Concept and first Implementation of an intracochlearly navigated Electrode Array for Cochlear Implantation.

Cochlear implants (CI) are an established treatment for people with deafness or severe hearing loss. To restore patients' hearing an electrode array (EA) of the CI is inserted into the cochlea to stimulate the auditory nerve. Thereby, the exact positioning and gentle insertion of the EA is crucial for optimal hearing perception outcome. Currently, only microscopic vision is available for entering the cochlea, but the critical intracochlear process during EA insertion is like a "black box" and the surgeon has to rely on haptic feedback. Methods for visualizing the insertion process during surgery are inaccurate or not suitable for routine use due to radiation exposure. To address this problem, we developed a computer-assisted and image-guided cochlear implantation system with an exact real-time visualization of the EA position during the insertion process. The system is based on an electromagnetic tracking system that measures the position and orientation of a sensor integrated into the tip of a EA prototype and visualizes it in presurgical image data. A first experiment with our system showed that a EA prototype could be inserted into a cochlea of a human temporal bone and placed with an accuracy of [Formula: see text]. A maximum insertion angle of 120° was achieved.

Cruciate-Ligament-Inspired Compliant Joints: Application to 3D-Printed Continuum Surgical Robots.

The rapid development of additive manufacturing technology makes it possible to fabricate a patient-specific surgical robot in a short time. To simplify the assembly process of the printed robotic system, compliant-joint-based monolithic structures are often used as substitutes for rigid-link mechanisms to realize flexible bending. In this paper, we introduce a cruciate-ligament-inspired compliant joint (CLCJ) to improve the bending stability of the 3D-printed continuum surgical robots. The basic structure of the tendon-driven CLCJ mechanism and its kinematic model were described in detail. The bending performance of CLCJ was also successfully evaluated by FEM simulation and experimental tests. Besides, a prototype of CLCJ-based surgical robotic system was presented to demonstrate its application in 3D-printed continuum surgical robots.

Design of a novel tendon-driven manipulator structure based on monolithic compliant rolling-contact joint for minimally invasive surgery.

PURPOSE: Compliant mechanisms are commonly used in the design of manipulator and surgical robotic tools for minimally invasive surgery (MIS) thanks to their compactness, ability of miniaturization and lower part count. However, conventional compliant joint has higher internal stiffness, which limits the bending radius. To overcome this problem, a novel tendon-driven manipulator structure based on monolithic compliant rolling-contact joint (CRCJ) is proposed. METHODS: The proposed rolling-contact mechanism is used to prevent cable slack during actuation, which occurs in conventional compliant joint design. By means of selective laser sintering (SLS) technique, the CRCJ can be fabricated in a monolithic structure, thus granting the CRCJ both the advantages of compliant joints and rolling-contact mechanism. Simulations with nonlinear finite element analysis (FEA) and experiments were conducted to evaluate and compare the mechanical properties of the proposed CRCJ with conventional leaf-type compliant joint including the bending and compliant motion. RESULTS: Experimental results showed that the CRCJ has lower bending stiffness, higher maximum bending angle (over [Formula: see text]) and a higher compliance compared to conventional compliant hinges, which allows a larger workspace and reduces the possibility of tissue injury. Agreement was also found between the nonlinear FEA and experiments regarding the relation between actuation force and bending angle. A primary prototype of a 3-DOF handheld laparoscopic manipulator with a diameter of 7 mm was further developed. CONCLUSION: A dexterous tendon-driven monolithic manipulator structure based on CRCJ for MIS is proposed. A preliminary prototype of a handheld laparoscopic manipulator demonstrates the capability of the CRCJ for steerable medical devices. However, design improvements based on FEA and application-orientated prototypes considering anatomical requirements still show room for improvements.

Patient-Specific Instrument with a Cutting Template for Mitral Valve Repair by Resection.

Mitral valve regurgitation is one of the most common heart valve diseases and mitral valve repair is the favored therapy, in which a part of the mitral valve is resected. To improve preoperative planning of this challenging surgery, patient-specific mitral valve replicas have been developed on which the repair can be simulated. However, there is no possibility yet to transfer the planning from the replica to the surgery of the patient. To solve this problem, we developed a patient-specific instrument with a cutting template, intraoperatively visualizing the part of the mitral valve to be resected as planned on the replica. To realize this instrument, the surgeon first simulates mitral valve repair by resection on a patient-specific mitral valve replica. This postoperative mitral valve replica is then digitalized and from it and a preoperative mitral valve model the instrument with cutting template is automatically designed and then 3D printed. An expert heart surgeon successfully tested the functional principle of the instrument on a pig mitral valve.

