Category Archives: Steerable Instruments

ACCI

ACCI – a non-assembly steerable instrument for eye surgery

Acci is a non-assembly steerable illumination instrument for eye surgery, with a tip diameter of 0.75 mm, 3D printed in one single step.

3D printing is especially useful for making small, highly precise instruments, like those used in eye surgeries. While 3D printing has its advantages, there are challenges when it comes to making tiny devices due to size limitations and the accuracy of current 3D printers, as well as being able to assemble many small parts.

Acci is an extremely thin and flexible light pipe designed for eye surgery that addresses these challenges. The instrument consists of a handle and a functional tip which can be bent by pushing on the handle. The functional tip has a diameter of only 0.75 mm, which is accomplished by printing a spiral structure. The 360-degree precision grip handle makes it easy to operate and maneuver. Both the tip and handle are printed one single step, after which only the optical fiber that provides the illumination has to be inserted. The optical fiber also functions as the control cable to actuate the instrument, eliminating the need for extra parts and assembly steps.

ACCI was a finalist in the 3D Pioneers Challenge 2024.

3D-GriP, Steerable Instruments

3D-GriP – A minimal assembly fully 3D printed instrument

Developed in 2020-2021, diameter Ø8 mm, bending angle ±60˚, consists of 5 separate parts.

In minimally invasive surgery, small incision sizes limit the manoeuvrability of surgical instruments. The number of degrees of freedom (DOF) of the instrument shaft can be increased by making the instrument tip steerable. Such instruments are controlled by the surgeon on the side of the handle. Steerable instruments offer many advantages in terms of DOF and functionality, however they have high mechanical complexity, and the steerable shaft can be difficult to operate for the surgeon.

Additive manufacturing (AM) can aid in the development of these instruments by reducing the mechanical complexity in the form of minimal assembly designs. The freedom of complexity offered by AM allows parts to be merged together into larger, more complex parts, that can be 3D printed in a single step. In addition, AM allows the production of one-off, personalized designs.

The 3D-GriP is a 3D printed steerable instrument that consists of only 5 separate parts. The handle part is designed based on ergonomic principles for handheld instruments, and can be adjusted to the size of the surgeon’s hands for a perfect fit. The joystick steers the instrument and works with a passive lock, which is automatically engaged when no pressure is applied. The grasper can be closed with the trigger, designed with two perpendicular flexures, which can be operated by one or two fingers, as the surgeon prefers.

Culmone C., Lussenburg K., Alkemade J., Smit G., Sakes A., Breedveld P. (2021). A fully 3D-printed steerable instrument for minimally invasive surgery. Materials, Vol. 14, No. 24, 18 p. 

SIGMA catheter, Steerable Instruments

SIGMA Catheter – steering inside the Heart

Developed in 2016-2017, diameter Ø3 mm, lumen Ø1 mm

In recent years, steerable catheters have been developed to combat the effects of the dynamic cardiac environment. However, current solutions are bound to a number of limitations: (1) low torsion, (2) shaft shortening, (3) high unpredictable friction, and (4) coupled tip-shaft movements. These effects make it very hard to steer in tortuous blood vessel and inside the heart.

In order to tackle these limitations we developed a novel multi-steerable catheter prototype with four degrees of freedom. The tip has two steering segments that can be steered in all directions, controlled by two joysticks on the handle: one for the thumb and one for the index finger. The prototype features automatic lock of the steering angle once the joystick is released.

To solve the four limitations mentioned above we used eight miniature Bowden-cables inside of the flexible shaft for independent omnidirectional steering of each tip segment. As each segment can steer in all directions, twisting the shaft is not needy for directing the catheter tip, which solves the issue with low torsion (1). The issue with shaft shortening (2) is solved with the Bowden-cables which are axially incompressible. The Bowden cables generate very low predictable friction (3) and coupled tip-shaft movements (4) are absent as the Bowden-cables transfer the joystick motions directly to the tip without influencing the shaft.

The ability to steer inside the heart with a variety of complex shapes and curves opens great possibilities for complex catheter interventions. We evaluated our SIGMA catheter in a transparent 3D printed heart, based on MRI-images and created by the company Materialize, as well as ex-vivo in a beating porcine heart at the LifeTec Group. Both evaluations show very promising results and superior behaviour as compared to conventional steerable catheters.

Publications:

Ali A., Sakes A., Arkenbout E.A., Henselmans P., Starkenburg R. van, Szili-Torok T., Breedveld P. (2019). Catheter steering in interventional cardiology: mechanical analysis and novel solution. Proc. Inst. Mech. Eng. Part H: Journal of Engineering in Medicine, 12 p.

Media

https://www.materialise.com/en/blog/how-a-modular-testbed-helps-medical-device-developers

Ovipositor Needle II, Steerable Instruments

Ovipositor Needle II – Self-Propelling & Steering through Tissue

Developed in 2016-2019, diameters ranging from 1.2 mm to 0.4 mm. 

