Loss of finger control complexity and intrusion of flexor biases are dissociable in finger individuation impairment after stroke.

The ability to control each finger independently is an essential component of human hand dexterity. A common observation of hand function impairment after stroke is the loss of this finger individuation ability, often referred to as enslavement, i.e., the unwanted coactivation of non-intended fingers in individuated finger movements. In the previous literature, this impairment has been attributed to several factors, such as the loss of corticospinal drive, an intrusion of flexor synergy due to upregulations of the subcortical pathways, and/or biomechanical constraints. These factors may or may not be mutually exclusive and are often difficult to tease apart. It has also been suggested, based on a prevailing impression, that the intrusion of flexor synergy appears to be an exaggerated pattern of the involuntary coactivations of task-irrelevant fingers seen in a healthy hand, often referred to as a flexor bias. Most previous studies, however, were based on assessments of enslavement in a single dimension (i.e., finger flexion/extension) that coincide with the flexor bias, making it difficult to tease apart the other aforementioned factors. Here, we set out to closely examine the nature of individuated finger control and finger coactivation patterns in all dimensions. Using a novel measurement device and a 3D finger-individuation paradigm, we aim to tease apart the contributions of lower biomechanical, subcortical constraints, and top-down cortical control to these patterns in both healthy and stroke hands. For the first time, we assessed all five fingers' full capacity for individuation. Our results show that these patterns in the healthy and paretic hands present distinctly different shapes and magnitudes that are not influenced by biomechanical constraints. Those in the healthy hand presented larger angular distances that were dependent on top-down task goals, whereas those in the paretic hand presented larger Euclidean distances that arise from two dissociable factors: a loss of complexity in finger control and the dominance of an intrusion of flexor bias. These results suggest that finger individuation impairment after stroke is due to two dissociable factors: the loss of finger control complexity present in the healthy hand reflecting a top-down neural control strategy and an intrusion of flexor bias likely due to an upregulation of subcortical pathways. Our device and paradigm are demonstrated to be a promising tool to assess all aspects of the dexterous capacity of the hand.

Novel Planar Strain Sensor Design for Capturing 3-Dimensional Fingertip Forces from Patients Affected by Hand Paralysis.

Assessment and therapy for individuals who have hand paresis requires force sensing approaches that can measure a wide range of finger forces in multiple dimensions. Here we present a novel strain-gauge force sensor with 3 degrees of freedom (DOF) designed for use in a hand assessment and rehabilitation device. The sensor features a fiberglass printed circuit board substrate to which eight strain gauges are bonded. All circuity for the sensor is routed directly through the board, which is secured to a larger rehabilitative device via an aluminum frame. After design, the sensing package was characterized for weight, capacity, and resolution requirements. Furthermore, a test sensor was calibrated in a three-axis configuration and validated in the larger spherical workspace to understand how accurate and precise the sensor is, while the sensor has slight shortcomings with validation error, it does satisfy the precision, calibration accuracy, and fine sensing requirements in orthogonal loading, and all structural specifications are met. The sensor is therefore a great candidate for sensing technology in rehabilitation devices that assess dexterity in patients with impaired hand function.

Robotic microlaryngeal phonosurgery: Testing of a "steady-hand" microsurgery platform.

