25 November 2020

Smart devices set to enhance surgical outcomes

MedTech is a fascinating field to follow. It evolves rapidly and there are many players involved, from small start-up entrepreneurial initiatives focussing on unmet-needs to large corporates developing the next iteration of a previously manufactured device. It is interesting to see how bioengineers and technologists are incorporating the latest tech discoveries into devices with the ultimate aim of improving the lives of patients.

It’s a highly competitive field, so there is an emphasis among biotech and bioengineering labs to develop something novel – a device that will ultimately result in a better outcome of a medical procedure and improve the quality of life of a patient. In addition, many of these devices are also designed to make the increasingly time-constrained work processes of healthcare providers more efficient.

There are so many devices coming to market or in the pre-commercial phase of development that it is virtually impossible to keep abreast of them all. In this section, with a focus MedTech in surgery, we have curated articles on a handful of these devices to provide a glimpse of some of the remarkable innovations taking place.

Origami-inspired miniature manipulator improves precision and control of teleoperated surgical procedures

Minimally invasive laparoscopic surgery has made surgical procedures safer for both patients and doctors over the last half-century. Recently, surgical robots have started to appear in operating rooms to further assist surgeons by allowing them to manipulate multiple tools at once with greater precision, flexibility, and control than is possible with traditional techniques. However, these robotic systems are extremely large, often taking up an entire room, and their tools can be much larger than the delicate tissues and structures on which they operate.

A collaboration between Wyss Associate Faculty member Robert Wood, Ph.D. and Robotics Engineer Hiroyuki Suzuki of Sony Corporation has brought surgical robotics down to the microscale by creating a new, origami-inspired miniature remote centre of motion manipulator (the “mini-RCM”). The robot is the size of a tennis ball and weighs about as much as a small coin.

The device has successfully performed a difficult mock surgical task, as described in a recent issue of Nature Machine Intelligence. Suzuki explained: “The Wood lab’s unique technical capabilities for making micro-robots have led to a number of impressive inventions over the last few years, and I was convinced that it also had the potential to make a breakthrough in the field of medical manipulators as well.” Suzuki began working with Wood on the mini-RCM in 2018 as part of a Harvard-Sony collaboration.

A mini robot for micro tasks
To create their miniature surgical robot, Suzuki and Wood turned to the Pop-Up MEMS manufacturing technique developed in Wood’s lab, in which materials are deposited on top of each other in layers that are bonded together, then laser-cut in a specific pattern that allows the desired three-dimensional shape to “pop up” as in a children’s pop-up picture book. This technique greatly simplifies the massproduction of small, complex structures that would otherwise have to be painstakingly constructed by hand.

The team created a parallelogram shape to serve as the main structure of the robot, then fabricated three linear actuators (mini-LAs) to control the robot’s movement: one parallel to the bottom of the parallelogram that raises and lowers it, one perpendicular to the parallelogram that rotates it, and one at the tip of the parallelogram that extends and retracts the tool in use. The result was a robot that is much smaller and lighter than other microsurgical devices previously developed in academia.

The mini-LAs are themselves marvels in miniature, built around a piezoelectric ceramic material that changes shape when an electrical field is applied. The shape change pushes the mini-LA’s “runner unit” along its “rail unit” like a train on train tracks, and that linear motion is harnessed to move the robot. Because piezoelectric materials inherently deform as they change shape, the team also integrated LED-based optical sensors into the mini-LA to detect and correct any deviations from the desired movement, such as those caused by hand tremors.

Steadier than a surgeon’s hands
To mimic the conditions of a teleoperated surgery, the team connected the mini- RCM to a Phantom Omni device, which manipulated the mini-RCM in response to the movements of a user’s hand controlling a pen-like tool. Their first test evaluated a human’s ability to trace a tiny square smaller than the tip of a ballpoint pen, looking through a microscope and either tracing it by hand, or tracing it using the mini-RCM. The mini-RCM tests dramatically improved user accuracy, reducing error by 68% compared to manual operation – an especially important quality given the precision required to repair small and delicate structures in the human body.

