The arm and the elbow

Question 1

What is the Axilla

Answer 1

An area that lies underneath the glenohumeral joint, at the junction of the upper limb and the thorax. It is a passageway by which neurovascular and muscular structures can enter and leave the upper limb

Question 2

What forms the Apex of the axilla?

Answer 2

Also known as the axillary inlet, it is formed by lateral border of the first rib, superior border of scapula, and the posterior border of the clavicle.

Apex decreases in size most markedly when the arm is fully abducted – leaving the contents of the axilla at risk of compression.

Question 3

What forms the Lateral border of the axilla?

Answer 3

Intertubercular groove of the humerus.

Question 4

What forms the Medial border of the axilla?

Answer 4

Serratus anterior and the thoracic wall (ribs and intercostal muscles).

Question 5

What forms the Anterior border of the axilla?

Answer 5

Pectoralis major and the underlying pectoralis minor and the subclavius muscles.

Question 6

What forms the Posterior border of the axilla?

Answer 6

Subscapularis, teres major and latissimus dorsi.

Question 7

What is contained within the neurovascular bundle of the axilla?

Answer 7

Axillary artery (and branches) – the main artery supplying the upper limb. It is commonly referred as having three parts; one medial to the pectoralis minor, one posterior to pectoralis minor, and one lateral to pectoralis minor. The medial and posterior parts travel in the axilla.

Axillary vein (and tributaries) – the main vein draining the upper limb, its two largest tributaries are the cephalic and basilic veins.

Brachial plexus (and branches) – a collection of spinal nerves that form the peripheral nerves of the upper limb.

4 groups of Axillary lymph nodes – they filter lymphatic fluid that has drained from the upper limb and pectoral region. Drain 75% of lymph from the breast therefore Axillary lymph node enlargement is a non-specific indicator of breast cancer.
Also Biceps brachii (short head) and coracobrachialis – these muscle tendons move through the axilla, where they attach to the coracoid process of the scapula.

Question 8

What is the Brachial Plexus

Answer 8

The brachial plexus is a network of nerves that extends from its origin in the neck, travels over the first rib inferior to the clavicle, and into the axilla. The plexus gives rise to nerves which provide the motor and sensory innervation to the whole of the upper limb.

Question 9

What are the roots of the brachial plexus?

Answer 9

anterior rami of 5 spinal nerves (C5-T1)

Question 10

What are the trunks of the brachial plexus?

Answer 10

superior-C5 and C6
middle- C7
inferior- C8 and T1

Question 11

What are the divisions of the brachial plexus?

Answer 11

Each trunk divides into two branches within the posterior triangle of the neck. One division moves anteriorly (toward the front of the body) and the other posteriorly (towards the back of the body).
We now have three anterior and three posterior nerve fibres. These divisions leave the posterior triangle and pass into the axilla. They recombine into the cords of the brachial plexus.

Question 12

What are the cords of the brachial plexus?

Answer 12

The lateral cord is formed by: the anterior division of the superior trunk and the anterior division of the middle trunk
The posterior cord is formed by: the posterior division of the superior trunk, the posterior division of the middle trunk and the posterior division of the inferior trunk
The medial cord is formed by: the anterior division of the inferior trunk.

Question 13

What are the Major Branches of the brachial plexus?

Answer 13

Musculocutaneous: Lateral cord
Axillary: Posterior Cord
Radial: Posterior Cord
Median: lateral and median cords.
Ulnar: Medial Cord

M shape formed over axillary A imp landmark

Question 14

Which structures can supracondylar fractures damage

Answer 14

Median N and Brachial A

Most common in children

Question 15

Which Nerve can humeral shaft fractures damage

Answer 15

Radial N as it comes from post humerus round to ant humerus

Question 16

Musculocutaneous Nerve- Roots and structures innervated

Answer 16

Roots: C5, C6, C7.
Motor Functions: Innervates the brachialis, biceps brachii and coracobrachialis muscles.
Sensory Functions: Gives off the lateral cutaneous branch of the forearm, which innervates the lateral half of the anterior forearm, and a small lateral portion of the posterior forearm.

