Tinel's sign in nerve regeneration progresses distally at approximately 1 mm per day. If a radial nerve injury occurs at the spiral groove (15 cm proximal to the extensor digitorum communis motor end-plate), the minimum expected time to appearance of early voluntary reinnervation of EDC (ignoring neuromuscular junction reformation time) is approximately:

• A 1–2 months
• B 10–12 months
• C 18–24 months
• D 5 months ✓

Explanation

Peripheral nerve regeneration occurs at approximately 1 mm/day (1 inch/month). A distance of 15 cm = 150 mm from the injury site to the motor end plate corresponds to 150 days ≈ 5 months. Tinel's sign advancing distally at the same rate provides a clinical guide. In practice, an additional 4–6 weeks is added for neuromuscular junction reformation and motor end-plate re-innervation. Therefore, clinical reinnervation of EDC would be expected at approximately 5–6 months. Nerve regeneration monitoring is critical — if Tinel's sign fails to progress or muscles show no reinnervation within the expected timeframe, surgical exploration for neuroma-in-continuity or nerve grafting is considered.

Reference: Maheshwari Essential Orthopaedics, 6th ed.

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Written and medically reviewed by the StethoPrep medical team.