A. Zimolong

CRIGOS: a compact robot for image-guided orthopedic surgery

The CRIGOS (compact robot for image-guided orthopedic surgery) project was set up for the development of a compact surgical robot system for image-guided orthopedic surgery based on user requirements. The modular system comprises a compact parallel robot and a software system for planning of surgical interventions and for supervision of the robotic device. Because it is not sufficient to consider only technical aspects in order to improve clinical routines the therapeutic outcome of conventional interventions, a user-centered and task-oriented design process has been developed which also takes human factors into account. The design process for the CRIGOS system was started from requirement analysis of various orthopedic interventions using information gathered from literature, questionnaires, and workshops with domain experts. This resulted in identification of conventional interventions for which the robotic system would improve the medical and procedural quality. A system design concept has been elaborated which includes definitions of components, functionalities, and interfaces, Approaches to the acquisition of calibrated X-rays will be presented in the paper together with design and evaluation of a first human-computer interface. Finally, the first lab-type parallel robot based on low-cost standard components is presented together with the first evaluation results concerning positioning accuracy.

Image guided Orthopedic Surgery using individual templates

Individual templates for Orthopedic Surgery provide a precise intraoperative reproduction of the geometries of work on bone planned preoperatively on the base of CT-image data. The general feasibility concerning the adaptation to different surgical applications has already been demonstrated in various in-vitro studies as well as within clinical application1,2,3,4,5. Within the framework of the European IGOS-project a demonstrator for image guided pelvis surgery as an exemplary clinical application will be developed. In contrast to initial feasibility studies with our first labtyp systems, the introduction into clinical routine induces additional constraints. To provide an adequate level of reliability and usability additional efforts are necessary especially concerning quality assurance, ergonomic design and standardisation of the related chain of image acquisition and surgical planning, manufacturing of individual templates and finally the intraoperative execution. Aspects of the integration into clinical routine as well as laboratory investigations concerning accuracy and integrated manufacturing are discussed.Individual templates for Orthopedic Surgery provide a precise intraoperative reproduction of the geometries of work on bone planned preoperatively on the base of CT-image data. The general feasibility concerning the adaptation to different surgical applications has already been demonstrated in various in-vitro studies as well as within clinical application1,2,3,4,5. Within the framework of the European IGOS-project a demonstrator for image guided pelvis surgery as an exemplary clinical application will be developed. In contrast to initial feasibility studies with our first labtyp systems, the introduction into clinical routine induces additional constraints. To provide an adequate level of reliability and usability additional efforts are necessary especially concerning quality assurance, ergonomic design and standardisation of the related chain of image acquisition and surgical planning, manufacturing of individual templates and finally the intraoperative execution. Aspects of the integration into clinical routine as well as laboratory investigations concerning accuracy and integrated manufacturing are discussed.

Entwicklung eines klinischen Demonstrators für die computerunterstützte Orthopädische Chirurgie mit CT-Bildbasierten Individualschablonen

Bei der Planung von Eingriffen in der orthopadischen Chirurgie kann der Orthopade auf eine Vielzahl von bildgebenden Verfahren zuruckgreifen, wie z.B. CT, MR, Ultraschall und Rontgenaufnahmen. Die jungsten Entwicklungen im Bereich der computerunterstutzten Chirurgie bieten verschiedene Losungsansatze, um die hohe geometrische Genauigkeit der praoperativen Bildgebung und Planung fur eine ebenso prazise intraoperative Ausfuhrung zu nutzen. Am Helmholtz-Institut wurde dafur das Prinzip der Individualschablonen entwickelt. Hierbei werden individuell angepaste Schablonen auf Basis von CT-Daten praoperativ gefertigt, die intraoperativ eine prazise Werkzeugfuhrung fur die geplanten Knochenbearbeitung darstellen. Die Realisierbarkeit des Konzeptes fur verschiedene chirurgische Anwendungen wurde bereits in Laboruntersuchungen sowie in klinischen Applikationen demonstriert. Im folgenden werden Aspekte der Entwicklung eines integrierten klinischen Demonstrators zur chirurgischen Planung und Fertigung von Individualschablonen fur periacetabulare Umstellungsosteotomien dargestellt.

