USMLE questions Flashcards
What innervates the supraspinatus? What action does this muscle perform?
suprascapular nerve (from the upper trunk); abduction of arm
Where is the most common rotator cuff injury?
superspinatus
What innervates the infraspintus? What action does this muscle perform? What kind of action commonly causes injury to this muscle?
suprascapular nerve (from the upper trunk); lateral rotation; pitching
What innervates the teres minor? What action does this muscle perform?
axillary nerve; lateral rotation and adduction
What innervates the subscapularis? What action does this muscle perform?
subscapular nerve; medially rotates and adducts arm
What nerve roots are the rotator cuff muscles primarily innervated by?
C5 and C6
3 nerves to the rotator cuff muscles??
suprascapular (supraspinotus and infraspinotis)
axillary (teres minor)
subscapular from posterior cord (subscapularis)
Entrapment of the median nerve, resulting in nerve compression. This leads to paresthesia, pain, and and numbness in the distribution of the median nerve.
Carpal Tunnel Syndrome
Compression of the ulnar nerve at the wrist or hand, classically seen in cyclists due to pressure from the handlebars
Guyon canal syndrome
Ulnar nerve passes through (blank) on its way to provide cutaneous innervation to the 1.5 digits on the ulnar side of the hand.
Guyon’s canal
This condition is the result of a tear to the upper trunk of the brachial plexus (Roots C5/C6)
Erb Palsy (“waiter’s tip”)
What causes Erb’s palsy?
Adults - trauma
Infants - lateral traction on the neck during delivery
What muscles does Erb palsy cause a deficit in?
SHOULDER - deltoid, supraspinotus, infraspinotus (axillary, suprascapular nerve) biceps brachii (musculocutaneous)
What is the functional deficit in Erb palsy? (what types of muscle function will you lose)
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
What’s this:
tear of the lower trunk of the brachial plexus (C8/T1)
Klumpke’s palsy
What can cause Klumpke’s palsy?
Infants: upward force on arm during delivery (yanking on arm)
Adults: trauma (grabbing a tree branch to break a fall)
What muscles does Klumpke’s palsy primarily affect?
intrinsic hand muscles: lumbricals (median and ulnar) interossei (ulnar) thenar (median) hypothenar (ulnar)
What is the functional deficit in Klumpke’s palsy?
TOTAL CLAW HAND; loss of interossei so no flexion at MP joint and no extension at DIP and PIP
Erb’s palsy
upper trunk of brachial plexus
Claw hand (Klumpke’s palsy)
lower trunk of brachial plexus
Wrist drop
damage to posterior cord of brachial plexus
Winged scapula
damage to long thoracic (C5, C6, C7 nerve roots)
Deltoid paralysis
axillary
Difficulty flexing elbow, variable sensory loss
damage to musculocutaneous
Decreased thumb function, Pope’s blessing
damage to median nerve
Loss of intrinsic muscles of the hand, claw hand
damage to ulnar nerve
Causes of injury to axillary nerve (C5 and C6)?
fractured surgical neck of humerus
anterior dislocation of humerus
What will injury to axillary nerve cause?
loss of deltoid
loss of abduction of shoulder (>15 degrees)
SUPRASPINOTUS can still assist in abduction
Causes of injury to musculocutaneous nerve? (C5, C6, C7)
upper trunk compression
What will injury to musculocutaneous nerve cause?
loss of forearm supination (coricobrachialis)
loss of forearm flexion (biceps)
loss of flexion at the elbow joint (brachialis)
Causes of injury to radial nerve? (C5 to T1)
midshaft fracture of humerus
compression of the axilla (crutches, sleeping with arm over chair)
What will injury to radial nerve cause?
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)
Causes of injury to the median nerve? (C5-T1)
supracondylar fracture of humerus
carpal tunnel syndrome
wrist laceration
What will injury to median nerve cause?
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
What can cause damage to the ulnar nerve?
fracture of medial epicondyle of humerus (funny bone)
compressing Guyan’s canal
What will injury to ulnar nerve cause?
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)
What do the dorsal interosseous muscles do?
What do the palmar interosseous muscles do?
DAB! abduct
PAD! adduct
What do the lumbricals do?
flex at MP, extend at PIP and DIP
What are the thenar compartment muscles?
OAF
opponens pollicis
abductor pollicis brevis
flexor pollicis brevis
What are the hypothenar compartment muscles?
OAF
opponens digit minimi
abductor digiti minimi
flexor digiti minimi brevis
