Jeremy Kooyman discusses the importance of usability in the design and use of medical devices.

In light of the FDA’s panel meeting in late summer on challenges and opportunities in the development of medical devices, Jeremy Kooyman, MASc, stresses usability and surgeon involvement in the design process.

There are a growing number of robotically-assisted surgery devices (RASD) and manufacturers entering the global market. However, an increase in the rate of adverse events related to these devices led to the FDA holding a panel meeting earlier this year to specifically address the challenges and opportunities associated with the rapidly evolving technology. Will the FDA’s involvement, with their upcoming Human Factors for Medical Guidance due to be issued soon, highlight the importance of usability in the development of these new devices?

Robotically-assisted surgical devices are considered by the FDA to be a subtype of computer-assisted surgery devices, typically consisting of several components which may include:

  • A console which allows the surgeon to sit and view the surgical field through a 3D endoscope while remotely manipulating the surgical instruments;
  • A bedside unit which houses the robotic arms that hold the surgical tools and endoscope, controlled by the surgeon through the console;
  • A cart which houses supporting hardware and software components like suction/irrigation pumps and the endoscope light source.
Doctors and nurses show Under Secretary of the Army Joseph W. Westphal their new remote control da Vinci Surgical System, which enables surgeons to perform operations through tiny incisions and is powered by high-tech robotics that gives the surgeon the best possible view with HD cameras at the Fort Belvoir Community Hospital, May 30, 2012, at Fort Belvoir, Va. Dr. Westphal visited Fort Belvoir Community Hospital to gain situational awareness and ensure the Army is correctly prioritizing, balancing and integrating resources to support the mission of this vital organization.
Doctors and nurses show Under Secretary of the Army Joseph W. Westphal their new remote control da Vinci Surgical System, which enables surgeons to perform operations through tiny incisions and is powered by high-tech robotics that gives the surgeon the best possible view with HD cameras at the Fort Belvoir Community Hospital, May 30, 2012, at Fort Belvoir, Va. Dr. Westphal visited Fort Belvoir Community Hospital to gain situational awareness and ensure the Army is correctly prioritizing, balancing and integrating resources to support the mission of this vital organization.

The most well-known example is Intuitive Surgical’s da Vinci Surgical System, videos of which can be seen peeling a grape or folding a paper crane to demonstrate its dexterity and accuracy. The system was designed to facilitate complex minimally invasive surgery while being controlled remotely from a comfortable seated position. It can be argued that much of the initial commercial traction from the system was due to its ease of use and reduction of physical exertion combined with the obvious marketing appeal it might create in a privatised medicine system, rather than a clearly demonstrated superiority to traditional operational approaches. It is widely regarded as the most successful surgical robot and has indeed gone on to prove superior to traditional surgical approaches in a range of procedures, with more than 600,000 procedures being performed in 2014 (up from 200,000 in 2009), paving the way for a number of other competing laparoscopic surgical robots to be commercialized.

Intuitive isn’t the only player in the field with hundreds of millions of US dollars being raised and spent by the likes of TransEnterix, Cambridge Medical Robotics, Magnetecs and Titan Medical. Also a partnership between Google and Johnson & Johnson has been announced.


With so many new devices arriving on the market, the FDA’s workshop was timely. While it covered topics ranging from essential performance characteristics (stemming from risk management standards) to technical design considerations, there was little to no discussion on what I believe is the most important aspect of these machines: usability. Put simply, it is usability that determines whether or not the RASD can be used by a human operator. Focusing on safety and efficacy from a regulatory and design standpoint lends itself to cumbersome design solutions that can introduce use and misuse hazards that haven’t been accounted for, as the surgeon finds himself trying to figure out ways to outwit clumsy safety controls.

Usability for medical devices is moving to the forefront of many manufacturers’ design approaches, as it has changed from being viewed as just another ’regulatory hurdle’ to an integral process implemented throughout development. It can often take time, however, for such shifts to propagate backwards to academia and be adopted and supported throughout the hospital environment. Having learnt from incorrect design decisions that led to usability issues during my early academic career, I’ve been sensitive to the importance of user-centred design processes/thinking for some time. At two conferences I attended earlier this year - the AAMI Human Factors for Medical Devices course, London, UK, and the International Society for Computer Assisted Orthopaedic Surgery annual meeting, Vancouver, Canada - where the audiences couldn’t have been more different (industry and regulatory professionals versus a predominantly academic research crowd), I was reassured to perceive that both hinted that the current state of medical devices is changing for the better.

Spend any appreciable length of time in a hospital environment and you’ll begin to notice examples of borderline systemic user abuse. I’ve witnessed issues such as operating theatre equipment fitted with so many alarms and notifications that alarm fatigue became severely problematic, and equipment control terminals with adhesive notes on the monitors advising on tricks to cope with a cumbersome UI. Spend extended periods of time wearing lead shielding to protect oneself from radiation exposure but maintain the strength required to carry out joint revision operations and it’s clear that the user of the equipment in these scenarios hasn’t necessarily been considered during the design process. This is most likely due to the regulatory emphasis on safety and efficacy of medical devices, which downplays the importance of non-safety related use error.

Use Errors

When developing a medical device, the FDA expects the manufacturer to treat use error as a risk, and identify/understand foreseeable use error risk through a variety of mechanisms including formative studies, where you observe representative users in a simulated use scenario, and Use Failure Mode and Effects Analysis (uFMEA), a more academic exercise in which scientists and engineers attempt to identify all the possible methods a user might fail to use the device correctly. Both of these methods identify associated risks by considering the clinical severity of identified use error and feed this information into the design process. Depending on the manufacturer’s approach, it’s easy to ignore use errors with negligible impact on safety during the subsequent design of the device unless they consider non-safety related use errors as a significant business issue. This can ultimately result in the production of a medical device that is safe and effective for use from a regulatory standpoint but completely terrible from a user’s perspective.

