In long-standing rheumatoid arthritis of the hand, progressive ulnar deviation of the fingers at the metacarpophalangeal joints occurs primarily because:

• A The radial collateral ligaments shorten and thicken with chronic synovitis
• B The common extensor tendons subluxate ulnarward off the metacarpal heads while the intrinsics tighten ✓
• C The abductor pollicis longus pulls the index metacarpal radially
• D Ulnar nerve palsy weakens the interossei on the radial side of each finger

Explanation

Synovial distension of the MCP capsules weakens the radial collateral ligaments and the sagittal bands, allowing the extensor digitorum communis tendons to displace ulnar to the metacarpal heads where they act as ulnar deviators, compounded by intrinsic muscle tightness and radial deviation of the carpus creating the zigzag collapse. Radial collateral ligaments are stretched, not shortened, so option A states the reverse. Ulnar nerve palsy gives clawing, not ulnar drift.

Reference: Campbell's Operative Orthopaedics, 14th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.