Socket-leg Interface Movements in Transtibial Amputees (SLMinTTA)

Socket-leg Interface Movements as a Measure of Dynamic Prosthetic Fit for Transtibial Amputees: An Exploratory Study

This exploratory interventional study investigates dynamic prosthetic fit in unilateral transtibial prosthesis users by objectively measuring socket-leg interface movements (SLMs) during functional activities. During one single study visit, participants complete standardized laboratory tasks using three different suspension systems (pin-lock, passive vacuum, and active vacuum) applied to a transparent replica of their current prosthetic socket. Motion capture, force measurements, and patient-reported outcomes are used to evaluate how suspension systems influence interface motion, rotation resistance, gait characteristics, and user comfort. The study aims to improve clinical understanding of prosthetic fit and support more informed prosthetic decision-making in routine care.

Study Overview

• Status: Not yet recruiting
• Conditions: Transtibial Amputation - Unilateral
• Intervention / Treatment: Device: Pin-Lock Suspension System; Device: Passive Vacuum Suspension System; Device: Active Vacuum Suspension System

Detailed Description

Transtibial prosthetic fit strongly influences user comfort, gait quality, and long term functional outcomes. Current clinical assessment methods rely primarily on subjective clinical observation and user feedback. Dynamic socket-leg interface motion (SLM) offers an objective biomechanical indicator of prosthetic fit, but existing studies are limited in sample size, measurement directions, and evaluation across different suspension systems.

This study evaluates SLMs using 3D motion capture, force sensors, and a dynamometer while participants perform three standardized task categories:

isometric rotation tasks to determine rotation resistance and torque thresholds for interface rotation; turning/rotational/pivoting walking tasks to assess functional performance and transverse plane dynamics; and treadmill walking at multiple speeds to quantify proximal-distal pistoning and gait kinematics.

Each participant is tested using three suspension system conditions (pin-lock, passive vacuum, active vacuum), starting with their preferred suspension system followed by a counterbalanced order to minimize bias. A transparent "test socket" replicating the participant's own socket allows interface visualization and marker tracking without altering the intended use of the prosthesis. The investigational device consists only of CE marked components used within their intended purpose.

Participants attend one study visit with a duration of approximately 4 to 5 hours, including prosthesis adjustment and placement, marker setup, data collection across all three task categories and with all three suspension system conditions.

The primary aim is to quantify the effects of suspension system and load conditions on SLMs and gait performance. Secondary aims assess relationships between objective SLM measures and patient reported comfort, functional ability with the prosthesis, and prosthesis satisfaction. Findings will support improved understanding of dynamic fit behavior, help characterize suspension system performance, and inform future development of objective prosthetic fitting assessment methods.

• Study Type: Interventional
• Enrollment (Estimated): 20
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Karin Roeleveld, PhD; Phone Number: +47 48177279; Email: karin.roeleveld@ntnu.no
• Study Contact Backup: Name: Maria J Lequerica, MSc; Phone Number: +47 48684299; Email: maria.j.lequerica@ntnu.no

Study Locations

• Norway
  • Trondheim, Norway, 7030
    • NTNU's Movement analysis laboratory at Helgasetr
    • Contact: Karin Roeleveld, PhD; Phone Number: +47 48177279; Email: karin.roeleveld@ntnu.no
    • Contact: Maria J Lequerica, MSc - PhD candidate; Phone Number: +47 48684299; Email: maria.j.lequerica@ntnu.no

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Child; Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Age ≥16 years
• Unilateral transtibial amputation
• Activity level K2-K4
• Actively using a prosthesis for ≥12 months
• Ability to understand and communicate in Norwegian (oral and written)
• Digital file of current socket model available (required for test socket fabrication)

Exclusion Criteria:

• Use of a thigh corset attached to the prosthesis
• Requirement of a walker for ambulation
• Open wounds, skin ulcers, or blisters on the residual limb
• No liner
• Missing digital socket model file
• Medical advice to avoid physical activity similar to study tasks
• Other medical conditions that may worsen with activity and have not been cleared by a healthcare professional

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Other
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm

Intervention / Treatment

Experimental: Single Cohort: Three Suspension Systems; Participants with unilateral transtibial amputation will attend one study visit at the research site. During this visit, they will complete three movement tasks-treadmill walking, overground turning, and isometric leg rotation-while using three different prosthetic suspension systems in a partly randomized order (pin lock, passive vacuum, and active vacuum). Each of the three movement tasks will be performed with each of the three suspension systems. Biomechanical, performance, and patient-reported outcomes will be recorded for each suspension condition.

