Trainees in orthopedic surgery are required to receive dedicated laboratory-based surgical skills training in their first year of residency. Simulators are often used in this training. Our group previously developed a hip fracture wire navigation simulator to train and assess skill in placing a K-wire within a femur bone surrogate using synthetic fluoroscopic images to aid in navigation. In this paper, we describe design considerations and challenges in modifying the existing simulator to enable the training of multi-wire pinning of a pediatric supracondylar humerus fracture. The design involves changing the bone of interest from the adult femur to the pediatric humerus, while using the same platform technology. Considerations include ease of use, minimizing motion of the fixed bone, and minimizing materials used. The robustness of the bone mounting was tested by running an experiment using 3D scans and surface deviation analysis to test repeatability of bone placement and its resistance to rotational motion after being placed in the fixture. After the new design was shown to hold the bone rigidly, a pilot study of the new simulator was conducted to confirm that the surgeons and residents consider the simulator experience as being a valid representation of the actual surgical skill.