Question 17

Damage to Musculocutaneous Nerve

Answer 17

Injury to the musculocutaneous nerve is relatively uncommon, as it is well protected within the axilla. The most common cause is a stab wound to the axilla region.

Coracobrachialis, biceps brachii and brachialis muscles are paralysed. Flexion at the shoulder is weakened, but can still occur due to the pectoralis major. Flexion at the elbow is also affected, but can still be performed because of the brachioradialis muscle. Also, supination of the affected limb is greatly weakened, but is produced by the supinator muscle.
Sensory functions – loss of sensation over the lateral side of the forearm.

Question 18

Axillary Nerve- Roots and structures innervated

Answer 18

Roots: C5 and C6.
Motor Functions: Innervates the teres minor and deltoid muscles.
Sensory Functions: Gives off the superior lateral cutaneous nerve of arm, which innervates the inferior region of the deltoid (“regimental badge area”).

Question 19

Damage to Axillary Nerve

Answer 19

The axillary nerve is most commonly damaged by trauma to the shoulder or proximal humerus – such as a fracture of the humerus surgical neck.
Motor functions: Paralysis of the deltoid and teres minor muscles. This renders the patient unable to abduct the affected limb.
Sensory functions: The upper lateral cutaneous nerve of arm will be affected, resulting in loss of sensation over the regimental badge area. Patients may report parathesia in this area
Characteristic clinical signs: In long standing cases, the paralysed deltoid muscle rapidly atrophies, and the greater tuberosity can be palpated in that area.

Question 20

Median Nerve- Roots and structures innervated

Answer 20

Roots: C6 – T1.
Motor Functions: Innervates most of the flexor muscles in the forearm, the thenar muscles, and the two lateral lumbricals associated with the index and middle fingers.
Sensory Functions: Gives off the palmar cutaneous branch, which innervates the lateral part of the palm, and the digital cutaneous branch, which innervates the lateral three and a half fingers on the anterior (palmar) surface of the hand.

Question 21

Damage to Median Nerve

Answer 21

Compression of the median nerve within the carpal tunnel can cause carpal tunnel syndrome (CTS).

It is the most common mononeuropathy, and is caused by an increased tissue pressure within the carpal tunnel.
Clinical features include numbness, tingling, and pain in the distribution of the median nerve. Importantly, the palm is usually spared – as the palmar cutaneous branch does not travel through the carpal tunnel. Symptoms can wake the patient from sleep, and are usually worse in the morning. If left untreated, chronic CTS can cause weakness and atrophy of the thenar muscles.
Tests for carpal tunnel syndrome can be performed during physical examination:
Tinel’s sign – tapping the nerve in the carpal tunnel to elicit pain in median nerve distribution.
Phalen’s manoeuvre – holding the wrist in flexion for 60 seconds to elicit numbness/pain in median nerve distribution.

Treatment involves the use of a splint, holding the wrist in dorsiflexion overnight to relieve symptoms. If this is unsuccessful, corticosteroid injections into the carpal tunnel can be used. In severe case, surgical decompression of the carpal tunnel may be required

Question 22

Radial Nerve- Roots and structures innervated

Answer 22

Roots: C5 – T1.
Motor Functions: Innervates the triceps brachii, and the muscles in the posterior compartment of the forearm (which are primarily, but not exclusively, extensors of the wrist and fingers).
Sensory Functions: Innervates the posterior aspect of the arm and forearm, and the posterolateral aspect of the hand.

Question 23

Ulnar Nerve- Roots and structures innervated

Answer 23

Roots: C8 and T1.
Motor Functions: Innervates the muscles of the hand (apart from the thenar muscles and two lateral lumbricals), flexor carpi ulnaris and medial half of flexor digitorum profundus.
Sensory Functions: Innervates the anterior and posterior surfaces of the medial one and half fingers, and associated palm area.