Bionic Design of a Disposable Compliant Surgical Forceps With Optimized Clamping Performance.

Disposable forceps are frequently used in different surgical procedures to prevent infections caused by poorly sterilized reusable metal forceps. Compared to traditional rigid-joint mechanisms, compliant mechanisms are much easier to sterilize due to their monolithic structure, hence they are widely used for designing disposable surgical forceps. However, the clamping performance of plastic compliant forceps is generally less robust than metal forceps, which has greatly limited their use in medical applications. To cope with this problem, a novel 3D-printed plastic compliant forceps with optimized clamping performance was developed in this paper for open surgery and physical nursing applications. Bio-inspired topology optimization techniques were employed to synthesize the forceps. The clamping capability of the proposed forceps was evaluated by finite element analysis and loading tests. Results showed that the proposed forceps can generate greater and more stable clamping forces than the previous model of disposable compliant forceps. The proposed bionic optimization method also has potential for synthesizing compliant devices for robotic surgery.

Evaluation of long-term stability of monolithic 3D-printed robotic manipulator structures for minimally invasive surgery.

PURPOSE: In the era of patient-centered medicine, clinical procedures, tools and instruments should be individually adapted to the patient. In this context, the presented 3D-printed Single-Port Overtube Manipulator System follows the aims to provide patient- and task-specific disposable manipulators for minimally invasive surgery. In a first experiment, the robustness of the monolithic flexure hinge structures in use as robotic manipulators will be investigated. METHODS: Customizable monolithic manipulator structures designed by means of an automated design process and manufactured with selective laser sintering were investigated with regard to long-term stability in an endurance test. Therefore, a bare manipulator arm, an arm equipped with a standard instrument and finally loaded with an additional load of 0.5 N were evaluated by continuously following a trajectory within the workspace of the manipulator arms over a period of 90 min. RESULTS: The unloaded manipulator as well as the manipulator arm equipped with a standard instrument showed a sufficient reproducibility (deviation of 1.5 mm and 2.5 mm, respectively, on average) with regard to an application as telemanipulated master-slave surgical robotic system. The 3D-printed manipulators showed no damage and maintained integrity after the experiment. CONCLUSION: It has been shown that 3D-printed manipulators in principle are suitable for use as disposable surgical manipulator systems and offer a long-term stability over at least 90 min. The developed manipulator design shows great potential for the production of patient-, task- and user-specific robot systems. However, the manipulator geometries as well as the control strategies still show room for improvements.

A handheld flexible manipulator system for frontal sinus surgery.

PURPOSE: Draf drainage is the standard treatment procedure for frontal sinus diseases. In this procedure, rigid angled endoscopes and rigid curved instruments are used. However, laterally located pathologies in the frontal sinus cannot be reached with rigid instrumentation. In order to assist surgeons with such complicated cases, we propose a novel handheld flexible manipulator system. METHODS: A cross section of 3 mm × 4.6 mm enables transnasal guiding of a flexible endoscope with 1.4 mm diameter and a standard flexible surgical instrument with up to 1.8 mm diameter into the frontal sinus with increased reachability. The developed system consists of an electrical discharge-machined flexure hinge-based nitinol manipulator arm and a purely mechanical handheld control unit. The corresponding control unit enables upward and left-right bending of the manipulator arm, translation, rolling, actuation and also quick exchange of the surgical instrument. In order to verify the fulfillment of performance requirements, tests regarding reachability and payload capacity were conducted. RESULTS: Reachability tests showed that the manipulator arm can be inserted into the frontal sinus and reach its lateral regions following a Draf IIa procedure. The system can exert forces of at least 2 N in the vertical direction and 1 N in the lateral direction which is sufficient for manipulation of frontal sinus pathologies. CONCLUSION: Considering the fact that the anatomical requirements of the frontal sinus are not addressed satisfactorily in the development of prospective flexible instruments, the proposed system shows great potential in terms of therapeutic use owing to its small cross section and dexterity.

