A patient with a fracture of the medial epicondyle of the humerus is found to have weakness of finger abduction and adduction, hypothenar atrophy, and loss of sensation over the medial 1.5 fingers. Which of the following tests best demonstrates the ulnar claw hand deformity?

• A Extension at MCP joints and flexion at IP joints of ring and little fingers ✓
• B Flexion at all MCP joints and extension at IP joints of all fingers
• C Flexion at MCP and extension at all IP joints with loss of thumb opposition
• D Extension at all MCP and IP joints with wrist drop

Explanation

Ulnar nerve injury causes loss of intrinsic muscles (lumbricals for ring and little fingers, interossei). The unopposed action of long flexors and extensors produces hyperextension at MCP joints and flexion at IP joints of ring and little fingers — the 'ulnar claw' or 'intrinsic minus' deformity. The index and middle fingers are less affected because their lumbricals are supplied by the median nerve. The deformity is paradoxically more pronounced with a wrist-level lesion than an elbow lesion (ulnar paradox) because FDP to ring/little is also paralyzed at elbow level, reducing IP flexion.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.