RA- SWAN NECK DEFORMITY

Question 1

Swan neck deformity definition

Answer 1

Deformity characterised by

1. PIPJ hyperextension
2. DIPJ flexion

Question 2

Pathoanatomy of swan neck deformity in RA

Answer 2

Primary = pathology at PIPJ (more common)
- PIPJ synovitis with attenuation of volar plate and FDS
- lateral bands volar to axis of rotation of DIPJ = flexion
Secondary = pathology at wrist, MCPJ or DIPJ
- wrist = wrist flexion contracture
- MCPJ = volar subluxation and intrinsic contracture
- DIPJ = mallet finger (PIPJ hyperextension due to overactivity of central slip)

Question 3

Classification of swan neck deformity in RA

Answer 3

Nalebuff/ Zancolli classification = clinical and radiographic classification with 4 stages based on correctability and arthritis
Stage I = flexible deformity in MP flexion and extension
Stage II = deformity due to intrinsic tightness, positive Bunnell’s test
Stage III = fixed deformity in MP flexion and extension\
Stage IV = PIPJ arthritis

Question 4

Main special test for swan neck deformity in RA

Answer 4

Bunnell’s test = test for intrinsic tightness

• stabilise MPJ in extension
• assess passive flexion at PIPJ
• normally PIPJ should flex to 90deg

Question 5

3 factors to consider in management of swan neck deformity in RA

Answer 5

1. Acuity
2. Correctability
3. Arthritis