Patient-specific catheter shaping for the minimally invasive closure of the left atrial appendage.

PURPOSE: The minimally invasive closure of the left atrial appendage is a promising alternative to anticoagulation for stroke prevention in patients suffering from atrial fibrillation. One of the challenges of this procedure is the correct positioning and the coaxial alignment of the tip of the catheter sheath to the implant landing zone. METHOD: In this paper, a novel preoperative planning system is proposed that allows patient-individual shaping of catheters to facilitate the correct positioning of the catheter sheath by offering a patient-specific catheter shape. Based on preoperative three-dimensional image data, anatomical points and the planned implant position are marked interactively and a patient-specific catheter shape is calculated if the standard catheter is not considered as suitable. An approach to calculate a catheter shape with four bends by maximization of the bending radii is presented. Shaping of the catheter is supported by a bending form that is automatically generated in the planning program and can be directly manufactured by using additive manufacturing methods. RESULTS: The feasibility of the planning and shaping of the catheter could be successfully shown using six data sets. The patient-specific catheters were tested in comparison with standard catheters by physicians on heart models. In four of the six tested models, the participating physicians rated the patient-individual catheters better than the standard catheter. CONCLUSION: The novel approach for preoperatively planned and shaped patient-specific catheters designed for the minimally invasive closure of the left atrial appendage could be successfully implemented and a feasibility test showed promising results in anatomies that are difficult to access with the standard catheter.

Development of a snake-like dexterous manipulator for skull base surgery.

Petrous apex lesions constitute considerable surgical challenges due to their location in the skull base and close relationship with critical structures such as inner ear, carotid arteries, facial nerves and jugular bulb. These lesions often cannot be treated completely with rigid tools due to the limited accessibility. We are aiming to develop a snake-like manipulator to assist surgeons with the infralabyrinthine treatment of petrous apex lesions with increased dexterity. This snake-like dexterous manipulator (SDM) with 3.3 mm outer diameter and 40 mm working length was designed including a tool channel with a diameter of 1.8 mm and an endoscope channel with a diameter of 0.7 mm. The SDM can be actuated in one plane and two directions enabling the C- and S-shaped bends and rotated around its longitudinal axis. The constant curvature modeling was implemented to predict the deflection in one direction. Experiments were carried out with optical microscope to find out different bending modes. Experimental bending modes were in a good agreement with the theoretical ones in terms of the bending behavior. However tip position prediction showed discrepancies up to 1 mm in X and 2 mm in Z axes.

A new evaluation and training system for micro-telemanipulation at the middle ear.

In this article, a new surgical model for evaluating telemanipulators used in middle ear surgery is presented. The purpose of this work was to develop an evaluation and training system which imitates a typical surgical task of middle ear surgery and which can easily be repeated in order to get significant result. The abstract task can be performed manually or by means of a microsurgical telemanipulator and guaranties stable experimental conditions between different subjects at any time. As a task the stapedotomy was chosen, due to the high demands in positioning and in applying forces to the delicate structures in the middle ear. The manual and telemanipulated performance of 15 ENT surgeons and 17 medical students was compared using this evaluation and training system.

A high resolution bladder wall map: feasibility study.

The aim of this work is to provide the surgeon-urologist with a system for automatic 2D and 3D-reconstruction of the bladder wall to help him within the treatment of bladder cancer as well as planning and documentation of the interventions. Within this small pilot-framework a fast feasibility study was made to clear if it is generally possible to build a bladder wall model using a special endoscope with an embedded laser-based distance measurement, an optical navigation system and modern image stitching techniques. Some experiments with a realistic bladder phantom have shown that this initial concept is generally acceptable and can be used with some extensions to build a system which can provide an automatic bladder wall reconstruction in real time to be used within a surgical intervention.

Distance measurement in middle ear surgery using a telemanipulator.

In this article, a new tool for the intraoperative measurement of distances within the middle ear by means of a micromanipulator is presented. The purpose of this work was to offer the surgeon a highly accurate tool for measuring the distances between two points in the 3D operational field. The tool can be useful in various operations; this article focuses, however, on measuring the distance between the stapes footplate and the long process of the incus of the middle ear. This distance is important for estimating the proper prosthesis length in stapedotomy for treating otosclerosis. We evaluated the system using a simplified mechanical model. Our results show that the system can measure distances with a maximum error of 0.04 mm.

