Scaphoid fracture

What it is

The scaphoid is a carpal bone, also named the carpal navicular. It is the most common carpal bone injured, given as 70% of carpal bone fractures, and the fracture in it is usually nondisplaced.

Its anatomy is what puts it at risk. It is a complex 3-dimensional structure, described as a twisted peanut, with a proximal and a distal pole, a tubercle and a waist, and 80% of it is covered with articular cartilage, which leaves little bare bone for its blood supply to enter.

The vascular supply is provided by two vascular pedicles, the dorsal branch of the radial artery, which is the major one at 80%, and the volar branch of the radial artery. Both come from the one radial artery, and on another page the supply is given as a single artery. Either way the direction is the same and it is the direction that matters: the blood supply arises from the dorsal distal pole and flows into the distal portion of the bone, so the proximal pole has poor blood supply and is less likely to heal than the distal pole.

The fracture is classified by where it sits, and the two pages that give figures do not agree. One gives waist 70%, proximal pole 5%, distal pole 10% and tuberosity 15%. The other gives a transverse fracture through the waist 65%, distal 10% and proximal 25%. Both put the waist first by a wide margin; hold the rest as approximate.