One of the most time consuming parts of fitting a prosthetic leg, is using a gait laboratory to analyse how the person's body normally moves. How they step, how they lean, weight distribution for a range of activities. This is used to find the optimal placement for the prosthetic, that fits most optimally with how the person is used to distributing their weight.

Unfortunately, in the lab, it is typically not possible to look at a long job, or a large number of steps. Its not possible to examine the full range of movements encountered in that person's daily life. A best guess is therefore required.

Now, there might be an alternative. Researchers at the Fraunhofer Institute for Surface Engineering and Thin Films IST in Braunschweig, Germany have developed a sensor system that fits into a prosthesis for a more long term analysis.

The prosthesis adapter is itself attached to a prosthetic leg, and is worn for a full day, by the person being fitted, and which calculates in real-time how the weight is distributed across it. The adapter measures 4 x 4 x 3 centimetres and sits at the ankle joint or above the knee. It measures the applied forces in three spatial dimensions and three torque moments. 32 strain gauges are placed at a number of different points and in different orientations, so the data provides a complete and accurate picture of the load acting on the prosthesis.

The first tests are underway at time of writing, with hopes that in the future this adapter will be fitted to all prosthetic limbs, to gauge how they interact under torque, with the rest of the body. This greatly aids final placement, and removes the guesswork from the equation.

References

Sensitive fitting process for leg prostheses