A wasp ovipositor is a needle-like structure composed out of three elements, called valves. A female wasp uses this structure to drill into wood or fruit and deposit eggs inside a living host. The propagation of the ovipositor through the substrate is achieved by a smart push-pull mechanism, in which one of the valves is pushed while the other two are pulled, using the surface-dependent friction properties with the soft substrate to move forward. Inspired by the ovipositor of parasitoid wasps, we developed a series of self-propelled steerable Ovipositor Needles with ultrathin diameters ranging from 1.2 mm to 0.4 mm.

Our first Ovipositor Needle prototype consists of six super elastic Nickel Titanium (NiTi) wires concentrically arranged around a seventh NiTi wire. The seven wires are interconnected at the tip with a small flower-shaped ring (Ø 1.2 mm) manufactured for minimal resistance during propulsion. The ring has a central hole to which the central wire is glued, surrounded by six concentric holes through which the six other wires can slide back and forth. Each proximal end of the six movable wires is connected to a miniature stepper motor, in which a leadscrew-slider mechanism converts rotational motion into linear motion.

We performed a series of experiments in which the needle was inserted in tissue-mimicking gel phantoms. The wires were sequentially moved back and forth, resulting in the needle moving forward inside the phantom using the surface-dependent friction properties between the wires and the gel. Different sequences of wire actuation were used to achieve both straight, curved and S-shaped trajectories.

In our second Ovipositor Needle prototype we changed the shape of the interlocking ring from cylindrical to conical to investigate the effect of pre-curved wires. We found out that pre-curved wires facilitate steering, however, at the drawback of a slightly larger tip diameter due to the use of a conical flower-ring.

In a final series of Ovipositor Needle prototypes, the flower-shaped ring was replaced by an thin-walled shrinking tube, glued to one of the outer wires, ultimately resulting in ultrathin 0.4 mm needle diameters three times the size of a human hair. The prototypes were tested in multi-layered gel phantoms with varying stiffness properties and artificial membranes, representing different organs and tissues. In a final series of ex-vivo experiments the needles were evaluated with success in porcine liver, kidney and brain tissue.

This project, in which we developed world’s thinnest self-propelled-steerable needles, shows the strength of a novel bio-inspired approach leading to a new generation of needles that can be used to reach deep targets inside the body without a risk of buckling and with the possibility to correct the trajectory. Our needles were developed within the WASP project that focused on the development of steerable needles for localized therapeutic drug delivery or tissue sample removal (biopsy). In a follow-up project, funded by the Netherlands Organization for Scientific Research (NWO) we will develop the needles further towards clinical application in urological interventions under MRI.

(Picture at the top adapted from “Braconid Wasp Ovipositing” by Katja Schulz is licensed under CC BY 2.0.)

Publications

Media

Accura, Steerable Instruments

Accura: 8DOF Accurately Steerable Platform

As of today, Chronic Total Occlusions (CTO) represent the most technically challenging lesions interventionists face during Percutaneous Coronary Interventions (PCI), with considerably lower success rates (50-90%) in comparison to semi-occluded and acutely occluded arteries [1]. The main technical challenge in PCI of CTOs lies in successfully puncturing and crossing the CTO with a guidewire.

In this section we will focus on crossing challenges. For solutions to puncture the CTO, see the Pulze Hammer I, Pulze Hammer II (coming soon), Cradle Catheter (coming soon), and Wave Catheter (coming soon).

Crossing is challenging as the guidewire cannot be actively steered and deflection can thus not be compensated. This can lead, amongst others, to dissection of the blood vessel wall or subintimal crossing, in which the guidewire crosses the CTO via the blood vessel wall (between the intima and adventitia). Furthermore, it is often challenging to navigate through tortuous CTOs.

A steerable crossing device could be the solution to current crossing challenges, as it will give the interventionist the freedom to actively navigate through the vascular system and CTO freely. Therefore, a steerable prototype nicknamed the Accura was designed with an 8 Degrees Of Freedom (DOF) cable actuated tip (Ø 2 mm, L = 32 mm) divided over 4 steering segments; allowing for constructing complex S-curves. The tip contains a lumen (Ø 1 mm) to allow for the insertion of, amongst others, a balloon catheter, a guidewire, or an IntraVascular UltraSound probe (for visualization purposes). The steerable tip is connected to a rigid shaft (Ø 2 mm, L = 200 mm), which in turn is connected to the handle. The handle consists of an innovative combined locking and steering mechanism to lock the tip position in place and to precisely steer each segment separately. This construction allows for both the tip position and direction to be changed independently, allowing for a scanning movement.

