Upper Limb Nerve Injury Flashcards
Why does the resting position of limbs change when there is nerve damage?
Due to unopposed pull of muscles that remain innervated
Sensory loss with nerve root damage will be ____.
Dermatomal
What would be the affects of musculocutaneous nerve damage?
Loss of most anterior arm compartment muscles but not part of brachialis (radial n.) so there will be:
- Weakened elbow flexion
- Weakened supination
- Weak flexion as brachioradiialis affected but part of brachialis (radial n.) and forearm flexors from common flexor origin (media and ulnar n.) are not
- Weakened biceps tendon (C5/6) reflex
- Sensory loss over lateral forearm (C6)
How could the axillary nerve be damaged? What would be the affects?
Dislocation of shoulder or surgical neck humerus # (may also damage circumflex humoral vessels which can lead to compartment syndrome and pain, colder and weaker limbs)
Loss of deltoid and teres minor so patient will not be able to adduct arm and shoulder becomes relatively immobile
What would be the affects of median nerve damage?
Loss of most anterior compartment forearm muscles, thenar muscles and lumbricals 1 and 2 resulting in the hand of benediction but also sensory changes/loss of lateral 3.5 digits on palmar side inc. thumb
What would be the affects of damaging the radial nerve?
Loss of posterior arm and posterior forearm compartment muscles
What would be the affects of ulnar nerve injury?
Loss of most small muscles of hand and a couple forearm muscles leading to an ulnar claw where the lateral 3 fingers are extended but the medial 2 are flexed
How/where is the median nerve injured?
- Median arm or cubital fossa puncture wound/laceration
- Trapped between 2 heads of pronator teres
- Forearm prior to carpal tunnel (e.g. defence wound or suicide attempt)
- CTS
What does the median nerve supply?
Everything in anterior forearm except FCU and FDP to digits 4 and 5 along with the thenar muscles and lumbricals to digits 2 and 3
What would be the effects of damaging the median nerve at the elbow or proximal?
- Cant make fist with digits 2 and 3
- No active flexion of IP joints of digits 1, 2 and 3
- Weaker flexion of digits 4 and 5 because you have no FDS but FDP from ulnar nerve
- No forearm pronation
- Weak wrist flexion that deviates to adduction as FCU is ulnar nerve
- Plus issues seen with wrist injury
What would be the effects of damaging the median nerve at the wrist?
- Thenar wasting and thumb opposition not possible
- Thumb laterally rotated and adducted looking like a finger
- Digits 2 and 3 lag in fist making as lumbricals 1 and 2 are paralysed
- Sensory changes: palm spared in CTS but inc. with volar distal forearm laceration
How/where is the ulnar nerve injured?
- Medial epicondyle by # or compression (e.g. haematoma as a result)
- Cubital tunnel compression
- Penetrating injury on anterior wrist near at pisiform
- Wrist compression superficial to flex`ior retinaculum (Guyon’s canal)
What does the ulnar nerve supply?
FCU and FDP to digits 4 and 5 along with all intrinsic hand muscles except the thenar and lumbricals to digits 2 and 3
What is the difference between the ulnar claw hand and hand of benediction?
Ulnar claw hand: MCP joints of the 4th and 5th fingers are extended and the IP joints of the same fingers are flexed passively due to tone of extensor expansion often accompanied with difficult ad/abducting 2nd, 3rd, 4th and 5th digits - most prominent at rest or when patient extends fingers
Hand of benediction: hyper-extension of MCPs from the unopposed extensor digitorum as well as weakened extension and flexion of the IP joints of the 2nd and 3rd digits often accompanied by difficulty opposing thumb - most prominent when patient asked to make a fist
Where will you see wasting with ulnar nerve and median nerve lesions?
Ulnar: 1st dorsal interosseous muscle of hand
Median: thenar eminence
How does the extensor expansion work?
Anything pulling from behind it will extend the digits however, anything pulling in front of MCP joint, will flex MCP joint but passively extend the IP joints
How are the metacarpophalangeal (MCP) joints finely controlled?
Interossei and lumbricals balance the crude powerful pull of the long extensors and flexors essentially acting as antagonists
What would happen if there was a lack of refined metacarpophalangeal (MCP) flexion by lumbrical contraction?
MCP extension at rest
What would be the effects of ulnar nerve damage at the elbow or proximal?
- No flexion of DIP joints of digits 4 and 5 due to lack of FDP
- Weaker wrist flexion where wrist will abduct on flexion due to lack of FCU
- No digit ab/adduction (exc. thumb abduction)
- Plus damage seen with wrist injury EXCEPT clawing is less as FDP no longer works = ULNAR PARADOX
- Sensory loss in ulnar territory of hand
What would be the effects of ulnar nerve damage at the wrist?
- Loss of most intrinsic hand muscles
- Hypothenar and interosseous wasting (guttering on dorsal hand)
- Pronounced clawing of digits 4 and 5 worse as FDP still work exacerbating IP joint flexion
- No clawing of digits 2 and 3 as lumbricals 1 and 2 are functional (median n.)
- Sensory loss may be limited to digits (palm and dorsum spread)
What are the roles of lumbricals and interossei muscles?
Lumbricals: attach to deep flexor tendon so look like their floating but they contract in front of extensor expansion on palmar side flexing MCP and extending PIPs/DIPs (important position for most dextrous activities of hand)
Interossei: same but also ab/abduction too
Why does the ulnar claw hand occur?
Lumbricals and interossei of digits 4 and 5 are lost so strong pull of extensor tendons now not resisted so MCP will become extended and PIP/DIP will become flexed passively due to extensor expansion tone
This will not be as severe if injured at elbow as deep flexors for digits 4 and 5 by the FDP of the forearm will be lost so there is less muscle to bring digits into a tighter claw but if they are still working if damaged at wrist, there will be more tone to pull the claw tighter
How/where is the radial nerve injured?
- Axilla (shoulder dislocation, crutch or asleep over upper limb)
- Spiral groove (humeral shaft # or compression due to sleeping arm again)
- Head/neck of radius issue would dislocation or # due to traction injury would damage PIN e.g. swinging or pulling a childs arm
- Arcade of Frohse entrapment of PIN between 2 heads of supinator
What would be the effects of damaging the radial nerve in the axilla?
All function lost:
- No elbow extension as triceps lost
- Wristdrop into flexion
- No digit extension
- Sensory loss on dorsolateral forearm and hand
