Interview: How a modern leg prosthesis can support active athletes

Modern, computer-assisted prostheses offer a great deal of comfort and freedom for people who want to surf, go mountaineering or do similar sports despite a transfemoral amputation. They have been equipped with powerful sensors and microprocessors for decades. Depending on the manufacturer and model, the prostheses are also waterproof and corrosion-resistant. Health insurance companies will cover the costs if required.

According to David Wucherpfennig, Market Manager Prosthetics at Ottobock, the Genium X4 is "a microprocessor-controlled prosthetic knee joint that adapts to the user's movements in real time". For the most natural gait possible, various sensors are built into the Genium X4 to detect the position and movement of the knee joint in real time and support people who are missing a leg, for example, when walking, standing, climbing stairs and cycling.

We spoke to Björn Eser, an enthusiastic user of the prosthesis, about the benefits. After suffering from bone cancer, he decided to have his leg amputated above the knee in 2005. His computer-controlled leg prosthesis offers him many advantages in everyday life, but also in his free time – when hiking or doing exotic sports such as canyoning.

heise online: What was it like for you after the amputation?

Björn Eser: Getting used to life with one leg went relatively well for me. My recovery went without a hitch. Three months after the amputation, I was back working full-time in development cooperation. After five months, I went on my first business trip to South Sudan again. I am very active and since 2017 I have also been running an information service, The Active Amputee, for people with amputations and walking or mobility impairments. Auf my blog I report on my own experiences and invite others to share their experiences in articles.

In this context, I approached Ottobock a few years ago to find out more about the prostheses I use. Ottobock and I have cooperated quite a lot in recent years, which is of course very exciting for me. In addition to sharing my experiences, I am also available for product tests, trade fairs and other events. For example, since mid-May I've also been wearing the Genium X4, one of the most highly developed knee joints.

How did the adjustment to the new high-tech prosthesis go?

If I take the first few weeks in the rehabilitation phase out of the equation, the Genium X4 is now the fourth microprocessor-controlled knee joint that I have used in the almost 20 years since my amputation. Of course, it was a huge advantage for me that I started out with a C-Leg –, i.e. also a microprocessor-controlled knee –. This made it possible to be active, mobile and independent in everyday life. After six years, I switched to the first Genium, which added a few new features. But if you can walk on a C-Leg, the changeover is not difficult.

You master some of the new functions immediately and intuitively. With other new features, I had to get used to them at first, which meant actively getting rid of old patterns and internalizing new movement sequences. I first had to learn to walk up the stairs alternately. When you've been dragging your leg up stairs for decades, it's difficult to alternate walking up stairs again. The movement pattern is no longer ready and the muscles for the movement sequence may no longer be the fittest.

After an amputation, many things in everyday life are unfamiliar at first, for example walking on different surfaces such as cobblestones, mud or wet slopes. So even supposedly small things in everyday life can be a challenge. You need more energy for almost everything, even for completely normal things. And the incorrect loading of joints and muscles also affects the entire musculoskeletal system. Modern prostheses help here and make life considerably easier - and often much safer. The latest prosthesis from Ottobock, for example, supports walking uphill. The prosthesis helps people to walk as naturally as possible. I'm out and about a lot, often covering 10 to 15 kilometers a day. I notice that I now have more energy at the end of the day. With the previous models, this was much more noticeable in the evening.

Can you control the functions of your prosthesis with an app?

Yes, that has been possible for some time. The prosthetist first makes certain settings. These depend on the respective user, i.e. weight, foot size, activity level and similar. When walking, these settings are then adapted very precisely to the respective needs, such as how much resistance you need when walking downhill or how much support you need when sitting down.

As a user, I can use an app to make even more fine adjustments, exactly when I need them in everyday life. The app is important when I'm using a ladder, for example. Then I have to go up and down and don't have a normal gait pattern. If I'm standing on the ladder and leaning forwards or backwards and my foot is perhaps not being loaded as usual, I don't want the knee joint to suddenly give way under me. It should buckle ten or 15 degrees at most and then lock. It would be unfortunate if, at a height of six meters, the leg suddenly thought it was in a gait phase and no longer gave me any support. I can set this via the app. As soon as the work on the ladder is over, I remove this limitation and switch back to everyday mode. That's very practical.

How often do you use the app in everyday life?

I have to admit, I don't use the app every day. That's because many of the new functions work automatically. It's no longer necessary to switch between them. Let's take cycling, for example. The knee has to swing freely; in other words, all the resistance that is so important when walking has to be removed. Until the previous model, this was done via an app. The prosthesis now recognizes this automatically when I start pedalling. Now I don't have to change the mode first. Especially in winter, it's very convenient not to have to get my phone out of my pocket.

Equally helpful is a new function called "Start to Walk". This simply means that I can take the first step with the prosthetic side. That doesn't sound like a big deal at first, but previously I always had to walk with the leg that was still attached and take the first step with it. This is also included in the basic patterns and doesn't have to be activated separately via the app. That's why I only use the app when I'm doing certain sports where the basic knee settings don't make sense and the prosthesis has completely different requirements,

What sensors are there in the leg?

There is a gyroscope and acceleration sensors, for example. The joint then knows the spatial position of the leg at all times. This is controlled by so-called rulesets, which are programmed and continuously optimized by the developers –. User requests are also taken into account. There are certain MyModes that can be set accordingly, for example for riding, playing golf and now also for walking under water. You can choose these modes.

I was canyoning, for example, and the resistance is much greater when walking in water and wearing a wet, heavy wetsuit. This is a challenge for the prosthesis and the user. Not really a good sport for amputees, you might think. It never occurred to me to "develop an underwater walking mode" because it seemed too specialized. And with the new Genium X4, I found out that there is now a setting for exactly that. Super! I've now tried it out in the swimming pool.

How long does the battery last?

Usually five days in my everyday life. However, I'm very active, so it can sometimes be less. We went hiking in the Eifel for four days in October – with luggage, covering more than 20 kilometers each day. The battery just about lasted. But it was short and I hadn't packed a charger. I had to charge my first prosthesis every other night. A lot has changed since then. And for us users, this is a huge advantage that makes us much more independent.

(mack)