Walking with added mass magnifies salient features of human foot energetics.

The human foot serves numerous functional roles during walking, including shock absorption and energy return. Here, we investigated walking with added mass to determine how the foot would alter its mechanical work production in response to a greater force demand. Twenty-one healthy young adults walked with varying levels of added body mass: 0%, +15% and +30% (relative to their body mass). We quantified mechanical work performed by the foot using a unified deformable segment analysis and a multi-segment foot model. We found that walking with added mass tended to magnify certain features of the foot's functions. Magnitudes of both positive and negative mechanical work, during stance in the foot, increased when walking with added mass. Yet, the foot preserved similar amounts of net negative work, indicating that the foot dissipates energy overall. Furthermore, walking with added mass increased the foot's negative work during early stance phase, highlighting the foot's role as a shock-absorber. During mid to late stance, the foot produced greater positive work when walking with added mass, which coincided with greater work from the structures spanning the midtarsal joint (i.e. arch). While this study captured the overall behavior of the foot when walking with varying force demands, future studies are needed to further determine the relative contribution of active muscles and elastic tissues to the foot's overall energy.

A sensorless force-feedback system for robot-assisted laparoscopic surgery.

The existing surgical robots for laparoscopic surgery offer no or limited force feedback, and there are many problems for the traditional sensor-based solutions. This paper builds a teleoperation surgical system and validates the effectiveness of sensorless force feedback. The tool-tissue interaction force at the surgical grasper tip is estimated using the driving motor's current, and fed back to the master robot with position-force bilateral control algorithm. The stiffness differentiation experiment and tumor detection experiment were conducted. In the stiffness differentiation experiment, 43 out of 45 pairs of ranking relationships were identified correctly, yielding a success rate of 96%. In the tumor detection experiment, 4 out of 5 participants identified the correct tumor location with force feedback, yielding a success rate of 80%. The proposed sensorless force-feedback system for robot-assisted laparoscopic surgery can help surgeons regain tactile information and distinguish between the healthy and cancerous tissue.

Performance of a Multifunctional Robot for Natural Orifice Transluminal Endoscopic Surgery.

Natural orifice transluminal endoscopic surgery (NOTES) has gained attention as a revolutionary technique with its potential advantages in eliminating skin incisions, shortening recovery time, and decreasing postoperative complications; however, its practical application is still constrained by the complexity of navigation through the surgical field and paucity of available instruments. Current progress on NOTES focuses on designing flexible articulated robots or fully inserted bimanual robots to address the limitations. However, the lack of multitasking tools, trade-offs between size and power, and lack of sufficient surgical force are too often neglected. The authors designed a bimanual robot with a multifunctional manipulator, which can realize on-site instrument-change according to surgeon needs. An articulated drive mechanism with 2 independent curvature sections was designed to deliver the robot to the surgical site. A corresponding reconfiguration operation sequence was formulated to ease insertion and thereby decrease the design trade-off between size and power. This article presents 3 benchtop and animal tests to evaluate the robotic surgery approach and demonstrate the effectiveness of the robot.

Virtual Reality Training System for Anytime/Anywhere Acquisition of Surgical Skills: A Pilot Study.

This article presents a hardware/software simulation environment suitable for anytime/anywhere surgical skills training. It blends the advantages of physical hardware and task analogs with the flexibility of virtual environments. This is further enhanced by a web-based implementation of training feedback accessible to both trainees and trainers. Our training system provides a self-paced and interactive means to attain proficiency in basic tasks that could potentially be applied across a spectrum of trainees from first responder field medical personnel to physicians. This results in a powerful training tool for surgical skills acquisition relevant to helping injured warfighters.

Eigenstrain as a mechanical set-point of cells.

