Fig. 7

Case 4: preoperative planning. Due to close proximity of the tumor (red) to the sacroiliac joint (cyan), an osteotomy plane (green) medially to the joint, but laterally to the sacroiliac foramina was chosen. a Preoperative imaging of chondrosarcoma of the right acetabulum (arrow). b Preoperative planning. Antero-posterior view of the tumor localization in the pelvis. c Preoperative planning. Antero-posterior view of the tumor and sacroiliac joint. d Preoperative planning. Axial view of the tumor and sacroiliac joint. e A patient-specific instrument (PSI) is shown after placement onto the ilium