G. Rau

Movement biomechanics goes upwards: from the leg to the arm

The analysis of lower limb movements has been well established in biomechanics research and clinical applications for a long time. For these studies, powerful and very advanced tools have been developed to measure movement parameters and reaction forces. The main focus of interest aims towards gait movements while the understanding of the basic concepts is supported by numerous models. Definitions of physiological ranges and detection of pathological changes in movements open an increasingly valuable clinical field of application. If, however, the primary function of the upper extremities as highly variable and adaptive organ for manipulating tasks is the subject of interest, the situation becomes considerably more complex. The nature of free arm movements is completely different from being restricted, repeatable or cyclic as compared to gait. Therefore, the transfer of the knowledge and experience gained in lower extremity movement analysis to the analysis of upper extremities turns out to be difficult. A proposal for how to proceed in measurements, e.g. where to place the markers and how to calculate movements and angles of segments involved, will be discussed which results in the description of the joint movements of wrist, elbow and shoulder joint. The definition of the motion is a specific step in upper extremity motion analysis which is important in terms of repeatability and significance of the results. An example of assessing movement disorders in children with plexus lesion will illustrate the implications and the potential of upper extremity movement analysis in clinical applications.

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.

Design and validation of an intelligent patient monitoring and alarm system based on a fuzzy logic process model

The process of patient care performed by an anaesthesiologist during high invasive surgery requires fundamental knowledge of the physiologic processes and a long standing experience in patient management to cope with the inter-individual variability of the patients. Biomedical engineering research improves the patient monitoring task by providing technical devices to measure a large number of a patients vital parameters. These measurements improve the safety of the patient during the surgical procedure, because pathological states can be recognised earlier, but may also lead to an increased cognitive load of the physician. In order to reduce cognitive strain and to support intra-operative monitoring for the anaesthesiologist an intelligent patient monitoring and alarm system has been proposed and implemented which evaluates a patients haemodynamic state on the basis of a current vital parameter constellation with a knowledge-based approach. In this paper general design aspects and evaluation of the intelligent patient monitoring and alarm system in the operating theatre are described. The validation of the inference engine of the intelligent patient monitoring and alarm system was performed in two steps. Firstly, the knowledge base was validated with real patient data which was acquired online in the operating theatre. Secondly, a research prototype of the whole system was implemented in the operating theatre. In the first step, the anaesthetists were asked to enter a state variable evaluation before a drug application or any other intervention on the patient into a recording system. These state variable evaluations were compared to those generated by the intelligent alarm system on the same vital parameter constellations. Altogether 641 state variable evaluations were entered by six different physicians. In total, the sensitivity of alarm recognition is 99.3%, the specificity is 66% and the predictability is 45%. The second step was performed using a research prototype of the system in anaesthesiological routine. The evaluation of 684 events yielded a sensitivity, specificity and predictability of the alarm recognition of more than 99%.

Noninvasive approach to motor unit characterization: Muscle structure, membrane dynamics and neuronal control

The standard surface EMG reflects the compound activity of a high number of motor units which is finally due to its low spatial resolution in the detection of the potential distribution on the skin surface. Therefore, detailed information about the structural and functional characteristics of the muscle consisting of populations of motor units, like the functional anatomy, the excitation spread or the innervation pattern cannot be obtained from the standard surface EMG. A novel noninvasive EMG-procedure with high spatial resolution (HSR-EMG) allows in contrast to the standard surface EMG even the detection of the single motor unit activity. In this way, the noninvasive determination of detailed information about the muscle structure, the membrane dynamics and the neuronal control becomes possible. First applications of the HSR-EMG have shown that especially the noninvasively measured conduction velocity of the excitation is highly affected by physiological details, like the muscle temperature, the relative muscle fibre diameter or inhomogeneities in the connective tissue forming part of the volume conductor around the muscle. From the results of the HSR-EMG investigations it can be concluded that the information about the structural and functional characteristics of the muscle as well as a deeper insight in the active state of the muscle is essential for a correct interpretation of the standard surface EMG.