Cell contraction regulates how cells sense their mechanical environment. We sought to identify the set-point of cell contraction, also referred to as tensional homeostasis. In this work, bovine aortic endothelial cells (BAECs), cultured on substrates with different stiffness, were characterized using traction force microscopy (TFM). Numerical models were developed to provide insights into the mechanics of cell-substrate interactions. Cell contraction was modeled as eigenstrain which could induce isometric cell contraction without external forces. The predicted traction stresses matched well with TFM measurements. Furthermore, our numerical model provided cell stress and displacement maps for inspecting the fundamental regulating mechanism of cell mechanosensing. We showed that cell spread area, traction force on a substrate, as well as the average stress of a cell were increased in response to a stiffer substrate. However, the cell average strain, which is cell type-specific, was kept at the same level regardless of the substrate stiffness. This indicated that the cell average strain is the tensional homeostasis that each type of cell tries to maintain. Furthermore, cell contraction in terms of eigenstrain was found to be the same for both BAECs and fibroblast cells in different mechanical environments. This implied a potential mechanical set-point across different cell types. Our results suggest that additional measurements of contractility might be useful for monitoring cell mechanosensing as well as dynamic remodeling of the extracellular matrix (ECM). This work could help to advance the understanding of the cell-ECM relationship, leading to better regenerative strategies.

Evaluation of Augmented Reality Feedback in Surgical Training Environment.

Providing computer-based laparoscopic surgical training has several advantages that enhance the training process. Self-evaluation and real-time performance feedback are 2 of these advantages, which avoid dependency of trainees on expert feedback. The goal of this study was to investigate the use of a visual time indicator as real-time feedback correlated with the laparoscopic surgical training. Twenty novices participated in this study working with (and without) different presentations of time indicators. They performed a standard peg transfer task, and their completion times and muscle activity were recorded and compared. Also of interest was whether the use of this type of feedback induced any side effect in terms of motivation or muscle fatigue. RESULTS: Of the 20 participants, 15 (75%) preferred using a time indicator in the training process rather than having no feedback. However, time to task completion showed no significant difference in performance with the time indicator; furthermore, no significant differences in muscle activity or muscle fatigue were detected with/without time feedback. CONCLUSION: The absence of significant difference between task performance with/without time feedback shows that using visual real-time feedback can be included in surgical training based on user preference. Trainees may benefit from this type of feedback in the form of increased motivation. The extent to which this can influence training frequency leading to performance improvement is a question for further study.

Design and Validation of a Biosensor Implantation Capsule Robot.

We have proposed a long-term, noninvasive, nonrestrictive method of delivering and implanting a biosensor within the body via a swallowable implantation capsule robot (ICR). The design and preliminary validation of the ICR's primary subsystem-the sensor deployment system-is discussed and evidence is provided for major design choices. The purpose of the sensor deployment system is to adhere a small biosensor to the mucosa of the intestine long-term, and the modality was inspired by tapeworms and other organisms that employ a strategy of mechanical adhesion to soft tissue via the combined use of hooks or needles and suckers. Testing was performed to refine the design of the suction and needle attachment as well as the sensor ejection features of the ICR. An experiment was conducted in which needle sharpness, needle length, and vacuum volume were varied, and no statistically significant difference was observed. Finally, preliminary testing, coupled with prior work within a live porcine model, provided evidence that this is a promising approach for implanting a biosensor within the small intestine.

Hydraulic Robotic Surgical Tool Changing Manipulator.

Natural orifice transluminal endoscopic surgery (NOTES) is a surgical technique to perform "scarless" abdominal operations. Robotic technology has been exploited to improve NOTES and circumvent its limitations. Lack of a multitasking platform is a major limitation. Manual tool exchange can be time consuming and may lead to complications such as bleeding. Previous multifunctional manipulator designs use electric motors. These designs are bulky, slow, and expensive. This paper presents design, prototyping, and testing of a hydraulic robotic tool changing manipulator. The manipulator is small, fast, low-cost, and capable of carrying four different types of laparoscopic instruments.

Disposable Fluidic Actuators for Miniature In-Vivo Surgical Robotics.

Fusion of robotics and minimally invasive surgery (MIS) has created new opportunities to develop diagnostic and therapeutic tools. Surgical robotics is advancing from externally actuated systems to miniature in-vivo robotics. However, with miniaturization of electric-motor-driven surgical robots, there comes a trade-off between the size of the robot and its capability. Slow actuation, low load capacity, sterilization difficulties, leaking electricity and transferring produced heat to tissues, and high cost are among the key limitations of the use of electric motors in in-vivo applications. Fluid power in the form of hydraulics or pneumatics has a long history in driving many industrial devices and could be exploited to circumvent these limitations. High power density and good compatibility with the in-vivo environment are the key advantages of fluid power over electric motors when it comes to in-vivo applications. However, fabrication of hydraulic/pneumatic actuators within the desired size and pressure range required for in-vivo surgical robotic applications poses new challenges. Sealing these types of miniature actuators at operating pressures requires obtaining very fine surface finishes which is difficult and costly. The research described here presents design, fabrication, and testing of a hydraulic/pneumatic double-acting cylinder, a limited-motion vane motor, and a balloon-actuated laparoscopic grasper. These actuators are small, seal-less, easy to fabricate, disposable, and inexpensive, thus ideal for single-use in-vivo applications. To demonstrate the ability of these actuators to drive robotic joints, they were modified and integrated in a robotic arm. The design and testing of this surgical robotic arm are presented to validate the concept of fluid-power actuators for in-vivo applications.

