Transfer accuracy and precision scoring in planar bone cutting validated with ex vivo data

Virtual Planning and Allograft Preparation Guided by Navigation for Reconstructive Oncologic Surgery: A Technical Report

Introduction

Advanced virtual simulators can be used to accurately detect the best allograft according to size and shape.

Indications & Contraindications

Step 1 Acquisition of Medical Images

Obtain a multislice CT scan and a magnetic resonance imaging (MRI) scan preoperatively for each patient; however, if the time between the scans and the surgery is >1 month, consider repeating the MRI because the size of the tumor may have changed during that time.

Step 2 Select an Allograft Using Virtual Imaging to Optimize Size Matching

Load DICOM images into a virtual simulation station (Windows 7 Service Pack 1, 64 bit, Intel Core i5/i7 or equivalent) and use mediCAS planning software (medicas3d.com) or equivalent (Materialise Mimics or Amira software [FEI]) for image segmentation and virtual simulation with STL (stereolithography) files.

Step 3 Plan and Outline the Tumor Margins on the Preoperative Imaging

Determine and outline the tumor margin on manually fused CT and MRI studies using the registration tool of the mediCAS planning software or equivalent (Materialise Mimics software.).

Step 4 Plan and Outline the Same Osteotomies on the Allograft

Determine and outline the osteotomies between host and donor using the registration tool of the mediCAS planning software or equivalent (Materialise Mimics software.).

Step 5 Assess the Patient and Allograft in a Virtual Scenario

Be sure to consider the disintegration of bone tissue that occurs during the osteotomy and corresponds to the thickness of the blade (approximately 1.5 mm).

Step 6 Navigation Settings

A tool of the mediCAS planning software allows the virtual preoperative planning (STL files) to be transferred to the surgical navigation format, DICOM files.

Step 7 Patient and Allograft Intraoperative Navigation

The tumor and allograft are resected using the navigated guidelines, which were previously planned with the virtual platform.

Results

The 3D virtual preoperative planning and surgical navigation software are tools designed to increase the accuracy of bone tumor resection and allograft reconstruction³.

Pitfalls & Challenges

Techniques in surgical navigation of extremity tumors: state of the art

Image-guided surgical navigation allows the orthopedic oncologist to perform adequate tumor resection based on fused images (CT, MRI, PET). Although surgical navigation was first performed in spine and pelvis, recent reports have described the use of this technique in bone tumors located in the extremities. In long bones, this technique has moved from localization or percutaneous resection of benign tumors to complex bone tumor resections and guided reconstructions (allograft or endoprostheses). In recent years, the reported series have increased from small numbers (5 to 16 patients) to larger ones (up to 130 patients). The purpose of this paper is to review recent reports regarding surgical navigation in the extremities, describing the results obtained with different kind of reconstructions when navigation is used and how the previously described problems were solved.