Purpose: There remains uncertain whether to fix an ulnar styloid fracture accompanied by distal radius fracture. Fixation should be required in cases of the fracture involving a fovea of ulnar head, an attachment site of deep portion of triangular fibrocartilage. We analyzed the patients with ulnar styloid fracture accompanied by distal radius fracture using simple radiograph and 3D computed tomography (3D CT) scan images, respectively, and compared accuracy of evaluation for the types of ulnar styloid fractures, which might designate the treatment methods. Materials and Methods: We retrospectively reviewed 168 patients who underwent surgery for distal radius fracture in our hospital from January 2005 to March 2015, and evaluated whether ulnar styloid base was involved using simple radiographs and 3D CT scan images. The accuracy of evaluation by simple radiographs was compared with the findings of 3D CT scan images. To avoid the effect of memory, evaluation using 3D CT scan images was performed in a randomized order 2 weeks after initial evaluation for simple radiograph. Results: On simple radiographs, 64 patients (38%) had ulnar styloid base fractures; however, 21 cases of these revealed nonbase fractures by 3D CT scan images. And 7 out of 104 cases, on simple radiographs, determined as nonbase fracture by simple radiographs, were diagnosed as base fractures by 3D CT scans. Based on the findings of 3D CT scan images, the accuracy of simple radiographic evaluation for types of ulnar styloid fractures was 83%, with 86% sensitivity and 82% specificity. The positive predictive value was 67% and the negative predictive value was 93%. Conclusion: Accuracy of radiographic evaluation of ulnar styloid base fracture accompanied by distal radius fracture, when compared with 3D CT, was 83%. Therefore, we recommend that 3D CT scan image–based evaluation should be performed in case of unclear involvement sites so as to determine whether to fix it or not.
