A 55-year-old man with long-standing rheumatoid arthritis has swan neck deformity of his right ring finger. The swan neck deformity is characterised by:

• A PIP joint extension (hyperextension) with DIP joint flexion ✓
• B PIP joint flexion with DIP joint extension
• C MCP joint flexion with IP joint extension
• D MCP joint hyperextension with PIP joint flexion

Explanation

Swan neck deformity in rheumatoid arthritis consists of PIP joint hyperextension combined with DIP joint flexion. It results from laxity of the volar plate at the PIP joint, intrinsic muscle tightness, and disruption of the terminal extensor tendon. This is the opposite of boutonnière deformity (PIP flexion + DIP hyperextension). Surgical options include soft-tissue stabilisation (lateral band translocation, volar plate reefing) for flexible deformities and PIP arthrodesis for rigid fixed deformities.

Reference: Maheshwari Essential Orthopaedics, 6th ed.

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Written and medically reviewed by the StethoPrep medical team.