Scaphoid nonunions: A 3-dimensional analysis of patterns of deformity

We tested the hypothesis that the fracture location of scaphoid nonunions r elates to the fracture displacement, development of dorsal intercalated seg ment instability (DISI) deformity, and changes in the contact area of the b ones in the radiocarpal joint. Eleven patients with scaphoid nonunions were examined with 3-dimensional computed tomography and a new method of proxim ity mapping. Two different patterns of displacement of scaphoid nonunions w ere demonstrated, 1 volar and 1 dorsal. All patients with a volar pattern s caphoid nonunion had a DISI deformity. Only a few of the patients with a do rsal pattern scaphoid nonunion, mostly in longstanding nonunions, had a DIS I deformity. The fracture line was generally distal to the dorsal apex of t he ridge of the scaphoid in the volar-type fractures and proximal in the do rsal displaced fractures. The proximity map of the distal fragment of the s caphoid on the radius in the volar type shifts radial compared with normal; in the distal type it shifts dorsal. Neither of the patterns showed any si gnificant changes of the proximity map in the radiocarpal joint at the prox imal scaphoid fragment and the lunate. Whether the fracture line passes dis tal or proximal to the dorsal apex of the ridge of the scaphoid appears to determine the likelihood of subsequent fracture displacement, DISI deformit y, and contact area of the bones in the radiocarpal joint. (J Hand Surg 200 0;25A:520-528. Copyright (C) 2000 by the American Society for Surgery of th e Hand.).