Custom osteotomy guides for resection of a pelvic chondrosarcoma

Open Access This article is distributed under the terms of the Creative Commons Attribution Noncommercial License which permits any noncommercial use, distribution, and reproduction in any medium, provided the source is credited. DOI 10.3109/17453674.2014.920988 Patients with malignant neoplasms of the pelvis often have poor outcomes (Marangolo et al. 1992). An important predictor of a poor surgical outcome is failure to achieve satisfactory resection margins (Ozaki et al. 2003, Fuchs et al. 2009). The complex bony anatomy of the pelvis and acetabulum makes surgery notoriously difficult. Rapid prototyping is a manufacturing technology whereby computerized image data are used to create high-precision 3D structures (Rengier et al. 2010). This is a relatively new technology; applications of rapid prototyping in clinical medicine are being discovered every day. Very little has been published on its uses in orthopedic surgery (Frame et al. 2012). We illustrate the use of rapid prototyping to create a 3D model of the pelvis in a patient with chondrosarcoma involving the left superior pubic ramus. From this model, custommade osteotomy guides were created, aiding tumor resection with adequate margins. Surgical technique A spiral CT series of the pelvis (500 slices at 0.5-mm spacing) was imported into Mimics 14.1 (Materialise, Leuven, Belgium) and the bony contours outlined. As the margins of the tumor were not well visualized on CT, an MRI scan was manually aligned with the CT series and the tumor borders checked against the CT outline. A 3D model of the pelvis and tumor was then created and exported as an STL file to Freeform v12 (Geomagic Sensable, Wilmington, MA). Using a sensable haptic manipulator, the planned resection planes were placed on the 3D model and checked against the position of the tumor (Figure 1). A cutting block was then modeled using Freeform to cover a region of the anterior acetabular rim that would be exposed during the resection. The pelvic model was extruded with 5° draft to a plane perpendicular to the resection plane and subtracted from the cutting block model. This extrusion filled in any re-entrant regions