[A concept to improve wet-lab training in ENT surgery]. / Ein Konzept zur Verbesserung von Präparationskursen in der HNO-Heilkunde.

BACKGROUND: In literature and scientific societies no binding methodical-didactic recommendations or guidelines exist in order to design surgical training courses. The educating institutions plan, organise and evaluate the educational program on their own initiative. MATERIAL AND METHODS: Through a research project surgical training courses were investigated through structured surveys, expert discussions with course responsibles and trainers and analysis of participant's questionnaires. The investigation was performed by an pedagogical-psychological research institution. First implementations were installed and immediately included in the running process of evaluation. RESULTS: From the evaluation, specific alterations in the organisational and micro didactic process were implemented. In addition, changes in a long term process had to be implemented such as: (a) conception of the trainer role, (b) giving feedback and judge performance and (c) provide contents in a sophisticated manner. CONCLUSION: For advanced medical training providers a long term cooperation with a pedagogical institution seems to be highly advisable.

Evaluation of a navigated and power controlled milling system "navigated control spine" for spinal surgery.

PURPOSE: The aim of this work was the evaluation of a navigated and power controlled milling system for spine surgery (navigated control spine). The navigation is based on a set of intraoperatively taken fluoroscopic images from different angles. A manually planned workspace limits the power of the mill and assures a higher automatisation degree than any other established navigation system for spine surgery. METHODS: Both a technical study in workspace planning from fluoroscopic images and a milling study on a spine phantom were performed with participants with different level of knowledge of spinal surgery. RESULTS: In the region of interest the workspace planning could be performed with a maximum excess of 1.40 mm for surgeons. In the study performing the milling of a standardised workspace the remnant bone after milling had a mean difference from the planned workspace margin of 1.96-2.12 mm in the region of most interest. Accurate handling of the mill still required a certain level of medical knowledge and experience. In both studies the time needed for application of the system proved acceptable for clinical purposes. DISCUSSION: This concept of navigated and power controlled spinal surgery has proven feasible in an experimental study. This navigation system seems therefore promising for clinical application.

[Evaluation of a training system for middle ear surgery with optoelectric detection]. / Evaluation eines Trainingssystems für die Felsenbeinchirurgie mit optoelektrischer Detektion.

PROBLEM: This work presents a new training concept for surgery of the temporal bone. It is based on a model of gypsum plastic with optoelectric detection of risk structures. A prototypical evaluation is given. MATERIAL AND METHODS: The training models are based on high-resolution computed tomographic data of a human skull. The resulting data set was printed by a three-dimensional (3D) printer. A 3D phantom is created from gypsum powder and a bonding agent. Risks structures are the facial nerve, semicircular canal, cochlea, ossicular chain, sigmoid sinus, dura, and internal carotid artery. An electrically conductive metal (Wood's metal) and a fiber-optic cable were used as detection materials for the risk structures. For evaluating the training system, a study was done with eight inexperienced and eight experienced ear surgeons. They were asked to perform temporal bone surgery using two identical training models (group A). In group B, the same surgeons underwent surgical training with human cadavers. In the case of injuries, the number, point in time, degree (facial nerve), and injured structure were documented during the training on the model. In addition, the total time needed was noted. RESULTS: The training systems could be used in all cases. Evaluation of the anatomic accuracy of the models showed results that were between 49.5% and 90% agreement with the anatomic origin. Error detection was evaluated with values between 79% and 100% agreement with the perception of an experienced surgeon. The operating setting was estimated to be better than the previous"gold standard." The possibility of completely replacing the previous training method, which uses cadavers, with the examined training model was affirmed. CONCLUSIONS: This study shows that the examined system fulfills the conditions for a new training concept for temporal bone surgery. The system connects the preliminary work with printed and sintered models with the possibilities of microsystem engineering. In addition, the model's digital database permits a complete virtual representation of the model with appropriate further applications ("look behind the wall," virtual endoscopy).

Surgery on the lateral skull base with the navigated controlled drill employed for a mastoidectomy (pre clinical evaluation).

Patients who are treated with a mastoidectomy usually suffer from an inflammation of the petrosal bone. The intervention is a time consuming landmark based surgery and usually performed with a powered drill. Delicate risk structures must be respected. Navigated Control (NC) describes the control for a power driven instrument which is controlled by a surgeon and additionally controlled according to the position of the instrument relatively to a deliberated position known from a preoperatively segmented work space which excludes risk structures. The force of a drill can be regulated by the principle of NC. Following results were received: 1. Risk structure segmentation is feasible 2. The drill and a phantom can be registered. 3. With NC the resection is faster, more accurate and with no risk structures damage. 4. The phantom is suitable.

[Manipulator assisted endoscope guidance in functional endoscopic sinus surgery: proof of concept]. / Ein Konzept für eine automatisierte Endoskopführung für die Nasennebenhöhlenchirurgie.

