Summary

Radial Nerve Palsy is the most common peripheral nerve injury associated with long bone fractures. It classically presents as "Wrist Drop" — the inability to extend the wrist and fingers. The radial nerve (C5-T1) is the primary extensor of the upper limb. The clinical picture depends entirely on the level of the lesion: Axillary injuries (crutches) cause triceps loss; Humeral shaft injuries (Spiral Groove) cause wrist drop but spare triceps; PIN injuries (Forearm) cause finger drop but spare the wrist (mostly). Most neuropraxic injuries (e.g., Saturday Night Palsy) recover spontaneously within 3-4 months. Permanent palsies are managed with Tendon Transfers, restoring excellent function.

Key Facts

• Function: Extension (Elbow, Wrist, Fingers, Thumb).
• Sensory: First Dorsal Webspace (dorsum of hand).
• Classic Level: Spiral Groove of Humerus.
• Mechanism: Compression (Saturday Night Palsy) or Fracture (Holstein-Lewis).
• Prognosis: 90% of fracture-associated palsies recover spontaneously.
• Splint: Dynamic Extension Splint (Thomas Splint).

Clinical Pearls

"Check the Triceps": The status of the triceps tells you the level. If triceps works, the lesion is distal to the axilla (likely Spiral Groove). If triceps is out, it's a high lesion.

"RADIAL Wrist Extension Spares the Nerve": In a PIN palsy (Posterior Interosseous Nerve), the patient CAN extend the wrist, but it deviates radially. Why? Because the ECRL (Extensor Carpi Radialis Longus) is supplied by the main radial nerve above the elbow. The PIN only supplies the ECU (Ulnar extensor) and fingers.

"Saturday Night Palsy": Named after falling asleep with the arm over a chair (or under a partner's head - Honeymoon Palsy) while intoxicated. It is a compression neuropraxia. Prognosis is excellent (weeks to months).

Motor Testing

• Triceps: "Push me away" (Elbow extension).
• Wrist Extension: "Cock your wrist back". (Check for radial deviation).
• Finger Extension: "Straighten your fingers at the big knuckle (MCPJ)".
• Thumb Extension: "Thumbs up" (EPL).

Sensory Testing

• Autonomous Zone: The anatomical snuffbox / First dorsal webspace.

          RADIAL NERVE PALSY MANAGEMENT
                      ↓
┌───────────────────────────────────────────┐
│              IS IT AN OPEN FRACTURE?      │
└───────────────────────────────────────────┘
       │                           │
      YES                         NO
       │ (Explore Nerve)           │ (Assume Neuropraxia)
       ↓                           ↓
┌──────────────┐          ┌──────────────────────┐
│  SURGERY     │          │    CONSERVATIVE      │
│ - Repair     │          │ - Dynamic Splint     │
│ - Graft      │          │ - Physio             │
└──────────────┘          │ - Wait 3-4 months    │
                          └──────────────────────┘
                                   ↓
                          NO RECOVERY @ 3-4 MONTHS
                                   ↓
                          ┌──────────────────────┐
                          │    NCS / EMG         │
                          └──────────────────────┘
                                   ↓
                          ┌──────────────────────┐
                          │ EXPLORE vs TRANSFER  │
                          └──────────────────────┘

The Dynamic Splint (Lively Splint)

• Because the flexors are working fine, the hand clenches into a fist.
• We need a splint that holds the wrist and fingers in extension but allows the patient to flex them against resistance (springs).
• Purpose: Keeps the muscles moving, prevents joint stiffness, improves function.

If the nerve is dead and won't grow back (or it's been >1 year), we "borrow" tendons from the working median/ulnar nerves. Standard Set (Jones Transfer Modified):

1. Pronator Teres (PT) -> ECRB. (Restores Wrist Extension).
2. Flexor Carpi Radialis (FCR) -> EDC. (Restores Finger Extension).
3. Palmaris Longus (PL) -> EPL. (Restores Thumb Extension). (Alternative: FDS of Ring finger -> EPL/EDC).

Outcome: Excellent. Radial nerve palsy is the best palsy to have, because tendon transfers work so well.

• Definition: Spiral fracture of the distal third of the humerus.
• Anatomy: The radial nerve is tethered by the lateral intermuscular septum here.
• Risk: High risk of nerve entrapment on reduction.
• Rule: If the nerve was working before manipulation, and stops working after reduction -> EXPORE IMMEDIATEY.

Key Studies

1. Shao et al. (Systematic Review): Spontaneous recovery rate for closed humeral fractures is 90%+. Early exploration does not improve outcomes.
2. Merle d'Aubigné: Described the classic tendon transfers still used today.

What is Wrist Drop?

The radial nerve powers the muscles that lift your wrist and fingers. If it stops working, your hand hangs limp.

Will it get better?

In most cases (especially after a fracture or sleeping on it), the nerve is just stunned (bruised). It will wake up.

• Saturday Night Palsy: Wakes up in 6-8 weeks.
• Fracture: Wakes up in 3-4 months.

What if it doesn't?

If the nerve is cut or doesn't recover, we can do a "rewiring" operation called a Tendon Transfer. We take a spare muscle from the front of your wrist (one that bends it) and move it to the back to lift it. It works incredibly well.