The multisteerable tip has been successfully combined with a single element forward-looking IVUS transducer and Optical Shape Sensing (OSS) fiber to reconstruct a wire frame in front of the tip. This combination will allow for reconstructing and scanning a 3D volume in front of the tip, which can be used to determine the most suitable entry location. Furthermore, the addition of the OSS fiber can potentially minimize the use of X-Ray and contrast fluid during the intervention.

Even though it is still a long way towards a fully applicable clinical tool, the tests have given first insights into the possibilities and advantages of having such a tool in PCI. Currently, a multisteerable catheter is under development.

Publications:

  • Sakes A., Ali A., Janjic, J., and Breedveld P. (2018). Novel Miniature Tip Design for Enhancing Dexterity in Minimally Invasive Surgery. Journal of Medical Devices. Accepted.

Accura_device2

Steerable Instruments, Volt

Volt – 3D-Printed Bipolar Laparoscopic Grasper

Developed in 2016, thickness 5 mm, complex components made by 3D-printing.

Controlling blood loss is a major challenge during laparoscopic surgery. In an effort to control blood loss, electrosurgical tools are often used. In current electrosurgical instruments, a high frequency electrical sinusoidal wave is passed through the patient’s body from an active electrode to a return electrode to minimize bleeding. Depending on the exact configuration of the electrosurgical instrument, it can be used to coagulate, cut, or destroy the tissue.

Even though current bipolar electrosurgical instruments have proven effective in minimizing blood loss, advancement is needed to improve the dexterity and adaptability of these instruments. With current advances in 3D-print processes and its integration in the medical field it has become possible to manufacture patient- and operation-specific instruments. Furthermore, by combining 3D-print technology with smart joint designs, the dexterity of the instruments can be significantly improved.

In order to overcome these challenges, we have developed the first 3D-printed steerable bipolar grasper (5 mm), named Volt, for use in laparoscopy. This 3D-printed design allows for easy adjusting of the geometry of the shaft and tip based on the patient’s anatomy and operation requirements. The grasper significantly improves dexterity by the addition of two planar joints allowing for ±65° for sideways and ±85° for up- and downwards movement. Furthermore, due to smart joint design, high bending stiffness of  4.0 N/mm for joint 1 and 4.4 N/mm for joint 2 is achieved, which is significantly higher than that of currently available steerable instruments. The tip consists of two 3D-printed titanium movable jaws that can be opened and closed with angles up to 170° and allows for grasping and coagulating of tissues. In order to actuate the joint, tip, and electrosurgical system, as well as to tension the steering cables, a ring handle was designed similarly in design to the one of Dragonflex.

In a proof-of-principle experiment, Volt was connected to a electrosurgical unit (Erbe) and was able to successfully coagulate fresh pig liver. Tissue temperatures of over 75 °C were achieved with an activation time of ~5 s.

Publications:

 

 

 

Ovipositor Needle I, Steerable Instruments

Ovipositor Needle I – Self-Propelling through Tissue

Developed in 2014, thickness 2 mm.

Wasp ovipositors  are thin and flexible needle-like structures used for laying eggs inside wood or larvae.  Wasp ovipositors are composed out of  longitudinal segments, called “valves”, that can be actuated individually and independently of each other with musculature located in the abdomen of the insect. In this way the wasp can steer the ovipositor along curved trajectories inside different substrates without a need for rotatory motion or axial push.

Inspired by the anatomy of wasp ovipositors, we developed an Ovipositor Needle containing a 2 mm thick “needle” composed out of four sharp and polished stainless steel rods, representing four ovipositor valves. The four valves can be individually moved forward and backward by means of  electromechanical actuators mounted in a propulsion unit that is standing on four passive wheels. If the needle is inserted into a gel that represents tissue, and if the four valves are sequentially moved forward and backward, the friction behaviour around the valves in the gel will result in a net pulling motion that drives the needle forward through the gel. The ovipositor needle is therefore self-propelling, meaning that it does not need a net pushing motion for moving forward through tissue like normal needles do.

Ovipositor Needle I is part of the  WASP project that focuses on the development of steerable needles for localized therapeutic drug delivery or tissue sample removal (biopsy). In a new prototype that is currently under development, we aim to extend the self-propelled needle with steering capabilities at an outer diameter of just 1 mm.

 

Publications

DragonFlex Micro, Steerable Instruments

DragonFlex Micro – Towards the Limits of 3D-Printing

Developed in 2012-2015, thickness 5 mm, steering range: ±90º in all directions, complex components made by 3D-printing.

The DragonFlex has been developed in close-collaboration with Dr. Filip Jelinek, former PhD from the BITE-Group and currently employed at ACMIT.

In follow-up of the successful DragonFlex Macro, the DragonFlex Micro has been miniaturized to a 5 mm scale, where special attention has been given to the reliability and precision of the mechanism and optimization of the 3D-printing technique for such small scale components. Developing and optimising new design methodologies for 3D-printing,  a number of prototypes have been manufactured from different materials, resulting in world’s first steerable surgical instrument made entirely by 3D printing.