OBJECTIVES/HYPOTHESIS: To evaluate gains in microlaryngeal precision achieved by using a novel robotic "steady hand" microsurgery platform in performing simulated phonosurgical tasks. STUDY DESIGN: Crossover comparative study of surgical performance and descriptive analysis of surgeon feedback. METHODS: A novel robotic ear, nose, and throat microsurgery system (REMS) was tested in simulated phonosurgery. Participants navigated a 0.4-mm-wide microlaryngeal needle through spirals of varying widths, both with and without robotic assistance. Fail time (time the needle contacted spiral edges) was measured, and statistical comparison was performed. Participants were surveyed to provide subjective feedback on the REMS. RESULTS: Nine participants performed the task at three spiral widths, yielding 27 paired testing conditions. In 24 of 27 conditions, robot-assisted performance was better than unassisted; five trials were errorless, all achieved with the robot. Paired analysis of all conditions revealed fail time of 0.769 ± 0.568 seconds manually, improving to 0.284 ± 0.584 seconds with the robot (P = .003). Analysis of individual spiral sizes showed statistically better performance with the REMS at spiral widths of 2 mm (0.156 ± 0.226 seconds vs. 0.549 ± 0.545 seconds, P = .019) and 1.5 mm (0.075 ± 0.099 seconds vs. 0.890 ± 0.518 seconds, P = .002). At 1.2 mm, all nine participants together showed similar performance with and without robotic assistance (0.621 ± 0.923 seconds vs. 0.868 ± 0.634 seconds, P = .52), though subgroup analysis of five surgeons most familiar with microlaryngoscopy showed statistically better performance with the robot (0.204 ± 0.164 seconds vs. 0.664 ± 0.354 seconds, P = .036). CONCLUSIONS: The REMS is a novel platform with potential applications in microlaryngeal phonosurgery. Further feasibility studies and preclinical testing should be pursued as a bridge to eventual clinical use. LEVEL OF EVIDENCE: NA. Laryngoscope, 128:126-132, 2018.

The robotic ENT microsurgery system: A novel robotic platform for microvascular surgery.

OBJECTIVE: Assess the feasibility of a novel robotic platform for use in microvascular surgery. STUDY DESIGN: Prospective feasibility study. SETTING: Robotics laboratory. METHODS: The Robotic ENT (Ear, Nose, and Throat) Microsurgery System (REMS) (Galen Robotics, Inc., Sunnyvale, CA) is a robotic arm that stabilizes a surgeon's instrument, allowing precise, tremor-free movement. Six microvascular naïve medical students and one microvascular expert performed microvascular anastomosis of a chicken ischiatic artery, with and without the REMS. Trials were blindly graded by seven microvascular surgeons using a microvascular tremor scale (MTS) based on instrument tip movement as a function of vessel width. Time to completion (TTC) was measured, and an exit survey assessed participants' experience. The interrater reliability of the MTS was calculated. RESULTS: For microvascular-naïve participants, the mean MTS score for REMS-assisted trials was 0.72 (95% confidence interval [CI] 0.64-1.07) and 2.40 (95% CI 2.12-2.69) for freehand (P < 0.001). The mean TTC was 1,265 seconds for REMS-assisted trials and 1,320 seconds for freehand (P > 0.05). For the microvascular expert, the mean REMS-assisted MTS score was 0.71 (95% CI 0.15-1.27) and 0.86 (95% CI 0.35-1.37) for freehand (P > 0.05). TTC was 353 seconds for the REMS-assisted trial and 299 seconds for freehand. All participants thought the REMS was more accurate and improved instrument handling and stability. The intraclass correlation coefficient for MTS ratings was 0.914 (95% CI 0.823-0.968) for consistency and 0.901 (95% CI 0.795-0.963) for absolute value. CONCLUSION: The REMS is a feasible adjunct for microvascular surgery and a potential teaching tool capable of reducing tremor in novice users. Furthermore, the MTS is a feasible grading system for assessing microvascular tremor. LEVEL OF EVIDENCE: NA. Laryngoscope, 127:2495-2500, 2017.

Accuracy assessment and kinematic calibration of the robotic endoscopic microsurgical system.

This paper explores the general stereotactic accuracy of the Robotic Endoscopic Microsurgical System (REMS) by calibrating with a standard optical tracking system. Based on a simple yet effective test protocol, the proposed calibration method combines hand-eye calibration with Bernstein polynomials to improve our kinematic pose accuracy.

Human eye phantom for developing computer and robot-assisted epiretinal membrane peeling.

