Auto Control of Volume Management for Limb Loss

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.

Study Overview

• Status: Completed
• Conditions: Lower Limb Amputation Below Knee (Injury)
• Intervention / Treatment: Device: Adjustable socket

Detailed Description

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.

• Study Type: Interventional
• Enrollment (Actual): 104
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Joan E Sanders, PhD; Phone Number: (206)221-5872; Email: jsanders@u.washington.edu

Study Locations

• United States
  • Washington
    • Seattle, Washington, United States, 98195
      • University of Washington Bioengineering

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years and older (Adult, Older Adult)
• Accepts Healthy Volunteers: No

Description

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.

Study Plan

How is the study designed?

Design Details

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

Number of Arms

8

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Aim 2 - Adjustable Socket - Researcher Controls; An adjustable socket is tested where researchers control the adjustments. This arm focuses on socket size adjustments while walking.	Device: Adjustable socket; 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.
Experimental: Aim 3 - Adjustable Socket - Participant Controls; An adjustable socket is tested where the study participant controls the adjustments. This arm focuses on socket size adjustments while walking.	Device: Adjustable socket; 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.
Experimental: Aim 4 - Adjustable Socket - Automatic Controls; 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; 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.
Experimental: Aim 6A - Release/Recovery - Researcher Controls; 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; 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.
Experimental: Aim 6B - Release/Recovery - Participant Controls; 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; 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.
Experimental: Aim 8 - Panel Pull During Resting; 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; 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.
Experimental: Aim 9 - Panel Pull During Ambulation; 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; 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.
Experimental: Aim 10 - Adjustable Socket Out of Lab Testing; 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; 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.

What is the study measuring?

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

Collaborators and Investigators

• Sponsor: University of Washington
• Investigators: Principal Investigator: Joan E Sanders, PhD, University of Washington

Study record dates

Study Major Dates

• Study Start (Actual): August 7, 2015
• Primary Completion (Actual): September 1, 2021
• Study Completion (Actual): January 1, 2022

Study Registration Dates

• First Submitted: May 3, 2018
• First Submitted That Met QC Criteria: May 25, 2018
• First Posted (Actual): June 8, 2018

Study Record Updates

• Last Update Posted (Actual): May 3, 2023
• Last Update Submitted That Met QC Criteria: April 28, 2023
• Last Verified: April 1, 2023

More Information

Terms related to this study

• Keywords: Amputee; Prosthetic Socket; Adjustable Socket
• Other Study ID Numbers: STUDY00001779

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: Yes
• product manufactured in and exported from the U.S.: No