Question 24

Damage to Ulnar Nerve

Answer 24

Trauma at the level of the medial epicondyle (e.g. isolated medial epicondyle fracture, supracondylar fracture). It can also be compressed in the cubital tunnel.
All the muscles of innervated by the ulnar nerve are affected.
Flexion of the wrist can still occur, but is accompanied by abduction (due to paralysis of flexor carpi ulnaris and medial half of flexor digitorum profundus).
Abduction and adduction of the fingers cannot occur (due to paralysis of the interossei).
Movement of the 4th and 5th digits is impaired (due to paralysis of the medial two lumbricals and hypothenar muscles).Adduction of the thumb is impaired, and the patient will have a positive Froment’s sign (due to paralysis of adductor pollicis).Characteristic signs: Patient cannot grip paper placed between fingers, positive Froment’s sign, wasting of hypothenar eminence.

Sensory functions: All sensory branches are affected, so there will be a loss of sensation over the areas that the ulnar nerve innervates.

Question 25

What is a Brachial Plexus block?

Answer 25

Anaesthesia alternative to general anaesthetic as it has fewer SE’s. Used for UL surgery.

Question 26

What is the Quadrangular Space (AKA quadrilateral)? What passes through this area?

Answer 26

The quadrangular space is a gap in the muscles of the posterior scapular region. It is a pathway for neurovascular structures to move from the axilla to the posterior shoulder and arm.
The axillary nerve and posterior circumflex humeral artery pass through the quadrangular space.

Question 27

What is the superior boundary of the Quadrangular Space?

Answer 27

teres minor.

Question 28

What is the inferior boundary of the Quadrangular Space?

Answer 28

Teres major.

Question 29

What is the lateral boundary of the Quadrangular Space?

Answer 29

Surgical neck of humerus.

Question 30

What is the medial boundary of the Quadrangular Space?

Answer 30

Long head of triceps brachii.

Question 31

Injury to the brachial plexus can result in what types of palsy?

Answer 31

Upper Brachial Plexus Injury – Erb’s Palsy
Erb’s palsy commonly occurs where there is an excessive increase in the angle between the neck and shoulder, which stretches (or even tears) the nerve roots of C5 and C6. It can occur as a result of result of a difficult birth or shoulder trauma. erves affected: Nerves derived from solely C5 or C6 roots: musculocutaneous, axillary, suprascapular and nerve to subclavius.

Lower Brachial Plexus Injury – Klumpke Palsy
A lower brachial plexus injury results from excessive abduction of the arm (e.g. person catching a branch as they fall from a tree). It has a much lower incidence than Erb’s palsy. Nerves affected: Nerves derived from the T1 root – ulnar and median nerves.

Question 32

What is the axillary artery? What does it become?

Answer 32

The axillary artery is the continuation of the subclavian artery after the subclavian border passes the lateral border of the clavicle.
The axillary artery travels through the axilla and becomes the brachial artery in the arm after it passes under the inferior margin of teres major.

Question 33

What are two branches of the axillary artery? Where do they arise? What does it supply? What N does it run alongside?

Answer 33

In the axilla, two important branches of the axillary artery are the anterior and posterior circumflex humeral arteries. These arise from the axillary artery inferior to pectoralis minor and form an anastomosis around the surgical neck of the humerus
The posterior circumflex humeral artery must travel backwards through the axilla to reach the posterior aspect of the surgical neck of the humerus. It travels backwards in the quadrilateral space alongside the axillary N.

Question 34

What branches does the brachial artery give off? where? What does it supply? What N does it run alongside?

Answer 34

As the brachial artery travels down through the anterior compartment of the arm, it gives off an important branch called the profunda brachii, or deep artery of the arm (profunda = deep). The profunda brachii is the main supplier of blood to the upper arm. This artery travels around the back of the humerus and runs down the posterior aspect of the humerus in the radial (or spiral) groove. The profunda brachii runs alongside the radial nerve, which also travels in the radial groove.

The brachial artery runs down the anterior arm. Around the level of the elbow joint, it bifurcates into two arteries, the radial and ulnar arteries. These arteries supply the forearm and hand.

Question 35

Where does the axillary V lie? what does it become and where?

