Quantitatively-informed Socket Design Process

Improving Physical Function and Patient-reported Outcomes Through a Quantitatively-informed Socket Design Process

This study will investigate the effects of specific standardized modifications to trans-femoral prosthetic sockets in a randomized within-subject design. This is in preparation for a subsequently planned clinical trial to validate the findings by implementing them into a fitting method for individual sockets.

Study Overview

• Status: Completed
• Conditions: Artificial Limbs
• Intervention / Treatment: Device: Trans-femoral prosthetic socket

Detailed Description

Background: Lower limb amputees experience chronic health challenges such as residual limb skin problems, low back pain, and osteoarthritis. These problems are exacerbated by high physical activity levels and by poor prosthetic socket fit. Prosthetists believe that limiting residual femur and skin motion will improve force coupling and thereby address these problems. However, there are no data demonstrating how changes in socket design affect residual femur and skin motion, and, by extension, lead to improved patient-reported outcomes.

Objective/Hypothesis: Goal of this research is to improve the current socket design optimization process that involves trial and error and relies heavily on the prosthetist's experience and intuition by using a quantitatively informed optimization process. The hypothesis is that modifiable in-socket mechanics, i.e. residual femur motion, skin strain, and pressure within the socket, are related to socket design and patient outcomes, and can be estimated using readily available clinical measurements.

Specific Aims: First aim is to identify the key characteristics of in-socket mechanics that are related to physical function and patient-reported comfort and function. The second aim is to identify readily available clinical measurements that are associated with the in-socket mechanical characteristics that are related to outcomes. The purpose of this aim is to correlate our laboratory findings from Aim 1 with more conventional modalities for clinical assessment.

Research Strategy: Preliminary data demonstrates the feasibility of the proposed research plan and will progress to a pilot clinical trial. The two aims will involve 30 transfemoral amputees. A highspeed biplane radiography system is used to image the residual limb while participants walk on a dual-belt instrumented treadmill both in their current socket and in sockets with purposely altered volume, brim height, cross-sectional geometry, and stiffness. Three-dimensional (3D) skin motion within the socket will be determined by tracking the motion of 40 to 50 small metal beads placed in a grid pattern on the skin of the residual limb before donning the socket. Residual femur motion within the socket will be determined with submillimeter accuracy using a validated tracking process that matches subject-specific bone models obtained from CT to the biplane radiographs. Discrete in-socket pressure will be recorded at four locations using pressure sensing pads. Readily available clinical measurements will be collected as well, including gait analysis, foot loading patterns, ground reaction forces, residual limb tissue stiffness, and hip range of motion hip strength. Each participant will complete clinical questionnaires to qualitatively evaluate comfort, fit, and overall satisfaction after wearing each socket. The different socket modifications are intended to affect the in-socket mechanics of the residual limb, physical function and patient-reported outcomes (Aim 1). These relationships will be assessed using a generalized linear model. Correlation between the research grade measurements and accessible clinical measures (Aim 2) will be evaluated using bivariate correlation analyses. The information gained in Aims 1 and 2 will be used to develop a quantitatively-informed socket optimization process, wherein the clinical measurements associated with in-socket mechanics will be used to inform socket design optimizations.

• Study Type: Interventional
• Enrollment (Actual): 8
• Phase: Not Applicable

Contacts and Locations

Study Locations

• United States
  • Pennsylvania
    • Pittsburgh, Pennsylvania, United States, 15206
      • University of Pittsburgh
    • Pittsburgh, Pennsylvania, United States, 15328
      • Delatorre Orthotics & Prosthetics

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years to 80 years (Adult, Older Adult)
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Transfemoral prosthesis user
• 18-80 years of age
• Body weight less than 125 kg
• Able to walk unassisted on a treadmill

Exclusion Criteria:

• Pregnant females
• Clinically diagnosed osteoporosis
• Previous high exposure to radiation

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• 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: Unmodified Socket + 8 Socket Modifications in Random Order; The sequence of the 9 different interventions (original socket and 8 versions derived from it) is randomized for each participant. The number of participants is smaller than the number of possible permutations. Therefore the enacted ordering is randomly selected from the pool of possible orderings. Participants walk for less than 10 minutes with every socket type while data is being collected.

Device: Trans-femoral prosthetic socket; Unmodified) A custom-made check socket serving as the interface between residual limb and prosthesis; Soft socket (Socket made from softer material than unmodified original); Stiff socket (Socket made from stiffer material than unmodified original); moderately lower brim height (Brim of the socket is lowered by 10% of socket length compared to unmodified original); slightly lower brim height (Brim of the socket is lowered by 5% of socket length compared to unmodified original); Oversized socket (The socket volume is 6% larger than the unmodified original); Undersized socket (The socket volume is 6% smaller than the unmodified original); CAT-CAM influenced geometry (The cross sectional geometry of the socket is modelled following the contoured adducted trochanteric-controlled alignment method (CAT-CAM)); MAS influenced geometry (The cross sectional geometry of the socket is modelled following the Marlo Anatomic Socket (MAS) template)

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Residual Femur motion	medial-lateral and superior-inferior translation of the distal femur relative to the socket from late swing through midstance	1 second
Skin strain	average and peak skin strain within each of four regions, expressed as a percentage of the gait cycle	1 second
Socket pressure	measure peak pressure and area under the pressure versus time curve, expressed as a percentage of the gait cycle	20 seconds

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Gait symmetry	average of the peak trunk lean, and the average peak hip flexion and extension, measured by motion capture system	20 seconds
Plantar pressure	peak plantar pressure from foot strike to midstance	20 seconds
Static displacement	distance from the most distal point of the residual femur to the inside surface of the socket under weightbearing	1 second
Tissue Stiffness	Average tissue stiffness for four regions of the residual limb	3 seconds
Trunk lean	Body angles based on markers placed on the shoulders and spine	20 seconds
Hip flexion/extension	Based on markers at greater trochanters, knee, ankle and foot.	20 seconds
Hip strength	Manual muscle testing of hip flexors and extensors	20 seconds
Hip Range of Motion	Manually measured using goniometer	20 seconds

Collaborators and Investigators

• Sponsor: University of Pittsburgh
• Collaborators: United States Department of Defense
• Investigators: Principal Investigator: William Anderst, PhD, University of Pittsburgh

Publications and helpful links

General Publications

• Anderst W, Fiedler G, Onishi K, McKernan G, Gale T, Paulus P. Within-subject effects of standardized prosthetic socket modifications on physical function and patient-reported outcomes. Trials. 2022 Apr 12;23(1):299. doi: 10.1186/s13063-022-06205-z.

Study record dates

Study Major Dates

• Study Start (Actual): September 1, 2021
• Primary Completion (Actual): March 1, 2024
• Study Completion (Actual): August 12, 2025

Study Registration Dates

• First Submitted: September 3, 2021
• First Submitted That Met QC Criteria: September 3, 2021
• First Posted (Actual): September 13, 2021

Study Record Updates

• Last Update Posted (Actual): August 14, 2025
• Last Update Submitted That Met QC Criteria: August 12, 2025
• Last Verified: August 1, 2025

More Information

Terms related to this study

• Other Study ID Numbers: STUDY20070123; W81XWH2010914 (Other Grant/Funding Number: US Dept of Defense)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: De-identified data may be shared with other researchers at Pitt in the future
• IPD Sharing Time Frame: upon conclusion of the study (in 2025) with no expiration
• IPD Sharing Access Criteria: commensurate with applicable restrictions posed by the study sponsor
• IPD Sharing Supporting Information Type: STUDY_PROTOCOL; SAP; ICF

Drug and device information, study documents

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