BACKGROUND: Functional endoscopic sinus surgery (FESS) is characterized by single-handed preparation and guidance of the endoscope by the nondominant hand. This results in an additional extension of operation time by up to 15% and ergonomic deficits. The aim of this study is the conception of an automated assistance system for FESS in view of the following questions: (1) Which degree of surgical automation is suitable for FESS? (2) Which design is suitable? (3) What are the properties of the technical system (planning, time, accuracy, precision) of the selected system? (4) Does the system offer potential for a clinical application? METHODS: In all 49 FESS were analyzed for surgical workflows. Measurement of the maximum forces within FESS was performed with 40 trials on an anatomical model. Three different mechanical systems were used in ten FESS and evaluated using the ICCAS Human-Machine Evaluation Scale. For realization of automated endoscope guidance an engine-driven and -braked manipulator (PA10-6c, Mitsubishi, Japan) was used. The technical parameters determined were expenditure of time for the preoperative planning of workspace, surgical accuracy and precision of the intraoperative endoscope positioning, maximal forces, and time. RESULTS: Concept-conditioned instrument changes amount to an average of 41.1 and 18.9% (5.21 min) time requirement for each FESS side. Maximum forces on the mucous membrane during a conventional FESS were measured at 9.8 N (5.9-9.8). Usability of the mechanical endoscope holder was estimated in 18 of 20 cases to be inferior to the standard procedure. The time needed for segmenting the intranasal workspace was 15.2 min (10.0-23.0). The maximum deviation of the automatically driven endoscope from a planned position amounted to 0.85 mm (manually 4.64 mm). The maximum force was measured with 1.1 N in the z direction (manually 9.8 N). Automated guidance of the endoscope to an intranasal position needed 7.25 s (6.4-7.9); manually 12.64 s (5.9-43.0). CONCLUSION: Guidance of the endoscope for FESS by an automated motor-driven system is possible. The conception which is based on workflow analysis favors a system with automatic definition of the workspace and a manual movement of the endoscope. The examined system offers a potential for clinical application. Definition of the automation level and development of a man-machine interface is more important than selection or reconstruction of a special manipulator for endoscope guidance in FESS from a surgical point of view.

[Improved accuracy and precision of the automated shaver (navigated control) in functional endoscopic sinus surgery]. / Verbesserte Umsetzung der Resektionsgrenzen in der Nasennebenhöhlenchirurgie mit dem navigiert-kontrollierten Shaver.

BACKGROUND: The feasibility of a navigate-controlled Shaver for the paranasal sinus surgery was proven in an initial study. Deficits showed up in the conversion of the planed cavity. Goal of this study is (1) the development and evaluation of a FESS demonstrator for the investigations to the surgical accuracy and (2) the evaluation of the resulting surgical accuracy for registration and conversion of the work space with an improved rigidity of the Shaver and a completely revised study design. METHODS: As a demonstrator for the navigate-controlled resection of a volume through the Shaver a two-piece plastic head with an anatomical head and soft tissue model was designed. The investigation of the surgical accuracy takes place with 417 measurements to 4 different fiducial markers on the demonstrator head. The measurements for the deviation of the resulting cavity from the planned volume was realised with a work space by 24 x 24 x 30 mm. The 5 walls of the cavity were seized with 80 measuring points for each level and thus altogether 2000 measured values (5 models x 5 levels x 200 points). RESULTS: The described demonstrator showed itself suitable for the close-to-application attempts to the surgical accuracy. The maximum deviation A (max) indicated position of the Shaver from the reference value amounted to 1,93 mm. The maximum average value of the exceeding of a planned cavity amounts to 1,62 mm. CONCLUSIONS: Based on these results a virtual safety passage of 2.00 mm is sufficient. The study refers the clinical serviceability of the navigate-controlled Shaver in paranasal sinus surgery.

[Clinical efficiency and the influence of human factors on ear, nose, and throat navigation systems]. / Ist der Vorteil eines Navigationssystems in der HNO-Chirurgie messbar? Ein Konzept zur Evaluation ergonomischer und chirurgischer Erfolgsparameter.

BACKGROUND: The aim of this study was to evaluate the Navibase navigation system for ear, nose, and throat (ENT) surgery. A new methodology for evaluating surgical and human factors is developed. PATIENTS AND METHODS: The evaluation is based on 102 ENT surgical applications, including 89 cases of functional endoscopic sinus surgery (FESS). The evaluation of surgical and human factors was performed by seven ENT surgeons. To evaluate surgical performance, level of quality (LOQ) in the 89 cases of FESS was determined, comparing the surgeon's own impressions with those of the navigation system on a scale from 0 to 100 and further comparing them with clinical results. Intraoperative changes in surgical strategy were documented. The human factors of total confidence (trust), situation awareness, skill set requirement and workload shift were recorded as level of reliance (LOR). RESULTS: The maximum deviation amounted to 1.93 mm. Averaging the quality of information resulted in an LOQ of 63.59. Every second application of the navigation system (47.9%) led to a change in surgical strategy. Total confidence showed a positive evaluation of 3.35 points in LOR. CONCLUSION: Application-relevant information relevant to the application beyond only technical details permits comparison with other assisting systems.

Establishing navigated control in head surgery.

