What is the distribution of the raidal nerve?
What happens if there is a radial nerve injury in the spiral groove of the humerus?
- Wrist drop: cannot extend fingers and wrist as paralysis of brachioradialis and extensors of fingers so when pronated everything flexed due to unopposed flexors and gravity
- Sensory impairment: Posterior cutaneous nerve and lower lateral cutaneous nerve in tact as branch before spiral groove. Paraesthesia in superficial branch of radial nerve
- Can still extend elbow: nerve gives off branch to long and medial heads of triceps before spiral groove and lateral head given off in spiral groove. Anconeus is paralysed but only assists extension so no issue
What is the distribution of the median nerve?
What happens anatomically if there is a high median nerve injury (above elbow level) ? e.g supracondylar fracture or stab (see pg 183 MSK workbook 2)
- No issue in arm only forearm
- Paralyse muscles in forearm and hand (pronators and wrist flexors)
- Senosry loss in hand
- HAND OF BENEDICTION AND APE HAND
What is the clinical presentation of a high median nerve injury?
- Hand of Benediction: when making fist not rest
- Ape Deformity: long standing lesion, at rest
- Sensory loss in whole region of median nerve
What happens if there is a low median nerve injury at the wrist, e.g compression of carpal tunnel or penetrating injury (broken glass)?
- Innervation to common flexor origin and FDP in tact
- Palmar cutaneous branch over thenar eminence spared
- LOAF muscles paralysed
- Loss of sensation in median nerve but not thenar eminence
- Ape Hand: flat thenar eminence, thumb adducted and externall rotated
What is the distribution of the ulnar nerve?
What happens in a low ulnar nerve lesion at the wrist? (E.g laceration or Guyon's canal compression)
- Muscles of hypothenar eminence functions impaired and long standing damage can lead to an ulnar claw
- Ulnar claw: ring and little fingers are hyperextended at MCPJ and flexed at DIPJ and PIPJ
- Loss of bulk of first webspacedue to atrophy of AP and first dorsal interossei
- Loss of bulk of hypothenar eminence
- Guttering between metacarpals due to wasting interoseei
- Sensation lost in palmar ulnar 1.5 digits and dorsum over distal phalanges
Why does an ulnar claw occur in a low ulnar nerve lesion?
What happens in high ulnar nerve lesion, e.g medial epicondylar fracture or compression in cubital tunnel?
- Sensation lost to all of ulnar nerve distribution
- High ulnar claw: less pronouced than low as FDP paralysed so no flexion of DIPJ at ring and little fingers. Only flexion of PIPJ and hyperextension of MCPS
' ULNAR PARADOX' - claw seen less than in low lesion
What are the differences between a high and low ulnar nerve lesion?
Low: no paralysis of FCU, FDP and no loss of sensation in dorsal and palmar cutaneous branches
Draw the sensory loss of the ulnar nerve in the hand if there is a laceration at the wrist?
What muscle paralysis causes this claw pattern?
- Lumbricals are paralysed
- Unopposed extension of extensor digitorum by lumbricals so hyperextension of MCP
- Unopposed flexion of flexor digitorum due to loss of lumbricals so flexion of IPJ
Where can you palpate the ulnar and radial pulses?
Ulnar: lateral to FCU
Radial: lateral to FCR