A Sensor for Three-Dimensional Limb-to-Prosthesis Interface Motion and Physiological Adaptations from Lower Extremity Prosthesis Use

Abstract

Lower extremity prosthesis use following amputation introduces stark environmental changes to the skin and underlying tissue of the residual limb. As prosthesis socket fit is considered one of the most integral elements of increasing the likelihood a user adopts their artificial limb, it is crucial to understand how the limb interacts with the prosthesis at the contact interface. The individualized nature of socket fabrication means that a prosthesis can create unique fit conditions, presenting a challenge when observations from various users are compared. Furthermore, it has been known that even within a single prosthesis the pressure and shear forces are not uniform, meaning that different locations of the residual limb experience different magnitudes of stressors. It is thought that the skin of the residual limb adapts to the new stressors imposed by the socket, but the physiologic and biologic mechanisms are poorly understood in humans. Herein, a longitudinal study was conducted in attempts to directly compare the limb-socket interface mechanics and the physiology of adapted residual limb skin. An innovative sensing modality is presented that provides three-dimensional movements of the limb relative to the socket surface and is shown to have the sensitivity to detect clinically meaningful changes in socket fit. This sensor is one of few high-fidelity modalities that is cost-effective, unobtrusive to users, and easy to instrument, making limb-to-socket interface mechanisms feasible to measure in large cohorts and in everyday circumstances. Additionally, vascular adaptations were found in the residual limb using Optical Coherence Tomography Angiography imaging, and it is plausible that the adaptions can be correlated to the localized, repetitive, limb-socket interface motions found within the socket.