= GUYON CANAL SYNDROME

= ulnar nerve entrapment / injury at wrist (2^nd most common site after elbow)

Cause:

1. Repetitive continuous pressure on ulnar nerve in sports: cycling (esp. mountain biking), martial arts, racket sport
2. Exposure to frequent vibration: work in foundry / with pneumatic drills
3. Adjacent mass: ganglion cyst, lipoma, ulnar artery aneurysm, dislocation of pisiform bone, fracture of hamulus, os hamuli proprium, osteoarthritis of pisotriquetral joint, anomalous muscle (abductor digit minimi, flexor digiti minimi brevis), abnormal tendon (flexor carpi ulnaris)

• tenderness over Guyon canal
• Tinel sign = tingling radiating to 4^th + 5^th fingers
• reduced strength of grip
• loss of motor function (= zone 2 injury): handlebar palsy
• sensory loss (= zone 3 injury) to hypothenar eminence + 4^th finger + part of 5^th finger
• combination of motor + sensory function (zone 1 injury): injury proximal to bifurcation of ulnar n.