A software framework for the development of Web-based medical education using learning object classes

A software framework for the development of Web-based medical education is proposed. The objective is to optimize the development process by introducing Learning Objects (LO) and Learning Object Classes (LO Classes) so that the content preparation can be separated from the educational issues, ergonomic design, and technical realization. Based on the concept of case-based, problem-oriented education, different learning scenarios were analysed and then modelled as different LOs. These LOs can be further abstracted in several reusable LO Classes that represent certain patterns of content structure, pedagogical concept, and user interface. With the help of LO input templates, the educational material can be prepared by the authors in the authoring process easily and appropriately. An LO content management system was developed to store and maintain different LOs and to generate the Web-presentation of LOs adaptively and dynamically in the tutoring process. This software framework has been applied to the exemplary development of an interactive course in orthopaedics. The LOs and LO Classes also help to maintain consistency of the course representation to users. As a result, more efficiency in the development phase and good usability and quality of the end products can be achieved.

Evaluation of deformable models for femoral neck surgery

Objective: Using fluoroscopic images alone, it is difficult to guarantee that screws are positioned within the femoral head and neck. This study evaluates whether the introduction of deformable 3D models limiting the planning and navigation space is a helpful approach to minimizing the incidence of misplaced screws, thereby enhancing patient safety. Background: Even though a screw may appear to lie within the femoral head and neck on fluoroscopic images, this may not, in fact, be the case. This is a particular problem for interventions such as fixation of a slipped femoral head or osteosynthesis of the femoral neck, where screws must be set close to the cortical bone without penetrating the joint or injuring the cortex of the femoral neck. Methods: A system was developed which permits computer-based planning and navigation of screws for femoral neck fracture fixation based on fluoroscopic images. Different approaches were employed which either a) make use of a deformable model adapted to the femoral head/neck, constraining the screw positions within this model; or b) allow the user to position the screws with or without geometrical constraints on the X-rays while maintaining parallelism of the screws. All designs were evaluated and compared by 7 test users using integral projection X-rays calculated from the CT dataset. Results were checked using a 3D model of the bone, also calculated from the CT dataset. Results: Positioning screws using the deformable model resulted in a significantly smaller distribution of screw tip locations and no penetrations into the hip joint, in contrast to the other approaches where up to 11% of screws were misplaced. Conclusions: Constraining the planning and navigation space by means of a deformable model allows better control of screw positioning and thus increases the chances of a successful intervention. In particular, CAS systems allowing for virtual fluoroscopy should consider supporting this planning approach.

CRIGOS – Entwicklung eines Kompaktrobotersystems für die bildgeführte orthopädische Chirurgie

ZusammenfassungIm folgenden Beitrag wird das Konzept und die Entwicklung eines Medizinroboters für die orthopädische Chirurgie behandelt, das den Chirurgen bei der Ausführung komplizierter Eingriffe intraoperativ unterstützten soll. Ein Schwerpunkt der Arbeit ist es, das System so einfach und kostengünstig zu realisieren, wie es die Anwendung erlaubt. Daher greifen wir bei der Bildgebung auf das gängige Verfahren der Röntgenbildgebung zurück.Zur robotischen Ausführung verwenden wir ein einfach, parallel aufgebautes Positioniergerät. Abschließend wird der mögliche operative Ablauf bei Verwendung des bildgeführten Kompaktrobotersystems (CRIGOS) anhand verschiedener orthopädischer Eingriffe exemplarisch aufgezeigt und unterschiedliche Ausführungsstrategien vorgestellt.AbstractIn this paper, we present a medical robot system dedicated to support the surgeon during challenging tasks within orthopedic interventions. The main goal of this work is to develop a system as technically simple as the surgical requirements allow to keep its cost and complexity to a minimum.Therefore, we primarily focus on calibrated X-ray imaging for image acquisition, an easy registration procedure and robotic execution using a positioning device with simple parallel kinematics. Examples of different orthopedic interventions using the compact robot system for image-guided orthopedic surgery (CRIGOS) are presented, as well as various modes of execution of the device.

