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Ottobock’s Harmony System Simplifies Residual Limb Volume Management

Posted by Bryan Potok on

Most prosthesis users—especially lower-limb amputees—complain that the volume of their residual limb diminishes throughout the day. In fact, by the time lunch rolls around, adding another prosthetic sock is common. Ottobock offers a solution to this problem by creating a system that actively manages residual limb volume.

 Ottobock Harmony Vacuum System actively manages residual limb volume.

Ottobock designed the Harmony System for transtibial as well as transfemoral prostheses users. The system features five components: PUR (Polyurethane) liner, sheath, Harmony socket, sleeve, and Harmony pump.

Researchers at St. Cloud State University in Minnesota found that using all five components together effectively prevents volume loss and minimizes residual limb volume fluctuations throughout the day. Furthermore, studies also found that using the Harmony System promotes better blood circulation in your residual limb.

Residual limb fluctuation  

As the day goes on, the residual limb loses its volume while wearing a prosthesis. This phenomenon is attributed to traditional weight-bearing sockets that squeeze fluid out of your residual limb. These conventional sockets “press” tissue fluid out of the residual limb during the phase of walking wherein the foot remains in contact with the ground.

Although the fluctuation of residual limb volume is expected, the extent of these fluctuations depends on various factors, including vascular diseases, the condition of the connective tissue, age of the prosthetic user, and the type and fit of the socket.  

To address volume loss, most lower-limb amputees will add a gel sock or a knitted prosthetic sock in the afternoon, which provides short-term relief. 

Conventional sockets that use either a one-way valve and pin liner system can not prevent volume fluctuations. Users of both systems often report movement between their residual limbs and the socket, which often leads to painful skin irritations. To counteract these effects, lower-limb prosthetic users need to implement effective volume management.    

An active volume management system  

The components of Ottobock's Harmony System simplifies residual limb volume management.

Credit: Ottobock US

Ottobock designed the Harmony System to prevent volume fluctuations in the residual limb. The Harmony system prevents pressure peaks in load-bearing areas of your socket, which makes maintaining a full connection between the prosthesis and residual limb effortless.

During the stance phase of walking, instead of squeezing tissue fluid out of your residual limb, the Harmony System distributes pressure over the entire surface of your limb evenly. This mechanism reduces the total load on your limb and stabilizes the amount of fluid in your residual limb. This stabilization and negative vacuum pressure created by the Harmony pump prevents your prosthesis from squeezing fluid out of your limb and requiring additional sock ply. 

Optimum socket fit  

It is widely known that prosthetic users can only make the most out of their prostheses if their socket fit is optimal. To date, existing prosthetic technology forces the natural contour of your residual limb to adapt to the walls of your prosthetic socket. The more the contours of your limb differed from the socket shape, the greater the compromise between comfort.

It’s a good thing that along with the Harmony System comes a new plaster cast and modeling technique that makes representing individual limb contours possible within a prosthetic socket. This new technique, performed by your prosthetist, optimizes socket fit and simplifies the modeling process. Coupled with a custom prosthetic liner that is formulated to change shape when pressure is applied, equals increased comfort. 

To be able to fit the Harmony System, prosthetists are required to learn this new plaster cast and modeling technique. This makes wearing leg prostheses more comfortable than before.

Do you use the Harmony System? Have you worn other systems? Please share your experiences in the comments section below.
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<a href="https://amputeestore.com/blogs/amputee-life/ottobock-harmony-system-simplifies-residual-limb-volume-management">Ottobock’s Harmony System Simplifies Residual Limb Volume Management</a>

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6 comments


  • Darryl- my prosthetist and I found a material you put between your outer sleeve and your socket. It effectively will stop any vacuum leaks with the outer sleeve. It’s a thin silicon material and acts as a barrier for these leaks. Works amazing and allows me to keto a sleeve for 4-6 months. I’m very active and this material is amazing!

    Peter M on

  • Is this system for AKA (above knee) amputees? How do you get measured for it? Where can you purchase it?

    Joseph on

  • Any information on the Harmony System specifically for AK amputees? I looked on Ottobock’s website and did not find any testimonials or information regarding AK and the Harmony System. Thank you.

    Tracy McNair on

  • Does this system apply to AK customers

    FAye on

  • I switched from pin lock to the Harmony system nearly 3 years ago. I’m very pleased. I’m an auto mechanic and do a lot of standing. I’d have to add prosthetic socks 2 or even 3 times daily depending on how much walking or standing I did. When I switched to the harmony system, after about a week I no longer had to add socks during the day. Whatever I stated with is what I end th day with. Also, the condition of my skin improved. It used to look rough. Now it looks just as good as the skin on my good leg. Finally, with the pin lock it seemed that the skin on the end of my stump would stretch and allow the stump to piston in the socket. This no longer occurs. The one down side is the fact that I’m always damaging the outer sleeve creating pinholes and vacuum leaks. So I have to replace the sleeve every 2-3 months at $160+ . That’s a significant expense. But it’s worth it due to the increased comfort.

    Darryl Forbes on


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