Abstract: Objective： To determine whether 3-dimentional CT scans is able to effectively improve the detection rate of AO B3 distal radius fractures in clinics. Methods: From Jan 2013 to Jan 2014, 30 patients with distal radius fractures were retrospectively enrolled in this study, all the patients directly visited the skeletal trauma emergency department in Beijing Jishuitan Hospital post injury and all of them accepted open reduction and internal fixation of distal radius fractures at last. All the radiographic data including X ray films and 3-dimentional CT scans of these patients were collected. Two independent observers were required to make primary AO classifications for each fracture by X rays at first, then to make final AO classifications by 3-dimentional CT scans. Finally, the detection rates of CT scans and plain films for AO B3 distal radius fractures and B3.3 distal radius fractures were compared, the agreements of the two methods for diagnosing AO B3 and B3.3 fractures were calculated by Cohen’s Kappa calculations. Results: All the 30 fractures were confirmed to be AO B3 distal radius fractures intraoperatively, and 10 of them were B3.3 fractures. The results were completely consistent with the results of 3-dimensional CT scans. However, only 80%(24/30) AO B3 distal radius fractures and 60%(6/10) B3.3 distal radius fractures could be diagnosed only by X rays. The detection rate of CT scans was proved to be significantly higher than X rays for diagnosing B3 distal radius fractures(100% vs. 80%，P<0.05), the detection rate of CT scans was also proved to be significantly higher than that of plain films for detecting B3.3 distal radius fractures(100% vs. 60%，P<0.05). The agreement of 3-dimentional CT scans and X ray was poor for detecting both the AO B3 distal radius fracture and B3.3 distal radius fracture (kappa=0). Most importantly, in the study process, two special kinds of B3 distal radius fracture were initially found and described by us. One was named as radial B3 fracture, and the other was named as ulna B3 fracture. Conclusion: 3-dimentional CT scans can effectively improve the detection rate of B3 and B 3.3 distal radius fractures, and also help find two special kinds of B3 fractures.

Key words: Radius fracture, Diagnosis, Classification, Computed tomography