Is A Motor-Driven Adaptive Prosthetic Socket Better for Below Knee Limb Loss?

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Properly fitted prosthetic sockets are crucial for people who wear lower-limb prostheses. However, existing prosthetic sockets require constant fit monitoring throughout the day. If they need adjustment, prosthetic users must remove the prosthesis to add socks or manually adjust the socket panels. This process can be quite burdensome, requiring constant attention and interfering with other daily responsibilities.

This is where the adaptive prosthetic socket comes in. It’s designed to sense fit changes and make appropriate adjustments automatically. Existing iterations can do this using various strategies, including fluid-filled bladders, powered actuators, and pressure sensors for feedback control. Researchers have also studied elevated vacuum technology and distance sensing for automated pressure control and socket size adjustment.

However, these versions still have room for improvement. Researchers are developing an adaptive socket that balances a stable limb-socket connection while maintaining the health of residual limb soft tissues. A prototype of a motor-driven adaptive prosthetic socket for below-knee prosthesis users has been tested, and the findings were published in the journal Scientific Reports in May 2024.

A new controller  

The research focused on expanding size-adjustable prosthetic socket technology in two ways: first, by adding motor-driven adjustment through a smartphone app, and second, by incorporating automated adjustment to maintain socket fit.

These advancements can potentially improve the quality of life for prosthesis users by lessening the mental and physical challenges associated with regular socket fit adjustments. 

This innovative prosthetic socket features motor-driven adjustable panels that can monitor physiological responses to stabilize limb volume. Study participants used a smartphone app to release the socket panels while sitting, enabling them to make precise adjustments to the socket size.

The study  

Twelve participants, ten males and two females, with single below-knee amputations who are classified as Level K-3 ambulators or higher, tested the prototype in auto, manual, and locked modes. Only the app’s socket size adjustment was active when in manual mode. Meanwhile, the participants couldn’t make any adjustments in locked mode.

Eleven of the participants lost their limbs from trauma; one was amputated due to diabetes complications. Eight residual limbs were conical in shape, three were cylindrical, and one was bulbous.

Results  

The study found that the participants used their prosthetic legs differently depending on the mode used—auto, manual, or locked. Generally, most participants were more active in auto or locked mode than in manual mode.

Step count and prosthesis use

There were differences in the number of steps they took and how long they wore the prosthetic leg each day. In auto mode, the control system was active for a significant amount of time while walking. This mode helped maintain a good fit for the prosthetic leg and provided support when needed.

Generally, participants who were already highly active got the most steps in auto mode, while those with low activity levels were more active in locked mode. 

Additionally, three out of the four least active participants who tested auto mode showed higher step counts in locked mode than in the other modes. Moreover, two participants who tested only manual and locked modes had higher step counts in locked mode.

Walk bout and doff time

This uptrend in step count was also seen in other activity metrics, like walk bout time, which refers to the time when four or more steps are strung together in one or multiple 10-second windows, and daily doff time, which refers to the process of taking off a prosthetic.

Of the six study participants who increased their daily step count in auto mode, five also increased their daily walk bout time in the same mode. Additionally, four out of six participants decreased their median daily doff time in auto mode.

Interestingly, the two participants who exclusively tested locked and manual modes demonstrated higher median daily walk bout times and less doff time in the locked mode compared to manual mode.

Comfort levels

The participants reported high comfort levels with minimal differences between the modes, except for one participant. Most liked using the auto or manual mode to maintain a suitable socket fit, while six out of nine participants didn’t like the locked mode.

The study participants also liked using the smartphone app control for prosthetic socket adjustments.

What could be improved?

The participants also reported some challenges while wearing the prosthetic socket, like the socket size. They suggested that the prosthesis would be better if it had a feature that allowed them to monitor battery power easily. The quick adjustment features could also be better.

The bottom line  

Motor-driven adaptive prosthetic sockets show great promise in improving the quality of life for prosthesis wearers. The study demonstrated that the adaptive prosthetic socket, particularly when used in auto or locked mode, led to increased step counts and improved comfort levels for participants.

These findings underscore the potential of motor-driven adjustable panels and smartphone app integration in providing automated and efficient adjustments to maintain socket fit.

Further refinement and development of this technology could lead to significant advancements in the field of prosthetics, ultimately enhancing the mobility and overall well-being of individuals with lower-limb amputations.