A number of technologies are being developed to facilitate key intraoperative actions in vitreoretinal microsurgery. There is a need for cost-effective, reusable benchtop eye phantoms to enable frequent evaluation of these developments. In this study, we describe an artificial eye phantom for developing intraocular imaging and force-sensing tools. We test four candidate materials for simulating epiretinal membranes using a handheld tremor-canceling micromanipulator with force-sensing micro-forceps tip and demonstrate peeling forces comparable to those encountered in clinical practice.

A force-sensing microsurgical instrument that detects forces below human tactile sensation.

PURPOSE: To test the sensitivity and reproducibility of a 25-gauge force-sensing micropick during microsurgical maneuvers that are below tactile sensation. METHODS: Forces were measured during membrane peeling in a "raw egg" and the chick chorioallantoic membrane models (N = 12) of epiretinal membranes. Forces were also measured during posterior hyaloid detachment and creation of retinal tears during vitrectomy in live rabbits (n = 6). RESULTS: With the raw egg model, 0.5 ± 0.4 mN of force was detected during membrane peeling. In the chorioallantoic membrane model, delaminating the upper membrane produced 2.8 ± 0.2 mN of force. While intentionally rupturing the lower membrane to simulate a retinal tear, 7.3 ± 0.5 mN (range, 5.1-9.2 mN; P < 0.001) of force was generated while peeling the upper membrane. During vitrectomy, the minimum force that detached the posterior hyaloid was 6.7 ± 1.1 mN, which was similar to the force of 6.4 ± 1.4 mN that caused a retinal tear. The rate of force generation, as indicated by the first derivative of force generation, was 3.4 ± 1.2 mN/second during posterior hyaloid detachment, compared with 7.7 ± 2.4 mN/second during the creation of a retinal tear (P = 0.04). CONCLUSION: Force-sensing microsurgical instruments can detect forces below tactile sensation, and importantly, they can distinguish the forces generated during normal maneuvers from those that cause a surgical complication.

A robotic assistant for trans-oral surgery: the robotic endo-laryngeal flexible (Robo-ELF) scope.

This paper describes the continued development of the Robotic EndoLaryngeal (Robo-ELF) Scope System, a simple clinically usable robot for manipulating flexible endoscopes, particularly in laryngeal surgery. The system includes a robot with three active and two passive degrees of freedom, a five degree of freedom passive positioning arm, a malleable scope shaft support, and a custom joystick controller. The Robo-ELF Scope allows a surgeon to control a flexible endoscope with only one hand and also to release the controls and perform bimanual surgery if desired. We have evaluated the Robo-ELF Scope system in both phantom and cadaver studies and found it superior to hand manipulation of flexible endoscopes and conventional rigid endoscopes.

Robotic endolaryngeal flexible (Robo-ELF) scope: a preclinical feasibility study.

OBJECTIVES/HYPOTHESIS: This article presents a novel robotic endolaryngeal flexible (Robo-ELF) scope driver for minimally invasive laryngeal surgery. The Robo-ELF consists of a simple, robust robotic scope driver with three active and two passive degrees of freedom, allowing it to manipulate any standard flexible endoscope. The system is controlled by a joystick-like three dimensional mouse that interfaces with the scope driver via a laptop. Because the scope is supported and controlled by the robot, motor control and therefore visualization are enhanced. Additionally, because the robot remains stationary when the mouse is not being manipulated, the surgeon can position it and operate bimanually. METHODS: The system was validated by performing visualization and biopsy procedures on two human cadavers with the Robo-ELF and comparing this with standard rigid endoscopes with three different angles. RESULTS: The Robo-ELF outperformed the rigid scopes in both image quality and range of motion, overcoming line of site constraints, and allowing visualization of otherwise hidden anatomy. The system also demonstrated a rapid learning curve and enhanced motor control over a manually operated flexible endoscope. CONCLUSIONS: The Robo-ELF is a novel robot to assist in driving a flexible endoscope for surgery of the upper aerodigestive tract.