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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