In Sunderland's classification of nerve injuries, a Grade 4 injury is characterised by which pathological finding and expected clinical outcome?

• A Disruption of all internal fascicular architecture with intact epineurium only; neuroma-in-continuity forms, poor spontaneous recovery, requires resection and grafting ✓
• B Loss of axonal continuity with intact endoneurium; complete spontaneous recovery expected within months
• C Disruption of axon and endoneurium with intact perineurium; regeneration occurs but is disorganised with unpredictable recovery — typically requires surgical exploration
• D Complete nerve trunk transection with complete loss of epineurium; requires end-to-end repair or nerve grafting

Explanation

Sunderland expanded Seddon's three types into five grades. Grade 1 = neuropraxia (conduction block, intact axon/endoneurium, full recovery). Grade 2 = axonotmesis (axon disrupted, endoneurium intact, guided regeneration with full recovery). Grade 3 = endoneurium disrupted, perineurium intact; partial recovery, some misdirection. Grade 4 = perineurium disrupted, epineurium intact; severely disorganised regeneration producing a neuroma-in-continuity, poor spontaneous recovery, requires surgical resection and nerve grafting. Grade 5 = complete nerve transection (neurotmesis); requires primary repair or grafting. Grades 1–2 are managed conservatively; Grades 4–5 require surgery.

Reference: Maheshwari Essential Orthopaedics, 6th ed.

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