After the mini-RCM’s success on the tracing test, the researchers then created a mock version of a surgical procedure called retinal vein cannulation, in which a surgeon must carefully insert a needle through the eye to inject therapeutics into the tiny veins at the back of the eyeball. They fabricated a silicone tube the same size as the retinal vein (about twice the thickness of a human hair), and successfully punctured it with a needle attached to the end of the mini-RCM without causing local damage or disruption.

In addition to its efficacy in performing delicate surgical manoeuvres, the mini-RCM’s small size provides another important benefit: it is easy to set up and install and, in the case of a complication or electrical outage, the robot can be easily removed from a patient’s body by hand.

“The Pop-Up MEMS method is proving to be a valuable approach in a number of areas that require small yet sophisticated machines, and it was very satisfying to know that it has the potential to improve the safety and efficiency of surgeries to make them even less invasive for patients,” said Wood, who is also the Charles River Professor of Engineering and Applied Sciences at Harvard’s John A. Paulson School of Engineering and Applied Sciences (SEAS).

The researchers aim to increase the force of the robot’s actuators to cover the maximum forces experienced during an operation, and improve its positioning precision. They are also investigating using a laser with a shorter pulse during the machining process, to improve the mini-LAs’ sensing resolution.

“This unique collaboration between the Wood lab and Sony illustrates the benefits that can arise from combining the real-world focus of industry with the innovative spirit of academia, and we look forward to seeing the impact this work will have on surgical robotics in the near future,” said Wyss Institute Founding Director Don Ingber, M.D., Ph.D., who is also the Judah Folkman Professor of Vascular Biology at Harvard Medical School and Boston Children’s Hospital, and Professor of Bioengineering at SEAS.

A video of the device operation can be viewed here: https://vimeo.com/449716409

Resources
Suzuki, H., Wood, R.J. Origami-inspired miniature manipulator
for teleoperated microsurgery. Nat Mach Intell 2, 437–446 (2020).
https://doi.org/10.1038/s42256-020-0203-4

Novel transcatheter heart valve for the treatment of aortic stenosis receives CE mark

SMT (Sahajanand Medical Technology), one of India’s leading medical device manufacturing companies with a focus on the cardiovascular market, has recently received the CE mark for a novel transcatheter heart valve for the treatment of patients diagnosed with aortic stenosis. The valve has a number of unique properties.

The so-called Hydra aortic valve is a self-expandable nitinol-based supra annular aortic system with a mechanism for recapturing of the valve during deployment. This unique property of the device helps in precise placement of the valve and ensures orthotopic deployment.

A spokesperson for the company explained that the benefits of the Hydra aortic valve system are enabled by its frame design and repositionable and retrievable delivery system. The non-flared inflow section of the frame and supra-annular valve leaflet design ensures better aortic valvular area in smaller annuli and in valve-in-valve settings. The frame features 3 tentacles or antenna for better anchorage and larger cells (10 mm) which give better access for future coronary interventional procedures if required. The delivery cable is highly flexible and 18 French compatible. The device can be recaptured, repositioned and retrieved even after 85-90% deployment of the valve, thereby eliminating the possibility of nearly all complications of deployment of TAVR devices. The precise orthotopic supraannular placement, positioning and deployment is facilitated by this unique property of being able to recapture the Hydra.

The Hydra is available in three sizes; 22 mm, 26 mm and 30 mm and is selected depending upon the diameter of the native annulus from 18 mm to 27 mm.

Clinical data from the Genesis trial conducted in India and presented at the India Valves Conference 2019 in Chennai, confirm the system’s ability to eliminate significant aortic regurgitation. In another CE clinical study conducted in Europe, the system also demonstrated a strong safety profile on 110 patients enrolled until February 2020.