Design and preliminary evaluation of a self-steering, pneumatically driven colonoscopy robot.

Colonoscopy is a diagnostic procedure to detect pre-cancerous polyps and tumours in the colon, and is performed by inserting a long tube equipped with a camera and biopsy tools. Despite the medical benefits, patients undergoing this procedure often complain about the associated pain and discomfort. This discomfort is mostly due to the rough handling of the tube and the creation of loops during the insertion. The overall goal of this work is to minimise the invasiveness of traditional colonoscopy. In pursuit of this goal, this work presents the development of a semi-autonomous colonoscopic robot with minimally invasive locomotion. The proposed robotic approach allows physicians to concentrate mainly on the diagnosis rather than the mechanics of the procedure. In this paper, an innovative locomotion approach for robotic colonoscopy is addressed. Our locomotion approach takes advantage of longitudinal expansion of a latex tube to propel the robot's tip along the colon. This soft and compliant propulsion mechanism, in contrast to minimally invasive mechanisms used in, for example, inchworm-like robots, has shown promising potential. In the preliminary ex vivo experiments, the robot successfully advanced 1.5 metres inside an excised curvilinear porcine colon with average speed of 28 mm/s, and was capable of traversing bends up to 150 degrees. The robot creates less than 6 N of normal force at its tip when it is pressurised with 90 kPa. This maximum force generates pressure of 44.17 mmHg at the tip, which is significantly lower than safe intraluminal human colonic pressure of 80 mmHg. The robot design inherently prevents loop formation in the colon, which is recognised as the main cause of post procedural pain in patients. Overall, the robot has shown great promise in an ex vivo experimental setup. The design of an autonomous control system and in vivo experiments are left as future work.

Kinematic and muscle demand similarities between motor-assisted elliptical training and walking: Implications for pediatric gait rehabilitation.

Many children with physical disabilities and special health care needs experience barriers to accessing effective therapeutic technologies to improve walking and fitness in healthcare and community environments. The expense of many robotic and exoskeleton technologies hinders widespread use in most clinics, school settings, and fitness facilities. A motor-assisted elliptical trainer that is being used to address walking and fitness deficits in adults was modified to enable children as young as three years of age to access the technology (Pedi-ICARE). We compared children's kinematic and muscle activation patterns during walking and training on the Pedi-ICARE. Eighteen children walked (self-selected comfortable speed), Pedi-ICARE trained with motor-assistance at self-selected comfortable speed (AAC), and trained while over-riding motor-assistance (AAC+). Coefficient of multiple correlations (CMCs) compared lower extremity kinematic profiles during AAC and AAC+ to gait. Repeated measures ANOVAs identified muscle demand differences across conditions. CMCs revealed strong similarities at the hip and knee between each motor-assisted elliptical condition and gait. Ankle CMCs were only moderate. Muscle demands were generally lowest during AAC. Over-riding the motor increased hip and knee muscle demands. The similarity of motion patterns between Pedi-ICARE conditions and walking suggest the device could be used to promote task-specific training to improve walking. The capacity to manipulate muscle demands using different motor-assistance conditions highlights Pedi-ICARE's versatility in addressing a wide range of children's abilities.

Estimating Tool-Tissue Forces Using a 3-Degree-of-Freedom Robotic Surgical Tool.