Automatic correction of registration errors in surgical navigation systems.

Surgical navigation systems are used widely among all fields of modern medicine, including, but not limited to ENT- and maxillofacial surgery. As a fundamental prerequisite for image-guided surgery, intraoperative registration, which maps image to patient coordinates, has been subject to many studies and developments. While registration methods have evolved from invasive procedures like fixed stereotactic frames and implanted fiducial markers toward surface-based registration and noninvasive markers fixed to the patient's skin, even the most sophisticated registration techniques produce an imperfect result. Due to errors introduced during the registration process, the projection of navigated instruments into image data deviates up to several millimeter from the actual position, depending on the applied registration method and the distance between the instrument and the fiducial markers. We propose a method that allows to automatically and continually improve registration accuracy during intraoperative navigation after the actual registration process has been completed. The projections of navigated instruments into image data are inspected and validated by the navigation software. Errors in image-to-patient registration are identified by calculating intersections between the virtual instruments' axes and surfaces of hard bone tissue extracted from the patient's image data. The information gained from the identification of such registration errors is then used to improve registration accuracy by adding an additional pair of registration points at every location where an error has been detected. The proposed method was integrated into a surgical navigation system based on paired points registration with anatomical landmarks. Experiments were conducted, where registrations with deliberately misplaced point pairs were corrected with automatic error correction. Results showed an improvement in registration quality in all cases.

The effects of real-time image navigation in operative liver surgery.

PURPOSE: In liver surgery, preoperative planning is usually performed by using CT scans. Ultrasonic probes are frequently used operatively to verify tissue deformations, for example when resecting a liver tumor with an ultrasonic dissector. Avoidance of dissecting vitally important hepatic vessels and the recrudescence of tumors are of crucial importance. The potential benefits of real-time image navigation in operative liver surgery were investigated experimentally. METHODS: Four model tumors with realistic ultrasonic features have been embedded into a bowl filled with candle gel. The aim was to locate these tumors with the ultrasonic probe and to puncture them safely with the ultrasonic dissector. The experiment was performed four times, once completely without navigation and three times with ultrasonic-based navigation but under different preconditions. RESULTS: Less attempts are needed to puncture a certain tumor with real-time image navigation than without navigation (P<0.02%). The effectiveness of ultrasonic-based navigation varied with the surgical preconditions. CONCLUSIONS: The use of a suitable navigation system improves safety and effectiveness in liver surgery for intraoperative localization of key structures such as tumors. However, resecting hepatic tumors with appropriate safety margin demands for further enhancements concerning the proposed methods.

Experimental validation of a tissue-joining implant providing flexible adaptation to the thickness of the stomach wall.

Endoscopy is gradually replacing open surgery in the gastrointestinal tract. Therefore, novel medical devices and instrumentation are required, such as flexible miniaturized mechanisms for tissue joining and manipulation. In this paper, an absorbable implant for the purpose of long-term tissue fixation is presented. An experimental validation of the implant design and functionality is introduced. The implant achieves tissue penetration and provides flexible adaptation according to the thickness of two stomach walls. This mechanism is easy as it is based on push-pull principle using unidirectional forces. The shape optimization of each implant part occurs by varying design-influencing factors. The load transmission on postmortem porcine tissue was measured in the frame of the experimental setup. The feasibility of the implant was tested, and the forces needed for the intended application quantified. The implant successfully achieves tissue penetration, load transmission, adjustment, and fixation. It is a new alternative to conventional tissue-joining mechanisms.

Ultrasound standoff optimization for maximum image quality of a robot-assisted flat-panel ultrasound device.

