question 43

Describe the cutaneous innervation of the axilla.

Answer 43

1. intercostobrachial nerve (T2)
2. small branches from T3

Question 44

List the contents of the cubital fossa from medial to lateral.

Answer 44

Acronym: MBBS
1. Median nerve
2. Brachial artery
3. Biceps brachii tendon
4. Superficial radial nerve

Question 45

Describe the cutaneous innervation of the arm.

Answer 45

1. upper medial part of the arm - intercostobrachial nerve (T2)
2. lower medial part of the arm - medial brachial cutaneous nerve (T1)
3. upper lateral half of the arm - superior lateral brachial cutaneous nerve (C5, 6) (branch of axillary nerve)
4. lower lateral half of the arm - inferior lateral brachial cutaneous nerve (C5, 6) (branch of radial nerve)
5. posterior aspect of the arm - posterior brachial cutaneous nerve (C5) (branch of radial nerve)

Question 46

What is the clinical significance of the cubital fossa?

Answer 46

1. Medial cubital vein - vein of choice for collecting blood samples and giving intravenous injections
2. Brachial pulse - easily felt in this region hence convenient point for measuring blood pressure
3. Dealing with supracondylar fracture of the humerus - brachial artery and median nerve are vulnerable in supracondylar fracture of the humerus (Question: Why will brachial artery be more vulnerable than median nerve to the fracture?)

Question 47

What are some of the anatomical events at the insertion of coracobrachialis. (at least 5)
Hint: Think in terms of: (1) shape of shaft of humerus, (2) brachial artery, (3) basilic vein, (4) median nerve, (5) radial nerve, (6) ulnar nerve (7) medial antebrachial cutaneous nerve, (8) nutrient artery, (9) deltoid muscle

Answer 47

1. The circular shaft of the humerus becomes triangular below this level.
2. Brachial artery passes from medial side of the arm to its anterior aspect.
3. Basilic vein pierces the deep fascia.
4. the median nerve crosses in front of the brachial artery from the lateral side to the medial side
5. the radial nerve pierces the lateral intermuscular septum to pass from the posterior compartment to the anterior compartment
6. the ulnar nerve pierces the medial intermuscular septum to go into the posterior compartment
7. medial antebrachial cutaneous nerve pierces the deep fascia
8. the nutrient artery pierces the humerus
9. insertion of deltoid muscle
10. [Diagram]

Question 48

Describe the origin and termination of the musculocutaneous nerve.

Answer 48

Origin: lateral cord of brachial plexus
Termination: continues in the forearm as the lateral antebrachial cutaneous nerve

Question 49

State two landmarks of the musculocutaenous nerve.

Answer 49

1. it pierces coracobrachialis
2. passes between biceps brachii and brachialis
3. [Diagram 1] [Diagram 2]

Question 50

What does the brachial artery branch into in the cubital fossa?

Answer 50

Ulnar and radial arteries

Question 51

After a shoulder injury, the patient is diagnosed with a dislocation of the tendon that traverses the intertubercular sulcus of the humerus. Which of the following tendons is most likely dislocated?
A. Tendon of long head of triceps brachii
B. Tendon of lateral head of triceps brachii
C. Tendon of medial head of triceps brachii
D. Tendon of short head of biceps brachii
E. Tendon of long head of biceps brachii

Answer 51

Choice E (Tendon of long head of biceps brachii)

Question 52

After an anteroinferior humeral dislocation that damaged the nerve that passes through the quadrangular space, you would expect:
A. Weakness in humeral abduction and no sensory loss
B. Weakness in humeral abduction and sensory loss along the lateral aspect of the upper arm
C. Weakness in humeral adduction and no sensory loss
D. Weakness in humeral adduction and sensory loss along the lateral aspect of the upper arm
E. Weakness in humeral flexion and no sensory loss

Answer 52

Choice B.

Question 53

A 36-year-old man falls from his bicycle and sustains a midhumeral fracture. Upon examination, he shows “wrist drop.” Which of the following nerves was most likely injured in the fall?
A. Median
B. Radial
C. Musculocutaneous
D. Ulnar
E. Axillary

Answer 53

Choice B: Radial

Note:
1. Lesion of ulnar nerve causes claw hand
2. Lesion of median nerve causes ape-like hand due to atrophy of thenar muscles
3. Lesion of radial nerve causes wrist drop or finger drop

Question 54

A patient comes to the ED with a severe knife wound to his arm that severs the biceps brachii and the underlying nerve. Which of the following is the most likely sequelae?
A. Weakness in elbow extension
B. Reduced sensation on the anterior medial aspect of the arm
C. Reduced sensation on the anterior lateral aspect of the arm
D. Reduced sensation over the olecranon
E. Reduced sensation over the lateral aspect of the forearm

Answer 54

Choice E.

Question 55

A 12-year-old female child was brought to the ED with a fractured olecranon process. Based on the location of this injury, you are most concerned about damage to which of the following nerves?
A. Median
B. Ulnar
C. Musculocutaneous
D. Radial
E. Anterior interosseous

Answer 55

Choice B

[Osteology of the Ulna]
[Osteology of the Radius]
[Diagram: Course of the Ulnar Nerve]

Question 56

What arteries supply the glenohumeral joint?

Answer 56

1. Anterior and posterior circumflex humeral arteries
2. Suprascapular artery
3. Circumflex scapular artery
4. [Diagram 1] [Diagram 2]

Question 57

What nerves supply the glenohumeral joint?

Answer 57

Axillary nerve
Suprascapular nerve
Lateral pectoral nerve

Question 58

Here are some MRI images of the upper limb. Click on Answer to view them.

Answer 58

[Image 1: Transverse section through the arm]
[Image 2: Transverse section through the arm]
[Image 3: Transverse section through the arm]