Pelvic Tumor Resection: Why Two Patient-Specific Guides

The tumor combined a bony component with an overlying soft tissue mass. To resect as closely as possible to the bony component, the cutting guide had to sit right against the bone, underneath the soft mass. Whether that mass could be displaced enough at the time of surgery to fit a single large guide beneath it could not be predicted with certainty.

The answer was two distinct guides.

The Design Logic

One guide inserts from a lateral approach, coming in anteriorly to the tumor. The other comes in from a posterior approach. They connect by a chevron-shaped geometry, with flanges grabbing onto the sciatic notch. Once in position, the two guides reconstitute the 4 cutting planes of the validated plan, with a 10 mm oncological safety margin across all of them.

The angulation of the anterior cutting plane was revised to move the saw blade trajectory further from the soft tissue mass and preserve surrounding healthy tissue.

Fixation and Stability

The chevron geometry provides congruency between the two parts. The flanges on the sciatic notch add extra stability to the assembly once both guides are in position.

Fixation uses 6 Kirschner wires of 2.0 mm: 2 on the lateral guide and 4 on the posterior guide. One of these is positioned close to the intersection of the two guides for added stability between the parts. The entire approach was planned from preoperative CT and MRI imaging.

What Makes Patient-Specific Instruments Valuable

In the OR, the surgeon finds exactly what was validated on screen: the same geometry, the same planes, the same landmarks. 3D planning becomes a reproducible surgical step, with no mental recalculation, no approximation, and no time lost on uncertain anatomical references.

This is the kind of case, where anatomy is unforgiving and margins are non-negotiable, that makes patient-specific instruments truly valuable.

Case performed at the H. Lee Moffitt Cancer Center, Tampa, Florida, May 5th, 2026.

We thank Dr. Lazarides for his trust.