Analysis of ulnar variance as a risk factor for developing scaphoid nonunion.

OBJECTIVE Ulnar variance may be a risk factor of developing scaphoid non-union. METHODS A review was made of the posteroanterior wrist radiographs of 95 patients who were diagnosed of scaphoid fracture. All fractures with displacement less than 1mm treated conservatively were included. The ulnar variance was measured in all patients. RESULTS Ulnar variance was measured in standard posteroanterior wrist radiographs of 95 patients. Eighteen patients (19%) developed scaphoid nonunion, with a mean value of ulnar variance of -1.34 (-/+ 0.85) mm (CI -2.25 - 0.41). Seventy seven patients (81%) healed correctly, and the mean value of ulnar variance was -0.04 (-/+ 1.85) mm (CI -0.46 - 0.38). A significant difference was observed in the distribution of ulnar variance (p<.05). These results remained significant after adjusting for age, with an OR of 0.69 (CI 0.49 to 0.95). The patients were categorized into two groups: ulnar variance less than -1mm, and ulnar variance greater than -1mm. It appears that patients with ulnar variance less than -1mm had an OR 4.58 (CI 1.51 to 13.89) with p<.007. DISCUSSION Desai et al. concluded that radiological features of acute scaphoid fractures cannot be used to predict the likelihood of fracture union. For this reason, the existence of other risk factors was analysed. According to the results of the present study, it can be concluded that patients with scaphoid fracture and ulnar variance less than -1mm have a greater risk of developing scaphoid nonunion, OR 4.58 (CI 1.51 to 13.89) with p<.007.