Robots are helping surgeons, but so can user-centred design

What makes a successful surgical user study?

If the facilities and resources are available, there are several key elements required to ensure a successful user study which will accurately inform the development of your surgical technology:

1. Objectivity

A quality human factors user study output must put preconceived ideas about solutions and their issues aside. The aim is to look for every opportunity to design a device which enables a surgeon to effortlessly perform their procedure. If the development team approaches the study with preconceptions or a key cause they wish to address, other opportunities may be missed. The art of Human Factors Engineering is to remain impartial and to observe as much as possible without applying any influence.

Another element of objectivity which needs to be maintained is the participants in the study. Quite often, a medical device developer (whether that be a start-up or multi-national organisation) will have a key opinion leader or a surgeon who is known to them. The best participants to have in your study are those who have no affiliation or vested interest in the technology being developed. Observing a range of objective, un-biased users will give you accurate insights to inform your medical device usability development and ensure you are solving the real and most important problems.

2. Accurate representation

Having a variety of people in your study is critical. Not everyone will face the same problems when using your device and to understand the range of issues, one must consider a range of users. From our experience, the key differentiators are related to anthropometric size range, geography and hospital type. There are several key questions to ask related to these differentiators. Who will use your device? In which countries and hospital/clinic types will your device be used? If 90% of your users will be women who are based in either Germany or the US for example, you need to ensure the users in your study reflect this.

Representation should also be extended to the patient being operated on. Patient size and position will affect what the surgeon does to perform the procedure. For example operating on an obese adult patient is very different to a child.

After the user study is complete, the outcome should be objective un-biased data, such as video, photo and sound recordings, which aren’t anecdotal and have no suggestions for solutions – they must be agnostic. The output from each user touchpoint can then be rigorously analysed to identify opportunities to improve the surgeon’s experience throughout the surgical procedure, which can then be fed into the user requirements.

Creative limits are external factors which are key to the success of the device. For example, cost is critical for technologies which are to be used within the National Health Service of the UK, which can limit the viability of some solutions. If a user study identified that surgeons experienced fatigue when using a scalpel for an hour during a procedure, an augmented arm would be a possible solution; however, it would be far too costly for widespread implementation in the NHS. Other creative limits may be materials, performance, or size. Concepts must both address the problems identified in the user study, whilst remaining feasible for their intended purpose.

2. Go unnoticed!

Many surgical instruments in use today have not changed for hundreds of years. Surgeons have been trained to operate using these tools and often have many years of experience using them. Innovation in surgery needs to bring new benefits to the user whilst retaining familiarity – you don’t want the surgeon to have to spend time learning how to use the instrument or create a sense of uncertainty while in the operating theatre. If you double the size of the grip of an instrument to improve ergonomics and comfort, for example, you need to consider if this has altered the instrument so much that it no longer resembles the original.

Good design is intuitive and purposeful. The semiotics of the device need to communicate to the user how it should be used. If the user is required to do something to activate a feature of the device, it should be an obvious and logical action to achieve the desired result. I have witnessed first-hand a product concept be thrown across an operating theatre because it did not instantly work for the surgeon. Instruments need to be safe, reliable and work how they are expected to the first time a surgeon picks them up.

As with the look and feel of the instrument, reliability is key – not just for patient safety, but for the surgeon’s experience during use. All medical devices should be underpinned by sound and reliable engineering to ensure the instruments work throughout the lifetime of the device. A surgeon can achieve a lot with their hands and some stainless-steel instruments which have not changed for hundreds of years. If your device is going to be used and trusted, reliability is absolutely critical.

3. Design it for the body

As discussed in the approach to a user study, what the surgeon’s body is doing whilst using the device is key to how comfortable they are. Your device can be designed to encourage the surgeon to adopt a less strenuous posture, or to fit the surgeon’s body so that it is comfortable, intuitive and easy to use.

The key to this is a combination of anthropometrics and ergonomics. Using data, you can ensure that the handle of an instrument is designed to fit the grip of all potential users, or that the mechanisms used to activate it are within an acceptable force limit for repeated use.

Creating concepts is the second step in your early development journey; however, it is certainly not the last. You cannot judge the success or failure of these concepts based solely on data from an initial user study. It is critical to get models of the concepts you have used back into the hands of potential users as soon as possible.

Iterative evaluation of your medical device concept

The influence of the user study should be prevalent throughout the design of your concepts and throughout their iteration, with an ever-present team member who is the champion for the end user. The interpretation of the output of the study should be considered and represented to ensure that concepts stay aligned with the needs of the surgeon and continue to address the problems facing them during the procedure.

Once your concepts have been developed into functional concept models, it’s important to test them iteratively with users in their real (or simulated) environment to ensure they solve the challenges you set out to address. As a device developer, you need to ensure that your new device hasn’t caused new problems by solving old ones. For example, if you have designed your device to encourage the surgeon to adopt a less strenuous position when operating, has this had unintended consequences? Can the surgeon still use other systems they use in partnership with this new instrument? Or is it now incompatible?

Some things are hard to quantify, so if you have set out to make the device intuitive or comfortable, you need to validate this. This evaluation should not be on a single concept, but several. User studies take time and cost money, so going to users early on in your development with a single concept will likely yield a binary response – it either is or isn’t intuitive to use. Having several concept variants will aid users to articulate the pros and cons of each concept and enable you to identify what makes a concept more intuitive and which concept, or aspects of your concepts, to progress further. Sometimes, the best medical device or surgical instrument design can be a combination of previous concepts.

As noted, during the user study you should make sure that you are observing the surgeon in a representative environment. This is equally important for testing concept models. However, for the rapid iteration required for early phase concepts, the costs and lead times associated with a user study may be unviable. This is where the development of a rig (custom machinery developed for testing) or use of a specialist laboratory can be extremely useful. Rigs can be specially developed to simulate surgical conditions and enable regular and robust testing of device concepts. If environmental conditions are key to accurately assess your device performance, environmentally controlled labs should also be used.

The combination of this type of testing, in addition to quantitative data capture, is key to the success of your device. Without regular interaction with users and testing in a representative environment, developments can stray and fail to meet their original objectives.

User-centred surgical tools

Despite advances in surgical robotics, open surgery and other minimally invasive surgical procedures will continue to be required for surgeries where robots are not an option and for countries where the cost is too high. To reduce surgeon fatigue and discomfort and attain similar levels of user benefits seen in robotic systems, a user-centred approach to device development is key. Observation of the procedure should be undertaken as early as possible to ensure that opportunities for improvement are identified and implemented into the device requirements from the start of the development.

By interpreting the outcome of the study and combining user centred design with robust engineering, device concepts can be created which are intuitive, comfortable, and reliable. These should be tested iteratively throughout the development with real users to validate that they meet initial requirements set out by the first user study.

Safety, reliability and regulatory compliance are non-negotiable for any medical device development. However, by following a user-centred design development approach, you can ensure that when your device gets past the regulators and is out in the market, it is not only commercially successful, but loved by your end users and provides a benefit to them as well as the patient.