II. History
- First described by Hippocrates in 5th century B.C.
III. Definition
- Bulbous digital deformity
- Watch-crystal deformity of Fingernail
IV. Pathophysiology
- Sign of Hypertrophic Osteoarthropathy (Acropachy)
- Thickening of nail bed's soft tissue (especially proximally)
- Typically affects all fingers
- Results from abnormal microvasculature with increased Blood Flow to the microvasculature
V. Signs: Schamroth's Window Test for Clubbing
- Oppose fingers of both hands
- Observe space formed between nail bases
- Normal: Diamond-Shaped "window" seen
- Clubbing:
- Window erased
- V-shaped gap at distal end of nail is wider
VI. Signs: Digital Index
- Use non-elastic string to measure digit circumference
- Measure circumference at 2 sites on all 10 digits
- Nailbed circumference (NB)
- Distal interphalangeal joint circumference (DIP)
- Calculate NB/DIP ratio
- Results suggestive of Digital Clubbing
- NB/DIP ratio exceeds 1 on all fingers or
- Sum of all ten NB/DIP ratios >10
VII. Signs: Lovibond Angle
- Line 1
- Draw a longitudinal line across the top of the distal digit soft tissue
- Line 2
- Draw a longitudinal line across the midpoint of the nail plate
- Angle
- Measure the angle at the intersection of the 2 lines (clockwise from proximal end of line 1)
- Interpretation
- Angle greater than 180 degrees is suggestive of Clubbing