A patient presents with inability to extend the fingers and thumb at the metacarpophalangeal joints after a humeral shaft fracture (Holstein-Lewis fracture). Wrist extension is partially preserved. The specific nerve injury pattern is:

• A High radial nerve palsy (above spiral groove) — posterior interosseous nerve + wrist extension lost
• B Low median nerve palsy — thumb opposition and lateral two fingers flexion lost
• C Anterior interosseous nerve palsy — finger flexion lost
• D Posterior interosseous nerve (PIN) palsy alone — finger extension lost, wrist extension (ECRL) preserved ✓

Explanation

Holstein-Lewis fracture is a spiral fracture of the distal third of the humeral shaft that injures the radial nerve after it has already given off the branch to extensor carpi radialis longus (ECRL). Thus, wrist extension is preserved (ECRL is still innervated by the radial nerve proper), but the posterior interosseous nerve (PIN) is damaged distally, causing loss of finger and thumb MCP extension. This is a PIN palsy pattern. A high radial nerve lesion above the spiral groove would also cause wrist drop.

Reference: Maheshwari Essential Orthopaedics, 6th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.