CT/MRI-based finite element model construction and biomechanical analysis of acetabular quadrilateral fractures

The study aims to construct a representative acetabular quadrilateral fracture model and compare the biomechanical performance of three internal fixation techniques. CT data from 70 fractures were analyzed to create fracture line mappings. A finite element model incorporating ligaments, cartilage, and fracture lines was developed using CT/MRI data from a healthy volunteer. Five loading conditions (standing, supine, lateral lying, sitting, femoroacetabular impingement) were simulated. Four groups were compared: unfixed (Group A), posterior column screw fixation (Group B), quadrilateral buttress screws fixation (Group C), and combined posterior column and quadrilateral buttress screws fixation (Group D). The most frequent fractures were both-column and anterior wall fractures. Fracture line displacement under standing conditions was Group A > Group B > Group C > Group D. In other conditions, the trend was Group A > Group C > Group B > Group D. Peak stress on posterior column screws occurred in the supine position for Group D, while Group B had greater stress in other conditions. Quadrilateral buttress screws showed peak stress in lateral lying for Group D, but Group C had greater stress in other conditions. The highest stress among cortical screws fixed via plates occurred in the posterior screws. Combined posterior column and quadrilateral buttress screws fixation may provide superior mechanical stability and could be considered as a preferred option for clinical fixation of acetabular quadrilateral fractures, pending further clinical validation. Placement of cortical screws near the fracture line is recommended, with additional screws at the sacroiliac joint if necessary. Early postoperative weight-bearing should be approached with caution, based on biomechanical evidence.