Day 1.3 MSK Flashcards by J W

How is the upper trunk lesioned? What happens when it is?

Lesioned by trauma- most often in birth, but also from hyperextension of neck- so MVA.
Causes Erb-Duchenne Palsy (waiter’s tip)

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What are the characteristics of Erb-Duchenne Palsy?

Traction/tear of upper trunk (C5, C6 roots). “Waiter’s tip”:
paralysis of abductors (limb hangs by side)
medially rotated (paralysis of lateral rotators)
forearm is pronated (loss of biceps to supinate)

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How is the C7 root injured?

Compressed by cervical disk lesion/herniation

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How is the axillary nerve lesioned?

Fracture of surgical neck of humerus
Dislocation of humerus
Intramuscular injection

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What are the characteristics of an axillary nerve lesion?

Axillary goes to deltoid m, which is the primary abductor of the arm. So loss of abduction, also decreased sensation over deltoid- check this before and after fixing a dislocation.

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How is the radial nerve in the spiral groove lesioned?

Midshaft fracture to the humerus

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How is the deep branch of the radial nerve injured?

Stretched by sublexation of the radius

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How is the recurrent branch of the median nerve injured?

Lesioned by superficial laceration

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How is the lower trunk of the brachial plexus injured?

Compressed by a cervical rib or by Pancoast’s tumor. Leads to Klumpke’s palsy

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What is klumpke’s palsy?

Childbirth defect affecting the inferior trunk of the brachial plexus (C8, T1)

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What is thoracic outlet syndrome?

Cervical rib can compress the subclavian artery and inf trunk of brachial plexus, resulting in thoracic outlet syndrome

atrophy of thenar and hypothenar eminance
atrophy of interosseous muscles
sensory deficits on medial side of forearm and hand
disappearance of radial pulse when head is moved toward opposite side

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Other than a cervical rib/Klumpke’s palsy, what can cause thoracic outlet syndrome?

Hypertrophy of the anterior scalene muscle

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What is Klumpke’s total claw?

Lesion of lower trunk (C8, T1), leading to loss of fn of all lumbricals.
forearm finger flexors (part of median nerve w C5-C7) and finger extensors radial nerve) are unopposed, so there is clawing of all digits

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How is the radial nerve injured in the axilla?

Compressed:
Incorrect use of crutch
Drunk on bench- Saturday night palsy

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How is the median nerve injured near the elbow?

Compressed by supracondylar fracture of the humerus

Pronator teres syndrome

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How is the ulnar nerve lesioned near the elbow?

Lesioned by repeated minor trauma

Fracture of the medial epicondyle of the humerus

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How is the anterior interosseous nerve lesioned?

Compressed in deep forearm

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How is the median nerve injured near the wrist?

Compressed by carpal tunnel syndrome (9 tendons run through carpal tunnel) or by dislocated lunate

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How is the ulnar nerve lesioned near the wrist?

Trauma to the heel of the hand

Fracture of the hook of the hamate

In general, what muscles do each of these nerves supply:
Musculocutaneous
Radial
Median
Ulnar

MC = flexors
Radial = extensors
Median = thumb, pronators
Ulnar = wimpy. pinky, interosseous, some lumbricals

Axillary nerve injury

Cause: fractured surgical neck of humerus, dislocation of humerus head
Motor deficit: can’t abduct arm at shoulder
Sensory: no sensation over deltoid m.
sign: flattened deltoid

Radial (C5-C8) nerve injury

Cause: fracture at midshaft of humerus, saturday night palsy (compresson of axilla)
Motor: can’t extend wrist, can’t extend fingers at MCP, can’t supinate, can’t extend or abduct thumb
Sensory: no sensation in posterior arm, dorsal hand, dorsal thumb
sign: wrist drop

Median (C6-T1) Proximal lesion

Cause: Fracture of supracondylar humerus
Motor: Can’t oppose thumb
Sensory: No sensation in dorsal and palmar aspects of lateral 3.5 fingers, thenar eminence
Sign: ape hand

ALSO: lose latera lumbricals, so can’t flex 2nd and 3rd digits –> pope’s blessing!

