Chapter 28 - Three-Dimensional Analysis of Nonunion Patterns

Abstract

There is wide variation in the natural history of scaphoid nonunion. The mechanism of development of the different deformity had been unclear until three-dimensional (3D) analysis of scaphoid nonunion was developed. There are mainly two patterns of carpal deformity in scaphoid nonunion based on the fracture location. When the fracture line runs distally to the dorsal scaphoid apex where dorsal scapholunate interosseous ligament (DSLIL) is attached (type B2), the scaphoid nonunion is unstable and humpback deformity and dorsal intercalated segment instability deformity progress quickly. In the surgery of type B2 scaphoid nonunion, a volar approach is preferable to allow easy correction of humpback deformity and implantation of the wedge-shaped bone graft. A rigid fixation is achieved by inserting the screw from the scaphoid tuberosity. On the other hand, when the fracture line runs proximal to the dorsal scaphoid apex (type B1), scaphoid nonunion is stable by the connection of DSLIL between distal fragment of scaphoid and lunate. Therefore, the only resection of the dorsal radial styloid process and osteophytes of dorsal scaphoid ridge without fixation could be selected for low-demand patients. If nonunion is treated with the internal fixation, resection of the dorsal osteophyte and cancellous bone graft from the dorsal approach is recommended. Screw insertion from the dorsal side allows easier vertical penetration at the fracture site.