Studies concerning critical incidents with technical equipment in the medical/clinical context have found out, that in most of the cases non-ergonomic and non-reliable user interfaces provoke use deficiencies and therefore hazards for the patient and the attending physician. Based on these studies, the authors assume that adequate and powerful tools for the systematic design of error-tolerant and ergonomic Human-Machine-Interfaces for medical devices are missing. In this context, the Chair of Medical Engineering (mediTEC) has developed the new software-based tool mAIXuse in order to overcome these difficulties and to support designers as well as risk assessors. Based on two classical formal-analytical approaches, mAIXuse provides a high-performance modelling structure with integrated temporal relations in order to visualise and analyse the detailed use process, even with complex user interfaces. The approach can be used from the very early developmental stages up to the final validation process. Results of a comparative study with the new mAIXuse tool and a conventional process-FMEA (Failure Mode and Effect Analysis) show, that the new approach clearly outperforms the FMEA technique.

Arthroscopy is one of the standard techniques in minimal-invasive knee surgery. During these interventions, the support of the treated leg is one of the main ergonomic problems. In this paper the development of a novel assistance device for arthroscopic surgery is described. The proposed tool enables the surgeon to fix the leg in any required position and to thereby improve his working posture and conditions.

Technological progress in the field of Computer-Assisted Surgery (CAS) not only leads to an enhancement in efficiency and effectiveness concerning therapeutic results but also to a change of the Human-Computer-Interaction characteristics in the operating room (OR). Deficiencies in the use process of CAS systems bring along high potential for hazardous human-induced failures implicating higher risks for patients and physicians during surgical interventions. To enhance safety and reliability in modern surgical work systems the design of the user interfaces has to be not only "ergonomic", - usability and reliability are major characteristics to be taken into consideration for the approval as well as for routine application of medical devices. While the experimental and the criteria-oriented usability-evaluation of interactive systems is getting increasing attention for manufacturers of medical devices, the design engineer has to examine and determine the usability of an envisioned system already in a very early developmental phase. In this context the presented mAIXuse method as well as a corresponding software tool have been developed and are currently being evaluated in order to support the application of prospective usability assessment for complex medical devices. Adapted from two model-based methods, the Concur Task Tree methodology and the CPM-GOMS approach, the software tool uses formal, normative models to predict user and system behaviour in order to estimate the usability of a new or re-designed system. The developed prospective usability investigation approach has already been evaluated in comparison to conventional risk assessment and usability evaluation methods and the corresponding software tool has been evaluated in cooperation with medical and industrial partners. The aim of the presented work is to support especially small and medium sized enterprises developing and manufacturing medical devices taking into account the required usability engineering and risk management process.

Non-ergonomic static working postures are generally considered to be a crucial factor for most work-related musculoskeletal disorders. Also in the intraoperative clinical context the assessment and optimization of working postures are subject of research as additional stress resulting from these postures potentially leads to increased strain, fatigue and higher risk for human error during the intervention as well as - exceeding individual thresholds - long term musculoskeletal diseases. The overall aim must therefore be to reduce posture-induced stress to a minimum while increasing the performance and efficiency of the complete work system.In the OrthoMIT project an integrated work system for smart hip-, knee-and spine-surgery is currently being developed. In this framework a novel concept for a knowledge-based OR-table-positioning system for orthopedic surgery was set up and realized in a first labtype.Based on video-supported timeline-analyses of selected orthopedic interventions, specific work-and posture-phases together with dedicated task-specifications were identified. The working postures were rated using standardized posture scales (OWAS, RULA). With these findings optimization strategies for adequate height of the OR-table with respect to anthropometric data of the surgeon and the patient as well as to the actual surgical task were developed and implemented in an assistance system. Using a graphical interface with touch screen or voice control the surgeon may set individual optimization parameters, store and recall preferred table positions and accept the assistant's suggestion shown in a preview window. If the suggestion is accepted the motorized OR-table is directly moved to the optimal position permanently controlled by the surgeon.

In the framework of the BMBF-funded project OrthoMIT a non-active remote pointing device for different purposes in Computer-Assisted Surgery (CAS) has been developed and is currently being evaluated. In the course of integration and interoperability for technical equipment within the operating room (OR) not only new hard- and software inter-faces but also innovative concepts for man-machine-interfaces have to be considered, in order to ease the use and the control process of planning- and navigation systems and their dedicated devices. Furthermore, for safety reasons the new man-machine-interaction concepts have to be integrated in the intraoperative workflow. The new developed multi-purpose Remote-Pointer (RP) combines three different input modalities and allows the usage out of the sterile area. It integrates the function of a conventional tracking probe, enables the operator to control graphical user interfaces (GUI) and offers, with the help of gesture detection, the possibility to handle dialog-based applications. The Remote-Pointer can be used from any position inside the OR, as long as it is located inside the workspace of the tracking camera. In this paper we describe the usability evaluation of the Remote-Pointer in comparison to a conventional mouse and the Logitech AIR-mouse. The focus of the usability investigation is on the performance character of the “mouse emulation” mode of the RP which allows the controlling of a GUI.