EMPIRISCHE STUDIEN ZUR ZUVERLÄSSIGKEIT VON CHIRURGISCHEN NAVIGATIONSSYSTEMEN

A number of studies demonstrate the clinical relevance of Systems for Computer assisted surgery (CAS Systems). As however studies on human error in medicine indicate, reliability ofthe results strongly depends on äspects ofusability and error tolerance ofthe System. This paper presents studies which aim to assess these aspects of reliability of CAS Systems. In a clinical study, interaction with a CAS System by 16 expert and novice surgeons was observed and assessed. From 133 recorded incidents 41% were rated to have significant impact on the clinical result or to inhibit successßil completion ofthe task, which indicates a low degree of error tolerance ofthe System. These findings are supported by the results obtainedfrom questionnaire, were learnability and error tolerance were judged to be not sufficient. Keywords— Learnability, error tolerance, usability, human error, suitabilityfor the task, risk analysis, FMEA

Assessment of video tracking usability for training simulators

Objective: A simulator was developed to mimic commercial CAS systems in implementing most tasks required to carry out a surgical operation. As tracking systems are generally expensive components, an alternative solution based on low-cost video-based tracking was used. Video tracking accuracy was assessed to determine whether or not this kind of approach was suitable for use in the training domain. Ultimately, video-based tracking should enable sufficiently accurate registration between a bony model and its virtual 3D representation. Materials and Methods: Video tracking was assessed using two types of camera. For each one, common accuracy tests were realized as a series of 10 trials at ranges of 0.5–1.0 m from the camera lens. The pointer used as a digitizer was equipped with tracked video markers. Three sizes of marker were evaluated to estimate the impact of marker size on accuracy. Results: For the better of the two cameras tested, results were encouraging. Results are presented as rounded whole-number values in millimeters. The noise test gave accuracies of 2 mm for the 80-mm marker, 3 mm for the 60-mm marker and 5 mm for the 40-mm marker. Relative accuracies, as evaluated on a grid of equally spaced dots, were 4 mm with the 80-mm marker, 7 mm with the 60-mm marker and 12 mm with the 40-mm marker. A pivoting test around the pointer tip gave 3 mm of accuracy for the 80-mm marker, 5 mm for the 60-mm marker and 11 mm for the 40-mm marker. An additional pivoting test was completed on increasing the distance of the marker from the pointer tip, giving accuracies of 5 mm for the 80-mm marker, 6 mm for the 60-mm marker and 13 mm for the 40-mm marker. The registration test gave accuracies of 8 mm for the 80-mm marker, 9 mm for the 60-mm marker and 11 mm for the 40-mm marker. Conclusions: The video-based approach offers sufficient accuracy to achieve registration in the domain of CAS training.

Integrating medical devices in the operating room using service-oriented architectures

Abstract With the increasing documentation requirements and communication capabilities of medical devices in the operating room, the integration and modular networking of these devices have become more and more important. Commercial integrated operating room systems are mainly proprietary developments using usually proprietary communication standards and interfaces, which reduce the possibility of integrating devices from different vendors. To overcome these limitations, there is a need for an open standardized architecture that is based on standard protocols and interfaces enabling the integration of devices from different vendors based on heterogeneous software and hardware components. Starting with an analysis of the requirements for device integration in the operating room and the techniques used for integrating devices in other industrial domains, a new concept for an integration architecture for the operating room based on the paradigm of a service-oriented architecture is developed. Standardized communication protocols and interface descriptions are used. As risk management is an important factor in the field of medical engineering, a risk analysis of the developed concept has been carried out and the first prototypes have been implemented.

Computer- und Robotertechnik für die bildgeführte Orthopädische Chirurgie (Computer and Robot Technology for Image guided Orthopaedic Surgery)

Seit einigen Jahren hält die Computer- und auch Robotertechnologie in der Orthopädischen Chirurgie Einzug, wird jedoch teilweise sehr kontrovers diskutiert. Wo liegen Vorteile und Probleme der Automatisierungstechnik für den chirurgischen Einsatz? In diesem Beitrag sollen Möglichkeiten und Techniken im Überblick dargestellt werden. Entwicklungspotentiale insbesondere im Hinblick auf robotische Unterstützungssysteme sollen am Beispiel des CRIGOS-Parallelrobotersystems aufgezeigt werden.