Fraunhofer-Institut für Produktionsanlagen und Konstruktionstechnik IPK

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Konzept und Prinzip eines Unterstützungssystems für die einzeitige, alloplastische Tumortherapie in der kraniofazialen Chirurgie

2008 , Rose, A. , Klein, M. , Krüger, T. , Tiesenhausen, C. von , Jank, E. , Krüger, J. , Keeve, E.

Dieser Artikel beschreibt Konzepte und Prinzipien eines Unterstützungssystems für die einzeitige alloplastische Therapie von Tumoren im Schädelknochen. Ziel ist es den behandelnden Arzt sowohl bei der Implantatplanung und -rekonstruktion als auch bei der anschließenden exakten umsetzung der Planung zu unterstützen. Es wird ein Arbeitsablauf für die Planung und Rekonstruktion entwickelt und vorgestellt, der die anatomische Symmetrie ausnutzt und somit weitgehende Automatisierung erlaubt. Bei der Behandlung soll durch wesentliche Zusatzinformationen über die Lage des Instruments bezüglich des Patienten und der Resektiopnslinien eine Unterstützung erreicht werden, die auwendige Nacharbeiten der Passgenauigkeit vermeidet. Anhand von drei Fällen wurde die Funktionsfähigkeit des Planungs- und Rekonstruktionsprinzips nachgewiesen. Zukünftige Arbeiten umfassen die Fertigstellung des Behandlungsteils und die Erbringung des Nachweises der Gesamtgenauigkeit für eine Zulassung nach MPG.

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Intraoperative bone modelling for autologous bone grafting

2007 , Tiesenhausen, C.V. , Klein, M.

For the reconstruction of a mandibular defect after tumour or trauma, a vascularized bone graft is taken from the iliac crest. In order to facilitate the healing process and to achieve a functional and aesthetic outcome, the geometry of the transplant has to be similar to the defect. We present a system that uses intraoperative tactile scanning to acquire the geometry of defect and donor site. If the tumour had been resected in a previous operation, its geometry has to be reconstructed by interpolating the remaining pieces of the mandible. The presented system uses the definition of two cut surfaces and the connecting path in order to construct a smooth interpolation. The accuracy of this interpolation was measured using a plastic replica of a human mandible where a piece had been cut out and bridged with a bone plate. The resected piece was scanned for reference using a laser surface scanner. The mean distance between the reconstructed cut surface and the reference was -2.17 mm. This distance includes the gap that is introduced by the saw (blade thickness 0.7 mm). The system was integrated into a navigation system and certified according to the European medical device directive. A patient with a large defect in the left mandible could be treated successfully using this device. The defect was reconstructed without the need for an additional adjustment of the bone graft.

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Intraoperative and experimental evaluation of an optical tactile surface scanning system for autologous bone grafting

2006 , Tiesenhausen, C.V. , Klein, M. , Lueth, T.C. , Bier, J.

We present a system that enables a surgeon to acquire precise information about the shape of a bone part intraoperatively and without the use of 3D imaging Using a navigation system, we track the position of the bone part and the position of a spatula with a known geometry. After initially creating a binary voxel-volume around the bone piece, we remove all voxel where the spatula was moved through. When the spatula is moved along the surface of the bone, we can iteratively create a model of the bone surface from the remaining voxels. This is done interactively with visual feedback to the user. We used three plastic bone replicas in order to access the system's accuracy. We compared the carved model with a high precision laser scanner model. The mean distance of 4.2 Mio measured surface points was 0.57 mm, standard deviation 0.39 mm, the maximum distance was 3.03 mm, 95% of all measured points were closer than 1.34 mm to the reference surface. We tested the applicability of the system during an intervention showing that the system can be used in clinical routine. In future work, the intraoperatively acquired models will be used to determine an optimal position for the bone graft donor site.

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