Image guided surgical navigation integrating “mirroring” computational planning based on intra-operative cone-beam CT imaging: A promising new approach for management of primary bilateral midfacial fractures

Modeling Methods in Craniofacial Virtual Surgical Planning

Despite the widespread use of virtual surgical planning (VSP), few papers describe the modeling methods used to generate the digital simulations that underpin VSP. This paper aims to review the modeling methods that are currently available for use in VSP and the implications of their use in clinical practice. A literature review was undertaken of the two broad categories of modeling techniques; contour-based planning-namely mirroring from the contralateral side, templating from a normative database, and extrapolation from surrounding landmarks-and occlusal-based planning (OBP). The indications for each modeling method were discussed, including mandibular/maxillary reconstruction, pediatric craniofacial surgery, and orthognathic, as well as the limitations to the accuracy of modeling types. Unilateral defects of the upper/midface, wherein contour accuracy is paramount, are best reconstructed using mirroring methods, whereas bilateral defects-or cases with asymmetry due to craniofacial dysmorphology-are most suited to normative-data-based methods. Cases involving resection of the alveolar margin, in which functional occlusion is the primary outcome are best managed with OBP. Similarly, orthognathic surgery typically uses OBP, although complex cases involving asymmetry, such as clefts, may benefit from a combination of OBP and normative data methods. The choice of modeling methods is, therefore, largely driven by the defect type and the goals of reconstruction.

Reduction of giant parietooccipital fibrous dysplasia using dynamic mirror image guidance: a case report and review of the literature

BACKGROUND

Craniofacial fibrous dysplasia (CFD) typically occurs in the facial bones and anterior cranial vault and can produce both disfigurement and functional limitations for patients disfigurement. Treatment consists of reducing the abnormal bone. Bone contouring can become challenging when the exposure does not extend to the corresponding normal contralateral structures for comparison or when normal landmarks are not available, which may compromise the overall aesthetic outcome. We describe a technique using dynamic mirroring to accurately contour the involved part of the cranium in a case of giant CFD.

OBSERVATIONS

A 49-year-old male presented with a giant deforming fibrous dysplasia of the right mastoid and parieto-temporo-occiput that was causing functional limitations due to the size of the bony mass. This was managed with multidisciplinary bony reduction. Several neurovascular structures were in proximity to the areas of planned drilling of the expansile lesion, and dynamic mirroring of the uninvolved left skull was utilized to maximize safety and symmetry of reduction. High-speed drilling of the right occipital bone was performed until the navigation system alerted the surgeon that symmetric depth had been achieved. There were no complications from the procedure and this technique maximized the limits of symmetric reduction without significantly increasing surgical complexity or duration.

LESSONS

Dynamic mirroring of bony structures in the posterior cranium is not commonly employed in neurosurgical practice. This technique may help improve the aesthetic outcomes of bony reduction in craniofacial dysplasia and a variety of similarly managed bony lesions, contour cranioplasties, and in unilateral craniosynostosis surgery.

Advances in the Resection and Reconstruction of Midfacial Tumors Through Computer Assisted Surgery

Curatively intended oncologic surgery is based on a residual-free tumor excision. Since decades, the surgeon’s goal of R0-resection has led to radical resections in the anatomical region of the midface because of the three-dimensionally complex anatomy where aesthetically and functionally crucial structures are in close relation. In some cases, this implied aggressive overtreatment with loss of the eye globe. In contrast, undertreatment followed by repeated re-resections can also not be an option. Therefore, the evaluation of the true three-dimensional tumor extent and the intraoperative availability of this information seem critical for a precise, yet substance-sparing tumor removal. Computer assisted surgery (CAS) can provide the framework in this context. The present study evaluated the beneficial use of CAS in the treatment of midfacial tumors with special regard to tumor resection and reconstruction. Therefore, 60 patients diagnosed with a malignancy of the upper jaw has been treated, 31 with the use of CAS and 29 conventionally. Comparison of the two groups showed a higher rate of residual-free resections in cases of CAS application. Furthermore, we demonstrate the use of navigated specimen taking called tumor mapping. This procedure enables the transparent, yet precise documentation of three-dimensional tumor borders which paves the way to a more feasible interdisciplinary exchange leading e.g. to a much more focused radiation therapy. Moreover, we evaluated the possibilities of primary midface reconstructions seizing CAS, especially in cases of infiltrated orbital floors. These cases needed reduction of intra-orbital volume due to the tissue loss after resection which could be precisely achieved by CAS. These benefits of CAS in midface reconstruction found expression in positive changes in quality of life. The present work was able to demonstrate that the area of oncological surgery of the midface is a prime example of interface optimization based on the sensible use of computer assistance. The fact that the system makes the patient transparent for the surgeon and the procedure controllable facilitates a more precise and safer treatment oriented to a better outcome.

Surgical approach to isolated bilateral orbital floor fractures

Isolated bilateral orbital floor fractures are uncommon and are rarely described in the scientific literature. They are usually seen in association with naso-ethmoidal fractures, zygomatic fractures, or fractures of the middle third. We report our experience in the management of a patient presenting bilateral isolated orbital floor fracture. The difficulties in management of these fractures are due to the lack of an uninjured contralateral side for intraoperative comparison.

