Acetabular fractures are a challenge in orthopedic surgery. Computer-aided solutions were proposed to segment bone
fragments, simulate the fracture reduction or design the osteosynthesis fixation plates. This paper addresses the
simulation part, which is usually carried out by freely moving bone fragments with six degrees of freedom to reproduce
the pre-fracture state. Instead we propose a different paradigm, closer to actual surgeon's requirements: to simulate the
surgical procedure itself rather than the desired result. A simple, patient-specific, biomechanical multibody model is
proposed, integrating the main ligaments and muscles of the hip joint while accounting for contacts between bone
fragments. Main surgical tools and actions can be simulated, such as clamps, Schanz screws or traction of the femur.
Simulations are computed interactively, which enables clinicians to evaluate different strategies for an optimal surgical
planning. Six retrospective cases were studied, with simple and complex fracture patterns. After interactively building
the models from preoperative CT, gestures from the surgical reports were reproduced. Results of the simulations could
then be compared with postoperative CT data. A qualitative study shows the model behavior is excellent and the
simulated reductions fit the observed data. A more quantitative analysis is currently being completed. Two cases are
particularly significant, for which the surgical reduction actually failed. Simulations show it was indeed not possible to
reduce these fractures with the chosen approach. Had our simulator being used, a better planning may have avoided a
second surgery to these patients.