Ulnar (C8-T1) Distal lesion

Cause: fracture of hook of hamate (fall on outstretched hand)
Motor: can’t abduct or adduct fingers (interossei), can’t adduct thumb, can’t extend 4th or 5th fingers (lumbricals)
Sign: can’t extend 4th and 5th fingers when trying to straighten fingers.

Median (C6-T1) Distal lesion

Cause: Carpal tunnel syndrome, dislocated lunate Motor: can't flex lateral finger, can't flex wrist Sensory: no sensation in dorsal and palmar parts of lateral 3.5 fingers Sign: ulnar deviation of wrist (when wrist is flexed)

Ulnar (C8-T1) proximal lesion

Cause: fracture of medial epicondyle of humerus Motor: can't flex medial finger, can't flex wrist Sensory: can't feel medial 1.5 fingers or hypothenar eminance Sign: radial deviation of wrist when flexing wrist

Musculocutanous nerve lesion

Cause: upper trunk compresison Motor: can't flex at elbow Sensory: can't feel lateral forearm

What causes Wrist Drop (can't extend wrist)?

Radial nerve injury

What does the radial nerve innervate?

``` BEST: Brachioradialis Extensors of wrist/fingers Supinator Triceps ```

What causes claw hand (can't flex DIP of 4th and 5th digits)

Ulnar nerve injury

What causes Saturday night palsy?

Radial nerve injury (compression in axilla)

What causes inability to pronate?

Median nerve injury

What causes Bishop's Hand/Benediction/Pope

Median nerve injury

What causes carpal tunnel syndrome?

Median nerve injury

What causes weak flexion?

MC nerve injury

What causes ape hand (can't oppose thumb)?

Median nerve injury

If the 2nd and 3rd (index and middle) digits are curled, what can it be?

If they are curled bc pt can't extend them: distal median nerve injury If they are curled bc pt is making a fist and can't curl the 4th and 5th digits: proximal ulnar nerve injury

If the 4th and 5th digits are curled, what can it be?

If the 4th and 5th are curled bc they can't be extended: distal ulnar nerve injury If they are curled bc pt is making a fist and can't curl 2nd and 3rd, it's median nerve injury (pope's blessing)

What happens in a distal ulnar nerve lesion?

Loss of medial lumbrical fn- 4th and 5th digits are clawed. (Hyperextension at MCP and flexion at IP)

What happens in a distal median nerve injury?

Loss of lateral lumbrical fn, so 2nd and 3rd digits are clawed. (Hyperextension at MCP and flexion at IP)

What happens in proximal median nerve injury?

Loss of oppnens pollicis muscle - so unopposable thumb. "ape hand"

What are the OAF muscles of the hand?

``` OAF = oppose, abduct, flex Thenar = OAF pollicis: opponens pollicis abductor pollicis brevis flexor pollicis brevis ``` Hypothenar = OAF digiti opponens digiti minimi abductor digiti minimi flexor digiti minimi

What are the non-OAF muscles of the hand?

Dorsal interosseous muscles (ABduct) Palmar interosseous muscles (ADduct) DAB, PAD. Innervated by ulnar nerve Lumbrical muscles- flex at the MP joint (if they are injured, get claws) Innervated: ulnar lumbricals by ulnar nerve; radial lumbricals (2) by median nerve

T/F Pope's blessing and ape hand arise from the same nerve injury.

TRUE! Proximal median nerve Pope's blessing is d/t lateral lumbrical loss, so can't flex 2nd and 3rd fingers Ape hand is d/t loss of opponens pollicis, so can't oppose thumb.

T/F Pope's blessing and ape hand arise from the same nerve injury.

TRUE! Proximal median nerve Pope's blessing is d/t lateral lumbrical loss, so can't flex 2nd and 3rd fingers Ape hand is d/t loss of opponens pollicis, so can't oppose thumb.