Robot-assisted minimally invasive surgery (MIS) has gained popularity due to its high dexterity and reduced invasiveness to the patient; however, due to the loss of direct touch of the surgical site, surgeons may be prone to exert larger forces and cause tissue damage. To quantify tool-tissue interaction forces, researchers have tried to attach different kinds of sensors on the surgical tools. This sensor attachment generally makes the tools bulky and/or unduly expensive and may hinder the normal function of the tools; it is also unlikely that these sensors can survive harsh sterilization processes. This paper investigates an alternative method by estimating tool-tissue interaction forces using driving motors' current, and validates this sensorless force estimation method on a 3-degree-of-freedom (DOF) robotic surgical grasper prototype. The results show that the performance of this method is acceptable with regard to latency and accuracy. With this tool-tissue interaction force estimation method, it is possible to implement force feedback on existing robotic surgical systems without any sensors. This may allow a haptic surgical robot which is compatible with existing sterilization methods and surgical procedures, so that the surgeon can obtain tool-tissue interaction forces in real time, thereby increasing surgical efficiency and safety.

Intravesical tunnel length to ureteral diameter ratio insufficiently explains ureterovesical junction competence: A parametric simulation study.

OBJECTIVE: In 1959, Paquin recommended a tunnel length five times the diameter of the ureter to prevent vesicoureteral reflux (VUR) during ureteral reimplants. In 1969, Lyon et al. challenged Paquin's conclusions and proposed that the ureteral orifice was more important than the intravesical tunnel for UVJ competence. It is not known if the two mechanisms of UVJ competence (tunnel length and UO spatial orientation) are interdependent or if one is more critical. Although in clinical practice Paquin's rule has stood the test of time, classical mechanics of materials would predict more coaptation (less reflux) with larger diameter ureters and this contradicts Paquin's rule. The aim of this study was to test Paquin's tunnel length theory by parametrically modeling the ureterovesical junction (UVJ) to determine variables critical for ureteral closure. STUDY DESIGN: LS-DYNA finite-element simulation software was use to model ureteral collapse (Figure). Intravesical tunnel length, ureteral diameter, ureteral thickness and ureteral stiffness were all modeled. Changes in the pressure required to collapse the ureter were studied as each variable was changed on the model. The modeled ureteral orifice was not affected by changes in bladder volume (in a real bladder, bladder distention would pull the ureteral office open) and had no constraints (which could occur by suturing the ureteral orifice to a stiff bladder). RESULTS: As predicted by classical mechanics of materials, the pressure required to collapse the ureter was inversely related to its diameter. Above 1 cm tunnel length, pressures required to collapse a ureter did not decrease by any significant amount. Increasing ureteral thickness or ureteral stiffness did increase the pressure required to collapse the ureter, but only significantly for ureteral thicknesses not commonly seen in practice (i.e. wall thickness of 2.5 mm in a 6.4 mm ureter). DISCUSSION: Our model showed that for most ureters seen in clinical practice (3-30 mm in diameter), and when the ureteral orifice is not constrained by the bladder mucosa, a 1 cm tunnel would allow the ureter to collapse under low pressures. Contrary to Paquin's belief, larger diameter ureters collapsed more easily. It is important to understand that our model's main limitation was that it did not study the effects of the ureteral orifice, which in light of our findings must play an important role in preventing reflux as suggested by Lyon et al., in 1969. For example, a 3 cm ureteral orifice sutured to the bladder mucosa would be difficult to collapse as the bladder distends and pulls open the orifice. One way of compensating for a difficult to collapse ureteral orifice would be creating a larger diameter tunnel, but another would be to create a better ureteral orifice, perhaps by narrowing the diameter of the UO (distal ureteral tapering) and making it protrude into the bladder like a volcano (i.e. advancement sutures, or creating an intravesical nipple). CONCLUSION: We hope that this new understanding of the variables involved in ureterovesical junction competence can lead to further refinement in our surgical techniques to correct vesicoureteral reflux.

Design and Analysis of a Novel Articulated Drive Mechanism for Multifunctional NOTES Robot.

This paper presents a novel articulated drive mechanism (ADM) for a multifunctional natural orifice transluminal endoscopic surgery (NOTES) robotic manipulator. It consists mainly of three major components including a snakelike linkage, motor housing, and an arm connector. The ADM can articulate into complex shapes for improved access to surgical targets. A connector provides an efficient and convenient modularity for insertion and removal of the robot. Four DC motors guide eight cables to steer the robot. The workspace, cable displacement and force transmission relationships are derived. Experimental results give preliminary validation of the feasibility and capability of the ADM system.

