Clinical Cases

Question 1

What is the anatomical mechanism behind Erb’s Palsy?

Answer 1

Stretching of nerve roots C5 & C6 by abnormal increase in angle between the neck and the shoulder

Question 2

What is the resulting deficit of an Erb’s Palsy?

Answer 2

Results in the upper limb hanging at the side, with medial rotation and the palm facing posteriorly

Question 3

What is the resulting deficit from a lower brachial plexus injury (Klumpke palsy), affecting C8-T1 including the ulnar nerve?

Answer 3

Interosseous muscle atrophy and claw hand

Question 4

What are the 5 terminal branches of the brachial plexus?

Answer 4

Axillary, musculocutaneous, median, ulnar and radial nerves

Question 5

Where is the axillary nerve most at risk of injury?

Answer 5

As it courses posteriorly around the surgical neck of the humerus

Question 6

What muscles does the axillary nerve supply?

Answer 6

Deltoid and teres minor muscles

Question 7

What deficit could a fracture to the surgical neck of the humerus cause?

Answer 7

Inability to abduct the arm at the shoulder to a horizontal position and sensory loss in the shoulder patch area due to axillary nerve injury

Question 8

What deficit does damage to the musculocutaneous nerve cause?

Answer 8

Weakness in supination and flexion of the shoulder and elbow

Question 9

Where does the ulnar nerve course through the elbow?

Answer 9

Curves posterior to the medial epicondyle

Question 10

Where does the ulnar nerve enter the forearm and what does it innervate?

Answer 10

Through the anterior compartment of the forearm where it innervates the flexor carpi ulnaris and the bellies of the flexor digitorum profundus to the ring and little fingers.

Question 11

Where does the ulnar nerve enter the hand and what does it supply?

Answer 11

Through Guyon Canal superficial to the flexor retinaculum, supplying all the intrinsic muscles of the hand except for the three thenar muscles and lumbricals of the index and middle fingers

Question 12

What deficit does ulnar nerve injury cause?

Answer 12

Radial deviation of the hand, weakness in flexion and adduction of the hand at at the wrist and loss of flexion at the DIP joint of the ring and little fingers. Also loss of abduction and adduction of the index, middle, ring and little fingers due to paralysis of the interossei muscles which causes a “Claw Hand”

Question 13

Which muscles are primarily responsible for abduction at the shoulder and what nerves innervate them?

Answer 13

Deltoid and supraspinatus muscles, which are innervated by the axillary nerve and suprascapular nerves respectively.

Question 14

What deficit would injury to the lateral cord of the brachial plexus cause and what muscles are affected? Given such an injury damages the musculocutaneous nerve?

Answer 14

Weakness of flexion at the elbow due to paralysis of the biceps brachii and brachialis muscles.

Question 15

A patient sustains an injury to the lower brachial plexus. Which nerve will be most likely affected?

Answer 15

The C8 and T1 portions of the lower brachial plexus make up the majority of the ulnar nerve

Question 16

What cord and nerve is injured causing a wrist drop?

Answer 16

The posterior cord, which supplies the radial nerve

Question 17

A patient with a displaced fracture of the humerus complains of an inability to open their left hand and loss of sensation to a portion of the hand. What is the most likely diagnosis?

Answer 17

Injury to the radial nerve as it spirals around the humerus resulting in an inability to extend the wrist or fingers at the MCP joints and a loss of sensation of the lateral side of the dorsum of the hand, dorsum of the thumb and index and middle digits

Question 18

Where is the radial nerve a particular risk of injury?

Answer 18

As it courses in the radial groove as it spirals around the midshaft of the humerus

Question 19

What other structure courses the radial groove of the humerus besides the radial nerve?

Answer 19

The deep brachial artery

Question 20

What two structures would a midshaft fracture of the humerus put at risk?

Answer 20

The radial nerve and the deep brachial artery

Question 21

What are the two main terminal branches of the radial nerve and what do they do?

Answer 21

The deep branch of the radial nerve and the superficial branch of the radial nerve. The deep branch is entirely motor to the muscles of the posterior compartment of the forearm. The superficial branch is sensory to the dorsum of the hand and to the dorsum of the thumb, index finger and the radial side of the middle finger.

Question 22

Describe the course of the radial nerve from the radial groove to the forearm.

Answer 22

It gives off multiple muscular branches to the triceps muscle in the posterior compartment, then pierces the lateral intermuscular septum to return to the anterior compartment of the arm, and descends to the level fo the lateral epicondyle of the humerus where it lies deep to the brachioradialis muscle where it divides into its two terminal branches.

