The scaphoid (navicular) is the most commonly broken of the small wrist bones. It can be felt at the base of the thumb, in the slight hollow we call the "anatomic snuffbox." The fracture usually happens when the hand lands open on the ground and the wrist is forced backward, especially in young, active people.
The most treacherous part of this fracture is that the pain is mild and it is often taken for a sprain. Yet the scaphoid's blood supply runs backward; blood enters the bone from its far end, so if the fracture is in the upper (proximal) part, the bone may not get enough blood and may fail to unite.
For that reason, when there is tenderness in the snuffbox even though the X-ray looks normal, I splint the wrist and repeat the X-ray after 10 to 14 days, or confirm the diagnosis with an MRI or CT. A missed scaphoid fracture can come back months later as a bone that never united.
Fractures that have not shifted are treated with a cast, but this bone heals slowly; the cast can stay on for months, and longer for upper-end fractures. For displaced fractures or those at the upper end, I prefer fixation with a screw; in old fractures that have not united, a bone graft has to be added. Because smoking clearly slows healing, I particularly ask patients to quit during this period.