Radiographic clues for determining carpal instability and treatment protocol for scaphoid fractures.

The magnitude of carpal instability following scaphoid fracture is closely related to the fracture location. Middle-third fractures of the scaphoid are classified into B1 (distal oblique fractures) and B2 (complete waist fractures). Deciding preoperatively whether a fracture is B1 or B2 is clinically important, because several studies have revealed that B1 is more stable than B2. Dorsal intercalated segment instability deformity often develops in B2, creating a large, wedge-shaped bone defect, while minimal humpback deformity develops in B1, and the bone defect is much smaller, even after long-standing nonunions. However, determination of the fracture types using X-rays may be less accurate than using three dimensional computed tomography. This article suggests two radiographic clues for estimation of post-fracture carpal instability along with a treatment protocol for each fracture type.