Navigated Control (NC) describes an additional control for a tracked power driven instrument within a preoperatively segmented work space. In head surgery the authors first implemented NC in functional endoscopic sinus surgery (FESS). Recently the feasibility of NC for surgery on the petrosal bone is evaluated. NC in FESS and in petrosal bone surgery may reduce the risk of comorbidity and the time effort compared to the conventional surgical interventions.

[Accuracy and precision in the evaluation of computer assisted surgical systems. A definition]. / Genauigkeit und Präzision in der Bewertung von chirurgischen Navigations- und Assistenzsystemen. Eine Begriffsbestimmung.

Accuracy represents the outstanding criterion for navigation systems. Surgeons have noticed a great discrepancy between the values from the literature and system specifications on one hand, and intraoperative accuracy on the other. A unitary understanding for the term accuracy does not exist in clinical practice. Furthermore, an incorrect equality for the terms precision and accuracy can be found in the literature. On top of this, clinical accuracy differs from mechanical (technical) accuracy. From a clinical point of view, we had to deal with remarkably many different terms all describing accuracy. This study has the goals of: 1. Defining "accuracy" and related terms, 2. Differentiating between "precision" and "accuracy", 3. Deriving the term "surgical accuracy", 4. Recommending use of the the term "surgical accuracy" for a navigation system. To a great extent, definitions were applied from the International Standardisation Organisation-ISO and the norm from the Deutsches Institut für Normung e.V.-DIN (the German Institute for Standardization). For defining surgical accuracy, the terms reference value, expectation, accuracy and precision are of major interest. Surgical accuracy should indicate the maximum values for the deviation between test results and the reference value (true value) A(max), and additionally indicate precision P(surg). As a basis for measurements, a standardized technical model was used. Coordinates of the model were acquired by CT. To determine statistically and reality relevant results for head surgery, 50 measurements with an accuracy of 50, 75, 100 and 150 mm from the centre of the registration geometry are adequate. In the future, we recommend labeling the system's overall performance with the following specifications: maximum accuracy deviation A(max), precision P and information on the measurement method. This could be displayed on a seal of quality.

ElePhant--an anatomical electronic phantom as simulation-system for otologic surgery.

This paper describes the ElePhant (Electronic Phantom)-an anatomical correct simulation system based on 3D rapid prototyping models for the otologic intervention "Mastoidectomy". The anatomical structures of the head are created with plaster as base material using 3D-printing as rapid prototyping technology (RPT). Structures at risk, represented by electrically conductible material and fiber optics, are realized as an electric circuit and can be detected during the simulation of the surgical procedure. An accuracy study of 15 identical RPT-models compared to the 3D reconstructed CT-dataset of the patient showed that the mean accuracy is lower than the reconstructed CT layer thickness of 0.5 mm. An evaluation study of the ElePhant-system for "Mastoidectomy" was performed by 7 ENT-surgeons. The mean value of the study questionnaire (evaluation range from -2 (not at all) to +2 (very good)) was +1.2. The results showed that the ElePhant can simulate "Mastoidectomy" realistically. It is especially suitable for the simulation of the correct representation and position of the anatomical structures, realistic operation setting, and realistic milling properties of the bone structure. Furthermore it is applicable for training of surgeons.

Robot-assisted craniotomy.

In the Special Research Centre 414 of the German Research Funding (DFG, Bonn) a system for robot-assisted cranial surgery was developed. It is designed for the accurate and safe execution of craniotomies and repositioning of bone pieces. The system is intended for use in the surgical therapy of craniosynostosis. Preoperatively, CT imaging is performed. In a computerized planning system the position and shape of the intended craniotomy is intuitively planned on a virtual model of the patient's skull. Intraoperatively, after conventional removal of the covering soft tissue, the robot performs the craniotomy autonomously. Extensive testing in phantom studies and animal tests confirmed the reliability and accuracy of the system. A thorough risk analysis of the system was performed. In this paper, the first clinical use of the system on a patient is described and the clinical importance is discussed.

Risk analysis and safety assessment in surgical robotics: a case study on a biopsy robot.

One of the most important issues in medical robotics is safety and integration into the clinical workflow. If a robot is not safe and its use is complicated by difficult handling and complex user interfaces physicians would not use a robotic system during clinical patient trials, whatever the other advantages are. However, there are only few publications on this topic, in particular on risk management in developing a robotic prototype (for clinical trials). In this paper risk management and the safety of using robot-assisted surgery equipment are discussed and demonstrated exemplarily in the process of developing a prototype biopsy robot.

Robots in the operating theatre--chances and challenges.

The use of surgical robots and manipulators is still being frequently discussed in the mass media as well as in the scientific community. Although it was already noted in 1985 that the first patient was treated by a joint team of robot and surgeon, today such systems are not routinely used. This can be explained by the high complexity of such systems and the often limited usability, but also, that it is difficult for surgeons to accept "automatic" machines. In this paper the possibilities and chances of robots and manipulators will be explained and it will be shown that robots will never work alone in the operating theatre as it is common in industry today. On the other hand, also limitations and challenges will be outlined. Therefore first a review on today's systems is given in different disciplines including oral- and cranio-maxillofacial surgery, then advantages and disadvantages are shown.