Question 23

What is the main blood supply to the upper limb?

Answer 23

Axillary artery -> brachial artery

Question 24

Describe the course of the brachial artery

Answer 24

From the lower border of the teres major muscle and accompanies the median nerve on the medial aspect of the humerus. Towards the elbow it branches off the deep brachial artery which supplies the posterior compartment of the arm and passes around the radial groove of teh humerus with the radial nerve. It also has ulnar collateral branches to the elbow joint. The brachial artery shifts anteriorly as it enters the forearm lying just medial to the tendon of the biceps brachii muscle in the cubital fossa. At the level of the neck of the radius to divides into the ulnar and radial arteries.

Question 25

Where does the brachial artery lie in relation to the tendon of the biceps brachii in the cubital fossa?

Answer 25

Just medial

Question 26

Which arteries supply the deep and superficial palmar arches?

Answer 26

The radial artery supplies the deep palmar arch and the ulnar artery supplies the superficial palmar arch

Question 27

What is the arterial supply of the digits of the hand?

Answer 27

An arterial anastomosis of the superficial and deep palmar arches

Question 28

Which muscles grossly does the radial nerve supply?

Answer 28

All of the muscles of the posterior compartment of the arm and forearm

Question 29

What is your concern in a FOOSH injury with tenderness to the anatomical snuffbox?

Answer 29

Scaphoid fracture

Question 30

What bone may dislocate in a FOOSH injury and what nerve may it impinge on?

Answer 30

Lunate dislocation, anteriorly into the carpal tunnel impinging on the median nerve

Question 31

What is a Colles fracture?

Answer 31

Transverse fracture of the distal radius which produces a dorsal displacement of the distal fragment causing a “dinner fork” deformity.

Question 32

What is a Smith fracture?

Answer 32

Transverse fracture of the distal radius (less common than Colles) where the distal radial fragment is displaced ventrally in a “spade” deformity.

Question 33

Which tendons form the anatomical snuffbox?

Answer 33

The extensor pollicis brevis and abductor pollicis longus anteriorly and the extensor pollicis longus posteriorly.

Question 34

Name the carpal bones from lateral to medial

Answer 34

Scaphoid, lunate, triquetrum, pisiform (proximal row) and trapezium, trapezoid, capitate and hamate (distal row) (“Some ladies try perfume that they can’t handle).

Question 35

Which ligament limits adduction (ulnar deviation) of the wrist?

Answer 35

Radial collateral ligament

Question 36

Which ligament limits abduction (radial deviation) of the wrist?

Answer 36

Ulnar collateral ligament

Question 37

Which is the most frequently fractured carpal bone?

Answer 37

Scaphoid

Question 38

Which is the most frequently dislocated carpal bone?

Answer 38

Lunate

Question 39

What structure transmits force from the radius to ulnar in a FOOSH injury?

Answer 39

The interosseous membrane

Question 40

What is the anatomical mechanism behind carpal tunnel syndrome?

Answer 40

Compression of the median nerve as it passes through the carpal tunnel of the wrist

Question 41

Which conditions have been associated with carpal tunnel syndrome?

Answer 41

Endocrine conditions (diabetes, hypothyroidism, hyperthyroidism, acromegaly and pregnancy), autoimmune diseases.

Question 42

What structures form the boundaries of the carpal tunnel?

Answer 42

Posteriorly by the concave surfaces of the carpal bones. Anteriorly by the flexor retinaculum

Question 43

What are the contents of the carpal tunnel?

Answer 43

9 structures ; Four tendons each of the flexor digitorum superficialis and flexor digitorum profundus, the tendon of the flexor pollicis longus, and the median nerve.

Question 44

What cervical levels contribute to the median nerve?

Answer 44

C6 through to T1

Question 45

Where does the median nerve pass in the cubital fossa/

Answer 45

Medial to the brachial artery

Question 46

Where is the median nerve in the forearm?

Answer 46

Between the FDS and the FDP

Question 47

In terms of median nerve lesions what would sparing of the skin sensation in the palm suggest?

Answer 47

Carpal tunnel entrapment. Loss of palmar skin sensation suggests a higher nerve lesion

Question 48

What are the boundaries of the Guyon canal?

Answer 48

Anteriorly - volar carpal ligament
Posteriorly - flexor retinaculum
Medially - pisiform
Laterally - hook of the hamate