Three-dimensional computed tomography mapping and analysis of distal femur fractures (AO/OTA types 33A, 33B, and 33C)

BACKGROUND: Distal femur fractures are complex injuries with a high rate of fracture healing problems. Since the widespread of computed tomographic imaging in the diagnosis of distal femur fractures, many fracture characteristics have been discovered. This study aimed to depict the location and frequency of distal femur fracture lines and further analyze the morphological characteristics using the 3-dimensional computed tomography (CT) mapping technique, thus providing more information to solve this challenging clinical problem. METHODS: In total, 217 distal femur fractures in 216 patients were retrospectively reviewed. Fracture fragments on CT were digitally reconstructed and virtually reduced to match a template model. The contour of every fracture fragment was then marked with smooth curves, and the overlap of all fracture lines allowed for the creation of 3-dimensional fracture maps and heat maps. Fracture characteristics were summarized based on these maps. RESULTS: This study included 114 left knee injuries, 101 right knee injuries, and 1 case with bilateral injury. Distal femur fractures were most likely to occur among patients aged 61 to 70 years. On the heat map of all 217 fractures, fracture line hot zones were mainly concentrated around the metaphysis, the lateral part of the intercondylar notch, and the patellofemoral joint. Distal femur fractures with three Arbeitsgemeinschaft für Osteosynthesefragen Foundation/Orthopaedic Trauma Association (AO/OTA) types demonstrated distinct fracture characteristics. In total, there were 58 coronal plane fractures (41.1%) in 141 intercondylar fractures. CONCLUSIONS: The intercondylar fracture patterns in AO/OTA type B and type C fractures were similar, while the supracondylar characteristics in AO/OTA type A and type C were different. The findings in this study can help orthopaedic surgeons better understand the fracture morphology on the basis of AO/OTA classification. Further studies are needed to establish a standard biomechanical fracture model and new fixation strategy for better clinical outcomes.