Answer 35

The axillary vein lies medial to the axillary artery. It commences at the lower border of teres major and ascends through the axilla. It becomes the subclavian vein at the lateral border of the first rib.

Question 36

which veins form the axillary vein?

Answer 36

Two major superficial veins the cephalic and basilic veins. They travel up into the arm and form the axillary vein.

Question 37

What are the three important superficial veins in the upper limb?

Answer 37

Basilic vein
Cephalic vein
Median cubital vein – this vein connects the cephalic and basilic veins in the region anterior to the elbow joint.

Question 38

What are the two compartments of the arm? What separates these two compartments?

Answer 38

The arm (‘brachium’) is divided into two morphological and functional compartments by the deep (brachial) fascia of the arm (inter muscular septa). These are the:
flexor compartment – this lies anterior to the humerus. It is called the flexor compartment because it contains muscles that flex the shoulder and elbow.
Extensor compartment – this lies posterior to the humerus. It is called the extensor compartment because it contains a muscle that extends the shoulder and elbow.

Question 39

What are the muscles of the anterior arm?

Answer 39

Biceps brachii
Brachialis
Coracobrachialis

Question 40

Which artery supplies the anterior compartment of the arm?

Answer 40

Brachial A

Question 41

Which nerve innervates the anterior compartment of the arm?

Answer 41

Musculocutaneous N

Question 42

Biceps brachii- proximal attachment, distal attachment and actions

Answer 42

Long head originates from the supraglenoid tubercle of the scapula, and the short head originates from the coracoid process of the scapula.
Both heads insert distally into the radial tuberosity and the fascia of the forearm via the bicipital aponeurosis.
Function: Supination of the forearm. It also flexes the arm at the elbow and at the shoulder.

Question 43

Coracobrachialis- proximal attachment, distal attachment and actions

Answer 43

Originates from the coracoid process of the scapula.
The muscle passes through the axilla, and attaches the medial side of the humeral shaft, at the level of the deltoid tubercle.
Function: Flexion of the arm at the shoulder, and weak adduction.

Question 44

Brachialis- proximal attachment, distal attachment and actions

Answer 44

The brachialis muscle lies deep to the biceps brachii, and is found more distally than the other muscles of the arm.
Originates from the medial and lateral surfaces of the humeral shaft.
Inserts into the ulna tuberosity, just distal to the elbow joint.
Function: Flexion at the elbow.

Question 45

What is the biceps reflex?

Answer 45

The tendon of the muscle is tapped with a tendon hammer. The muscle fibres stretch, and this is detected by stretch receptors within the muscle spindles. This information is carried to the spinal cord by afferent fibres which synapse with efferent (motor) fibres, which then stimulate contraction of the muscle, producing movement. The patient’s arm should rest on their lap with the elbow slightly flexed. The examiner palpates the bicips tendon in the cubital fossa and places the thumb or forefinger over the tendon, and then allows the head of the hammer to swing down onto their thumb / finger.

Question 46

What are the muscles of the posterior arm?

Answer 46

one muscle in the extensor compartment - triceps brachii. Triceps has three muscle bellies which converge distally onto one common tendon.
The tendon of the long head of triceps brachii crosses teres major and teres minor at right angles. This point marks an important anatomical landmark - the quadrilateral (quadrangular) space.

Question 47

Triceps brachii– proximal attachment, distal attachment and actions

Answer 47

Long head – originates from the infraglenoid tubercle. Lateral head – originates from the humerus, superior to the radial groove. Medial head – originates from the humerus, inferior to the radial groove.
Distally, the heads converge onto one tendon and insert into the olecranon of the ulna.
Function: Extension of the arm at the elbow. and extension of arm at shoulder

Question 48

Which nerve innervates the posterior compartment of the arm?

Answer 48

Radial Nerve

Question 49

What is the triceps reflex?

Answer 49

The triceps reflex is another tendon reflex tested as part of the peripheral neurological examination. To test the triceps reflex, the patient’s arm is held across their body and the weight of the limb supported. The examiner palpates the triceps tendon superior to its insertion onto the olecranon process and taps it with the tendon hammer.

