USMLE questions

Question 1

What innervates the supraspinatus? What action does this muscle perform?

Answer 1

suprascapular nerve (from the upper trunk); abduction of arm

Question 2

Where is the most common rotator cuff injury?

Answer 2

superspinatus

Question 3

What innervates the infraspintus? What action does this muscle perform? What kind of action commonly causes injury to this muscle?

Answer 3

suprascapular nerve (from the upper trunk); lateral rotation; pitching

Question 4

What innervates the teres minor? What action does this muscle perform?

Answer 4

axillary nerve; lateral rotation and adduction

Question 5

What innervates the subscapularis? What action does this muscle perform?

Answer 5

subscapular nerve; medially rotates and adducts arm

Question 6

What nerve roots are the rotator cuff muscles primarily innervated by?

Answer 6

C5 and C6

Question 7

3 nerves to the rotator cuff muscles??

Answer 7

suprascapular (supraspinotus and infraspinotis)
axillary (teres minor)
subscapular from posterior cord (subscapularis)

Question 8

Entrapment of the median nerve, resulting in nerve compression. This leads to paresthesia, pain, and and numbness in the distribution of the median nerve.

Answer 8

Carpal Tunnel Syndrome

Question 9

Compression of the ulnar nerve at the wrist or hand, classically seen in cyclists due to pressure from the handlebars

Answer 9

Guyon canal syndrome

Question 10

Ulnar nerve passes through (blank) on its way to provide cutaneous innervation to the 1.5 digits on the ulnar side of the hand.

Answer 10

Guyon’s canal

Question 11

This condition is the result of a tear to the upper trunk of the brachial plexus (Roots C5/C6)

Answer 11

Erb Palsy (“waiter’s tip”)

Question 12

What causes Erb’s palsy?

Answer 12

Adults - trauma

Infants - lateral traction on the neck during delivery

Question 13

What muscles does Erb palsy cause a deficit in?

Answer 13

SHOULDER - deltoid, supraspinotus, infraspinotus (axillary, suprascapular nerve)
biceps brachii (musculocutaneous)

Question 14

What is the functional deficit in Erb palsy? (what types of muscle function will you lose)

Answer 14

loss of abduction (supraspinotus), so arm will hang by side
loss of lateral rotation (infraspinotus), so arm will be medially rotated
loss of flexion and supination (biceps), so arm will be extended and pronated

Question 15

What’s this:

tear of the lower trunk of the brachial plexus (C8/T1)

Answer 15

Klumpke’s palsy

Question 16

What can cause Klumpke’s palsy?

Answer 16

Infants: upward force on arm during delivery (yanking on arm)
Adults: trauma (grabbing a tree branch to break a fall)

Question 17

What muscles does Klumpke’s palsy primarily affect?

Answer 17

intrinsic hand muscles:
lumbricals (median and ulnar)
interossei (ulnar)
thenar (median)
hypothenar (ulnar)

Question 18

What is the functional deficit in Klumpke’s palsy?

Answer 18

TOTAL CLAW HAND; loss of interossei so no flexion at MP joint and no extension at DIP and PIP

Question 19

Erb’s palsy

Answer 19

upper trunk of brachial plexus

Question 20

Claw hand (Klumpke’s palsy)

Answer 20

lower trunk of brachial plexus

Question 21

Wrist drop

Answer 21

damage to posterior cord of brachial plexus

Question 22

Winged scapula

Answer 22

damage to long thoracic (C5, C6, C7 nerve roots)

Question 23

Deltoid paralysis

Answer 23

axillary

Question 24

Difficulty flexing elbow, variable sensory loss

Answer 24

damage to musculocutaneous

Question 25

Decreased thumb function, Pope's blessing

Answer 25

damage to median nerve

Question 26

Loss of intrinsic muscles of the hand, claw hand

Answer 26

damage to ulnar nerve

Question 27

Causes of injury to axillary nerve (C5 and C6)?

Answer 27

fractured surgical neck of humerus | anterior dislocation of humerus

Question 28

What will injury to axillary nerve cause?

Answer 28

loss of deltoid loss of abduction of shoulder (>15 degrees) SUPRASPINOTUS can still assist in abduction

Question 29

Causes of injury to musculocutaneous nerve? (C5, C6, C7)

Answer 29

upper trunk compression

Question 30

What will injury to musculocutaneous nerve cause?

Answer 30

loss of forearm supination (coricobrachialis) loss of forearm flexion (biceps) loss of flexion at the elbow joint (brachialis)

Question 31

Causes of injury to radial nerve? (C5 to T1)

Answer 31

midshaft fracture of humerus | compression of the axilla (crutches, sleeping with arm over chair)

Question 32

What will injury to radial nerve cause?

Answer 32

``` wrist drop (loss of extensor muscles in posterior compartment) decreased grip strength (need wrist extendors to allow maximal flexion) loss of sensation over posterior arm/forearm and dorsal hand (3.5 digits) ```

Question 33

Causes of injury to the median nerve? (C5-T1)

Answer 33

supracondylar fracture of humerus carpal tunnel syndrome wrist laceration

Question 34

What will injury to median nerve cause?

Answer 34

``` 2LOAF: Ape hand (loss of thenar muscles - derotated thumb) Pope's blessing (loss of lateral finger function due loss of 2 lumbricals for digits 2 & 3 -- hyperextension of these digits) loss of sensation over thenar eminence and dorsal and palmar aspects of lateral 3.5 digits ```

Question 35

What can cause damage to the ulnar nerve?

Answer 35

fracture of medial epicondyle of humerus (funny bone) | compressing Guyan's canal

Question 36

What will injury to ulnar nerve cause?

Answer 36

Claw hand... Loss of interossei (no flexion at MP joint, no extension at fingers) Loss of medial 2 lumbricals Radial deviation of wrist upon flexion Loss of sensation to medial 1.5 fingers and hypothenar eminence Loss of wrist flexion (flexor carpi ulnaris)

Question 37

What do the dorsal interosseous muscles do? | What do the palmar interosseous muscles do?

Answer 37

DAB! abduct | PAD! adduct

Question 38

What do the lumbricals do?

Answer 38

flex at MP, extend at PIP and DIP

Question 39

What are the thenar compartment muscles?

Answer 39

OAF opponens pollicis abductor pollicis brevis flexor pollicis brevis

Question 40

What are the hypothenar compartment muscles?

Answer 40

OAF opponens digit minimi abductor digiti minimi flexor digiti minimi brevis