Filip Jelínek

A state of the art review and categorization of multi-branched instruments for NOTES and SILS

BackgroundSince the advent of Natural Orifice Translumenal Endoscopic Surgery (NOTES) and single incision laparoscopic surgery (SILS), a variety of multitasking platforms have been under development with the objective to allow for bimanual surgical tasks to be performed. These instruments show large differences in construction, enabled degrees of freedom (DOF), and control aspects.MethodsThrough a literature review, the absence of an in-depth analysis and structural comparison of these instruments in the literature is addressed. All the designed and prototyped multitasking platforms are identified and categorized with respect to their actively controlled DOF in their shafts and branches. Additionally, a graphical overview of patents, bench test experiments, and animal and/or human trials performed with each instrument is provided.ResultsThe large range of instruments, various actuation strategies, and different direct and indirect control methods implemented in the instruments show that an optimal instrument configuration has not been found yet. Moreover, several questions remain unanswered with respect to which DOF are essential for bimanual tasks and which control methods are best suited for the control of these DOF.ConclusionsConsidering the complexity of the currently prototyped and tested instruments, future NOTES and SILS instrument development will potentially necessitate a reduction of the available DOF to minimize the control complexity, thereby allowing for single surgeon bimanual task execution.

DragonFlex – Smart Steerable Laparoscopic Instrument

Despite its success, e.g., in prostatectomy, da Vincis steerable grasper EndoWrist from Intuitive Surgical has a complex design prone to steel cable fatigue, potential sterilization issues and high associated costs, all of which insinuate a need for an alternative. The aim of this paper is to demonstrate a design of a structurally simple handheld steerable laparoscopic grasping forceps free from cable fatigue, while attaining sufficient bending stiffness for surgery and improving on EndoWrists maneuverability and dimensions. Having equal joint functionality to EndoWrist, DragonFlexs instrument tip contains only four parts, driven and bound by two cables mechanically fixed in the handle. Two orthogonal planar joints feature an innovative rolling link mechanism allowing the cables to follow circular arc profiles of a diameter 1.5 times larger than the width of the instrument shaft. Besides maximizing the cable lifespan, the rolling link was designed to equalize the force requirements on both cables throughout joint rotation, making the handling fluid and effortless. The smart joint design and stacked instrument construction enable control of seven degrees of freedom by only two cables and seven instrument components in tip, shaft and handgrip altogether. Two DragonFlex prototypes were developed by means of additive manufacturing technology, allowing grasping and omnidirectional steering over ±90 deg, exhibiting promisingly high bending stiffness and featuring extreme simplicity at 5 mm dimensions. DragonFlex concept sheds new light on the possibilities of additive manufacturing of surgical instruments, allowing for a feature-packed design, simple assembly, suitability for disposable use and potential MRI compatibility.

Attaining high bending stiffness by full actuation in steerable minimally invasive surgical instruments

Abstract Introduction: Steerable instruments are a promising trend in minimally invasive surgery (MIS), due to their manoeuvring capabilities enabling reaching over obstacles. Despite the great number of steerable joint designs, currently available steerable tips tend to be vulnerable to external loading, thus featuring low bending stiffness. This work aims to provide empirical evidence that the bending stiffness can be considerably increased by using fully actuated joint constructions, enabling left/right and up/down tip rotations with the minimum of two degrees of freedom (DOF), rather than conventional underactuated constructions enabling these rotations with more than two DOF. Material and methods: A steerable MIS instrument prototype with a fully actuated joint construction was compared to state-of-the-art underactuated steerable instruments in a number of tip deflection experiments. The tip deflections due to loading were measured by means of a universal testing machine in four bending scenarios: straight and bent over 20°, 40° and 60°. Results and conclusions: The experimental results support the claim that a fully actuated joint construction exhibits a significantly larger bending stiffness than an underactuated joint construction. Furthermore, it was shown that the underactuated instrument tips show a considerable difference between their neutral positions before and after loading, which could also be greatly minimised by full actuation.

Design for Additive Manufacture of Fine Medical Instrumentation—DragonFlex Case Study