We live in an era where the latest high-tech devices have stopped coming with instruction manuals, with companies opting instead to invest heavily in usability and UX researchers to design novel user interfaces, both graphic and physical, that embody the idea that use-errors are due to poor design not human error. Since there are substantially reduced regulatory hurdles regarding the safety and efficacy of consumer devices, these non-safety related use errors become the focus of the device’s development process, ultimately resulting in devices whose function is inextricably tied to the user’s abilities and enjoyment of the interaction. But when was the last time you heard a colleague exclaim how much they enjoyed using their blood glucose or blood pressure monitor, or even a more advanced piece of equipment like PACS or a C-Arm?


Computer assisted orthopaedic surgery (CAOS) is a great example of what can happen with a lack of user focus. CAOS applies computer science, engineering and robotics principles to traditional orthopaedic procedures with the goal of improving operative and post-operative outcomes. This can take the form of a surgeon using CAOS technology during a joint replacement to preoperatively plan the implant size and location, interoperatively track and/or guide the placement of the implant, and determine post-operatively how closely the procedure adhered to the preoperative plan, providing insight into the long-term survivability of the implant.

CAOS is a focused application of the broader field of computer assisted surgery (CAS), which includes the creation of accurate 3D models of patient anatomy from medical scans, diagnostics and preoperative planning, surgical simulation, interoperative navigation, and finally robotic surgery. The field as a whole aims to use technology to deliver greater surgical precision and better operative outcomes for the patient, similar to the goals of RASD manufacturers, just focusing on different anatomy.

A notable example of this is the ROBODOC surgical robot which first entered human trials in the early 90s. ROBODOC was first designed to mill the femoral canal to accept cementless implants, which were thought to have better survival rates than cemented implants which were failing at that time. Interoperatively, after the surgeon spent 30+ minutes setting up and calibrating the robot to the patient’s anatomy, the robot, designed by a team of engineers, would perform the milling procedure entirely autonomously without any input from the surgeon with decades of training and intuition. While the robot could perform this task with sub-mm precision, I’m sure you can see why the surgeon might not be so fond of the robot! And that’s before ROBODOC’s intimidating operating theatre presence and price tag are considered in the evaluation. So while the project was an engineering success, it can be argued that the company would struggle to gain commercial traction as they initially neglected to consider the entire workflow of the operation and stakeholder (surgeon) opinions, including the importance of interoperative surgeon input and guidance.

“These systems have always been accurate. It’s whether or not they’ve been easy to use” remarked a surgeon at the International Society for CAOS meeting I attended. Looking back at some of the early systems like ROBODOC, it’s easy to see why early adopters abandoned the technology and there seems to be limited incentive to welcome it back. Some modern systems require around 10-15 cases (40+ in the case of the da Vinci) before a surgeon can achieve the required accuracy of implantation, or they add 30+ minutes to an intervention (which would reduce the total number of operations a surgeon can do in a day). How can this be seen as an acceptable compromise for improved implantation accuracy from cutting-edge technology?

The Stryker MAKO RIO uses a bone milling tool on the end of a robotic arm whose position is controlled by the surgeon throughout the procedure. The robotic arm creates virtual cutting guides to prevent the over-resection of bone while preparing the surface for an implant. Image Credit: Jeremy Kooyman

Yet, CAOS systems do seem to have one kinaesthetic advantage over their RASD brethren – their lack of telesurgery capabilities. Allegedly due to lessons learnt from the automated milling functions of the ROBODOC, companies like Stryker MAKO and BlueBelt Orthopaedics both manufacture bone shaping systems that are fully controlled by the surgeon, with the robot/computer intervening only when the surgeon attempts to remove bone beyond the preoperative plan. This has the added bonus of keeping the surgeon connected to the anatomy that they’re shaping, providing a physical reminder of the person underneath the drapes. Anecdotally, I’ve heard from physicians working with the da Vinci systems that their inability to feel the underlying anatomy during the procedure leads them to feel disconnected and apply forces beyond what would be considered appropriate for traditional laparoscopic procedures. While there have been advancements in this area, any tactile feedback provided to the surgeon is still vastly inferior to our inherent sense of touch, reportedly capable of sensing ridges no higher than 13 nanometres. Perhaps future developments in the field of CAS should instead focus on augmenting the surgeon’s capabilities with technology that is intuitive to use and keeps them connected with the patient instead of isolating them behind feats of engineering.

Similar to the Stryker MAKO RIO, the Blue Belt Technologies Navio PFS is a handheld tool that shapes bone for arthoplasty, however instead of a robotic arm it can retract the burr inside the tool to prevent inaccurate cutting. Image Credit: Jeremy Kooyman

So, with the final version of the FDA’s Human Factors for Medical Devices Guidance due out in the near future, factors such as increasing recognition of AAMI/IEC 62366, and a willingness from healthcare institutions to consider increased capital costs when they’ve been demonstrated to benefit the institution in the long run, are helping to make a positive impact towards acceptance. I believe that we’ll begin to see CAS and CAOS adoption rates increase in the coming years but only if manufacturers begin to leverage usability as a mechanism for winning over surgeons who have abandoned or refuse to allow the technology into their operating theatres.

About the Author

Jeremy Kooyman is a Medical Device Design Engineer with Cambridge Design Partnership (CDP), an award winning technology development partner based in Cambridge, UK. His interests in computer-assisted surgery began in graduate school at the University of British Columbia, Canada, where he focused on the design of novel orthopaedic surgical tools to enhance surgeon performance during bone removal. At CDP, he works with engineers, physicists, and human factors researchers on next generation medical devices and drug delivery systems designed from a user-centred perspective that are safer and more effective than their competition.