Sensorless Force Sensing for Minimally Invasive Surgery.

Robotic minimally invasive surgery (R-MIS) has achieved success in various procedures; however, the lack of haptic feedback is considered by some to be a limiting factor. The typical method to acquire tool-tissue reaction forces is attaching force sensors on surgical tools, but this complicates sterilization and makes the tool bulky. This paper explores the feasibility of using motor current to estimate tool-tissue forces and demonstrates acceptable results in terms of time delay and accuracy. This sensorless force estimation method sheds new light on the possibility of equipping existing robotic surgical systems with haptic interfaces that require no sensors and are compatible with existing sterilization methods.

Virtual laparoscopic surgical skills practice using a multi-degree of freedom joystick.

The objective of this study was to compare three different surgical skills practice environments while performing a virtual laparoscopic surgical training task using a multi-degree of freedom joystick, a commercial manipulator or a training box. Nine subjects performed a virtual peg transfer task and their upper extremity muscle effort and fatigue were measured. The results demonstrated a similar muscle effort and fatigue of the upper extremity among the three training environments. Subjects with medical backgrounds used significantly higher muscle effort when they performed the training task using the joystick than the manipulator, but used similar muscle effort between the joystick and the training box. This study suggests that the multi-degree of freedom joystick could provide more options to practice virtual laparoscopic surgical training tasks with muscle effort and fatigue similar to other traditional training boxes.

Improvements in robotic natural orifice surgery with a novel material handling system.

BACKGROUND: Natural orifice translumenal endoscopic surgery (NOTES) has many potential advantages over other minimally invasive surgical techniques, but it presents a number of challenges introduced by the restrictive natural access points. Fully insertable dexterous in vivo robots have been developed that eliminate the spatial restrictions of the entry point, but they also are isolated within the abdomen. A material handling system (MHS) developed to bridge the gap between the in vivo robots and the surgical team promises a number of improvements over other current technologies. METHODS: The MHS was implemented with two different nonsurvival swine models to validate the utility and benefits of the system. The first procedure was attempted transgastrically but proved too difficult because the geometry of the esophagus was prohibitively small. The system was instead inserted via a 50-mm GelPort and tested for robustness. The second procedure used a transvaginal insertion via a custom 25-mm trocar. Throughout both procedures, the practitioners were asked for qualitative feedback regarding the effectiveness of the device and its long-term efficiencies. RESULTS: The MHS was able to deliver a standard surgical staple securely to the peritoneal cavity. The practitioner was able to use the laparoscopic grasper both to insert and to remove the staple from the MHS. The system also proved capable of maintaining insufflation pressure throughout a procedure. It was cycled a total of five times in both the insertion and the retraction directions. Visualization from the MHS camera was poor at times because the lighting on the system was somewhat inadequate. No excessive bleeding or collateral damage to surrounding tissues was observed during the procedure. CONCLUSIONS: This study demonstrated that the MHS is fully capable of achieving payload transport during a NOTES operation. The system is intuitive and easy to use. It dramatically decreases collateral trauma in the natural access point and can advantageously reduce the overall duration of a procedure.

Material selection indices for design of surgical instruments with long tubular shafts.

In any medical device design process, material selection plays an important role. For devices which sustain mechanical loading, strength and stiffness requirements can be significant drivers of the design. This paper examines the specific case of minimally invasive surgical instruments, including robotic instruments, having long, tubular shafts. Material properties-based selection indices are derived for achieving high performance of these devices in terms of strength and stiffness, and the use of these indices for informing the medical device design problem is illustrated.

A novel vending machine for supplying root canal tools during surgery.

A root canal surgery involves the successive use of several tools one after another. Typically dozens of tools are laid out for possible use, and the process of tool selection is done manually. This is a rather inefficient process and uses up a large area on the mobile cart or cabinet of the dental chair due to the large number of tools. In this article, a novel 'tool vending machine' is introduced which will be capable of solving those problems and at the same time move a step closer to robot-assisted dental surgery. The tool vending machine was designed considering the needs of the dentists and also from the perspective of the entire product life cycle. For these reasons the design process was implemented using a rigorous analysis of effective manufacturing processes and product quality. To show the feasibility of using such a machine in improving work efficiency during operations, a study of the associated motion patterns and the required time increments were demonstrated.