Commenting on the device, Prof Lars Sondegaard, Principal Investigator of the trial, said: “Features that favour this self-expanding technology with supra-annular position of the leaflet include a small-size delivery system allowing transfemoral access despite small access vessels, a flexible system favouring a challenging anatomy, a large efficient orifice area of the valve, and a low rate of paravalvular leakage.”

New titanium spinal implants are bio-inspired

Surgical implant maker Xenco Medical recently launched its CancelleX porous titanium lumbar interbodies, the first injection-moulded titanium foam spinal implants pre-attached to disposable, composite polymer instruments.

Inspired by cancellous bone, the CancelleX lumbar interbodies feature interconnected porosity throughout each implant and break new ground in the application of injection moulding to the manufacturing of titanium spinal implants.

The bio-inspired implants are designed to promote bone apposition and facilitate vascularization, and feature high compressive strength.

The sterile-packed CancelleX is the first titanium foam implant of its kind to come pre-attached to a disposable, composite polymer delivery instrument which are optimally calibrated for once-off patient-specific use. This also has the advantage of increasing efficiency in the operating room as well as eliminating the internal logistics associated with the autoclave process.

Jason Haider, CEO and founder of Xenco Medical explained that the implants are optimized for energy absorption and bone in-growth. “The interconnected network of pores that permeate each CancelleX porous titanium implant serve to achieve bone-like mechanical properties.”

Researchers develop a novel active photonic wireless system to power medical implants

Over the past few decades, medical technology has seen various advances in terms of the scope and efficiency of implant devices. For example, developments in medical research have led to the emergence of electronic implants, such as pacemakers to regulate the heart rate and cerebral spinal shunts to control the flow of spinal fluid. Most of these medical devices, including the pacemaker, require a constant source of energy to operate. Naturally, this causes some limitations: batteries, which provide an energy source for the implants, have a finite lifespan. Once the battery power gets exhausted, there is no other option but to perform invasive surgery to replace the battery, which poses a risk of surgical complications, such as bruising, infections, and other adverse events.

In a new study published in PNAS, a research group from South Korea, led by Professor Jongho Lee at the Gwangju Institute of Science and Technology (GIST), dug deeper to find a solution: They attempted to develop a strategy to recharge the internal battery of devices without invasive surgery.

Prof Lee explained: “One of the greatest demands in biomedical electronic implants is to provide a sustainable electrical power for extended healthy life without battery replacement surgeries.”

Although this is a tricky concept, Prof Lee believes that the answer lies in the “translucency” of living tissue.

This can be explained through an interesting phenomenon. When you hold your hand up to a powerful light, you can see that the edges of your hand glow as the light passes through your skin. Taking inspiration from this, Prof Lee and his team developed an “active photonic power transfer” method, which can generate electrical power in the body. This novel system consisted of two parts: a skin-attachable micro-LED source patch – which can generate photons that would penetrate through the tissues – and a photovoltaic device integrated into a medical implant – which can capture the photons and generate electrical energy. This system provides a sustainable way of supplying the medical implant device with enough power to avoid any high-risk replacement methods.

Prof Lee explained: “Currently, a lack of a reliable source of power limits the functionality and performance of implant devices. If we can secure enough electrical power in our body, new types of medical implants with diverse functions and high performance can be developed.”

When the scientists tested this power system in mice, they found that this wireless power transfer system is easy to use, regardless of weather, clothes, indoor or outdoor conditions, etc. The light photons emitted from the source patch successfully penetrated live tissues in mice and recharged the device in a wireless and convenient manner.

“These results enable the long-term use of currently available implants, in addition to accelerating emerging types of electrical implants that require higher power to provide diverse, convenient diagnostic and therapeutic functions in human bodies,” said Prof Lee.

Prof Lee, looking forward to furthering their experiments, concluded: “Our device would probably not work for ‘Iron Man,’ but it can provide enough power for medical implants.”