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MSK (USMLE) > Shoulder > Flashcards

Shoulder Flashcards

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USMLE® Step 1 flashcards
1
Q

Shoulder muscles that form the rotator cuff

A

Supraspinatus, Infraspinatus, Teres minor, Subscapularis (SItS)

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2
Q

Supraspinatus: innervation, action, and injury (+ test)

A

suprascapular nerve, abducts arm initially (before the action
of the deltoid); most common rotator
cuff injury (trauma or degeneration and impingement leads to tendinopathy/tears (empty/full can test)

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3
Q

Infraspinatus: innervation, action, and injury

A

suprascapular nerve, externally rotates arm; pitching injury

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4
Q

Teres minor: innervation, action

A

axillary nerve, adducts and externally rotates arm

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5
Q

Subscapularis: innervation, action

A

upper and lower subscapular nerves, internally rotates and adducts arm

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6
Q

Arm abduction 0 to > 90 degrees

A

Supraspinatus (0-15), deltoid (15-90), trapezius and serrates ant (>90)

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7
Q

Causes of injury to axillary nerve

A

Fractured surgical neck of humerus/Anterior dislocation of humerus

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8
Q

Presentation of axillary nerve lesion

A

Flattened deltoid
Loss of arm abduction at shoulder (> 15°)
Loss of sensation over deltoid and lateral arm

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9
Q

Causes of injury to musculocutaneous

A

Upper trunk compression

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10
Q

Presentation of musculocutaneous nerve lesion

A

decreased biceps (C5-6) reflex
Loss of forearm flexion and supination
Loss of sensation over radial and dorsal forearm

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11
Q

Causes of radial nerve lesion

A

Compression of axilla, eg, due to crutches or sleeping with arm over chair (“Saturday night palsy”)
Midshaft fracture of humerus
Repetitive pronation/supination of forearm, eg, due to screwdriver use (“finger drop”)

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12
Q

Presentation of radial nerve lesion

A

above elbow: loss of sensation over posterior arm/forearm and dorsal hand, wrist drop (loss of elbow, wrist, and finger extension) with decreased grip strength (wrist extension necessary for maximal action of flexors)
below elbow: cause distal paresthesias without wrist drop
Tricep function and posterior arm sensation spared in midshaft fracture

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13
Q

Causes of injury to median nerve (proximal & distal)

A

Supracondylar fracture of humerus (proximal lesion)
Carpal tunnel syndrome and wrist laceration (distal lesion)

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14
Q

Presentation of median nerve lesion

A

“Ape hand” and “Hand of benediction”
Loss of wrist flexion and function of the lateral two Lumbricals, Opponens pollicis, Abductor pollicis brevis, Flexor pollicis brevis (LOAF)
Loss of sensation over thenar eminence and dorsal and palmar aspects of lateral 3 1/2 fingers with proximal lesion

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15
Q

Causes of ulnar nerve lesion (proximal, distal, compression)

A

Fracture of medial epicondyle of humerus (prox lesion)
Fractured hook of hamate (distal lesion) from fall on outstretched hand
Compression of nerve against hamate as the wrist rests on handlebar during cycling

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16
Q

Presentation of ulnar nerve lesion

A

“Ulnar claw” on digit extension
Radial deviation of wrist upon flexion (proximal lesion)
Decreased flexion of ulnar fingers, abduction and adduction of fingers (interossei), thumb adduction, actions of ulnar 2 lumbrical muscles
Loss of sensation over ulnar 1 1/2 fingers including hypothenar eminence

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17
Q

Causes of recurrent branch of median nerve injury

A

superficial laceration of palm

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18
Q

Presentation of recurrent branch of median nerve lesion

A

“Ape hand”
Loss of thenar function (opposition, abduction, & flexion of thumb)
no loss of sensation

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19
Q

What is injured in Erb’s palsy

A

Upper trunk (C5-C6 roots)

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20
Q

How does upper trunk lesions (Erb’s) occur in infants & adults

A

Infants: lateral traction of neck on delivery
Adults: trauma = neck traction

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21
Q

Presentation of Erb’s palsy

A

Arm hangs by the side (no abduction)
Arm medially rotated (no lateral rotation)
Arm extended & pronated (no flexion, supination)

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22
Q

Injury in Klumpke’s palsy

A

Lower trunk (C8-T1)

