Transurethral Anastomosis after Transurethral Radical Prostatectomy: A Phantom Study on Intraluminal Suturing With Concentric Tube Robots.

Current surgical approaches to radical prostatectomy are associated with high rates of erectile dysfunction and incontinence. These complications occur secondary to the disruption of surrounding healthy tissue, which is required to expose the prostate. The urethra offers the least invasive access to the prostate, and feasibility has been demonstrated of enucleating the prostate with an endoscope using Holmium laser, which can itself be aimed by concentric tube robots. However, the transurethral approach to radical prostatectomy has thus far been limited by the lack of a suitable means to perform an anastomosis of the urethra to the bladder after prostate removal. Only a few intraluminal anastomotic devices currently exist, and none are small enough to pass through the urethra. In this paper we describe a new way to perform an anastomosis in the small luminal space of the urethra, harnessing the dexterity and customizability of concentric tube manipulators. We demonstrate a successful initial proof-of-concept anastomosis in an anthropomorphic phantom of the urethra and bladder.

Pre-operative Screening and Manual Drilling Strategies to Reduce the Risk of Thermal Injury During Minimally Invasive Cochlear Implantation Surgery.

This article presents the development and experimental validation of a methodology to reduce the risk of thermal injury to the facial nerve during minimally invasive cochlear implantation surgery. The first step in this methodology is a pre-operative screening process, in which medical imaging is used to identify those patients that present a significant risk of developing high temperatures at the facial nerve during the drilling phase of the procedure. Such a risk is calculated based on the density of the bone along the drilling path and the thermal conductance between the drilling path and the nerve, and provides a criterion to exclude high-risk patients from receiving the minimally invasive procedure. The second component of the methodology is a drilling strategy for manually-guided drilling near the facial nerve. The strategy utilizes interval drilling and mechanical constraints to enable better control over the procedure and the resulting generation of heat. The approach is tested in fresh cadaver temporal bones using a thermal camera to monitor temperature near the facial nerve. Results indicate that pre-operative screening may successfully exclude high-risk patients and that the proposed drilling strategy enables safe drilling for low-to-moderate risk patients.

Increasing Safety of a Robotic System for Inner Ear Surgery Using Probabilistic Error Modeling Near Vital Anatomy.

Safe and effective planning for robotic surgery that involves cutting or ablation of tissue must consider all potential sources of error when determining how close the tool may come to vital anatomy. A pre-operative plan that does not adequately consider potential deviations from ideal system behavior may lead to patient injury. Conversely, a plan that is overly conservative may result in ineffective or incomplete performance of the task. Thus, enforcing simple, uniform-thickness safety margins around vital anatomy is insufficient in the presence of spatially varying, anisotropic error. Prior work has used registration error to determine a variable-thickness safety margin around vital structures that must be approached during mastoidectomy but ultimately preserved. In this paper, these methods are extended to incorporate image distortion and physical robot errors, including kinematic errors and deflections of the robot. These additional sources of error are discussed and stochastic models for a bone-attached robot for otologic surgery are developed. An algorithm for generating appropriate safety margins based on a desired probability of preserving the underlying anatomical structure is presented. Simulations are performed on a CT scan of a cadaver head and safety margins are calculated around several critical structures for planning of a robotic mastoidectomy.

A walking controller for a powered ankle prosthesis.

This paper describes a walking controller implemented on a powered ankle prosthesis prototype and assessed by a below-knee amputee subject on a treadmill at three speeds. The walking controller is a finite state machine which emulates a series of passive impedance functions at the joint in order to reproduce the behavior of a healthy joint. The assessments performed demonstrate the ability of the powered prosthesis prototype and walking controller to reproduce essential biomechanical aspects (i.e. joint angle, torque, and power profiles) of the healthy joint, especially relative to a passive prosthesis.

Minimally invasive image-guided cochlear implantation surgery: first report of clinical implementation.

