Mathieu Miroir

Friction force measurement during cochlear implant insertion: application to a force-controlled insertion tool design

Hypothesis The aim of the study was to evaluate force profiles during array insertion in human cochlea specimens and to evaluate a mechatronic inserter using a 1-axis force sensor. Background Today, the surgical challenge in cochlear implantation is the preservation of the anatomic structures and the residual hearing. In routine practice, the electrode array is inserted manually with a limited sensitive feedback. Materials and Methods Hifocus 1J electrode arrays were studied. The bench test comprised a mechatronic inserter combined to a 1-axis force sensor between the inserter and the base of the array and a 6-axis force sensor beneath the cochlea model. Influence of insertion tube material, speed (0.15, 0.5, and 1.5 mm/s) and lubricant on frictions forces were studied (no-load). Different models were subsequently evaluated: epoxy scala tympani model and temporal bones. Results Frictions forces were lower in the plastic tube compared with those in the metal tube (0.09 ± 0.028 versus 0.14 ± 0.034 at 0.5 mm/s, p < 0.001) and with the use of hyaluronic acid gel. Speed did not influence frictions forces in our study. Insertion force profiles provided by the 1- and 6-axis force sensors were similar when friction forces inside the insertion tool (no-load measurements) were subtracted from the 1-axis sensor data in the epoxy and temporal bone models (mean error, 0.01 ± 0.001 N). Conclusion Using a sensor included in the inserter, we were able to measure array insertion forces. This tool can be potentially used to provide real-time information to the surgeon during the procedure.

RobOtol: from design to evaluation of a robot for middle ear surgery

Middle ear surgery requires micro-surgical techniques and may benefit from robotic assistance. A prototype of tele-operated system is presented. Methods to determine design specifications, kinematic structure and optimization of the micro-manipulator are described. First evaluation of the robot by a stapedial removal through the external auditory meatus in human temporal bone specimens, simulating the surgery of otosclerosis, is presented. In this procedure, the robot yielded accessibility to the target area with a reduced visual impairment and, an enhanced tool stability compared to the surgeons hand.

Design, Kinematic Optimization, and Evaluation of a Teleoperated System for Middle Ear Microsurgery

Middle ear surgery involves the smallest and the most fragile bones of the human body. Since microsurgical gestures and a submillimetric precision are required in these procedures, the outcome can be potentially improved by robotic assistance. Today, there is no commercially available device in this field. Here, we describe a method to design a teleoperated assistance robotic system dedicated to the middle ear surgery. Determination of design specifications, the kinematic structure, and its optimization are detailed. The robot-surgeon interface and the command modes are provided. Finally, the system is evaluated by realistic tasks in experimental dedicated settings and in human temporal bone specimens.

Definition of Metrics to Evaluate Cochlear Array Insertion Forces Performed with Forceps, Insertion Tool, or Motorized Tool in Temporal Bone Specimens

Introduction. In order to achieve a minimal trauma to the inner ear structures during array insertion, it would be suitable to control insertion forces. The aim of this work was to compare the insertion forces of an array insertion into anatomical specimens with three different insertion techniques: with forceps, with a commercial tool, and with a motorized tool. Materials and Methods. Temporal bones have been mounted on a 6-axis force sensor to record insertion forces. Each temporal bone has been inserted, with a lateral wall electrode array, in random order, with each of the 3 techniques. Results. Forceps manual and commercial tool insertions generated multiple jerks during whole length insertion related to fits and starts. On the contrary, insertion force with the motorized tool only rose at the end of the insertion. Overall force momentum was 1.16 ± 0.505 N (mean ± SD, n = 10), 1.337 ± 0.408 N (n = 8), and 1.573 ± 0.764 N (n = 8) for manual insertion with forceps and commercial and motorized tools, respectively. Conclusion. Considering force momentum, no difference between the three techniques was observed. Nevertheless, a more predictable force profile could be observed with the motorized tool with a smoother rise of insertion forces.

Validation method of a middle ear mechanical model to develop a surgical simulator.

Ossicular surgery requires a high dexterity for the manipulation of the fragile and small middle ear components. Currently, the only efficient technique for training residents in otological surgery is through the use of temporal bone specimens, where any existing surgical simulator does not provide useful feedback. The objective of this study was to develop a finite-element model of the human ossicular chain dedicated to surgical simulation and to propose a method to evaluate its behavior. A model was developed based on human middle ear micromagnetic resonance imaging. The mechanical parameters were determined according to published data. To assess its performance, the middle ear transfer function was analyzed. The robustness of our model and the influence of different middle ear components were also evaluated at low frequency by static force pressure simulations. The mechanical behavior of our model in nominal and pathological conditions was in good agreement with published human temporal bone measurements. We showed that the cochlea influences the transfer function only at high frequency and could be omitted from a surgical simulator. In addition, surgeons were able to manipulate the validated middle ear model with a real-time haptic feedback. The computational efficiency of our approach allowed real-time interactions, making it suitable for use in a training simulator.

