Day 1.3 MSK Flashcards
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)
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)
How is the C7 root injured?
Compressed by cervical disk lesion/herniation
How is the axillary nerve lesioned?
Fracture of surgical neck of humerus
Dislocation of humerus
Intramuscular injection
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.
How is the radial nerve in the spiral groove lesioned?
Midshaft fracture to the humerus
How is the deep branch of the radial nerve injured?
Stretched by sublexation of the radius
How is the recurrent branch of the median nerve injured?
Lesioned by superficial laceration
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
What is klumpke’s palsy?
Childbirth defect affecting the inferior trunk of the brachial plexus (C8, T1)
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
Other than a cervical rib/Klumpke’s palsy, what can cause thoracic outlet syndrome?
Hypertrophy of the anterior scalene muscle
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
How is the radial nerve injured in the axilla?
Compressed:
Incorrect use of crutch
Drunk on bench- Saturday night palsy
How is the median nerve injured near the elbow?
Compressed by supracondylar fracture of the humerus
Pronator teres syndrome
How is the ulnar nerve lesioned near the elbow?
Lesioned by repeated minor trauma
Fracture of the medial epicondyle of the humerus
How is the anterior interosseous nerve lesioned?
Compressed in deep forearm
How is the median nerve injured near the wrist?
Compressed by carpal tunnel syndrome (9 tendons run through carpal tunnel) or by dislocated lunate
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.
