What is Arachnodactyly? What is Metacarpal Index?

• Arachnodactyly ("Spider fingers") means abnormally long and thin fingers compared to the size of the palm
• Derived from the Greek word " Arachne" - Spider, "Daktylos" - Finger
• Arachne word is derived from Greek mythology where a maiden named Arachne was cursed and turned to a spider by the Greek Goddess Athena, when Arachne  a skilled weaver challenged her to a weaving contest
• Seen in Marfan's Syndrome, Homocysteinuria
• Arachnodactyly is assessed by-

1. Ratio of Middle finger length to total hand length
2. METACARPAL INDEX - 

FINGER INDEX LENGTH/ WIDTH + MIDDLE L/W + RING L/W + LITTLE L/W DIVIDED BY 4 
METACARPAL INDEX > 8.4 SUGGESTS ARACHNODACTYLY