Ulnar variance in scaphoid nonunion.

BACKGROUND Negative ulnar variance can be a risk factor in Kienböck's disease, wrist instability, and scaphoid bone fracture. This study focused on the ulnar variance in wrists with scaphoid bone nonunion. METHODS We retrospectively reviewed posteroanterior wrist radiographs of 65 patients who were diagnosed as established scaphoid nonunion and underwent open reduction and bone grafting between 2005 and 2010. We used reference radiographs from contralateral wrists of 65 consecutive skeletally- mature patients with distal radius fracture as the control group and then measured ulnar variance and compared it in both groups.  RESULTS Ulnar variance was measured in standard posteroanterior wrist X-rays of 65 scaphoid nonunion and 65 normal controls. Twenty five patients (38.5%) in the scaphoid nonunion group had negative ulnar variance, and the mean value was -0.26 (± 1.24) mm (range: -3, +2). In the control group, 15 subjects (23.1 %) had an ulnar minus wrist, and the mean ulnar variance was + 0.54 (± 1.47) mm (range: -3, +4) .The difference in ulnar variance was significant between the two groups (P-value = 0.001). CONCLUSION Ulnar variance may influence developing of nonunion process in scaphoid bone fracture.