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i-Socket: Design, Development, and Pilot Evaluation of an Individualized Multi-Material, Multi-Thickness Transtibial Prosthetic Socket

Noor Alhuda Ameen, Omid Arfaie, Ramazan Unal

TL;DR

The i-Socket study tackles prosthetic socket discomfort and instability by introducing a multi-material, multi-thickness transtibial socket guided by Pressure-Pain Threshold (PPT) testing. It combines PPT-driven regional material/thickness selection with CAD-based modeling and finite-element analysis of stance-phase loading, followed by pilot functional testing with a transtibial amputee. Results show substantial pressure reductions inside the socket (e.g., approximately $45\%$ in the Tibia and $31\%$ in the Fibula) and improvements in gait symmetry and walking speed, all while achieving a $22\%$ mass reduction compared to the participant's own socket. These findings indicate that region-specific material design can improve comfort, stability, and mobility, supporting broader adoption and further optimization for daily activities.

Abstract

The prosthetic socket is an essential part in ensuring comfort and stability for the overall prosthesis system. This study proposes a multi-material/thickness individualized transtibial prosthetic socket that focuses on providing comfort. This study aims to identify the proper material and thickness to protect Calf areas and reduce the pressure around bone areas. First, the socket is divided into four parts depending on the pressure-sensitive/tolerant regions. After identifying the thickness range for each concerned area, the thickness and material are selected based on the Pressure-Pain Threshold (PPT) test, and the finalized design is then prototyped. The prototyped individualized socket (i-Socket) is 22% lighter than the participant's own socket. Results of the pilot experiments with an amputee participant showed that the pressure inside the socket decreased by 45% and 31% for the Tibia and Fibula regions, respectively. Additionally, the self-selected CoM velocity for the walking experiment is increased by 15% compared to the similar studies in the literature. Regarding the kinematic results, symmetry in the knee and ankle joints increased by 65% and 2% when using the i-Socket compared to the results with the participant's own socket.

i-Socket: Design, Development, and Pilot Evaluation of an Individualized Multi-Material, Multi-Thickness Transtibial Prosthetic Socket

TL;DR

The i-Socket study tackles prosthetic socket discomfort and instability by introducing a multi-material, multi-thickness transtibial socket guided by Pressure-Pain Threshold (PPT) testing. It combines PPT-driven regional material/thickness selection with CAD-based modeling and finite-element analysis of stance-phase loading, followed by pilot functional testing with a transtibial amputee. Results show substantial pressure reductions inside the socket (e.g., approximately in the Tibia and in the Fibula) and improvements in gait symmetry and walking speed, all while achieving a mass reduction compared to the participant's own socket. These findings indicate that region-specific material design can improve comfort, stability, and mobility, supporting broader adoption and further optimization for daily activities.

Abstract

The prosthetic socket is an essential part in ensuring comfort and stability for the overall prosthesis system. This study proposes a multi-material/thickness individualized transtibial prosthetic socket that focuses on providing comfort. This study aims to identify the proper material and thickness to protect Calf areas and reduce the pressure around bone areas. First, the socket is divided into four parts depending on the pressure-sensitive/tolerant regions. After identifying the thickness range for each concerned area, the thickness and material are selected based on the Pressure-Pain Threshold (PPT) test, and the finalized design is then prototyped. The prototyped individualized socket (i-Socket) is 22% lighter than the participant's own socket. Results of the pilot experiments with an amputee participant showed that the pressure inside the socket decreased by 45% and 31% for the Tibia and Fibula regions, respectively. Additionally, the self-selected CoM velocity for the walking experiment is increased by 15% compared to the similar studies in the literature. Regarding the kinematic results, symmetry in the knee and ankle joints increased by 65% and 2% when using the i-Socket compared to the results with the participant's own socket.
Paper Structure (13 sections, 16 figures, 10 tables)

This paper contains 13 sections, 16 figures, 10 tables.

Table of Contents

  1. Introduction
  2. Methods
  3. Conceptual design
  4. Thickness range determination
  5. PPT Experiments
  6. Prosthetic Socket Model and Stance Phase Analysis
  7. Prosthetic Socket Manufacturing and Parts Connection
  8. Results
  9. Mechanical Evaluation
  10. Pressure distribution Evaluation
  11. Kinematic Evaluations
  12. Discussion
  13. Conclusion

Figures (16)

  • Figure 1: This diagram shows the pressure-tolerant and pressure-sensitive areas physiopedia_lower_limb_sockets. Anterior view (a), Lateral view (b), Posterior view (c). Pressure-sensitive areas are highlighted in blue, and Pressure-tolerant areas are highlighted in red.
  • Figure 2: CAD model of Design 1 (a): Pressure-sensitive areas (1) and pressure-tolerant areas (2). CAD model of Design 2 (b): Pressure-sensitive areas (1&3) and pressure-tolerant areas (2&4).
  • Figure 3: CAD model of Design 3: Pressure-sensitive areas (1 & 3), and Pressure-tolerant areas (2 & 4).
  • Figure 4: Design 3 structural analysis, a) Stress analysis using Carbon fiber for pressure-tolerant areas, b) Stress analysis using Kevlar for pressure-tolerant areas.
  • Figure 5: PPT setup: - from tough PLA (a), 3D model for the setup, residual limb, specimen, load cell, and force applier (b).
  • ...and 11 more figures