Ambroise GENUX 2 ORTHOSIS User - Page 5

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THE GENUX 2 – DYNAMIC 4 POINT BALANCING

The GENUX 2 is the first brace in the world with Dynamic 4 Point Balancing. This is a truly unique systems that we've developed with various

positive effects. Dynamic 4 Point Balancing is a system in which the straps of the brace just above and just below the knee are connected to

each other by means of a smart cable. This cable runs posteriorly of (behind) the centre of

rotation of the knee joint. As a result the cable allows the straps to become loose in flexion,

but to tighten in extension. The positive effects of this system are subsequently described below:

Extension Preloading

When the knee extends, the straps of the interface just above the knee and just below

the knee tighten themselves because the cable, that connects these two straps and

that runs behind the centre of rotation of the knee joint gets tightened. With this

tightening of these two straps the soft tissues of the leg at all 4 interface locations of

the brace are compressed/tensioned, gradually 'gripping' the brace tightly to the leg.

When the leg reaches full extension brace and leg form a rigid combination with a

direct transfer of the stabilising forces from the brace to the leg.

This is (and feels!) much more stable because you prevent that the brace, once you

start loading the leg by standing on it is first pressed into the soft tissues, before it

actually does anything, allowing the leg to give way a little.

Extension Triggering

Patients that need to control a hyperextension feel the built up of the correction

forces of the straps just below and just above the knee increasing before their foot

is on the floor and the leg gets loaded by body weight. That triggering reduces the

active component of pushing the knee in hyperextension that patients often have. They do actively push their knee into

(hyper)extension, because the body needs to feel that the knee is stable enough to start loading the leg. There are no sensors in the

leg that accurately tell the brain the alignment of the leg, so feeling the 'end' of extension (even if that's in hyperextension) is the

only trigger left. With the extension triggering the brace gives that signal a lot earlier, combined with a more rigid grip of the brace

to the leg leading to a reduction of the excessive extension forces.

Force Balancing

Because of the cable that connects the straps around the knee, the force in these straps need to be equal. If not, the cable is pulling

the strap with the lower force until the forces are equal again. This balancing of these two forces ensures that not one is taking most

of the load, whereas the other does little to nothing. Furthermore, since the lever arms of the lower leg are made equal to that of

the upper leg, the forces on the pelottes (interfaces) at the top and bottom of the brace are equal as well and equal to the balanced

strap force. This is a very nice feature, because we now never have the situation in which one interface doing a lot more than another.

This prevents excessive interface forces that can be uncomfortable. But it also means that we know a lot more precise what the

maximum loading on the system will be and that allows for a huge step in optimization of the weight of the orthosis.

Sitting Comfort

A very tight, snug fitting of the brace is nice in having a direct action of the brace to what the leg is doing. However it's not so nice

in sitting, particularly if we realise that the shape of the leg (due to a different alignment of muscles and tendons in a 90° flexed

position, compared to a straight leg) is somewhat different. For instance, the upper leg just above the knee is narrower but somewhat

higher (in front side to back side of the leg) in sitting than in stance. The coupling of the straps just around the knee loosens these

straps in bending the knee. This allows for a great increase in comfort during sitting.

Anti slipping

In the earlier model (the GENUX I) we've proven the need for skin migration underneath the brace just above the knee at the front

side of the leg in flexing the knee to prevent the skin from pulling the brace downwards (see https://www.ambroise.nl/en/leg-

User information | +31 (0)53 4302 836 | [email protected] | www.ambroise.nl

GENUX.2023.01

Figure 3: When the knee extends the cable of the

Dynamic 4 Point Balancing System pulls the straps just

above and just below the knee tighter to the leg. When

the knee flexes, the opposite happens: the straps are

loosened.