Radial nerve-mnemonics
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Radial nerve mnemonics
Origin
- “Posterior cord, C5 to T1, makes the extensors shine.”
- Radial nerve arises from the posterior cord of the brachial plexus.
- Main action: extension at elbow, wrist, fingers, and thumb.
Course
- “P-T-R-L”
Posterior cord → Triangular interval → Radial groove → Lateral epicondyle/radial tunnel
Key muscular actions
-
“Radial = Raise it”
- Raises or extends the elbow, wrist, MCP joints, and thumb.
-
“T-B-S-E”
- Triceps: elbow extension
- Brachioradialis: elbow flexion in mid-pronation
- Supinator: supination
- Extensors: wrist, fingers, thumb
Terminal branches at the elbow
- “Superficial senses, Deep does.”
- Superficial radial nerve: sensory
- Deep branch / posterior interosseous nerve (PIN): motor
Sensory autonomous zone
- “Radial reads the first web.”
- Test sensation in the first dorsal web space between thumb and index finger.
Lesion-level mnemonic
| Site | Classic setting | Quick mnemonic | Findings |
|---|---|---|---|
| Axilla | Crutch palsy | “Crutch crushes everything” | Loss of triceps plus wrist/finger extension, wrist drop, broad dorsal sensory loss |
| Radial groove | Humeral shaft fracture, “Saturday-night palsy” | “Saturday spares triceps” | Wrist drop, finger-extension weakness; elbow extension usually preserved |
| PIN | Radial tunnel/Monteggia-related injury | “PIN = Palsied INdex and fingers, No numbness” | Finger drop; no sensory loss. Wrist extension may remain but can deviate radially |
| Superficial radial nerve | Compression near wrist, tight watch/handcuffs | “Superficial = sensation only” | Dorsolateral hand numbness, no motor deficit |
High-yield distinction
- Wrist drop + numbness: radial nerve lesion proximal to sensory branch.
- Finger drop without numbness: PIN palsy.
- Numbness without weakness: superficial radial nerve lesion.
Textbook descriptions support that radial-groove lesions are the common injury pattern and typically preserve triceps, while the nerve divides near the elbow into superficial and deep terminal branches. See Gray’s Anatomy for Students and Campbell’s Operative Orthopaedics; also review NCBI’s radial nerve overview.
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