Natural History of Scaphoid Nonunion.

Abstract

Scaphoid fracture is the most common fracture of the carpus. The excessive extension force with axial loading in the wrist can fracture the scaphoid or in the slightly flexion position with excessive axial loading, such as in a punching machine. Once the scaphoid is fractured, gradually, the distal fragment flexes, due to the force from the flexor carpi radialis, and the proximal fragment extends, as the extension force passes through the scapholunate ligament from the triquetrum. This motion inside the proximal row indicates the dorsal intercalated segment instability (DISI) deformity after scaphoid fracture/nonunion.[1] Sometimes, scaphoid fracture patients were claimless and easily neglected or misdiagnosed in the initial period of trauma. Watson[2] described degenerative arthritis with chronic scapholunate dissociation as scapholunate advanced collapse (SLAC) wrist. Similar behavior had occurred in scaphoid nonunion as SLAC wrist, and it was termed as scaphoid nonunion advanced collapse (SNAC) wrist, in which stage 1 showed degenerative condition around the radial styloid process; stage 2 showed degenerative changes between distal fragment of the scaphoid and scaphoid fossa of the radius; and stage 3 indicated degenerative changes in the midcarpal joint, resulting in the capitate proximal migration collapse. That is why we, as clinicians, usually attempted to reconstruct the scaphoid nonunion, even in cases with more than 10 years history from initial injury. However, in daily clinical practice, sometimes we observed normal alignment of the proximal carpal row in chronic scaphoid nonunion with long-term neglect.