This fracture is well known for several reasons. The scaphoid is the most common carpal fracture sustained in a fall. The scaphoid acts as the primary mechanical link between the proximal and distal carpal rows. Differential forces on these these rows serve both to produce fracture and then to maintain motion and instability at the fracture site despite external immobilization (Fig. 9b). Scaphoid fractures are not always obvious on initial x-rays. Patients with wrist pain and tenderness in the anatomic snuffbox after a wrist hyperextension injury should be assumed to have a scaphoid fracture even if initial radiographs are normal. They are best treated in a cast for two weeks and then reevaluated with repeat films. As little as two millimeters of displacement can indicate gross instability and high risk for nonunion. Many patients believe that they have sprained their wrist when in fact they have fractured their scaphoid, and may have intermittent symptoms for years before seeking medical attention. Scaphoid fractures are prone to nonunion because the proximal pole of the scaphoid is entirely articular and the blood supply to the proximal pole of the scaphoid is largely from the distal pole, which is disrupted by fracture. Avascular necrosis of the proximal pole can occur, changing the alignment of the other carpal bones and over years resulting in degenerative arthritis of the radioscaphoid joint, the midcarpal joint and ultimately the remaining wrist joints, referred to as scapholunate advanced collapse or "SLAC" wrist (Fig. 9a). Some believe that even asymptomatic scaphoid fractures should be treated to prevent this late problem. Although the role of vascular supply to the proximal pole has received much attention in the experimental study of scaphoid nonunion, since the introduction of the Herbert screw, adequate bone fixation has been recognized to be at least as important. There has been a trend away from the extreme of conservative management (four to eight months of immobilization in an above-elbow-to-fingertip cast) to earlier surgical intervention. Herbert has classified scaphoid fractures, and this classification can be used as a basis for treatment recommendations (Fig. 10). Indications for open reduction of acute scaphoid fractures currently include displaced fractures, perilunate fracture dislocations, and selected minimally displaced fractures to reduce recovery time. A volar surgical exposure is used for fractures involving the middle or distal third, and a dorsal surgical exposure is best for proximal fractures or those associated with perilunate injuries. Scaphoid fractures may not heal despite bone graft and internal fixation, and pose a variety of management options as outlined in Fig. 10a.