The mirroring technique: a navigation-based method for reconstructing a symmetrical orbit and cranial vault

BACKGROUND

The reconstruction of orbital structures and the cranial vault curvature can be challenging after trauma or wide resections for tumors. Sophisticated methods have been developed recently, but these are resource- and time-consuming.

OBJECTIVE

We report the mirroring technique, which is an effective and costless application for navigation-guided reconstruction procedures.

METHODS

At the time of the reconstruction, high-resolution images are reloaded while forcing a left-right axial flip. The pointer subsequently enables a virtual 3-dimensional projection of the position of the contralateral normal anatomy.

RESULTS

This method was applied successfully in 2 cases of en plaque sphenoid wing meningiomas with secondary exophthalmia.

CONCLUSION

The mirroring technique represents an accurate method of outlining the contralateral normal anatomy onto the pathological side based on navigation guidance.

Advances and innovations in computer-assisted head and neck oncologic surgery

Over the past years, computer-assisted surgery has gained more importance in craniomaxillofacial surgery, especially in primary and secondary treatment of head and neck malignancies. The basis for oncologic treatment of the head and neck region requires detailed planning using computed tomography, cone-beam computed tomography, or magnetic resonance imaging in combination with computer-assisted, infrared-based navigation system. These techniques allow a preplanned image-guided path to the tumor region for taking biopsies, resection, or reconstruction. The aim of this work was to show the advances and technical benefits for tumor surgery in a daily clinical routine from the view of the craniomaxillofacial surgeon. The target of our working group was to develop and clinically evaluate a novel three-dimensional planning and navigation software solution for treatment of craniofacial tumors. This work was carried out on 5 categories for oncologic surgical procedures in which computer-assisted surgery was applied from 2005 to 2011: preplanned trajectorial-guided tumor biopsy, intraoperative image-controlled tumor resection, tumor mapping, reconstruction after tumor surgery (true to original), and oral rehabilitation (backward planning). Successful preoperative planning, import of image data suitable for navigation, and intraoperative precise infrared-based navigation were obtained for all 5 categories without any complications. Image-guided navigation technique for head and neck oncologic surgery provides a precise, safe surgical method with real-time excellent anatomic orientation. Regarding the advantages of computer-assisted surgery, this technique will play a major part in craniofacial reconstructive surgery and will address widespread general methodologic solutions that are of great interest in multidisciplinary oncologic treatment.

[Interventional multidimodal hybrid unit: from pre-operative planning to immediate post-operative control]

INTRODUCTION

Computer assisted surgery has rapidly developed over the last decade, essentially due to the development of navigation and 3D virtual surgical planning and image fusion technologies. The recent introduction of intra-operative cone-beam CT scan (CBCT), which integrates flat panel technology, allows for high resolution bone imaging, the quality and accuracy of which is similar to the one obtained by conventional spiral CT scan. The combination of these two technologies in a "hybrid" operating unit enables the convergence of the pre-, intra- and post-operative steps in a linear computer-assisted processing chain, which optimises surgery accuracy, predictability and patient outcomes while potentially reducing costs, operating times and need for further surgical revision.

TECHNICAL NOTE

The "hybrid" unit includes: 1) the operating room (65 m(2)) equipped with horizontal laminar-flow, a mobile monoplane ceiling suspended C-arm CBCT scan system with a flat panel detector, a wireless navigation system, and an interactive wall-mount touch screen 2) the control room (18 m(2)) separated from the operating room by an X-ray lead protective glass window, including two separate computer workstations for 3D image integration and processing 3) the scrub room (17 m(2)) with two separate stainless steel surgical wash-basins. The intra-operative protocol includes the following steps: 1) elaboration of the patient specific pre-operative computed planning and simulation based on pre-operatively and/or intra-operatively acquired patient images 2) intra-operative navigational guidance setting 3) surgical procedure 4) intra-operative 3D CT imaging 5) suture.

Image quality of two different mobile cone beam computed tomographs for maxillofacial surgery

PURPOSE

We evaluated two mobile cone beam computed tomographs (mCBCT) comparing image quality with respect to radiation dosage. Image quality was analyzed by using different scanning modes.

MATERIALS AND METHODS

The skulls of three human cadavers were scanned by use of conventional Computed Tomography (CT) as well as with two mobile cone beam computed tomographs (Siemens Arcadis Orbic 3D and Ziehm Vision Vario 3D). Six different acquisition modes with different radiation dosages were used. The axial views of all scans were evaluated by five medical doctors regarding image quality by identifying predefined anatomical structures of the skull. A five-point ranking scale was used. The inter-rater reliability was statistically depicted by Cohen's Kappa coefficient. A Wilcoxon signed rank test was used to evaluate the rater's results. For evaluating the signal-to-noise ratio (SNR) a Catphan 600 reference body with two different inlays was used.

RESULTS

Comparing the mCBCTs, the image quality of the Siemens Arcadis Orbic 3D in high-dosage mode received the best score (median: 2.27). The inter-rater reliability was fair (Kappa=-0.030 to 0.328). The Wilcoxon test showed significant (p<0.05) different median rating values in 18 out of 21 imaging modes. The SNR was higher (better) in the high-dosage modes.

CONCLUSION

Intra-operative 3D imaging by using mCBCT for maxillofacial surgery in low-dose mode acquisition is adequate in terms of signal-to-noise ratio and image quality. The image quality does not correlate in a linear manner with a higher radiation dosage. Surgeons using this technique should gather their own experience with the different acquisition modes.