Grid-enabled Medical Simulation Services (GEMSS) in 
Oral & Maxillofacial Surgery 
 
Guntram Berti, Jochen Fingberg, Jens Georg Schmidt 
NEC Europe Ltd., C&C Research Laboratories, Sankt Augustin. 
 
 
Extended Abstract: 
 
The GEMSS project has developed a Grid-service for maxillo-facial surgery planning. 
Recently a prototype of the GEMSS Grid client software has been installed at the 
Department of Oral-, Maxillo- and Facial Plastic Surgery of the University Clinic of 
Leipzig connecting to NECīs C&C Research laboratory as service provider. 
 
Severe malformations of the midface such as maxillary retrognathia or hypoplasia can be 
treated efficiently by distraction osteogenesis. During an operation the appropriate bony 
part of the midface is separated from the rest of the skull (osteotomy) and slowly moved 
into the ideal position by way of a distraction device. Thus, even large displacements 
over 20 mm can be treated successfully. 
 
A critical point in this procedure is osteotomy design and the resulting outcome with 
respect to aesthetics. In the current clinical practice, planning is based on CT scans and 
the surgeon's experience. Our tool chain allows the surgeon to specify arbitrary cuts of 
facial bones and to simulate the displacements of bones and soft tissue. It therefore 
provides the possibility to predict and compare the outcome of different surgical 
treatments in silico. 
 
An important component of the planning chain is a tool for virtual bone cutting. For this 
purpose, a CT image of the patient's head is segmented, and a surface mesh of the bone is 
generated. Onto this surface mesh, the surgeon can interactively draw closed curves 
corresponding to bone cuts. Moreover, the distraction of individual bone components can 
be specified. The geometric information describing the cuts is handed to an image 
manipulation tool which transforms them into a 3D cut volume with user-controllable 
thickness and modifies the image data accordingly. This image and the distraction 
specification is further processed by a volume mesh generator, producing a model 
suitable for a finite element (FEM) simulation of the distraction process. 
 
A number of visual aids for the user are implemented or currently under development: 
Colouring strategies allow to visualize connectivity of components, and to detect bridges 
resulting from insufficient cuts. Mapping of a head template allows the reuse of 
predefined boundary conditions. Clipping and adapting opacity of surfaces allows dealing 
with complex geometries. Finally, interpolating the simulation results back onto the 
original image data allows for the use of state-of-the-art volume rendering for 
visualization of the predicted outcome. 
 


The bone cutting tool is built on top of OpenDX, for which a number of additional 
modules have been developed. OpenDX is a general and powerful data visualization 
engine, featuring a graphic programming language which allows easy integration of 
additional functionality; it is also used to visualize the simulation results. These 
developments are carried out in the context of the GEMSS project (Grid Enabled Medical 
Simulation Services, http://www.gemss.de). Compute-intensive tasks like the FEM 
simulation are made available as Grid services and can be run remotely on HPC 
platforms in a transparent way. Thus, advanced simulation is brought to the desktop of 
the medical practitioner.