23
Q

Causes of Klumpke’s in infants & adults

A

Infants: upward force on arm in delivery
Adults: trauma (grabbing tree branch in fall)

24
Q

Muscle deficit in Klumpke’s

A

intrinsic hand muscles (lumbricals, interossei, thenar, hypothenar)

25
Q

Presentation of Klumpke’s

A

Claw hand (lumbricals flex MCP, extend DIP & PIP)

26
Q

Injury in thoracic outlet syndrome

A

compression of lower trunk & subclavian vessels (usu wi scalene triangle)

27
Q

Causes of thoracic outlet syndrome

A

Cervical/anomalous first ribs
Pancoast tumour

28
Q

Muscle deficit in thoracic outlet syndrome

A

Intrinsic hand muscles (same as Klumpke)

29
Q

Presentation of thoracic outlet syndrome

A

atrophy of hand muscles
ischemia, pain, and edema due to vascular compression

30
Q

Injury in winged scapula

A

lesion of long thoracic nerve (C5-C7)

31
Q

Causes of winged scapula

A

Axillary node dissection after mastectomy/stab wounds

32
Q

Muscle deficit in winged scapula

A

Serratus anterior

33
Q

Presentation of winged scapula

A

Inability to anchor scapula to thoracic cage (can’t abduct arm above horizontal position)

34
Q

Bones of the wrist

A

scaphoid, lunate, triquetrum, pisiform, trapezium, trapezoid, capitate, hamate

35
Q

What is the most commonly fractured carpal bone and how

A

Scaphoid (palpate in anatomical snuffbox) via fall on outstretched hand

36
Q

Complications of proximal scaphoid fractures

A

AVN, nonunion due to retrograde blood supply from radial artery

37
Q

What bone dislocation can result in carpal tunnel syndrome

A

Lunate dislocation may impinge median nerve

38
Q

What bone fracture causes ulnar syndrome

A

Fracture of the hook of hamate

39
Q

Name the thenar muscles and innervation

A

Opponens pollicis, abductor pollicis brevis, flexor pollicis brevis (superficial head) innervated by median
Deep head of FPB is by ulnar nerve

40
Q

Name the hypothenar muscles and innervation

A

Opponens digiti minimi, abductor digiti minimi, flexor digiti minimi brevis by ulnar nerve

41
Q

Innervation + action of dorsal interossei

A

Ulnar nerve; abduct fingers

42
Q

Innervation + action of palmar interossei

A

Ulnar nerve; adduct fingers

43
Q

Lumbrical innervation and action

A

1st/2nd by median, 3rd/4th by ulnar
Flex MCP, extend PIP, DIP joints

44
Q

When does ulnar claw present and what is the lesion

A

Extension of fingers/at rest
Lesions is of distal ulnar nerve

45
Q

When does the Hand of Benediction present + lesion

A

Making a fist
Lesion of prox median nerve

46
Q

When does median claw present + lesion

A

Extending fingers/at rest
Lesion of distal median nerve

47
Q

When does the OK gesture present + lesion

A

Making a fist
Lesion of prox ulnar nerve

48
Q

Muscles involved in abduction of the hip (+ nerve)

A

Gluteus medius & minimus (superior gluteal nerve)

49
Q

Muscles involved in adduction of the hip (+ nerve)

A

Adductor magnus, longus, brevis (obturator nerve)

50
Q

Muscles involved in flexion of the hip (+ nerve)

A

iliacus, pectineus, rectus femoris (femoral nerve)
psoas major (anterior rami of L2-L4)

51
Q

Muscles involved in extension of the hip (+ nerve)

A

Gluteus maximus (inferior gluteal nerve)
Semimembranosus, semitendinosus, long head of biceps femoris (sciatic nerve)

52
Q

Muscles involved in internal rotation of the hip (+ nerve)

A

Gluteus medius & minimus, TFL (superior gluteal)

53
Q

Muscles involved in external rotation of the hip (+ nerve)

A

Gluteus maximus (inferior gluteal)
Piriformis (nerve to piriformis)
Obturator externus (obturator)
Superior gemellus & obturator internus (nerve to obturator internus)
Inf gemellus & quadratus femoris (nerve to quadratus femoris)

54
Q

Muscle deficits in Erb’s palsy

A

Deltoid, infraspinatus, biceps brachii, supraspinatus

MSK (USMLE) (16 decks)

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