Blood supply to the carpal bones can be divided in two

• Extraosseous
• Intraosseous

Extraosseous
There are six transeverse arches formed around the carpal bones with radial and ulnar artery forming longitudinal medial & lateral borders of these arches

These transverse arches are

• Dorsal Intercarpal
• Palmar Intercarpal
• Dorsal Radiocarpal
• Palmar Radiocarpal
• Dorsal Basal Metacarpal
• Deep Palmar

Dorsal intercarpal, palmar radiocarpal and deep palmar arches are dominant suppliers.

Scaphoid, pisiform & trapezium have direct branches off the Radial & Ulnar arteries

Intraosseous

There are three types of blood supplies in carpal bones and varies with bone

• Scaphoid, capitate and lunate in 20% cases in few have only a single  vessels entering one surface.  In these large areas of bone is  dependent on single vessel
• Hamate and trapezoid have more than one sites of vessel entry but lack significant anastomosis
• Trapezium, 80% lunates, triquetrum and pisiform have got numerous anastomoses and rich internal network

The blood supply to most carpal bones enters the distal half, leaving the proximal half at risk