Abstract External ring fixators are widely used in orthopaedics for the purposes of fracture fixation, bone lengthening and deformity correction. In these fixators, the clinician typically brings the bone fragments to an anatomically desired position by changing the lengths of the rods connecting the fixator rings. This task is accomplished by the clinician based on experience and expertise. As an alternative, commercial systems exist where the same task is automatized with the help of an accompanying software that implements a mathematical model of the fixator. In this work, we have developed a graphical user interface (GUI) implementing a mathematical theory introduced previously. The GUI also allows visualization and simulation of the patient specific bone-fixator system, something that lacks in the available software systems. The information gathered from the bone X-ray images is used to convert a canonical bone model to the patient-specific bone model. This conversion algorithm has been tested on eight different bone models and found to be effective. The visualization tool has been used in the simulation of two orthopaedic procedures, one involving a tibia and the other a femur. In both examples, the visualization tool has provided a realistic depiction of the treatment procedure. We believe that the developed GUI equipped with the visualization module could be a useful clinical tool where the clinician can visualize the applied treatment or evaluate different treatment scenarios a priori per patient.