Ultrasonography is a widespread intraoperative imaging modality. However, it suffers from several shortcomings e.g. its dependance on the skills of the operator for the image quality. To overcome this shortcoming, Gumprecht et al. [1] recently proposed a new robot-assisted flat-panel ultrasound device for continuous intraoperative imaging during laparoscopic tumor resection in urology. This device is integrated in the OR-table and performs its imaging through the back of a supine patient. The ultrasound probe resides in a tank, filled with a fluid that is traversable by the ultrasound waves. A flexible membrane is stretched over the tank and is in contact with the fluid and the patient. Through is flexibility, the membrane can adapt to the shape of the patient. Therefore, the membrane assures for sufficient coupling of ultrasound waves into the patient. We based the selection of the membrane and the fluid upon the quality of the ultrasound images that can be recorded with this combination. In this paper, we present the results of the experiment that lead to the standoff used in the robotic device of Gumprecht et al. [1].

Basic concepts of optical measuring of bone thickness with IR-beam.

This paper describes a new concept for measuring bone thickness via optically analyzing of hard tissue. In many surgical disciplines effecting bone treatment, like oral and maxillofacial surgery or otolaryngology, the knowledge of existing bone material is very important in order not to hurt anatomically sensitive structures. The existing bone material can be determined preoperatively using imaging procedures. However, the surgeon has no information about the residual bone thickness during the intervention. As a consequence of this, the distance between the tip of his instrument and sensitive structures is also unknown. Therefore, it would be very useful, if the bone thickness could be measured concurrently to the bone ablation. In this work, bone was irradiated with IR-Light and the reflection was detected. It would be examined, if there was an interrelation between bone thickness and reflection and how it could be measured. The results of the experiments show, that by means of this method it is possible to detect different bone thicknesses for a bone thickness < 1 mm.

Evaluation of a resectable ultrasound liver phantom for testing of surgical navigation systems.

A formerly developed ultrasound liver phantom for testing of surgical navigation systems and liver resection trainings was evaluated experimentally. The phantom was scanned with CT and the dataset was analyzed with existing segmentation techniques. A virtual 3D model was generated on the basis of the segmentation; it was later used for phantom registration in a surgical assistance navigation system. Within an experiment, ten test persons have tried to touch three tumor models hidden in the phantom with the tip of a resection instrument. In 67% of overall 30 touch trials it was a successful touch at the first go. It means that the developed liver phantom is appropriate for testing of surgical navigation systems, as well as for computer assisted liver resection trainings.

Official measurement protocol and accuracy results for an optical surgical navigation system (NPU).

Image-guided surgical navigation is on the rise in many different areas of modern medicine and is already an established standard in some disciplines like ear nose and throat (ENT) or maxillofacial surgery. When evaluating surgical navigation systems the absolute accuracy of the device is of major concern to the surgeon. The following work presents two different ways of measuring the accuracy of surgical navigation systems using the example of the KARL STORZ Navigation Panel Unit (NPU). According to these protocols the FDA approval of the NPU navigation system was prepared. In a first series of experiments the accuracy under realistic surgical conditions is evaluated with a phantom of a human head, which is manufactured in rapid-prototyping processes. In another series of experiments a custom registration board is used, which provides means to evaluate the accuracy under optimal conditions and also allows further measurements regarding the registration error, that are not possible with the phantom. In the experiments an accuracy of 1.44 mm ± 0.18 mm was measured in the surgical setup and 0.63 mm ± 0.07 mm under ideal conditions.

Design and accuracy evaluation of a new navigated drill system for computer assisted ENT-surgery.

In this article a new navigated drill system for computer assisted ear, nose and throat (ENT) surgery is presented. The navigated drill and the microscope probe are part of a surgical navigation system for ENT-surgery. In particular, the accuracy of the new navigated drill is compared to an existing navigated drill experimentally under conditions close to the surgical workflow. For the technical accuracy experiment, the new navigated drill in combination with the new microscope probe and a particular navigated measurement board have been integrated, together with the current navigated drill, in a navigation system by a special navigation software with measuring function, based on a standard ENT navigation software. The developed navigated measurement board provided the implementation of reproducible experiments and the direct accuracy comparison of the two navigated instruments under the same conditions. Thereby, N = 15 accuracy experiments are performed with both navigated drill systems with three possible tracker positions. The distance between the planned and the touched points were calculated and compared. The average distances from the planned points to the touched points with the new navigated drill is in the left tracker position 1.10 mm, in the middle tracker position 1.14 mm and in the right tracker position 1.59 mm. In comparison to the existing drill, the new navigated drill, measured with each tracker position, is 0.62 mm more accurate.