Prostheses today – from mechanics to myoelectric technology
How you create good working conditions for the staff
Prostheses have been part of the orthotist trade since humans first lost a body part and needed to regain some function. Today, prosthesis technology ranges from simple mechanical solutions to advanced systems with sensors, microprocessors, and electric motors. Common to them all is that they must be fitted to the individual user by an orthotist who understands both the craftsmanship and the technology behind it.
§Mechanical prosthetics – still a solid foundation
Recycled metal
§Microprocessor-controlled knees
At the other end of the scale are microprocessor-controlled prosthetic knees, where a built-in computer continuously adjusts the knee's resistance. Manufacturers like Ottobock use sensors such as gyroscopes, accelerometers, force sensors, and angle gauges in the knee joint itself to read how the user is moving and adjust the hydraulic resistance accordingly. Some models have features that react if the user stumbles, while others are designed for step-over-step stair descent and to provide a more stable standing function.
§Myoelectric arm and hand prostheses
For arms and hands, myoelectric prostheses are available, in which electrodes on the skin surface register the weak electrical signals from the user's own muscle activity. A built-in microprocessor converts the signals into specific movement commands, so the prosthesis can, for example, switch between different grip patterns. The advantage is that the user has a high degree of control over the prosthesis through their own residual musculature, but it also demands that the electrodes are positioned correctly and that the signals are calibrated to the individual user.
| Type | Steering | Typical use |
|---|---|---|
| Mekanisk/hydraulisk | Physical movement and spring force | Robust everyday use |
| Microprocessor-controlled knee | Sensors and electronically adjusted resistance | Uneven terrain and stairs. |
| Myoelectric hand/arm | Electrical signals (EMG) from the skin. | Fine motor skills and handling of objects |
§Orthotists work with among other things plaster, thermoplast, leather, metal and carbon fiber - not with building concrete.
Regardless of how advanced a device is, it builds on these concepts. When you troubleshoot, you constantly return to them: Is there voltage here? Is there current flowing? What's stopping it? Is the signal as it should be? The one who has mastered the fundamentals can work with almost anything — the one who skips it gets stuck at the first fault.
“A prosthesis is never better than the socket it sits in – regardless of how much electronics are inside.”
— Practice from the workshop