The key is to choose a specific muscle and action that can indicate whether a nerve is intact or not.
Eg motorcyclist landing on shoulder avulsing nerve roots
- ¨ whole immobile desensate limb and HornerŐs syndrome (connect with sympathetic trunk)
- if serratus anterior and rhomboids still intact: damage distal to roots
- if supra/infraspinatus intact: damage is distal to upper trunk.
Most common traction injury: eg birth injury
- ¨ C5,6 (upper trunk)
- lateral shoulder rotators and abductors, elbow flexors damaged ¨ waiters tip position.
- Sensation loss: lateral arm & forearm
Uncommon, includes KlumpkeŐs paralysis in Breech delivery
- ¨C8,T1 paralysis, affecting small hand muscles (claw hand, unable to extend fingers)
- Sensation loss: ulnar forearm
Pec Major is a useful guide to extent of plexus injury, as supplies all 5 segments of plexus.
Expose supraclavicular plexus in angle b/n SCM and clavicle
- divide inferior omohyoid and lateral branches of thyrocervical trunk.
Roots are behind scalenus anterior (retract or sever; *beware phrenic*) display lower trunk.
Infraclavicular part: open deltopectoral groove, detach pec minor from coracoid.
- may need to remove middle part of clavicle.
5% of dislocations of the shoulder damage it.
- also in upper humeral #s, or misplaced deltoid injections.
¨ weak shoulder abduction (supplies deltoid) and small area of anaesthesia over lower deltoid.
Rarely injury. Test for biceps.
Surgical approach: open deltopectoral groove, it enters coracobrachialis below teres minor.
Most commonly injured in humeral shaft fractures high up in its course.
Also in Saturday night palsy: draping arm over chair when inebriated.
¨ Wrist drop: unable to extend wrist / MCP jts
- note lumbricals and interossei will be ok, so finger extension still possible.
¨ Sensory loss: small area over 1st dorsal interosseus (lots of overlap
Test: look for elbow extension (triceps): should be OK, because given off near axilla.
Surgery: open interval between long and lateral heads of triceps; it crosses over medial head to reach radial groove.
- at elbow, retract ECR and CR laterally to show where it terminally divides.
- May need to follow deep branch (post interosseous n) under supinator.
Usually injured behind elbow or at wrist
¨ classic claw hand: hyperextended MCP of ring & little finger, flexion of IP jts
- due to paralysis of interossei and lumbricals with unopposed extensor & FDP action
- ulnar paradox: injury at elbow ¨ straighter fingers, as ulnar half of FDP out of action so cannot flex.
- Guttering of metacarpals due to intrinsic muscle wasting
¨ Sensory loss on ulnar side of hand and little ring / fingers often less than expected.
Test: abduction of index finger; extending DIP jt of little finger tests for high lesion (FDP)
Surgery: expose long medial biceps, where it is medial to brachial artery.
- easily approached behind medial epicondyle, and in forearm followed upwards from pisiform (displace FCU medially).
Most commonly at wrist (cuts or carpal tunnel syndrome)
¨ Sensory loss: theoretically over radial 3 1/2 fingers and palm but autonomous pulp pads index and middle fingers.
High lesions: Benedictine Expression: index finger straight but all others flexed (even middle usually has some ulnar supply via FDP; branch to index arises near mid-forearm)
- wasting of front of forearm will be evident.
Test: for high lesions: FPL and finger flexors by pinching pads of forefinger and thumb together
- at wrist level, palmar abduction of thumb is not possible.
Surgery: incise along medial border biceps, where nerve adjacent to brachial artery.
- in forearm: display by detaching radial head of FDS from radius, turning muscle medially (nerve adhered to deep surface)
Relief of carpal tunnel compression: incise flexor retinaculum on ulnar side of nerve: avoid damage to muscular recurrent branch distal to retinaculum, curving radially into thenar muscles. (Pl429)