The anatomy of the scaphoid.

The scaphoid is a critical link in the mechanism of the carpus. Its complex shape allows it to participate in the kinematics of both the proximal and distal row. Because of its offset proximal and distal articular surfaces, it has a natural tendency to palmar-flex with longitudinal loading. Because of this, extension of the scaphoid places progressively increasing tension on the palmar cortex of the curved waist of the scaphoid. Excessive extension or ulnar deviation of the wrist, coupled with excessive loading, mechanically predisposes the scaphoid to fracture. This is especially true if the strong ligaments attaching to the scaphoid retain their integrity. When a fracture occurs proximal to the waist of the scaphoid, it is predisposed to displacement because of the opposing forces on the proximal [table: see text] and distal fragments as well as the distribution of ligament attachments. This, in turn, predisposes the proximal fragment to ischemic conditions because of the distal location of nutrient vessels and a retrograde intraosseous blood supply.