A 3D CT-based fracture map study of intra-articular distal radial fractures

Objective To map OTA/AO type B and type C distal radial fractures according to three-dimensional (3D) CT scan data, and to describe the morphological distribution of fracture lines. Methods A total of 468 cases of distal radius fractures admitted to the Affiliated Hospital of Chengdu University from January 2016 to March 2019 were analyzed and AO classification were performed. AO type B and type C fractures meet the inclusion criteria and then CT data were 3D reconstructed, and morphological description were performed on the fracture lines of each joint surface, including fracture shape angle, fracture area and fracture ratio. At the same time, the articular surface fracture model was superimposed on the standard model, then fracture line and fracture area distribution map were drawn to create the fracture map of intra-articular distal radial fractures. Result Intra-articular fractures of the distal radius were 209 cases, accounting for 44.7% (209/468) of the distal radius fractures, among which 67 cases of AO type B fracture. In type B fractures, average fracture height were 20.30±11.26 mm, average fracture width were 12.24±6.83 mm, average fracture area were 189.61±101.84 mm2, average angle were 57.23°±14.95°, and average area ratio of fracture (fracture zone area/joint surface area ratio) were 32.42%±10.24%. 142 cases were OA type C fracture, the average fracture height were 24.43±11.37 mm, average fracture width were 20.38±7.59 mm, average fracture area were 425.26±314.31 mm2, average angle were 51.26°±13.17°, and average area ratio of fracture were 73.81%±26.29%. According to fracture map formed by main fracture lines, five different fracture areas were identified: ① 63 cases in central area; ② 25 cases in Lister's nodule area; ③ 59 cases in scaphoid area; ④ 36 cases in lumbar fossa area; ⑤ 26 cases in lower iliac area. Main fracture lines were concentrated in the area on the dorsal side of the central area and the scaphoid area. The fracture lines of type B fracture mainly concentrated in scaphoid region, which accounted for 29.85% (20/67), and dorsal side and central area accounted for 26.87% (18/67). The fracture lines of type C fracture accounted for 27.46% (39/142) in scaphoid area and 31.69% (45/142) in central area. The fracture line of type C fracture increased in the lumbar fossa region (17.61%, 25/142) and the lower ulnar region (12.68%, 18/142) compared with type B fracture (28.69%). Compared with the type B fracture, the overall distribution of the fracture line of the type C fracture is more central. Conclusion The map of intra-articular fracture of distal radius was drawn and morphological distribution of fracture lines were quantified. Fracture-prone site and shape of fracture line were visually recognized. At the same time, description of articular surface fracture line and fracture area of type B and type C fractures of OA classification were improved, which may help with new classification and diagnosis. Key words: Radius fractures; Intra-articular fractures; Imaging, three-dimensional; Maps