Question 50

How do the muscles in the anterior and posterior compartments work together for flexion and extension?

Answer 50

Flexion: Biceps contract and triceps relax (bulging biceps when showing of muscles)
Extension: Triceps contract and biceps relax.

Question 51

What are the articulations at elbow joint?

Answer 51

Humero-Ulnar: Between trochlea of humerus and trochlear notch of ulna.

Humero-radial: Between capitulum of humerus and upper surface of radial head.

Question 52

What ligaments reinforce the joint capsule?

Answer 52

The joint capsule of the elbow is relatively thin anteriorly and posteriorly. allowing flexion and extension. Collateral ligaments strengthen the lateral and medial aspects of the joint.
Laterally by the radial collateral ligament and medially by the ulnar collateral ligament.

Question 53

What ligament holds the head of the radius in place?

Answer 53

The anular ligament hold the radius head in place in the ulnar radial notch.

The head of the radius may sublux or dislocate from the anular ligament – this is commonly seen in children <4yrs rather than adults and is referred to as a ‘pulled elbow’ . Usually caused by an adult swinging a child by their arm/pulling child up by one arm. sometimes referred to as nursemaids elbow- usually a lump appears on the arm due to displacement.

Question 54

where does the ulnar N run?

Answer 54

The ulnar nerve runs behind the medial epicondyle of the humerus within a fibro-osseous tunnel called the cubital tunnel. The nerve may be damaged here by injuries around the elbow.

Question 55

What accounts for the most elbow joint dislocations?

Answer 55

The elbow is one of the most stable joints in the body thanks to the good ‘fit’ (congruity) between the trochlear notch of the ulna and trochlea of the humerus
Sports activities account for up to 50% of elbow dislocations and this type of injury is more commonly seen in adolescent and young adult populations

Question 56

Posterior dislocation of the elbow- Causes, Associated findings, symptoms / signs , what N is injured?

Answer 56

80-90% of elbow dislocations.
through the weak anterior part of the joint capsule

Causes:
Fall onto hands with elbows flexed/Hyperextension (blow that drives ulna posteriorly or posterolateral

Associated findings:
Ulnar collateral ligament torn
Fractures- head of radius, coronoid process, olecranon process/Ulnar nerve injury
Symptoms / signs of posterior dislocation: Severe pain in the elbow region
Elbow area appears to have become widened
Prominent olecranon process

Ulnar N injured therefore: numbness of medial part of palm and medial one and a half fingers AND weakness of flexion and adduction of the wrist

Question 57

Bursitis: what are bursa? what is bursitis? symptoms?

Answer 57

Olecranon bursa protects the olecranon process of the ulna
Excessive, repeated pressure and friction over the olecranon can cause inflammation of the bursa.
This causes swelling of the bursa which may be visible and is painful on palpation
Sometimes called ‘student’s elbow’

Question 58

Epicondylitis: what is it? Types?

Answer 58

Inflammation (‘itis’) at the humeral epicondyles
Medial epicondylitis = inflammation at attachment / origin of the wrist flexor tendons at the medial epicondyle= ‘golfer’s elbow’

Lateral epicondylitis = inflammation at attachment / origin of the wrist extensor tendons at the lateral epicondyle
= ‘tennis elbow’
Local tenderness. Pain radiates into forearm on along the affected muscles
Treatment: rest or injection of corticosteroids if pain severe

Question 59

What muscles are involved in pronation of the hand?

Answer 59

Pronator quadratus and prontator teres. Radius crosses the ulna when the arm is pronated

Question 60

What muscles are involved in supination of the hand?

Answer 60

supinator and biceps brachii

Question 61

What is a ‘Pulled elbow’?

Answer 61

Anular ligament relatively weak in childhood: the radius is more prone to subluxation or dislocation
Generally children age < 4 – fairly common
Usually caused by an adult swinging the child by their arms or pulling the child up by one arm. (e.g. when trying to lift the child over a kerb).
Sometimes referred to as “nursemaid’s elbow”