The recently popularized domain of additive manufacturing (AM) has much to offer to medical device development, especially to the growing field of minimally invasive surgery (MIS). With the advancements in AM materials, one could soon envision materializing not only the proofs of concept but also the final clinically approved instruments. DragonFlex—the world’s first AM steerable MIS instrument prototype—was recently devised with the aim to follow this vision. Apart from the medical device design restrictions, several limitations of AM materials and processes had to be considered. The aim of this paper is to present these insights to those opting for this means of manufacture, serving as a helpful design and material guide. Over the course of its development, DragonFlex has gone through four design generations so far, each differing in the AM material and process used. Due to being a prototype of a MIS instrument of miniature dimensions, the printing processes were limited to stereolithography (SLA), as to achieve the best possible precision and accuracy. Each SLA process and material brought along specific advantages and disadvantages affecting the final printout quality, which needed to be compensated for either at the design stage, during, or after printing itself. The four DragonFlex generations were printed using the following SLA techniques and materials in this order: polymer jetting from Objet VeroBlue; SLA Digital Light Processing (DLP) method from EnvisionTEC R NanoCure RCP30 and R5; conventional SLA from 3D Systems Accura R 60; and DLP based SLA process from a ceramic composite. The material choice and the printing orientation were found to influence the final printout accuracy and integrity of thin features, as well as material’s postproduction behavior. The polymeric VeroBlue proved structurally sound, although suffering from undermined accuracy and requiring postprocessing, hence recommended for prototyping of upscaled designs of looser manufacturing tolerances or overdimensioned experimental setups. The NanoCure materials are capable of reaching the best accuracy requiring almost no postprocessing, thus ideal for prototyping small intricate features. Yet their mechanical functionality is undermined due to the high brittleness of RCP30 and high flexibility of R5. The transparent Accura R 60 was found to lose its strength and appeal due to high photosensitivity. Finally, the ceramic composite shows the best potential for medical use due to its biocompatibility and superior mechanical properties, yet one has to compensate for the material shrinkage already at the design stage. [DOI: 10.1115/1.4030997]

Bioinspired Spring-Loaded Biopsy Harvester—Experimental Prototype Design and Feasibility Tests

Current minimally invasive laparoscopic tissue–harvesting techniques for pathological purposes involve taking multiple imprecise and inaccurate biopsies, usually using a laparoscopic forceps or other assistive devices. Potential hazards, e.g., cancer spread when dealing with tumorous tissue, call for a more reliable alternative in the form of a single laparoscopic instrument capable of repeatedly taking a precise biopsy at a desired location. Therefore, the aim of this project was to design a disposable laparoscopic instrument tip, incorporating a centrally positioned glass fiber for tissue diagnostics; a cutting device for fast, accurate, and reliable biopsy of a precisely defined volume; and a container suitable for sample storage. Inspired by the sea urchin’s chewing organ, Aristotle’s lantern, and its capability of rapid and simultaneous tissue incision and enclosure by axial translation, we designed a crown-shaped collapsible cutter operating on a similar basis. Based on a series of in vitro experiments indicating that tissue deformation decreases with increasing penetration speed leading to a more precise biopsy, we decided on the cutter’s forward propulsion via a spring. Apart from the embedded springloaded cutter, the biopsy harvester comprises a smart mechanism for cutter preloading, locking, and actuation, as well as a sample container. A real-sized biopsy harvester prototype was developed and tested in a universal tensile testing machine at TU Delft. In terms of mechanical functionality, the preloading, locking, and actuation mechanism as well as the cutter’s rapid incising and collapsing capabilities proved to work successfully in vitro. Further division of the tip into a permanent and a disposable segment will enable taking of multiple biopsies, mutually separated in individual containers. We believe the envisioned laparoscopic optomechanical biopsy device will be a solution ameliorating timedemanding, inaccurate, and potentially unsafe laparoscopic biopsy procedures. [DOI: 10.1115/1.4026449]

Design of an endovascular morcellator for the surgical treatment of equine Cushing's disease.

Background: A new paradigm of surgical treatment of equine Cushings disease has been developed using the vascular system combined with a flexible morcellation instrument to reach the pituitary gland. Objective: The goal was twofold: (1) to design, prototype, and test an instrument that can reach the pituitary gland using the vascular system unique to equids and (2) to test the feasibility of the endovascular approach. Animals and methods: The morcellator consists of a radial rotating cutting blade for tissue resection, a flexible shaft incorporating a cable drive for flexible actuation, and central morcellated tissue transportation lumen. The morcellator prototype was tested on a horses cadaver head for the validation of the cutting blade design, actuator design, and feasibility of the endovascular approach. Results: The overall assembled length of the morcellator tip was 13.9 mm, allowing for non-traumatic steering through the vascular system from the proximal end. The radially rotating cutting blade (barrel of Ø 4 and 4.4 mm width) incorporated multiple cutting edges to deliver the action force during resection and provides the necessary grasping force to draw the tissue towards the second cutting edge of the morcellator incorporated inside the blunted cuboidal static tip element (5 mm square and wall-thickness of 0.3 mm). In the tests, the morcellator was successfully guided towards the pituitary and managed to sample pituitary tissue. Conclusion and clinical importance: Continued development of the prototype and the endovascular approach may in time improve the outcome and quality of life of horses suffering from Cushings disease.

