Hand 1 Flashcards by Lo Kola

Order from inner to outer
Myelin
Perineurium
Endoneurium
Fascicles
Epineurium
Axon

Axon
Myelin
Endoneurium around individual axons
Fascicle = group of axons
Perineurium around fascicle
Epineurium around group of fascicles

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What cells make myelin

Schwann cells

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What is the intrinsic vs extrinsic BS to nerves

Intrinsic: plexus within loose connective tissue / epineurium
Extrinsic : vasa nervosum

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How do APs move between areas of myelin? What are these areas called?

Nodes of Ranvier
Saltatory conduction here

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How care for the following nerve injuries:
Laceration
Open wound w/ nerve rupture
Closed injuries

Laceration = fix ASAP to avoid fibrosis/retraction
Open wound w/ nerve rupture = allow demarcation (2-3wks) so you can resect all dead tissue for a healthy wound bed at time of repair
Closed injuries = watch 3-6mo recovery

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Define following terms and recovery time
Neurapraxia
Axonotmesis
Neurotmesis

Neurapraxia - axonal level nerve block
Conduction block, architecture preserved
<3mo

Axonotmesis - discontinuity of axons
Surrounding nerve tube acts as a guide to allow nerve to grow in the right direction
1mm/day

Neurotmesis - complete disruption of entire nerve
Requires surgical intervention

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What are the EMG findings for the following
Neurapraxia
Axonotmesis
Neurotmesis

Neurapraxia
- Normal insertional activity
- No spont activity

Axonotmesis and neurotmesis hard to differentiate on EMG
- Increased insertional activity
- Fib/positive sharp waves spont activity

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What are the best options for nerve repair in the given circumstances:
No tension
<2-3cm gap in sensory nerve
<5cm defect
>5cm defect

No tension - direct repair!
= epineurium repair (not fascicle repair bc more scarring)
- Max 10% stretch

<2-3cm gap in sensory nerve - conduit

GRAFT
<5cm defect - allograft but only for sensory n
>5cm defect or any motor involvement - autograft

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What are your options for a digital nerve defect?

SENSORY only!!!
Primary repair
<3cm = conduit
>3cm = allograft of autograft
Autograft of choice is MABC > LABC

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What is the double Oberlin transfer? What is it done for?

Gain elbow flexion (feeding goal)
Ulnar n from FCU
Median n from FDS/FCR
To motor br biceps/brachialis

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What does EMG vs NCS measure?

EMG: electrical activity of muscle w/ voluntary contraction

NCS: nerve conduction velocity, latency, amplitude

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NCS
- What happens w/ axonal loss
- What happens w/ demyelination

Axonal loss: drop amplitude
- Still conducting, just not as strong

Demyelination: drop velocity -> increase latency

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What is most common cause of CTS

Edema / vascular sclerosis
Reduced epineurial blood flow
Splinting keeps pressure at neutral to keep blood flow constant

In theory a CSI should work for CTS bc not inflammatory

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What are the 2 ways to test sensory nerves? Examples of each

Threshold test = measures 1 nerve fiber innervating a receptor. Best for eval nerve after repair
- Static vs moving 2 pt discrimination

Innervation density test = multiple overlapping receptive fields. Best for gradual nerve changes (compressive neuropathy)
- Semmes Weinstein monofilament
- Vibration tests

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What are the best provocative tests for CTS

Direct compression > Phalen > Tinel

Semmes Weinstein (density test) > 2 pt discrim (threshold)

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Findings on EMG for CTS

Distal motor latencies > 4.5 msec
Sensory latencies > 3.5 msec

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Benefit of endoscopic > open CTR

Endoscopic = open long term

Quicker return to work (less incisional/pillar pain early)

Cons: $$, higher risk complication

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4 sites of median nerve compression (not CTS)

Ligament of struthers = supracondylar process humerus (get an XR)
Lacertus fibrosis (aka biceps aponeurosis)
Deep head pronator (medial epicondyle/deep volar forearm) - why pronator syndrome often associated with medial epicondylitis
FDS arcade

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How do you determine a proximal compressive median neuropathy vs CTS

Proximal compression you’ll have the sensory br median nerve involved (palm numbness)

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AIN syndrome
- Sx
- Muscles innervated
- Causes
- Trt

Sx: forearm pain, inability to make O sign index/thumb

Different than other median compressive neuropathy bc motor involvement
- FPL
- FDP index/long
- PQ

Causes:
- Compression by FDS/FCR/PT/FPL
- Parsonage Turner (viral)
- Ddx = tendon rupture (think RA)