Fuzzy logic approaches to intelligent alarms

The application of fuzzy methods as presented in the examples shows that the fuzzy logic approach has a great potential in biomedical engineering, where the difficulty of highly nonlinear and complicated dynamic properties are dramatic. The main advantage of utilising fuzzy methods is based on the nature of the model: the problems occurring can not and need not be modelled in a conventional mathematical manner. In the field of decision support systems, vague, redundant, and partly incomplete expert knowledge of complex biological systems can be handled by computers using a fuzzy logic approach by avoiding unnecessary accuracy. In the field of technical assist devices or systems, which will replace organs, the adaptation to the physiological requirements can be improved by the application of fuzzy control. The main properties of fuzzy control are: (a) reduction of effort on the sensor side, and (b) high dynamic stability in control, which is essential in controlling processes with a long dead- or transition time to a step response. In addition, powerful tools are available, allowing in short development times and high cost efficiency for the design and test of adequate fuzzy controllers. The expert knowledge of both the experienced physician and the biomedical engineer is an important source of information for the design of medical decision support systems and control systems for biomechanic devices. These attractive features will open new fields of application in the future.<<ETX>>

Different Types of Scaffolds for Reconstruction of the Urinary Tract by Tissue Engineering

Introduction: Tissue engineering is an important and expanding field in reconstructive surgery. The ideal biomaterial for urologic tissue engineering should be biodegradable and support autologous cell growth. We examined different scaffolds to select the ideal material for the reconstruction of the bladder wall by tissue engineering. Materials and Methods: We seeded mouse fibroblasts and human keratinocytes in a co-culture model on 13 different scaffolds. The cell-seeded scaffolds were fixed and processed for electron microscopy, hematoxylin and eosin stain, and immunohistochemistry. Cell density and epithelial cell layers were evaluated utilizing a computer-assisted optical measurement system. Results: Depending on the growth pattern, scaffolds were classified into the following three distinct scaffold types: carrier-type scaffolds with very small pore sizes and no ingrowth of the cells. This scaffold type induces a well-differentiated epithelium. Fleece-type scaffolds with fibers and huge pores. We found cellular growth inside the scaffold but no epithelium on top of it. Sponge-type scaffolds with pores between 20 and 40 µm. Cellular growth was observed inside the scaffold and well-differentiated epithelium on top of it. Conclusion: To our knowledge, this is the first time three distinct scaffold types have been reported. All types supported the cell growth. The structure of the scaffolds affects the pattern of cell growth.

A compact robot for image-guided orthopedic surgery: concept and preliminary results

This paper deals with a new approach towards computer assisted surgery by means of a surgical robot device specially designed for the treatment of bone structures. Considering the constraints due to the medical environment one main aim is to improve the accuracy of surgical execution by only minor changes of the intraoperative workprocess itself. Therefore, the surgical planning of the proposed system is based on multiple x-ray images taken intraoperatively with a conventional c-arm including a non-invasive registration technique. In contrary to former approaches the robot supported execution is performed by a special purpose manipulator with a new kinematic structure optimized for orthopedic interventions. First results of the feasibility study concerning the surgical planning and execution based on x-ray images as well as the design study of the robots kinematics are presented in this paper.

Development of an automatic surgical holding system based on ergonomic analysis

Introducing new surgical techniques and technical devices into the conventional working system „operating theatre“ as well as efforts integrating new technologies (CAS) require basic analysis of thereby caused problems. Therefore we investigated in cooperation with our clinical partners the surgical workplace concerning posture and holding work using ergonomic analysing methods. From these analyses about endoscopic and orthopaedic surgical interventions a high contribution of critical static working postures is noticed. Particularly the assisting surgeons are additionally stressed by static holding work because of the lack of sufficient support devices and holding systems.

Stereoscopic visualization in endoscopic surgery: Problems, benefits, and potentials

In recent years the application of 3D video endoscopic systems in clinical routine, especially in the field of endoscopic surgery, has increased steadily. The number of 3D video endoscopic systems used in the operating theatre today is obviously lower than the number of established traditional 2D video endoscopic systems. The hesitant application of the new technology can be mainly explained by the lack of evaluation of its influence on the surgical procedure and on patient benefit as well as by the need for specific economic analysis. The starting point for our investigations was to analyze the influence of 3D video endoscopy on endoscopically guided manipulations in general. In order to achieve quantitative statements we performed laboratory experiments using human factors analyzing methods. In the next step we performed clinical field studies of the application of 3D video endoscopic systems for a side-by-side comparison of 2D and 3D systems. These studies showed that the use of 3D video endoscopy has an improving influence on endoscopically guided surgical manipulations as well as on the intraoperative procedures. We also found that spatial visual perception of stereoscopic images of 3D video systems may cause problems for some users. For the validation of stereoscopic visualization systems we additionally studied the influence of isolated technical, optical, and physiological parameters on visual perception as well as on transposition into visually guided manipulations. Detailed results of these investigations concerning the influence of 3D video endoscopy on binocular perception are presented.