Abstract
Computed tomography (CT) is increasingly used not just to diagnose union but also
to estimate the percentage of the fracture gap that is bridged by healing bone. This
study tested the primary null hypothesis that there is no agreement between observers
on the extent of union of a scaphoid waist fracture on CT. CT scans of 13 nondisplaced
scaphoid waist fractures treated nonoperatively were rated by 145 observers. CT scans
were done 10 to 12 weeks after injury. Observers were asked to “eyeball” measure percentage
of union. We found that there was a moderate agreement on the categorical degree of
partial union of a scaphoid waist fracture on CT (k = 0.34). Agreement on the location
of bony bridging was slight (k = 0.31). We concluded that there is limited reliability
of diagnosis of partial union of a scaphoid waist fracture on CT and that this should
be taken into account in both patient care and research. This is a Level III, diagnostic
study.
Keywords
scaphoid waist fracture - computed tomographic scan - interobserver study - union