Method for minimising rolling joint play in the steerable laparoscopic instrument prototype DragonFlex

Abstract Introduction: The steerable laparoscopic instrument prototype DragonFlex was recently developed with the vision of a minimalistic fully functional design, readily produced by additive manufacturing and requiring little assembly. Steering functionality is provided by rolling joints that, besides simplifying the assembly, help minimise cable fatigue and equalise force requirements on steering cables. However, the perfectly circular rolling joint design introduced some mechanism play, undermining the joint’s bending stiffness. Hence, the aim of this paper is to present an innovative solution for play reduction in rolling joints. Material and methods: The original play-compensating mechanism, a shaft-embedded compression spring, proved unsatisfactory for play reduction. Therefore, a new non-circular rolling joint curvature was designed with the objective to compensate for any cable slack and thus minimise the joint play. The new rolling joint design was evaluated in several tip deflection experiments and compared to the original one. Results and conclusions: The experimental results proved that the optimised rolling joint curvature significantly minimises play, thus being a major improvement compared to the original design. The optimised rolling joint was implemented in a new real-scale DragonFlex prototype. The presented optimisation method enables elimination of a conventionally used cable tensioning device and it is generally applicable to steerable minimally invasive instruments that use a rolling joint.

Minimally invasive surgical instruments with an accessory channel capable of integrating fibre-optic cable for optical biopsy: a review of the state of the art.

This review article provides a comprehensive overview and classification of minimally invasive surgical instruments with an accessory channel incorporating fibreoptics or another auxiliary device for various purposes. More specifically, this review was performed with the focus on the newly emerging field of optical biopsy, its objective being to discuss primarily the instruments capable of carrying out the optical biopsy and subsequent tissue resection. Instruments housing the fibreoptics for other uses, as well as instruments with an accessory channel capable of housing the fibreoptics instead of their original auxiliary device after relevant design modifications, supplement the review. The entire Espacenet and Scopus databases were searched, yielding numerous patents and articles on conceptual and existing instruments satisfying the criteria. The instruments were categorised based on the function the fibreoptics or the auxiliary device serves. On the basis of their geometrical placement with respect to the tissue resector or manipulator, the subcategories were further defined. This subdivision was used to identify the feasibility of performing the optical biopsy and the tissue resection in an accurate and successive fashion. In general, the existing concepts or instruments are regarded as limited with regard to such a functionality, either due to the placement of their accessory channel with or without the fibreoptics or due to the operational restrictions of their tissue manipulators. A novel opto-mechanical biopsy harvester, currently under development at Delft University of Technology, is suggested as a promising alternative, ensuring a fast and accurate succession of the optical and the mechanical biopsies of a flat superficial tissue.

Control devices and steering strategies in pathway surgery

For pathway surgery, that is, minimally invasive procedures carried out transluminally or through instrument-created pathways, handheld maneuverable instruments are being developed. As the accompanying control interfaces of such instruments have not been optimized for intuitive manipulation, we investigated the effect of control mode (1DoF or 2DoF), and control device (joystick or handgrip) on human performance in a navigation task. The experiments were conducted using the Endo-PaC (Endoscopic-Path Controller), a simulator that emulates the shaft and handle of a maneuverable instrument, combined with custom-developed software animating pathway surgical scenarios. Participants were asked to guide a virtual instrument without collisions toward a target located at the end of a virtual curved tunnel. The performance was assessed in terms of task completion time, path length traveled by the virtual instrument, motion smoothness, collision metrics, subjective workload, and personal preference. The results indicate that 2DoF control leads to faster task completion and fewer collisions with the tunnel wall combined with a strong subjective preference compared with 1DoF control. Handgrip control appeared to be more intuitive to master than joystick control. However, the participants experienced greater physical demand and had longer path lengths with handgrip than joystick control.

Bioinspired Crown-Cutter—The Impact of Tooth Quantity and Bevel Type on Tissue Deformation, Penetration Forces, and Tooth Collapsibility

Current keyhole biopsy devices are rather ungainly, inaccurate, and limited in application. A keyhole biopsy harvester was designed to facilitate peripheral cancerous tissue detection and resection at high speed and accuracy. The harvesters cutting tool, the crown-cutter, was bioinspired by the sea urchins chewing organ—Aristotles lantern. This paper focuses on the optimization of the crown-cutter with regard to the impact of different tooth quantity and bevel type on tissue deformation, penetration forces, and tooth collapsibility. Two sets of crown-cutter designs were manufactured and tested in push-in experiments using gelatin—the first set having no bevel and differing tooth quantity (4, 6, 8, 10 teeth) and the second set of constant tooth quantity and differing bevel type (no, inner, outer, and inner and outer bevel). The gelatin surface deformation and the penetration forces were evaluated utilizing a high speed camera and a universal testing machine, respectively. The experimental results on the crown-cutters of different tooth quantity (no bevel) showed a steady increase in the tissue deformation with the increasing amount of teeth. Unlike the bevel type, the different tooth quantity revealed significant differences with regard to the tissue deformation in between 4 versus 6-teeth and 10 versus 6-teeth cutters. As for the penetration forces, the significant difference was found only between 10 and 6-teeth cutters. In conclusion, reducing the cutters tooth quantity resulted in lower tissue deformation, whereas differing the bevel type was found to have a negligible influence. Ultimately, a high ratio of outward to inward tooth collapsibility and a relatively low inner moment of inertia proved the 6-teeth cutter to be the most optimal.