Abstract
Introduction
Three-dimensional preoperative planning and bone tumour resection by navigation have been used in the past ten years. According to literature this workflow increases the surgical “accuracy”. However, there are a few and not completely clear reports describing accuracy in preoperative planning and navigation. The objective of this preliminary study was to determine the accuracy of osteotomies planned and guided by navigation in pelvis tumour resection. We assume that the surgical specimen scanned and 3D reconstructed is an acceptable method to determine the accuracy qualitatively and quantitatively of a virtual planning and navigation surgical workflow.
Materials and Methods
A total of four patients were evaluated between May 2010 and February 2011, age range: 6–38, 17.4 mean; 2 males and 2 females. There were 4 malignant tumours: Malignant Schwannoma (1), Ewing's tumor (1) and Chondrosarcoma (2).
All anatomic regions compromised by the tumour were preoperatively CT scanned (Mutislice 64, Aquilion, Toshiba Medical Systems, Otawara, Japan). Magnetic resonance images (MRI) of the corresponding region were acquired using a 1.5-T unit (Magnetom Avanto, Siemens Medical Solutions, Erlangen, Germany).
Image fusion was applied to CT and MRI studies in order to determine the bone cortex and the intra-extraosseous soft tissues tumour extension. Once the fusion was obtained osteotomies were planned, taking into account the tumour extension in a three-dimensional virtual scenario.
All patients were planned for two uniplanar osteotomies (intercalary resection). The minimal margin was determined in each plane by measuring the closest distance between malignant tumour and osteotomy plane.
These studies allowed the visualisation of the tumour and the application of a virtual osteotomy. The simulation was carried out by using a computer-aided design (CAD) software, Mimics (Materialise, Leuven, Belgium).
Three-dimensional preoperative planning was obtained in CAD format. Next, 3D models were exported to CT data sets in Digital Imaging and Communications in Medicine (DICOM) format and uploaded to the navigation system (3D OrthoMap navigation software v1.0, Stryker Navigator, Freiburg, Germany). Using the standard navigation tools (navigated pointer, camera and infrared tracker devices applied to the patient) the surgeon was able to establish a correspondence in a computer monitor between 3D images and real bone.
Once osteotomies were performed, the tumour surgical specimen obtained was CT scanned and 3D reconstructed similarly to what was done previously to surgery to CT images acquired with the preoperative protocol in patients.
Results
The correlation between the osteotomies preoperatively planned and the osteotomies achieved by navigation was in a global mean of 0.73 millimeters (SD: 3.14) in a total of 6 planes evaluated.
Conclusion
According to clinical relevance, this work shows an acceptable accuracy in preoperative planning and navigation. Furthermore, we demonstrate the usefulness of three-dimensional models of surgical specimens when surgeons need to determine quantitative and qualitative accuracy of 3D planning and navigation procedures.
