Definition
Loss of PIN motor function with no pain
- multiple potential causes
- may be caused by compression as per radial tunnel
- may be post fracture or surgery
- may be caused by synovits / ganglion / rheumatoid nodules etc
Symptoms
Often heralded by deep aching pain in forearm that resolves
- is followed by PIN weakness
Most commonly is incomplete lesion
- weakness of extension of index and middle or just thumb
Examination
No sensory loss
Characteristic radial deviation with wrist extension
- BR & ECRL functioning
- supplied by radial nerve
NCS / EMG
Can be helpful
EMG of appropriate muscles
- demonstrates denervation
MRI
Looking for mass lesion
Site of Compression
FREAS
Trauma - Monteggia fracture
Iatrogenic - surgery radial head / radius
Inflammation - RA nodule / synovitis of radio-capitellar joint DRUJ
Masses - lipoma / ganglia
Local injections
Lead poisoning - usually bilateral / motor palsy without sensory
Conversion reaction
Polyarteritis Nodosa
Muscle rupture
DDx
Locked trigger finger
Tendon rupture
Management
Non operative
Splint / therapy
- wait 3 months for recovery
Operative
Indications
- ganglion / rheumatoid nodule / synovitis
- failure to recover post operatively
Technique
Operative release
- posterior approach
- between EDC and ECRB
- divide supinator
