UMEM Educational Pearls

Category: Orthopedics

Title: Posterior Interosseous Nerve Compression Syndrome

Keywords: Posterior Interosseous Nerve, Compression, Radial Tunnel (PubMed Search)

Posted: 5/11/2008 by Michael Bond, MD (Updated: 10/21/2021)
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Posterior Interosseous Nerve Compression Syndrome

As eluded to last week Posterior Interosseous Nerve (PIN) Compression Syndrome, a deep branch of the radial nerve, is felt to be radial tunnel syndrome with paralysis.

  • Symptoms depend on whether the PIN is compressed before or after it divides into medial and lateral branches.
    • Before: Results in complete paralysis of the digital extensors, and extensor Capri ulnaris. Wrist will become dorsoradial deviated.
    • After-Medial Branch: Paralysis of extensor carpi ulnaris, extensor digiti quinti, and extensor digitorum communis
    • After-Lateral Branch: Paralysis of abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus, and extensor indicis proprius
  • Common causes:
    • Synovitis and Joint Ganglions
    • Nerve compression following fracture repair
    • Idiopathic Compression can occur at these sites
      • Fibrous bands anterior to the radial head
      • Tendinous origin of Extensor Carpri Radialis Brevis
      • Arcade of Froshe –Most common, it is the tendinous proximal border of supinator
      • Distal Edge of Supinator –Least Common
  • Exam:
    • Increased pain with resisted supination of the forearm
    • Supination with Wrist Flexion symptoms will likely be reproduced.
    • Pain with resisted extension of the middle finger
    • Unable to extend thumbs or fingers at MCP joints, but can extend at PIP and DIP joints