Hand deformities in rheumatoid arthritis

*1. What is a Boutonniere's deformity? How is it treated?
2. What is a swan neck deformity? How is it treated?
3. What is the mechanism of ulnar deviation of the fingers? How is it treated?
4. What occurs in tenosynovitis of the flexor tendon sheath?
5. What is a pseudobenediction sign?

Answers:
1. Caused by weakness/rupture of terminal portion of extensor hood resulting in extensors of the PIP slipping and becoming flexors. This causes flexion of the PIP, hyperextension of the DIP and MCP. (Position of finger as if buttoning a button.) Treat with tripoint finger splint.
2. Caused by contracture of intrinsic and deep flexor muscles and tendons of fingers, resulting in flexion contracture of MCP, hyperextension of PIP, and flexion of DIP. Treat with swan neck ring splint.
3. Weakening of ECU, ulnar and radial collateral ligaments, resulting in wrist and finger deviation in the ulnar direction. Treated with ulnar deviation splint.
4. Diffuse swelling of volar surfaces of the phalanges between the joints with grating of flexor tendon sheath.
5. Extensor tendons rupture due to abrasion from rubbing on sharp elevated ulnar styloid, resulting in inability to extend 4th and 5th digits.