Effect of embedded dexamethasone in cochlear implant array on insertion forces in an artificial model of scala tympani.

Hypothesis Loading otoprotective drug into cochlear implant might change its mechanical properties, thus compromising atraumatic insertion. This study evaluated the effect of incorporation of dexamethasone (DXM) in the silicone of cochlear implant arrays on insertion forces. Background Local administration of DXM with embedded array can potentially reduce inflammation and fibrosis after cochlear implantation procedure to improve hearing preservation and reduce long-term impedances. Methods Four models of arrays have been tested: 0.5-mm distal diameter array (n = 5) used as a control, drug-free 0.4-mm distal diameter array (n = 5), 0.4-mm distal diameter array with 1% eluded DXM silicone (n = 5), and 0.4-mm distal diameter array with 10% eluded DXM silicone (n = 5). Via a motorized insertion bench, each array has been inserted into an artificial scala tympani model. The forces were recorded by a 6-axis force sensor. Each array was tested seven times for a total number of 140 insertions. Results During the first 10-mm insertion, no difference between the four models was observed. From 10- to 24-mm insertion, the 0.5-mm distal diameter array presented higher insertion forces than the drug-free 0.4-mm distal diameter arrays, with or without DXM. Friction forces for drug-free 0.4-mm distal diameter array and 0.4-mm distal diameter DXM eluded arrays were similar on all insertion lengths. Conclusion Incorporation of DXM in silicone for cochlear implant design does not change electrode array insertion forces. It does not raise the risk of trauma during array insertion, making it suitable for long-term in situ administration to the cochlea.

Middle-Ear Microsurgery Simulation to Improve New Robotic Procedures

Otological microsurgery is delicate and requires high dexterity in bad ergonomic conditions. To assist surgeons in these indications, a teleoperated system, called RobOtol, is developed. This robot enhances gesture accuracy and handiness and allows exploration of new procedures for middle ear surgery. To plan new procedures that exploit the capacities given by the robot, a surgical simulator is developed. The simulation reproduces with high fidelity the behavior of the anatomical structures and can also be used as a training tool for an easier control of the robot for surgeons. In the paper, we introduce the middle ear surgical simulation and then we perform virtually two challenging procedures with the robot. We show how interactive simulation can assist in analyzing the benefits of robotics in the case of complex manipulations or ergonomics studies and allow the development of innovative surgical procedures. New robot-based microsurgical procedures are investigated. The improvement offered by RobOtol is also evaluated and discussed.

Design of a robotic system for minimally invasive surgery of the middle ear

The tele-operated system with three arms for the microsurgery of the middle ear is composed of an operator console from where the surgeon tele-operates three robotized arms that hold surgery tools with a high level of accuracy. The main difference between these micromanipulators and the conventional minimally-invasive surgery robots is the increased field of vision capacity to carry out complex operational gestures without using dexterous tool with intra-body mobility. The method used to design the micromanipulator tool holder is described. A first task consists of analyzing functional specifications. The next step is to define and select a kinematic structure adapted to the task. Finally, a dimensional optimization is carried out by using Pareto front method.

Registration of a Validated Mechanical Atlas of Middle Ear for Surgical Simulation

This paper is centered on the development of a new training and rehearsal simulation system for middle ear surgery. First, we have developed and validated a mechanical atlas based on finite element method of the human middle ear. The atlas is based on a microMRI. Its mechanical behavior computed in real-time has been successfully validated. In addition, we propose a method for the registration of the mechanical atlas on patient imagery. The simulation can be used for a rehearsal surgery with the geometrical anatomy of a given patient and with mechanical data that are validated. Moreover, this process does not necessitate a complete re-built of the model.

Super paramagnetic nanoparticles delivery through a microcatheter by solenoids

In order to design a drug delivery system to the human cochlea, a magnetic pump driving Fe3O4 super paramagnetic nanoparticles (MNP) attachable to a drug was evaluated. Such a device could be inserted into the cochlea by a minimally invasive technique. In this study, the effect of a magnetic field generated by solenoids coiled around a 1 mm diameter catheter filled with 200 nm MNP was studied. Results showed that, particles can be concentrated at different locations of the catheter for a precise delivery at different cochlear locations. The particles could also be driven between 2 solenoids 50 mm apart with 150 mA which is compatible with current sources in available cochlear implants.