JMIR Publications

ABSTRACT

Background:

Relative motion between the residual limb and socket for individuals with transtibial limb loss can lead to significant consequences that limit mobility. While assessments of the relative motion between the residual limb and socket have been performed, there remains a substantial gap in understanding the complex mechanics of the residual limb-socket interface during dynamic activities that limits the ability to improve socket design. However, dynamic stereo x-ray is an advanced imaging technology that can quantify 3D bone movement and skin deformation inside a socket during dynamic activities.

Objective:

The primary goal of this investigation is to develop the analytical tools using dynamic stereo x-ray to quantify the dynamic, in-vivo kinematics between the residual limb and socket and the mechanism of residual tissue deformation.

Methods:

A lower limb cadaver study will first be performed to optimize the placement of an array of radiopaque beads and markers on the socket, liner, and skin to simultaneously assess dynamic tibial movement and residual tissue and liner deformation. Five cadaver limbs will be utilized in an iterative process to develop an optimal marker setup. Stance phase gait will be simulated during each session to induce bone movement and skin and liner deformation. The number, shape, size, and placement of each marker will be evaluated after each session to refine the marker set. Once an optimal marker setup is identified, 21 participants with transtibial limb loss will be fit with a socket capable of being suspended via both elevated vacuum and traditional suction. Participants will undergo a 4-week acclimation period and then be tested in the dynamic stereo x-ray system to track tibial, skin, and liner motion under both suspension techniques during 3 activities: treadmill walking at self-selected speed, at a walking speed 10% faster, and during a step-down movement. The performance of the 2 suspension techniques will be evaluated by quantifying the 3D bone movement of the residual tibia with respect to the socket and quantifying liner and skin deformation at the socket-residuum interface.

Results:

This study was funded in October 2021. Cadaver testing began in January 2023. Enrollment began in February 2024. Data collection will conclude by June 2025. The initial dissemination of results is expected in February 2026.

Conclusions:

The successful completion of this study will help develop analytical methods for the accurate assessment of residual limb-socket motion. Results will significantly advance the understanding of the complex biomechanical interactions between the residual limb and the socket, which can aid in evidence-based clinical practice and socket prescription guidelines. This critical foundational information can aid in the development of future socket technology that has the potential to reduce secondary comorbidities that result from complications of poor prosthesis load transmission. Clinical Trial: ClinicalTrials.gov NCT05287646; https://clinicaltrials.gov/study/NCT05287646