 

Publications

DragonFlex Macro, Steerable Instruments

DragonFlex Macro – Smart Steering by 3D-Printing

Developed in 2010-2011, thickness 15 mm, steering range: ±90º in all directions, made entirely by 3D-printing.

Despite its success, e.g. in prostatectomy, da Vinci’s 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 our DragonFlex project 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 EndoWrist’s maneuverability and dimensions.

Having equal joint functionality to EndoWrist, DragonFlex’s 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 stacked joint design enables control of seven Degrees of Freedom (DOF) by only two cables and seven instrument components in tip, shaft and handgrip altogether.

The DragonFlex prototype was developed by means of 3D-printing, allowing grasping and omnidirectional steering over ±90°, exhibiting promisingly high bending stiffness and featuring extreme simplicity. 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.

 

Publications

Dendritic Instruments, Steerable Instruments

NWO VICI – Dendritic Instruments – Outreaching the Squid

This VICI-research project is funded by the Netherlands Organization for Scientific Research NWO.

Background

In ‘standard’ minimal access surgery, the surgeon inserts rigid instruments through small incisions in the skin or natural orifices to reach targeted areas inside the human body. This approach drastically reduces the invasiveness of surgery compared to conventional open approaches, yet the reduced size of the surgical entry-point does also severely restrict the maneuverability of the used instrumentation. This lack of instrument maneuverability becomes especially apparent when considering Endoscopic Skull Base Surgery (ESBS). A prime target of ESBS are tumors on the pituitary gland positioned at the skull base, the region that separates the brain from the rest of the head. The nose is used as the surgical entry-point, and due to the rigid nature of the used instrumentation, the surgeon needs to create a straight surgical pathway to the pituitary gland. The limited width of this pathway in combination with the need for multiple instruments severely limits sideway movements of the instruments. This situation leads to a phenomenon called swordfighting wherein the shafts of instruments collide and, moreover, it severely restricts the maneuverability of the individual tools (i.e. grasper, scissors, etc.).

We strive to improve on overall instrument maneuverability with the development of dendritic instruments. A dendritic instrument is a maneuverable single-shaft instrument that branches into multiple independently steerable tools. Such an instrument would eliminate the occurrence of swordfighting, as the number or shafts is reduced to one, while providing the surgeon sufficient maneuverability of the individual tools. This research project is divided into two main topics; the mechanical construction and methods of control of dendritic instruments, such that these instruments are able to be implemented in operating theatre in the near future.

Steering

The mechanical construction of a dendritic instrument consists of two basic parts. First, there is the shape memory shaft that should be capable of following a curved trajectory up to the targeted area while providing a stable base. Secondly, there are the individual steerable branches that sprout from this stable base and provide independent maneuverability of each individual tool.

Creating a steerable branch starts with a flexible structure, either containing joints or a compliant backbone. The actuation of such this flexible structure can then be realized by several actuation methods, including the use of electric motors, hydraulic actuators, and shape memory alloys. Our research is focused on a fully mechanical actuation method based on cable-structures. This allows for structures that are easy to miniaturize, eliminates the need for possibly dangerous electric currents, high pressures or high temperatures, and shows high potential for reducing the costs of fabrication.

Besides the obvious requirement that the branches need to be maneuverable, they should also have a certain stiffness in order to cope with external forces that will be present during, for example, tissue manipulation. In our search for a suitable cable-structure to achieve high maneuverability and stiffness, we have developed a cable-structure in which multiple cables are placed at different angles along the longitudinal axis. This structure has already shown great promise and is now in the process of further optimization.

Control

Dendritic instruments consist of many small joints and branches which the surgeon(s) needs to actively steer, in order to perform complex surgical tasks (e.g. suturing or tissue manipulation). The amount of joints in dendritic instruments are even so many, that currently existing prototypes require the cooperation of two surgeons to perform a task which is actually meant for only one surgeon. In other words, dendritic instruments have more Degrees of Freedom (DOF) than any  surgeon can control alone. However, the large amount of DOFs combined with an intuitive method of control is exactly what is required for dendritic instrumentation to become a reality.

The BITE research method to dendritic instrument control is one which is exploration driven. The optimal mechanical construction and DOF configuration are still being researched. Hence, the accompanying control interface or instrument handle cannot be designed yet. To investigate the best methods of control, virtual instruments are simulated in a Virtual Environment (VE). Physical hand movements and gestures are measured with RGB-D Kinect cameras, and mapped to virtual instrument movements. By playing with the coupling between hand DOF and instrument DOF, new control strategies are tested and reverse engineered to ultimately discover the best method for dendritic instrument control.

Dendritic_control_simulation_setup

Image adapted from  www.nimblevr.com (previously www.threegear.com)