PosterPDF Available

Computer-aided Reconstruction of Facial Defects

Authors:

Abstract

Facial reconstruction after bone fractures is an important application of computer-aided surgery. A common method of osteosynthesis are adaptive miniplates, titanium made metal plates placed with at least two ring sections per fracture fragment. For plate fixation on the bone special fixation screws are drilled. The implants are available in different sizes and dimensions and are usually bent intraoperativly to adapt them on the underlying bone. In this contribution, we propose a novel method for computer-aided planning and the creation of individually designed patient implants in facial reconstruction using miniplate osteosynthesis.
Figure 1 Overview of the implant generation. In the orange section, the user loads the patient's data set which is then visualized
by the viewer block. Followed by the implant set up (grey section) where the user sets the initial point (implant center). Next, the
baseline is to calculated which shows the user the current position and direction of the implant, depending on the mouse wheel
value, the selected implant model and the initial set point is also visualized by the viewer. In the apricot section the implant is
calculated Implant Generation Block) by activating the Visualize ON/Off button. For the implant generation also the implants ring
sections, middle and end parts, are required. The final implant is then visualized together with the baseline and the patient's data
set. By using the block Implant Save, the user saves the current implant(s) for this session and starts setting up new ones. By
exporting, the current visualized implants are stored as a STL file on a local path.
Purpose
Facial reconstruction after bone fractures is an important application of computer-aided surgery1. A common method of osteosynthesis are adaptive miniplates2,
titanium made metal plates placed with at least two ring sections per fracture fragment. For plate fixation on the bone special fixation screws are drilled. The implants
are available in different sizes and dimensions and are usually bent intraoperativly to adapt them on the underlying bone. In this contribution, we propose a novel
method for computer-aided planning and the creation of individually designed patient implants in facial reconstruction using miniplate osteosynthesis.
Methods
Results
Conclusion
The software was used on patient CT data provided from the clinical routine by the Clinical Department of Oral and Maxillofacial Surgery of Medical University Graz.
Bone plates were well adapted with respect to the underlying surface and anatomical structures, providing an perfectly fitting osteosynthesis material for an ideal
postoperative result in a reduced operation time. Further, the generated implant models can be stored in STL-file format, which is a common format used in 3D-
printing. Therefore, surgeons have the opportunity to create the individually designed implant with a 3D printer, instead of time consuming intraoperative bending of
osteosynthesis materials. Moreover, the physicians describe the handling as very user-friendly and accurate. By selecting the placement point on the patient’s
surface, the surgeons are able to place the implant at any desired position with the option of further change in position as well as changes in the implant’s pointing
direction and implant type. In summary, the developed software provides a tool for surgeons, to design and in a second step produce individually created patient
implants for osteosythesis of facial defects, within the clinical center but without using any monetary services provided by the industry. Additionally this tool can easily
be tested and further developed by other groups, since the software is based on an open-source platform.
There are several areas for future work, like offering more complex implants to the user and a comparison and evaluation with commercial software products.
M. Gall aJ. Wallner bK. Schwenzer-Zimmerer bD. Schmalstieg aK. Reinbacher b J. Egger a,c
a TU Graz, Institute for Computer Graphics and Vision, Inffeldgasse 16, 8010 Graz, Austria
b MedUni Graz, Medical University of Graz, Auenbruggerplatz 2, 8036 Graz, Austria
c BioTechMed, Krenngasse 37/1, 8010 Graz, Austria
References
1L. E. Ritacco, F. E. Milano, and E. Chao, “Computer-Assisted Musculoskeletal Surgery,” Springer Press, pp. 1-326, Nov. 2015.
2D. A. Hidalgo, “Titanium Miniplate Fixation in Free Flap Mandible Reconstruction,” Annals of Plastic Surgery, 23(6):496-507 Dec. 1989.
3J. Egger, et al., “Integration of the OpenIGTLink Network Protocol for Image-Guided Therapy with the Medical Platform MeVisLab,”
International Journal of Medical Robotics, 8(3):282-90, Feb. 2012.
CT-datasets from the clinical routine were used in a prospective study for the creation of individual designed
osteosynthesis materials. An interactive planning software has been implemented in C++ with the medical prototyping
platform MeVisLab3. Computation runs in real-time on a standard desktop computer (Intel Core i7930 CPU, 4×2.80
GHz, 6 GB RAM, Windows 8.1), allowing for interactive feedback. On the workstation the user chooses an implant
type and selects any location on the surface of the facial model to place the implant’s center point. Using the center as
a seed point, the baseline curvature is calculated by casting rays along the baseline and checking for surface
intersection positions. Using the resulting curved baseline, the implant shape is generated by placing precomputed
polygonal meshes at the locations along the curved baseline corresponding to the implant’s dimensions. Each ring
element of the implant is oriented to be aligned with the surface tangent plane so that the plate fits perfectly to the
underlying bone structure. Finally, the straight sections bridging the rings are generated by deforming a template mesh
with rectangular footprint. Runtime is optimized by limiting computations to the region of interest around the seed
