Ulnar nerve
roots and course
Origin: medial cord of brachial plexus c8, t1
Passes posterior to medial epicondyle
Deep branch of ulnar nerve lies in Guyon's canal - between hook of hamate and flexor tendons
branches
- deep branch - Hypothenar eminence, 2 lumbricals, adductor pollicis, interossei
- superficial branch - palmaris brevis, palmar surface of 5th and half of 4th finger
important supply:
motor
- Small hand muscles
- flexor carpi ulnaris
- medial portion of flexor digitorum profundus
sensory
- medial 1 ½ fingers - palmar and dorsal surfaces
Lesion
mechanism
- proximal: medial epicondyle injury
- distal: laceration at wrist
ulnar claw
- Pathogenesis: unopposed extension at MCPJ and unopposed flexion interphalangeal joints of 4th and 5th fingers
- Paradoxical effect: refers to absent sign with proximal ulnar nerve injury due to paralysis of flexor digitorum profundus
positive Froment's sign
caused by paralysis of adductor pollicis (see Small hand muscles)