OBJECTIVES/HYPOTHESIS: Minimally invasive image-guided approach to cochlear implantation (CI) involves drilling a narrow, linear tunnel to the cochlea. Reported herein is the first clinical implementation of this approach. STUDY DESIGN: Prospective cohort study. METHODS: On preoperative computed tomography (CT), a safe linear trajectory through the facial recess targeting the scala tympani was planned. Intraoperatively, fiducial markers were bone-implanted, a second CT was acquired, and the trajectory was transferred from preoperative to intraoperative CT. A customized microstereotactic frame was rapidly designed and constructed to constrain a surgical drill along the desired trajectory. Following sterilization, the frame was employed to drill the tunnel to the middle ear. After lifting a tympanomeatal flap and performing a cochleostomy, the electrode array was threaded through the drilled tunnel and into the cochlea. RESULTS: Eight of nine patients were successfully implanted using the proposed approach with six insertions completely within the scala tympani. Traditional mastoidectomy was performed on one patient following difficulty threading the electrode array via the narrow tunnel. Other difficulties encountered included use of the backup implant when an electrode was dislodged during threading via the tunnel, tip fold-over, and facial nerve paresis (House-Brackmann II/VI at 12 months) secondary to heat during drilling. The average time of intervention was 182 ± 36 minutes. CONCLUSIONS: Minimally invasive image-guided CI is clinically achievable. Further clinical study is necessary to address technological difficulties during drilling and insertion, and to assess potential benefits including decreased time of intervention, standardization of surgical intervention, and decreased tissue dissection potentially leading to shorter recovery and earlier implant activation.

Clinical testing of an alternate method of inserting bone-implanted fiducial markers.

BACKGROUND: Deep brain stimulation (DBS) surgery utilizes image guidance via bone-implanted fiducial markers to achieve the desired submillimetric accuracy and to provide means for attaching microstereotactic frames. For maximal benefit, the markers must be inserted to the correct depth since over-insertion leads to stripping and under-insertion leads to instability. PURPOSE: The purpose of the study was to test clinically a depth-release drive system, the PosiSeat™, versus manual insertion (pilot hole followed by manual screwing until tactile determined correct seating) for implanting fiducial markers into the bone. METHODS: With institutional review board approval, the PosiSeat™ was used to implant markers in 15 DBS patients (57 fiducials). On post-insertion CT scans, the depth of the gap between the shoulder of the fiducial markers and the closest bone surface was measured. Similar depth measurements were performed on the CT scans of 64 DBS patients (250 fiducials), who underwent manual fiducial insertion. RESULTS: Median of shoulder-to-bone distance for PosiSeat™ and manual insertion group were 0.03 and 1.06 mm, respectively. Fifty percent of the fiducials had the shoulder-to-bone distances within 0.01-0.09 mm range for the PosiSeat group and 0.04-1.45 mm range for the manual insertion group. These differences were statistically significant. CONCLUSIONS: A depth-release drive system achieves more consistent placement of bone-implanted fiducial markers than manual insertion.

Validation of minimally invasive, image-guided cochlear implantation using Advanced Bionics, Cochlear, and Medel electrodes in a cadaver model.

PURPOSE: Validation of a novel minimally invasive, image-guided approach to implant electrodes from three FDA-approved manufacturers-Medel, Cochlear, and Advanced Bionics-in the cochlea via a linear tunnel from the lateral cranium through the facial recess to the cochlea. METHODS: Custom microstereotactic frames that mount on bone-implanted fiducial markers and constrain the drill along the desired path were utilized on seven cadaver specimens. A linear tunnel was drilled from the lateral skull to the cochlea followed by a marginal, round window cochleostomy and insertion of the electrode array into the cochlea through the drilled tunnel. Post-insertion CT scan and histological analysis were used to analyze the results. RESULTS: All specimens ([Formula: see text]) were successfully implanted without visible injury to the facial nerve. The Medel electrodes ([Formula: see text]) had minimal intracochlear trauma with 8, 8, and 10 (out of 12) electrodes intracochlear. The Cochlear lateral wall electrodes (straight research arrays) ([Formula: see text]) had minimal trauma with 20 and 21 of 22 electrodes intracochlear. The Advanced Bionics electrodes ([Formula: see text]) were inserted using their insertion tool; one had minimal insertion trauma and 14 of 16 electrodes intracochlear, while the other had violation of the basilar membrane just deep to the cochleostomy following which it remained in scala vestibuli with 13 of 16 electrodes intracochlear. CONCLUSIONS: Minimally invasive, image-guided cochlear implantation is possible using electrodes from the three FDA-approved manufacturers. Lateral wall electrodes were associated with less intracochlear trauma suggesting that they may be better suited for this surgical technique.

Percutaneous cochlear implant drilling via customized frames: an in vitro study.