point. Finally plate positions and adaption was independently assessed by two specialists for maxillofacial surgery by
completing given tasks by the system. Figure 1 gives an overview of the workflow.
Computer-aided bone plate adaption was able for every type of minplate that was used with the software. Virtual plate adaption. provided correct positioning and
satisfying results at any position on the facial bones. Medical specialists did neither require any further training time to use the software’s functions, nor they fail in
completing any given task by the system. Figure 2 shows the result of adaptive miniplate placements at a variety of positions and Figure 3 shows the user interface
including a loaded data object, baseline and individually generated implant.
Figure 2 Result of
computer aided adaptive
miniplate placements in
various directions and
locations.
August 16-20, 2016
Orlando, FL, USA
Acknowledgement
BioTechMed-Graz (“Hardware accelerated intelligent medical imaging”) and MedArtis for providing technical details about the Modus 2.0 series.
Video Tutorial
https://www.youtube.com/watch?v=Od5xxuERJ8E
Computer-aided Reconstruction of Facial Defects
Figure 3 User interface
including object, baseline
and generated implant.
Conference Paper
Virtual Reality (VR) is an immersive technology that replicates an environment via computer-simulated reality. VR gets a lot of attention in computer games but has also great potential in other areas, like the medical domain. Examples are planning, simulations and training of medical interventions, like for facial surgeries where an aesthetic outcome is important. However, importing medical data into VR devices is not trivial, especially when a direct connection and visualization from your own application is needed. Furthermore, most researcher don’t build their medical applications from scratch, rather they use platforms, like MeVisLab, Slicer or MITK. The platforms have in common that they integrate and build upon on libraries like ITK and VTK, further providing a more convenient graphical interface to them for the user. In this contribution, we demonstrate the usage of a VR device for medical data under MeVisLab. Therefore, we integrated the OpenVR library into MeVisLab as an own module. This enables the direct and uncomplicated usage of head mounted displays, like the HTC Vive under MeVisLab. Summarized, medical data from other MeVisLab modules can directly be connected per drag-and-drop to our VR module and will be rendered inside the HTC Vive for an immersive inspection. © (2017) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Book
This book presents the latest advances in computer-aided methods for musculoskeletal surgery. Topics including preoperative planning, navigational tools, patient-specific resections, and robotic devices used in computer-assisted surgery are discussed. The various simulation and training materials currently available are described. Computer-Assisted Musculoskeletal Surgery: Thinking and Executing in 3D is aimed at surgeons, oncologists, and research and development scientists, especially those working with computer-assisted technologies.
Article
OpenIGTLink is a new, open, simple and extensible network communication protocol for image-guided therapy (IGT). The protocol provides a standardized mechanism to connect hardware and software by the transfer of coordinate transforms, images, and status messages. MeVisLab is a framework for the development of image processing algorithms and visualization and interaction methods, with a focus on medical imaging. The paper describes the integration of the OpenIGTLink network protocol for IGT with the medical prototyping platform MeVisLab. The integration of OpenIGTLink into MeVisLab has been realized by developing a software module using the C++ programming language. The integration was evaluated with tracker clients that are available online. Furthermore, the integration was used to connect MeVisLab to Slicer and a NDI tracking system over the network. The latency time during navigation with a real instrument was measured to show that the integration can be used clinically. Researchers using MeVisLab can interface their software to hardware devices that already support the OpenIGTLink protocol, such as the NDI Aurora magnetic tracking system. In addition, the OpenIGTLink module can also be used to communicate directly with Slicer, a free, open source software package for visualization and image analysis.
Article
The use of miniplate fixation in free flap mandible reconstruction was reviewed in a series of 27 patients. Flap donor sites included the radius, scapula, and fibula. The bone defect ranged from 5 to 16 cm (mean, 11.5 cm). The number of fixation sites per graft ranged from 2 to 6 (mean, 3.96). Three to 10 (mean, 5.51) titanium miniplates (Wurzburg) were used for fixation. All free flaps survived. In no patient did the plate pressure on the periosteum or the multiple screws through the bone compromise flap circulation to a critical degree. Nonunion occurred in 2 of 107 osteotomy sites. Wound healing problems that required plate removal occurred in 4 patients. In each patient the plates were retained until bone healing was complete. Intermaxillary fixation was not necessary for purposes of additional stability. Miniplates have the advantages of ease of application, decreased fixation time, and the lack of need for additional forms of fixation. Their small size and malleable nature allow precise graft contouring. This contributes to a superior aesthetic result.
Titanium Miniplate Fixation in Free Flap Mandible Reconstruction Integration of the OpenIGTLink Network Protocol for Image-Guided Therapy with the Medical Platform MeVisLab
  • A Hidalgo
  • J Egger
A. Hidalgo, " Titanium Miniplate Fixation in Free Flap Mandible Reconstruction, " Annals of Plastic Surgery, 23(6):496-507 Dec. 1989. 3 J. Egger, et al., " Integration of the OpenIGTLink Network Protocol for Image-Guided Therapy with the Medical Platform MeVisLab, " International Journal of Medical Robotics, 8(3):282-90, Feb. 2012.