Periacetabular Chondrosarcoma: Why the First Resection Is the Only One That Counts

Dr. Orlando Gabriel Wevar Cruz, Instituto Traumatológico Dr. Teodoro Gebauer Weisser, Santiago, Chile

For Sarcoma Month, this case is a reminder of a reality specific to grade 2 chondrosarcoma: the surgical margin carries the full oncological weight on its own. Chemotherapy and radiation offer no safety net for this tumor grade. Too conservative a margin risks local recurrence, and at the pelvis, re-resection with adequate margins is often not possible. The first resection is usually the only opportunity to get it right.

Dr. Orlando Gabriel Wevar Cruz referred a periacetabular grade 2 chondrosarcoma requiring a patient-specific guide for bone tumor resection across the acetabular and pubic regions.

Three cutting planes were planned with a 10 mm oncological safety margin, through an antero-lateral approach requiring femoral dislocation to reach the full tumor volume.

One Tumor, Two Regions, One Guide

The tumor's extension across both the acetabular and pubic bone changed the geometry of the problem. A single cutting guide could not simply span the two regions as one rigid piece: each area needed its own stable seat on the bone, and its own access for instrumentation, while the three resection planes still had to be executed as one coherent plan carrying one continuous 10 mm margin.

The solution was a single patient-specific guide built in two connected parts, one for the acetabular cuts and one for the pubic cut, joined during positioning and separated once fixation was secure.

Patient-Specific Guide Design for Bone Tumor Resection

Planning began with tumor delineation on MRI, matched to the CT scan used to build the resection plan. The validated plan carried three cutting planes and a 10 mm margin, reviewed and confirmed before manufacturing.

Positioning and fixation. The guide sits on the bone in a single fitting position, reachable through the antero-lateral approach after femoral dislocation. It is held by five 2.0 mm K-wires, one of them at the intersection of the cutting planes for stability during the three-plane osteotomy.

Splitting the guide. Once all five K-wires are placed, the two cylinders connecting the acetabular and pubic cutting planes are cut, separating the guide into its two working parts.

Cutting. Each section then guides its own resection plane, saw blade kept parallel to the corresponding K-wire, following the planned cutting lines to the depth inscribed on the guide. One plane, at the acetabulum, is too confined for the saw: a chisel completes that cut instead, following the same guide geometry.

Closing the Case

With the three planes cut, the K-wires are removed with a power drill, the guide sections lifted off, and the resection specimen delivered intact.

In this context, preoperative planning is not a convenience; it is part of the oncological requirement. When the margin is the only defense the tumor grade allows, the plan has to be executed exactly once, and exactly as designed.

We thank Dr. Orlando Gabriel Wevar Cruz for his trust.