Computer-assisted surgery (CAS) aims to improve surgical precision. This approach integrates computed tomography (CT) and magnetic resonance imaging (MRI) to plan and intraoperatively execute an operation, using navigation techniques and software5. CAS represents an improvement over traditional techniques such as correlating anatomic landmarks with measurements on preoperative imaging6 or relying on fluoroscopy7. CAS showed promising results in pelvic8,9 and extremity10-12 surgery, facilitating planning, accuracy of tumor resection, and joint preservation5. Furthermore, operating rooms with intraoperative 3-dimensional (3D) imaging capability present a new opportunity for CAS development and are becoming more readily available. On-the-table 3D imaging using cone-beam CT (CBCT) can be used for navigation system registration, resection assessment, and confirmation of post-resection reconstruction, thus improving surgical proficiency13-15.
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Fig. 2-A An osteotome tracked by navigation was employed to resect the tumor guided by the in-house navigation software. Figs. 2-B and 2-C Visualization of the entire trajectory of the cutting instrument with respect to the tumor is shown in a 2D view (Fig. 2-B) and a 3D view (Fig. 2-C). Fig. 2-D The 3D view also has the ability to show a virtual resection using dynamic clipping planes.
Imaging and navigation workflow. Fig. 3-A Two UTTs with 3 and 4 spheres each secured to the skin overlying the bone lesion with sterile adhesive. The rigid tracker mounted to the bone adjacent to the tumor using cortical pins is also displayed. Fig. 3-B An intraoperative CBCT scan is obtained after rotation of the C-arm. Fig. 3-C The corresponding tracker landmarks were captured using an NDI Polaris infrared camera. Fig. 3-D The centers of the tracking spheres in CBCT imaging were localized automatically. Fig. 3-E The navigation system accuracy over the bone surface was depicted in a color-coded surface rendering. Fig. 3-F Surgical resection assisted by intraoperative navigation of cutting tools (e.g., osteotomes, saws) was performed using the in-house navigation software (GTx-Eyes, University Health Network).
Because CAS demonstrated enhanced precision in spine surgery and hip and knee arthroplasty31,32, orthopaedic oncologists endeavored to exploit the benefits of this technology. The potential for reduced surgical exposure and improved safety related to the proximity of vital, functional structures during pelvic bone tumor surgery make CAS especially appealing. Navigation has shown promising results, reducing intralesional resection rates for pelvic and sacral tumors9 and improving margins33. Improved disease-free survival and reduction in blood loss and operative times were also reported34. Joint-preserving resections for extremity bone sarcomas require high accuracy that can be facilitated with CAS10. Different 3D virtual resection scenarios can be analyzed preoperatively35,36, followed by implementation of the best plan for complete tumor removal and reconstruction. CAS has improved tumor resection precision, allowing negative margins and preservation of articular surfaces. This provides enormous benefits for limb-sparing surgery, especially in skeletally immature patients11. Different limb reconstruction alternatives using allografts and modular and custom-made prostheses are facilitated, and limb-length discrepancies and rotational concerns can be prevented12,24,37.
Our main limitation was the lack of formal virtual margin assessment, which represents the ultimate confirmation of bone tumor surgery. Moreover, because patients with simple benign bone tumors were enrolled in this proof-of-principle study, the bone cuts were limited in size and extent compared with what would be required for malignant tumors. Nevertheless, all of the tumors were completely resected, and multiple navigated osteotomies were performed for 6 osteochondromas and a navigated burr was used to remove the osteoid osteoma. We acknowledge that surgical resection for osteoid osteoma is rarely necessary due to the high success rate of RFA; however, this patient had undergone 2 unsuccessful CT-guided RFA attempts. It would have been interesting to confirm the previous findings of our group with regard to the accuracy of our navigation software, especially having intraoperative CBCT scans available, as we could have compared preoperative and postoperative resection plans to quantify the discrepancy due to not only registration error but also instrument calibration and user implementation24,25. 2ff7e9595c
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