Auto Control of Volume Management for Limb Loss

Study Overview
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Brief Summary
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The aim of this research is to create a prosthetic system that will automatically adjust the fit of the socket and create a well-fitting prosthesis for people with leg amputations who experience volume fluctuations when using their prosthesis.

Detailed Description
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People with lower limb amputations often experience daily changes in the size (volume) of their residual limb. These daily changes can cause a prosthesis to fit poorly. They can also cause limb health problems including skin breakdown and injury to deeper tissues. Prosthetic socket systems that accommodate limb volume changes can help address these issues, but they require users to make adjustments throughout the day. The objective of this research is to develop and test an automatically-adjusting prosthetic socket system for prosthesis users. The system integrates with a range of adjustable socket technologies, including those that are commercially available. The system allows small size adjustments for both tightening and loosening the socket. In early aims of the study, the prosthesis will be adjusted manually, but can be controlled remotely, eliminating the need to remove the prosthesis or bend down to make adjustments. The system will later be enhanced to automatically change the fit of an adjustable socket at the appropriate times, without distracting the user. We hypothesize that this system will help to maintain consistent limb fluid volume while the prosthesis user is wearing the socket and that socket fit will be improved. The system functions by continuously collecting measurements from sensors within the socket and uses small motors to control adjustable panels in the socket wall.

Official Title
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Auto Control of Volume Management for Limb Loss

Conditions
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Lower Limb Amputation Below Knee (Injury)

Intervention / Treatment
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* Device: Adjustable socket


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: 18 years of age or older Unilateral transtibial amputee At least 6 months post-amputation Wear prosthesis at least 3 hours per day Use an elastomeric (i.e. gel) liner K3 or higher Medicare Functional Classification Level Able to walk continuously with prosthesis for at least 5 minutes at a time, sit, stand, and step up a height of 5.0 cm. Residual limb of 9.0 cm or longer Experience problems with volume fluctuations that affect their prosthetic socket fit Exclusion Criteria: Participants experiencing skin breakdown on enrollment will be excluded, but can enter after having been free of clinically visually-apparent skin breakdown for two weeks.

