Mateusz Gładysz FESSH prep

FESSH prep Compressive neuropathies ulnar nerve — anatomy, claw mechanism, nerve transfers

Ulnar nerve lesions — overview and reconstruction

Last reviewed v1.0

FESSH-013Compressive neuropathies●●○ intermediate

Regarding ulnar nerve lesions and their reconstruction, which of the following statements are true?

  1. 1.Clawing of the ring and little fingers is more prominent in low (distal) than in high (proximal) ulnar nerve lesions — the ulnar paradox.

  2. 2.A supercharge end-to-side (SETS) transfer of the anterior interosseous nerve to the ulnar motor fascicle can augment a proximal ulnar nerve repair.

  3. 3.End-to-end transfer of the entire palmar cutaneous branch of the median nerve is the standard technique for restoring sensation in the ulnar territory after irreparable ulnar nerve injury.

  4. 4.A lesion confined to Guyon's canal spares dorsal hand sensation because the dorsal cutaneous branch of the ulnar nerve originates in the distal forearm, proximal to the canal.

  5. 5.Adding a distal AIN-to-ulnar motor nerve transfer to repair of a proximal ulnar nerve injury can shorten the regeneration distance to the intrinsic motor end-plates.

FESSH marking: +1 per correct statement, 0 for blank, −1 for incorrect. Click the same TRUE/FALSE button twice to clear it.

Question ID
FESSH-013
First published
Last reviewed
Version
v1.0
Answer key and explanations — open after answering

  1. 1. Clawing of the ring and little fingers is more prominent in low (distal) than in high (proximal) ulnar nerve lesions — the ulnar paradox.

    True

    In low lesions the intrinsics are denervated but flexor digitorum profundus to the ring and little fingers remains innervated, producing unopposed IP-joint flexion and visible clawing. In high lesions the ulnar half of FDP is also denervated, so IP-joint flexion is weak and the claw posture is less pronounced — paradoxically improving the resting appearance of a more proximal injury.

  2. 2. A supercharge end-to-side (SETS) transfer of the anterior interosseous nerve to the ulnar motor fascicle can augment a proximal ulnar nerve repair.

    True

    The SETS transfer coapts the distal anterior interosseous nerve end-to-side into the ulnar motor fascicle through a perineural window in the distal forearm, delivering axons to the intrinsic motor end-plates while the proximal ulnar nerve regenerates. The intent is to reach motor end-plates before irreversible degeneration.

    • Barbour J, Yee A, Kahn LC, Mackinnon SE. Supercharged end-to-side anterior interosseous to ulnar motor nerve transfer for intrinsic musculature reinnervation. J Hand Surg Am. 2012;37(10):2150-9. PMID 23021177
    • Davidge KM, Yee A, Moore AM, Mackinnon SE. The supercharge end-to-side anterior interosseous-to-ulnar motor nerve transfer for restoring intrinsic function: clinical experience. Plast Reconstr Surg. 2015;136(3):344e-352e. PMID 26313839

  3. 3. End-to-end transfer of the entire palmar cutaneous branch of the median nerve is the standard technique for restoring sensation in the ulnar territory after irreparable ulnar nerve injury.

    False

    The standard sensory transfer harvests the third common digital nerve from the median nerve, or uses side-to-side cross-palm sensory grafting. Sacrificing the entire palmar cutaneous branch would denervate the radial palm without offering a comparable advantage and is not the established technique.

    • Brown JM, Yee A, Mackinnon SE. Distal median to ulnar nerve transfers to restore ulnar motor and sensory function within the hand: technical nuances. Neurosurgery. 2009;65(5):966-977; discussion 977-978. PMID 19834412

  4. 4. A lesion confined to Guyon's canal spares dorsal hand sensation because the dorsal cutaneous branch of the ulnar nerve originates in the distal forearm, proximal to the canal.

    True

    The dorsal cutaneous branch typically arises 5–7 cm proximal to the ulnar styloid, courses dorsally beneath flexor carpi ulnaris, and is therefore not affected by compressive lesions confined to Guyon's canal — sensation over the dorsoulnar hand and dorsum of the medial 1½ digits is preserved.

    • Puna R, Poon P. The anatomy of the dorsal cutaneous branch of the ulnar nerve. J Hand Surg Eur Vol. 2010;35(7):583-585. PMID 20498153
    • Botte MJ, Cohen MS, Lavernia CJ, von Schroeder HP, Gellman H, Zinberg EM. The dorsal branch of the ulnar nerve: an anatomic study. J Hand Surg Am. 1990;15(4):603-7. PMID 2380524

  5. 5. Adding a distal AIN-to-ulnar motor nerve transfer to repair of a proximal ulnar nerve injury can shorten the regeneration distance to the intrinsic motor end-plates.

    True

    Reinnervation depends on the time taken for regenerating axons to reach motor end-plates before irreversible degeneration. A SETS or end-to-end AIN-to-ulnar transfer at the wrist or distal forearm provides axons close to the target intrinsics; published series report improved first dorsal interosseous strength compared with repair alone, although the evidence remains low-quality.

    • Baltzer H, Woo A, Oh C, Moran SL. Comparison of Ulnar Intrinsic Function following Supercharge End-to-Side Anterior Interosseous-to-Ulnar Motor Nerve Transfer: A Matched Cohort Study of Proximal Ulnar Nerve Injury Patients. Plast Reconstr Surg. 2016;138(6):1264-1272. PMID 27879594
    • Thakkar M, Rose A, King W, Engelman K, Bednarz B. Anterior interosseous nerve to ulnar nerve transfer: a systematic review. JPRAS Open. 2022;32:195-210. PMID 35498818