OBJECTIVE: Percutaneous cochlear implantation (PCI) surgery uses patient-specific customized microstereotactic frames to achieve a single drill-pass from the lateral skull to the cochlea, avoiding vital anatomy. We demonstrate the use of a specific microstereotactic frame, called a "microtable," to perform PCI surgery on cadaveric temporal bone specimens. STUDY DESIGN: Feasibility study using cadaveric temporal bones. SUBJECTS AND METHODS: PCI drilling was performed on six cadaveric temporal bone specimens. The main steps involved were 1) placing three bone-implanted markers surrounding the ear, 2) obtaining a CT scan, 3) planning a safe surgical path to the cochlea avoiding vital anatomy, 4) constructing a microstereotactic frame to constrain the drill to the planned path, and 5) affixing the frame to the markers and using it to drill to the cochlea. The specimens were CT scanned after drilling to show the achieved path. Deviation of the drilled path from the desired path was computed, and the closest distance of the mid-axis of the drilled path from critical structures was measured. RESULTS: In all six specimens, we drilled successfully to the cochlea, preserving the facial nerve and ossicles. In four of six specimens, the chorda tympani was preserved, and in two of six specimens, it was sacrificed. The mean +/- standard deviation error at the target was found to be 0.31 +/- 0.10 mm. The closest distances of the mid-axis of the drilled path to structures were 1.28 +/- 0.17 mm to the facial nerve, 1.31 +/- 0.36 mm to the chorda tympani, and 1.59 +/- 0.43 mm to the ossicles. CONCLUSION: In a cadaveric model, PCI drilling is safe and effective.

Clinical validation study of percutaneous cochlear access using patient-customized microstereotactic frames.

OBJECTIVE: Percutaneous cochlear implant (PCI) surgery consists of drilling a single trough from the lateral cranium to the cochlea avoiding vital anatomy. To accomplish PCI, we use a patient-customized microstereotactic frame, which we call a "microtable" because it consists of a small tabletop sitting on legs. The orientation of the legs controls the alignment of the tabletop such that it is perpendicular to a specified trajectory. STUDY DESIGN: Prospective. SETTING: Tertiary referral center. PATIENTS: Thirteen patients (18 ears) undergoing traditional cochlear implant surgery. INTERVENTIONS: With institutional review board approval, each patient had 3 fiducial markers implanted in bone surrounding the ear. Temporal bone computed tomographic scans were obtained, and the markers were localized, as was vital anatomy. A linear trajectory from the lateral cranium through the facial recess to the cochlea was planned. A microtable was fabricated to follow the specified trajectory. MAIN OUTCOME MEASURES: After mastoidectomy and posterior tympanotomy, accuracy of trajectories was validated by mounting the microtables on the bone-implanted markers and then passing sham drill bits across the facial recess to the cochlea. The distance from the drill to vital anatomy was measured. RESULTS: Microtables were constructed on a computer-numeric-control milling machine in less than 5 minutes each. Successful access across the facial recess to the cochlea was achieved in all 18 cases. The mean +/- SD distance was 1.20 +/- 0.36 mm from midportion of the drill to the facial nerve and 1.25 +/- 0.33 mm from the chorda tympani. CONCLUSION: These results demonstrate the feasibility of PCI access using customized microstereotactic frames.

Accuracy evaluation of microTargeting Platforms for deep-brain stimulation using virtual targets.

Deep-brain-stimulation (DBS) surgery requires implanting stimulators at target positions with submillimetric accuracy. Traditional stereotactic frames can provide such accuracy, but a recent innovation called the microTargeting Platform (FHC, Inc.) replaces this large, universal frame with a single-use, miniature, and custom-designed platform. Both single-target and dual-target platforms are available for unilateral and bilateral procedures, respectively. In this paper, their targeting accuracies are evaluated in vitro. Our approach employs "virtual targets," which eliminates the problem of collision of the implant with the target. We implement virtual targets by mounting fiducial markers, which are not used in platform targeting, on an artificial skull and defining targets relative to the skull via that fiducial system. The fiducial system is designed to surround the targets, thereby reducing the overall effect of fiducial localization inaccuracies on the evaluation. It also provides the geometrical transformation from image to physical space. Target selection is based on an atlas of stimulation targets from a set of 31 DBS patients. The measured targeting error is the displacement between the phantom implant and the virtual target. Our results show that the microTargeting Platform exhibits submillimetric in vitro accuracy with a mean of 0.42 mm and a 99.9% level of 0.90 mm.