Microprocessor Controlled Prosthetics
Microprocessor controlled (MPC) prosthetic knees have revolutionised the performance and safety of lower limb prostheses over the past couple of decades, inspiring confidence and improving function for many amputees.
In more recent years, a good number of microprocessor-controlled foot and ankle components have also appeared, offering equivalent function in the prosthetic ankle joint.
This video of Pace patient and physiotherapist demonstrates the function and stability of a MPC in a variety of everyday environments.
‘Move in a natural way’
MPC components differ from conventional ones in that they carry an on-board computer (micro-processor) which gather information from the environment and detects how the user is behaving. The information is interpreted by the microprocessor which then dictates the behaviour of the component.
Most components measure these properties in real time, generating continuous small adjustments, influencing the foot or knee to move in a natural way whilst keeping the user safe.
‘Improving comfort & stability’
Using the MPC foot/ankle systems as an example, the rate of movement of the ankle and the resistance to that movement will be generated according to user weight, walking speed, orientation of the surface underfoot etc.
If a user walks or stands on a ramp, the MPC will adapt the ankle position to the incline, enabling the user to maintain a good, safe posture without the effort required for non-MPC feet.
At the same time, the forces acting within the socket are minimised, improving comfort and stability. If he/she picks up a heavy bag, the resistance setting will adjust, ramping up the resistance to movement to compensate for the added weight.
‘Mimic normal movement’
Similar principles apply to the MPC knees. If there is pressure under the heel of the prosthetic foot, it indicates the user is putting weight through the prosthesis, making the knee resist bending so it carries the user’s bodyweight safely. When the pressure moves forward under the foot and the toes leave the ground, it means the knee has entered the “swingphase” of gait and the knee moves freely to mimic normal movement.
MPC knees differ in performance and sophistication, but they all have user safety in common as an important part of their function. They keep people upright if they trip or stumble. A “stumble recovery” feature is activated if the user makes a mistake like stubbing their prosthetic toe whilst crossing a threshold.
A patients’ perspective
When people feel safe, they gain confidence. With better confidence, they become more active and try new things, resulting in improved function and quality of life. Not much else is more important.
This video demonstrates is a example of how appropriate provision of a MPC device can have a huge and positive impact on a patients’ every life and help them return to activities the enjoyed prior to their life changing incident.
‘Trials can support prescription’
Choosing the correct components for an individual requires understanding of the individual need. Given that many MPC components are fairly costly, a trial is often indicated which can both give the individual an opportunity to use it for a time and generate some objective data to support prescription.