BackgroundQuadrilateral plate fractures are a challenging group of acetabular fractures to manage. However, there is little literature that describes the fracture lines of the quadrilateral plate. The aim of this study was to explore the fracture lines of the quadrilateral plate and relevant clinical significance.MethodsCT data from a series of acetabular fractures were retrospectively analyzed. According to the X-ray, CT, and operative records of the patients, Judet-Letournel classification was carried out for acetabular fractures involving quadrilateral plate. Then, the fracture maps of different types of acetabular fractures in the quadrilateral plate were drawn. To facilitate the characterization of fracture maps, we defined six basic fracture lines.ResultsThe fracture lines of the three types of acetabular fractures (double-column fracture, T-type fracture, and anterior column with posterior hemitransverse fracture) mainly included upper transverse lines and upper oblique lines. Although the fracture lines of posterior wall fracture and anterior column fracture were mainly upper transverse lines, the fracture lines of the former were in a low position. The fracture lines of transverse fracture and transverse with posterior wall fracture were similar, both of which were mainly upper oblique lines. The fracture lines of posterior column fractures mainly included posterior vertical lines.ConclusionsThe fracture lines of different types of acetabular fractures have certain regularity respectively. Observation of the fracture lines of the quadrilateral plate based on fracture mapping can help orthopedic surgeons to enhance the understanding of the Judet-Letournel classification, which may have some significant guidance on the choice of operation approach and the design of internal fixation devices.