Background: Germline mutations in the Chek2 kinase gene ( CHEK2) have been associated with a range of cancer types. Recently, a large deletion of exons 9 and 10 of CHEK2 was identified in several unrelated patients with breast cancer of Czech or Slovak origin. The geographical and ethnic extent of this founder allele has not yet been determined.Participants and methods: We assayed for the presence of this deletion, and of three other CHEK2 founder mutations, in 1864 patients with prostate cancer and 5496 controls from Poland.Results: The deletion was detected in 24 of 5496 ( 0.4%) controls from the general population, and is the most common CHEK2 truncating founder allele in Polish patients. The deletion was identified in 15 of 1864 ( 0.8%) men with unselected prostate cancer ( OR 1.9; 95% CI 0.97 to 3.5; p = 0.09) and in 4 of 249 men with familial prostate cancer ( OR 3.7; 95% CI 1.3 to 10.8; p = 0.03). These ORs were similar to those associated with the other truncating mutations ( IVS2+ 1GRA, 1100delC).Conclusion: A large deletion of exons 9 and 10 of CHEK2 confers an increased risk of prostate cancer in Polish men. The del5395 founder deletion might be present in other Slavic populations, including Ukraine, Belarus, Russia, Baltic and Balkan countries. It will be of interest to see to what extent this deletion is responsible for the burden of prostate cancer in other populations.

BACKGROUND:In cases of cranial tumour, manual resection of the cancerous tissue can be very stressful and time-consuming, due to the adhesion of the subjacent dura mater. Computer-assisted planning, navigation and robotic craniotomy, with optional skull reconstruction using customized implants, are of increasing clinical interest in craniofacial and neurosurgery.METHODS:Using preoperative computed tomography (CT) images, an automatic segmentation of the tumour is performed, followed by resection planning. The skull reconstruction is performed using computer-assisted implant modeling and manufacturing. Risk analysis of the robot-guided intervention led to the development of a new hexapod robot system.RESULTS:Results from registration and robot accuracy on plastic and Anatomical skull are shown. The concept of a stand-alone safety system is presented to supervise the robot during the intervention. The entire process from preoperative CT scan to intraoperative robot assisted removal of tumourous bone is shown in laboratory and anatomical trials.CONCLUSION:The laboratory and anatomy studies conducted so far provided a substantial basis for further improvement of the system's integration in the surgical workflow and the final approval of the system for initial clinical studies.

There are a large number of patients after cystectomy, which for various reasons does not qualify for ileal bladder. Continent urinary reservoir as an option not requiring wearing any appliances like urostomy plates and bags or not causing inconveniences like rectal bladder is a very attractive solution for some patients.

A compact, semi-robotic manipulation-platform for a stereoscopic digital exoscope has been developed, intended to be used as a steerable lightweight electronic microscope during endoscopically assisted neurosurgical interventions The platform comprises a novel multifunctional arch for its fixation on the OR-table, a manual pre-positioning device for coarse spatial adjustment and a robotic unit for freehand fine-positioning of the exoscope. It is operated by the surgeon by means of a combination of speech control for mode selection and head-tracking for intuitive adjustment of the camera's perspective onto the operating field. The system has been realized and first tests concerning system dynamics and intra-operative man-machine interaction have been accomplished. Evaluation of head-tracking has shown its good controllability and high intuitivity-of-use as well as the clear advantage of position-over rate-control. Dynamic characteristics of the platform have been analyzed and compared to those of OR-microscopes determined in field tests and manufacturer interviews. Abating times and resonant frequencies of the platform turned out to be comparable to commercial systems, vibration caused by robotic fine-positioning died out within approximately 2s.

In last years we have been observing an increase of both urologists’ and patients’ interest in plastic surgery of the penis. Such procedures performed in male older than 40 years require diligent postoperative rehabilitation programs in order to achieve best possible result and to enable the patient to restore his sexual activity. In this film as an example we are presenting the treatment of patient with Peyronie disease.