Device: Pin-Lock Suspension System; Participants perform all tasks using a pin-lock suspension system applied to their test socket.; Device: Passive Vacuum Suspension System; Participants perform all tasks using a passive vacuum suspension system applied to their test socket.; Device: Active Vacuum Suspension System; Participants perform all tasks using an active vacuum suspension system applied to their test socket.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Socket-Liner Motion [mm]	Socket-liner motion is quantified using a 3D optical motion-capture system to measure the relative movement between the prosthetic socket and liner during functional activities. Motion is recorded in millimeters (mm). Typical motion values are expected to fall within the range of 0-20 mm.	Within 1 hour after fitting the suspension system
Proximal-distal Socket-Leg Motion [mm]	Proximal-distal Socket-Leg Motion is quantified using a 3D motion-capture system to measure the relative movement between the prosthetic socket and the remaining leg during functional activities. Motion is recorded in millimeters (mm). Typical motion values are expected to fall within the range of 0-30 mm.	Within 1 hour after fitting the suspension system

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Torque Required to Initiate Socket-Liner Rotation [Nm]	This measure quantifies the torque at which transverse rotation begins between the prosthetic socket and liner. Torque is measured in Newton-meters (Nm) using a dynamometer.	Within 1 hour after fitting the suspension system
Step length [cm]	Step length is quantified using a 3D motion-capture system during functional activities. Step length is recorded in centimeters (cm).	Within 1 hour after fitting the suspension system
Step length asymmetry index	Step length asymmetry will be assessed using 3D motion analysis instrumentation. Asymmetry is computed on step length (cm) of the prosthetic and intact legs, by dividing the difference between legs by the average of both legs. 0 marks perfect symmetry and greater values higher asymmetry. There is no maximum limit, but most values are expected to be below 1.	Within 1 hour after fitting the suspension system
Gait velocity [m/s]	Gait velocity is quantified using a 3D motion-capture system during functional activities. Gait velocity is recorded in meters per second (m/s).	Within 1 hour after fitting the suspension system
Patient-Reported Socket Comfort Score (SCS)	The Socket Comfort Score is a patient-reported numerical rating scale used to assess prosthetic socket comfort. Participants rate their comfort on a 0-10 scale, where 0 represents the most uncomfortable socket imaginable and 10 represents the most comfortable socket imaginable. Comfort is evaluated for each of the three suspension conditions. For every condition, the participant provides the score immediately after completing the turning task and treadmill-walking task, both performed within 60 minutes of fitting the corresponding suspension system.	Within 1 hour after fitting the suspension system
Perceived Functional Ability	Perceived functional ability is assessed using a patient-reported numerical rating scale that captures the participant's subjective evaluation of how well they are able to perform functional activities with the prosthesis. Participants rate their perceived functional ability on a 0-10 scale, where 0 indicates the lowest perceived functional ability and 10 indicates the highest perceived functional ability. For each of the three suspension conditions, participants provide this rating immediately after completing the turning task and treadmill-walking task, both performed within 60 minutes of fitting the respective suspension system.	Within 1 hour after fitting the suspension system
Prosthesis Satisfaction Score	The Prosthesis Satisfaction Score is a patient-reported numerical rating scale used to assess overall satisfaction with the prosthetic limb. Participants rate their satisfaction on a 0-10 scale, where 0 represents the lowest possible satisfaction and 10 represents the highest possible satisfaction. For each of the three suspension conditions, participants provide this rating immediately after completing the turning task and treadmill-walking task, both performed within 60 minutes of fitting the corresponding suspension system.	Within 1 hour after fitting the suspension system

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Socket-Leg rotation [degrees]	Socket-Leg rotation is quantified using a 3D motion-capture system to measure the relative movement between the prosthetic socket and the remaining leg during functional activities. Motion is recorded in angles (degrees). Typical values are expected to fall within the range of 0-15 degrees.	Within 1 hour after fitting the suspension system
Step length [% of bodyheight]	Step length is quantified using a 3D motion-capture system during functional ctivities activities. Step length is recorded in centimeters (cm) and presented as percentage of bodyheight.	Within 1 hour after fitting the suspension system
Knee angle [degrees]	The knee angle is quantified using a 3D motion-capture system during the functional activities and presented in degrees as a function of the gait cycle.	Within 1 hour after fitting the suspension system
Hip angle [degrees]	The hip angle is quantified using a 3D motion-capture system during the functional activities and presented in degrees as a function of the gait cycle.	Within 1 hour after fitting the suspension system
Foot progression angle [degrees]	The foot progression angle is quantified using a 3D motion-capture system during the functional activities and presented in degrees.	Within 1 hour after fitting the suspension system

Collaborators and Investigators

• Sponsor: Norwegian University of Science and Technology
• Collaborators: Trøndelag Ortopediske Verksted (English translation: Trøndelag Orthopedic Workshop)
• Investigators: Principal Investigator: Karin Roeleveld, National Taiwan Normal University

Study record dates

Study Major Dates

• Study Start (Estimated): April 20, 2026
• Primary Completion (Estimated): February 27, 2027
• Study Completion (Estimated): December 27, 2029

Study Registration Dates

• First Submitted: March 5, 2026
• First Submitted That Met QC Criteria: April 7, 2026
• First Posted (Actual): April 13, 2026

Study Record Updates

• Last Update Posted (Actual): April 13, 2026
• Last Update Submitted That Met QC Criteria: April 7, 2026
• Last Verified: April 1, 2026

More Information

Terms related to this study

• Keywords: gait; 3D motion capture; Transtibial amputation; Pistoning; Prosthetic alignment; Prosthetic suspension systems; Lower-limb prosthesis; Prosthetic socket fit; Prosthesis comfort; Prosthetic rotation resistance
• Other Study ID Numbers: 938884

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: Individual participant data (IPD) from this study cannot be shared because the data are not anonymous. According to REK regulations and GDPR requirements, the research team must retain the identification key for as long as the data are used for research purposes. As long as this key exists, the dataset is considered identifiable, and sharing identifiable or potentially re-identifiable data externally is not permitted. Therefore, IPD cannot be shared.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No