Upper limb
Ulnar nerve
Nervus ulnaris
- Origin
- Terminal branch of the medial cord of the brachial plexus (C8–T1, often receiving C7 fibers)
- Insertion
- Passes down the medial arm, pierces medial intermuscular septum, travels posterior to the medial epicondyle in the cubital tunnel, runs down the medial forearm under FCU, traverses Guyon's canal at the wrist, and divides into superficial and deep terminal branches
- Function
- Motor to FCU, medial half of FDP, all hypothenar muscles, all interossei, lumbricals 3 & 4, adductor pollicis, and deep head of FPB; sensory to the medial one and a half digits and corresponding palmar/dorsal hand
- Innervation
- Mixed sensorimotor nerve designated as the 'nerve of fine manual dexterity'
- Movement & chain
- Mediates finger abduction and adduction, powerful key pinch, and metacarpophalangeal stability
- Palpation
- Directly palpable in the groove behind the medial epicondyle ('funny bone') and at the wrist lateral to the pisiform bone
- Clinical
- Cubital tunnel syndrome (entrapment at elbow), Guyon canal syndrome (cyclist's palsy), 'Claw hand' deformity (Duchenne sign), positive Froment's sign (hyperflexion of thumb IP joint during key pinch test)
- Segmental innervation
- C8–T1 spinal cord segments
- In clinical practice
- Avoidance of prolonged elbow flexion, elbow padding, nerve gliding techniques, and surgical decompression with optional anterior subcutaneous/submuscular transposition
- Region in the model
- Upper limb