This study was performed to evaluate the surgical strategy in patients with calvarial tumours, in order to design and modify a robot-assisted trepanation system. A total of 75 patients underwent craniectomy for the treatment of calvarial tumours during the 10-year period from 1993 to 2002. The patients' complaints, the size, location and histology of the tumour, and the various cranioplasty techniques used were analysed retrospectively. In a second procedure several craniectomies at typical locations according to the study's results were performed in a laboratory setting using a hexapod robotic tool, constructed at the Helmholtz-Institute, RWTH Aachen University, and plastic model heads. The workflow was documented and the reproducibility and the accuracy of the procedure were registered. A total of 83 surgical procedures were performed on 75 patients. The majority (87%) of lesions treated surgically were located in the frontal, temporal and anterior parts of the parietal region. Histological examination revealed benign lesions in 66% of the patients and dural involvement in 46%. According to these results craniectomies were performed using the robotic system. Mean positioning accuracy of the robotic system while milling was 0.24 mm, with a standard deviation of 0.04 mm, and maximum error under 1 mm. Craniectomies leaving a 1-mm layer of the tabula interna intact to ensure a healthy dura were performed in several regions successfully. The majority of calvarial tumours, requiring surgical treatment in our patients, were located in cosmetically relevant areas in which drilling can be carried out with the robotic trepanation system. Consequently, the surgical approach had to be planned carefully in order to achieve a good cosmetic outcome.

We developed a visual assistance system for image guided neurosurgery, consisting of a stereoscopic digital camera (exoscope) mounted on a semi-robotic manipulator. In order to minimize the operation time, the application-specific multimodal user interface enables hands-free manipulation of the exoscope. The surgeon wears thereby a head-mounted unit with a binocular display, a head tracker, a microphone and earphones. Different modes of view positioning and adjustment can be selected by voice and controlled by head rotation while pressing a miniature confirmation button mounted on a finger ring or suction device. Apart from the development of the mechatronic and software modules of the semi-robotic manipulator, initial studies focused on the evaluation and optimization of the intuitiveness, comfort and precision of different modes of operation. For the user based evaluation of different control modes, a simulation has been implemented in stereoscopic virtual reality. Results of user tests with neurosurgeons are presented in this paper. Based on these findings, the multimodal user interface has been implemented into the first labtype. The system has been demonstrated in the operating room in first tests on a phantom together with the clinical partner.

The milling of bone is a time-consuming and straining effort during surgery at the cranial vault. In order to determine possible advantages of a robotic system, the registration of different milling parameters during defined surgical procedures was the aim of this study. Eleven neurosurgeons were asked to mill a bovine scapula. The task consisted of geometric figures (one line and a circle) that had to be milled in a depth of 3 mm. Main focus was laid on the accuracy of the milling. In addition, the registered parameters such as forces, temperature and speed will be used as a reference for the design and validation of the robotic system. The same task was done by a robotic (hexapod) system, constructed at the Helmholtz-Institute Aachen (HIA). In comparison with the surgeon, the robotic system showed a higher accuracy at a greater velocity. The forces and temperatures showed minor differences. If further test results are consistent, it would be advantageous to use a robotic system to perform large craniectomies, especially in cosmetically relevant areas due to its advantage in accuracy and speed compared to a surgeon.

Within the framework of the development of a new neurosurgical robot system, parameters of conventional manual neurosurgical bone milling had to be determined. These results were used as a reference for the design and validation of the robotic versus manual milling task. Bovine scapulae were used for the tests because their bicortical structure is similar to the bone structure of the skull. The exercise was to cut defined geometries that had been registered on the bone prior to the start of the milling operation. The geometries had to be milled with a depth of 3 mm, which corresponded to the radius of the ball of the cutter. Different parameters like tool position, rotary speed, temperature, forces and time were registered. Eleven experienced neurosurgeons with practical experience of 80-1200 skull operations participated in this study. First results show a large variation in depth along the line. The lateral deviation was up to 5 mm, the depth error up to 2.5 mm, the tool temperature was 22°C to 65°C, and rotary speed varied from 15,000 to 80,000 rpm. Registered forces had maxima of 16 N in the feed direction and 21 N normal to the surface; average forces were approximately 1-2 N.

In the context of the development of a new, electronic microscope for surgical interventions a semirobotic motion platform for the spatial placement and fixation of a stereoscopic camera is currently being developed. Based on an inquiry about the medical, technical and user-requirements, different phases and characteristics concerning frequency, workspace, speed and accuracy of camera movement during an intervention have been specified. To meet these requirements, a differentiated concept for the platform has been developed including a serial structure for manual pre-positioning, a parallel robot for motor-movement during surgical work and different user-interfaces for suitable robot-control.

As the removal of femoral bone cement is one of the most challenging tasks in cemented total Hip Revision, a lot of different technical devices have been developed to aid the surgeon. All of their pros and cons are partly consequences of the specific system-design but mainly arise from the basic physical principles used. The known methods and devices as well as their data-handling have therefore been analysed, reduced to their principles according to the criteria of systematic engineering design and systematized in order to provide a better comparability and starting point for the development of new devices.