The proximal pole of the scaphoid is notoriously prone to delayed union, nonunion, and avascular necrosis following a fracture due to its retrograde intraosseous blood supply. Which primary artery provides this critical retrograde perfusion via dorsal carpal branches?

Explanation:
The correct option is d. The scaphoid bone possesses a tenuous and unique vascular anatomy that dictates its clinical behavior following trauma. The major blood supply (representing 70-80% of total perfusion) originates from branches of the radial artery, specifically via the dorsal carpal branch. These vessels enter the scaphoid strictly at the dorsal ridge, which is located in the distal third of the bone. Once inside the bone, the vessels run in a retrograde fashion (from distal to proximal) to supply the proximal pole. Because there is little to no direct vascular inflow to the proximal pole itself, fractures at the waist or proximal third completely sever this retrograde intraosseous blood supply, resulting in an exceptionally high incidence of avascular necrosis and nonunion. Reference: Gelberman RH, Menon J. The vascularity of the scaphoid bone. J Hand Surg Am.