ETB-PEGASUS JOINT ANGLE SYSTEM
Carrying out a test
The straps are attached and the sensors placed in the strap pockets. The wearer stands still for 5 seconds to calibrate the sensors and then the test begins. Each test can have an appropriate protocol; it can be just level walking, or can include stair climbing and descent.
Analysing data
The sensor data is processed and all the parameters automatically presented, simply by connecting the sensors to the notebook and selecting “Analyse”.
Knee flexion
An example of a person walking on level ground is shown at the foot of the page. This shows the left and right knee angles over a period of 12 strides, the stride duration and the relative phasing between the left and right leg.
The plot directly below shows the typical stride from the yellow region chosen, plus the standard deviation. From this it is clear that the left and right legs straighten at the end of the swing phase, with the angle close to zero. The right leg remains almost straight throughout the stance phase at around 5 degrees, whereas the left knee flexes during load.
The statistics for the highlighted region are produced as a table, shown on the left. The average stride duration is 1.23s, which is quite slow for a normal person, with a 5% variation. The relative phasing between the left and right leg is 49%, only 1% lower than the 50% expected for a symmetric gait. The person tested had considerably less flexion on the right leg than the left.
Thigh and Calf motion
In this example above the left and right thigh angle for a typical stride is plotted, together with the standard deviation (dotted lines). The sagittal (blue line) and coronal angles (green line) are shown on one plot for the left thigh and a second plot for the right thigh. Similar graphs are also produced for the calf.
A summary of the findings for the example provided
The person tested has a full right leg prosthesis. From the knee flexion angle analysis it can be seen that the right knee flexes less than the left knee in the swing phase. In the stance phase the right knee does not flex, whereas the left knee does. The left knee flexion of 64 degrees is typical of a healthy subject, whereas the right knee flexion of 48 degrees is noticeably less. When the analysis is broken down to the calf and thigh segments it is clear that the right thigh profile is different to that expected from a person with a normal gait, whereas the left thigh closely resembles a normal gait profile. There is greater retraction in the swing phase on the right thigh.