Trt: obs obs obs obs

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Name the sites of ulnar nerve compression at cubital tunnel

Tunnel itself = osborne’s ligament
Arcade struthers = fascia as nerve passes from ant to post in the arm
Medial triceps
Medial IM septum
FCU
Deep flexor/pronator
Anconeus

What is Wartenberg sign

Lose adductor interosseous of 5th digit
Unopposed EDM (radial n.)
abducted small finger
Ulnar n palsy

What is Froment sign

Weak thumb adduction - compensatory FPL flexion during pinch
Ulnar n palsy

What are the 3 zones of ulnar n compression a Guyons canal + cause

1 = proximal to nerve bifurcation = sens + motor
- Ganglion

2 = motor only
- Hook hamate frx

3 = sensory only
- Ulnar art thrombosis

**Dorsal sensory br comes off proximal to the wrist so would not be involved in a Guyon issue

What is the anatomy of Guyon tunnel

Roof = volar carpal lig Floor = transverse carpal lig Radial = hamate Ulnar = pisiform

What are sites of radial n compression (FLEAS)

Fascial band radial head Leash of Henry ECRB Arcade Froshe (proximal supinator) Supinator distal

Presentation of PIN syndrome, which patients, trt

Motor deficit - Extending MP joints, thumb IP - Wrist extension w/ radial dev (ECU out, ECRL intact) Think RA w/ boggy capsule off radio-capitellar jt Trt non op as long as not a space occupying lesion

Sx radial tunnel syndrome Most likely compression site Trt

No motor/sens deficit - EMG/NCS normal Pain syndrome Arcade of Froshe most common Think lateral epicondylitis Nonop

Presentation of radial sens n compression Cause Trt

Forearm pain +Tinel between BR/ECRL tendon Direct trauma - tight handcuffs/watch Diagnostic inj - remove offending agent

What is the Adson test for?

Thoracic outlet syndrome Decrease radial a pulse w/ inhalation bc subclavian compression

Which nerves create the upper middle lower trunks

C5/6 - upper C7 - middle C8/T1 - lower

How do the trunks divide to make divisons

top 2 ant divisions combine = lateral cord Lower ant div continues own own = medial cord All 3 posterior divisions combine into 1 = posterior cord

What are the 2 branches off C5?

Dorsal scapular Phrenic

What nerve roots contribute to long thoracic n?

C5/6/7

Where does suprascap nerve come from?

Upper trunk (C5/6)

Name branches off the Lateral cord (1) Posterior cord (3) Medial cord (3)

Lateral cord (1) - Lateral pec Posterior cord (3) - Upper, middle, lower subscap Medial cord (3) - Medial pec - Medial brachal - MABC

What are the 5 terminal branches and the cranial nerve contributions

MCN - C5/6/7 Ax - C5/6 Rad - C5-T1 (all) Med - C5-T1 (all) Ulnar - C7-T1 (low plexus)

What nerve roots indicate Horners syndrome

C8-T1 avulsion

What is the Smith 3-5-7 rule for donor tendon transfer selection

Estimates excursion: Wrist flexors/extensors 3cm MCP extensors 5cm FDP 7cm

What differentiates a radial nerve injury from PIN?

Radial nerve will involve BR and ECRL

What are 3 transfers for radial nerve out

FCR -> EDC PL -> EPL PT -> ECRB

What are 2 transfers for median nerve out to regain opposition

PL -> thumb prox phalanx Think elderly severe CTS ADM -> thumb prox phalanx Think congenital absence

Trt subungal hematoma w/ intact nail plate

Nail plate perforation for pain relief

How much nail bed must be intact to prevent a hook nail

At least 50% of distal phalanx must be there as a bony support to the nail bed

Treat finger tip pulp loss up to 1cm

2ary intention FT skin graft 2nd choice

Treat finger tip volar oblique injury with exposed bone

Adult: cross finger Kid/younger: moberg (thumb) flap - Do this in the young bc more likely to overcome any IP contracture

Treat finger tip dorsal oblique or transverse injury w/ exposed bone

V-Y advancement

Treat volar thumb fingertip injury with exposed bone

<2cm = moberg volar thumb advancement >2cm = FDMA (from dorsal 1st digit)

Treat dorsal thumb fingertip injury with exposed bone

FDMA

What is a complication of shortening and closing fingertip injuries

Lumbrical plus finger

Order the following from which recovers first to last after nerve injury Motor Sympathetic Proprioception Pain Temp

Return (lose in the opposite order) 1 sympa 2 pain 3 temp 4 proprioception 5 motor