NONUNION OF THE SCAPHOID DISTAL POLE

This study was undertaken to determine the incidence of and assess factors affecting nonunion of scaphoid distal pole fractures. A total of 193 established scaphoid nonunions were treated in our clinics between the years 1999 and 2004; of which, eight cases involved the distal pole of the scaphoid. These were further analyzed to determine factors that may have contributed to the development of nonunion. This study reveals that distal pole nonunions account for 4.1% of all scaphoid nonunions. We found inadequate initial treatment to be the cause for nonunion in 63% of patients. Type IIC fracture pattern according to Posser's classification was seen in 100% of patients and a persistent Dorsal Intercalated Segmental Instability (DISI) pattern in 100% patients. In addition, 100% of fractures occurred at the watershed zone between the two vascular networks of the scaphoid. We believe the key features leading to the likelihood of nonunion at the distal pole include a Type IIC fracture pattern associated with a continued deforming force that eventually leads to a DISI deformity. The watershed area between the proximal vascular network supplying the waist and the distal one supplying the distal pole is especially vulnerable to poor healing.