Sunderland's classification of nerve injuries has five grades. Which grade corresponds to disruption of axon and endoneurium but intact perineurium, and what is the expected recovery pattern?
- A Grade 2 (Seddon's axonotmesis) — intact endoneurium; complete spontaneous recovery
- B Grade 4 — only epineurium intact; no spontaneous recovery without surgery
- C Grade 3 — axon and endoneurium disrupted, perineurium intact; incomplete/misdirected recovery possible ✓
- D Grade 5 (neurotmesis) — complete nerve transection; requires surgical repair
Correct answer: C. Grade 3 — axon and endoneurium disrupted, perineurium intact; incomplete/misdirected recovery possible
Explanation
Sunderland Grade 3 corresponds to disruption of axon and endoneurium (the inner tube guiding axon regrowth) while the perineurium (fascicle sheath) is intact. Endoneurial disruption means axons may regenerate across the injury site but do so misdirectedly, forming intraneural scar (fibrosis within fascicles); recovery is incomplete and erratic, sometimes requiring neurolysis. Grade 2 (endoneurium intact) has excellent predictable recovery; Grade 4 (only epineurium intact) requires surgery as perineurium loss prevents organised regeneration; Grade 5 is complete transection.
Reference: Maheshwari Essential Orthopaedics, 6th ed.
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