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Supportive Care
Allocation: Non-Randomized
Intervention Model: Single Group Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Aim 2 - Adjustable Socket - Researcher Controls<br>An adjustable socket is tested where researchers control the adjustments. This arm focuses on socket size adjustments while walking. | Device: Adjustable socket<br>* The adjustable prosthetic socket will be used to test the influence of socket size adjustments during sitting, standing, and walking activities to determine if these strategies can be used to improve socket fit and reduce fluctuations in limb volume.<br>|
| Experimental: Aim 3 - Adjustable Socket - Participant Controls<br>An adjustable socket is tested where the study participant controls the adjustments. This arm focuses on socket size adjustments while walking. | Device: Adjustable socket<br>* The adjustable prosthetic socket will be used to test the influence of socket size adjustments during sitting, standing, and walking activities to determine if these strategies can be used to improve socket fit and reduce fluctuations in limb volume.<br>|
| Experimental: Aim 4 - Adjustable Socket - Automatic Controls<br>An adjustable socket is tested where a control system is used to automatically control the adjustments. This arm focuses on socket size adjustments while walking. | Device: Adjustable socket<br>* The adjustable prosthetic socket will be used to test the influence of socket size adjustments during sitting, standing, and walking activities to determine if these strategies can be used to improve socket fit and reduce fluctuations in limb volume.<br>|
| Experimental: Aim 6A - Release/Recovery - Researcher Controls<br>An adjustable socket is tested where researchers control the adjustments. This arm focuses on a socket release and recovery mechanism that allows for full or partial doffing of the socket while seated. | Device: Adjustable socket<br>* The adjustable prosthetic socket will be used to test the influence of socket size adjustments during sitting, standing, and walking activities to determine if these strategies can be used to improve socket fit and reduce fluctuations in limb volume.<br>|
| Experimental: Aim 6B - Release/Recovery - Participant Controls<br>An adjustable socket is tested where the study participant controls the adjustments. This arm focuses on a socket release and recovery mechanism that allows for full or partial doffing of the socket while seated. | Device: Adjustable socket<br>* The adjustable prosthetic socket will be used to test the influence of socket size adjustments during sitting, standing, and walking activities to determine if these strategies can be used to improve socket fit and reduce fluctuations in limb volume.<br>|
| Experimental: Aim 8 - Panel Pull During Resting<br>The purpose of Aim #8 was to determine if vacuum-like action (panel pull) during resting between periods of activity facilitated limb fluid volume recovery and retention in transtibial prosthesis users. Liner attached to panels. | Device: Adjustable socket<br>* The adjustable prosthetic socket will be used to test the influence of socket size adjustments during sitting, standing, and walking activities to determine if these strategies can be used to improve socket fit and reduce fluctuations in limb volume.<br>|
| Experimental: Aim 9 - Panel Pull During Ambulation<br>Extending from the Aim #8 results, we sought to determine in Aim #9 if vacuum-like action during ambulation facilitated limb fluid volume recovery and retention. Vacuum-like action was achieved by quickly pulling the panels and liner (liner attached to panels) radially outward during late stance phase and then moving them back to their original position during early swing. | Device: Adjustable socket<br>* The adjustable prosthetic socket will be used to test the influence of socket size adjustments during sitting, standing, and walking activities to determine if these strategies can be used to improve socket fit and reduce fluctuations in limb volume.<br>|
| Experimental: Aim 10 - Adjustable Socket Out of Lab Testing<br>Participants took the investigational device home in one of three test modes. In the first mode, the panels were in a locked flush position, similar to their traditional prosthesis. Participants were not able to adjust the panels in this first mode. The second mode allowed participants to manually make panel adjustments, incrementally enlarging or tightening the panels radially. Lastly, the third mode implemented the automated controller developed in the previous aims. Participants were still able to make manual adjustments to the panel positions but during walks adjustments would also occur automatically. Each mode was tested for a minimum of 1 week. | Device: Adjustable socket<br>* The adjustable prosthetic socket will be used to test the influence of socket size adjustments during sitting, standing, and walking activities to determine if these strategies can be used to improve socket fit and reduce fluctuations in limb volume.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in Limb Volume | Limb volume fluctuations will be measured in real-time as socket adjustment strategies are tested. This will be accomplished using a portable bioimpedance device with thin sticky electrodes that are placed on the residual limb. Specifically, the change in limb volume will be assessed from a baseline period where no socket adjustments are made to another period within the same test session where socket adjustments are made. | Change from baseline period (non-adjustment) to test period (adjustment), commonly each 1 hour long and separated by a seated period of approximately 30 minutes. | 
| Change in Limb Movement | Limb movement within the socket will be measured as socket adjustment strategies are tested. It will be used as an indicator of how well the socket is fitting (loose, tight, etc). The measurement will be made using an inductance sensor that is placed in the socket which measures the displacement of a sensor patch on the prosthetic liner. Specifically, the change in limb movement will be assessed from a baseline period where no socket adjustments are made to another period within the same test session where socket adjustments are made. | Change from baseline period (non-adjustment) to test period (adjustment), commonly each 1 hour long and separated by a seated period of approximately 30 minutes. | 
| Number of Participants With Increase in Limb Fluid Volume After Panel Pull | Limb volume fluctuations will be measured in real-time as socket adjustment strategies are tested. This will be accomplished using a portable bioimpedance device with thin sticky electrodes that are placed on the residual limb. Specifically, the change in limb volume will be assessed from a baseline period where no socket adjustments are made to another period within the same test session where socket adjustments are made. | Change from baseline period (non-adjustment) to test period (adjustment), commonly each 1 hour long and separated by a seated period of approximately 30 minutes. | 
| Integral of Absolute Error to Maintain Set Point | Clinically acceptable socket volume error as measured by an automatically adjusting prosthetic socket attempting to maintain a set socket volume set point, based on sensed distance (measured in mm). | Over 30 minutes of controlled use of the auto-adjusting socket | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Adjustable Socket Mode Preference | Participants tested the adjustable prosthesis in their home environment in one of three adjustment configurations: locked where panels were kept in position and did not move, similar to their own prosthesis manual where panels were able to be adjusted inward or outward radially, by the participant via a phone app automatic where panels adjusted inward or outward radially as when the participant walked for a sufficiently continuous amount of time. Participants were also able to manual adjust panels as needed in this mode as well. | After 3 weeks of use, where each mode was tested for about 1 week | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Prosthetic Socket, Amputee, Adjustable Socket