Prosthetic leg socket design: New insight on different tibia length and distal bevelled angle using finite element...

Area of Science:

• Biomedical Engineering
• Orthopedics
• Prosthetics and Orthotics

Background:

• Socket fit significantly impacts user comfort and prosthesis control in amputees.
• Inadequate selection of amputation morphological parameters can lead to pain and functional limitations.
• Understanding residual limb variability is essential for effective prosthetic prescription.

Purpose of the Study:

• To investigate the impact of residual limb morphological variations on prosthetic socket stress distribution.
• To determine optimal parameters for tibial length, distal tibial bevelling angle, and soft tissue stiffness.
• To predict pain and discomfort based on stress thresholds in the residual limb.

Main Methods:

• 3D scanning of a volunteer's residual limb to design a custom socket.
• CT-derived 3D bone models with varying tibial lengths (12.5, 15, 17.5 cm) and bevelling angles (30°, 45°, 60°).
• Simulation of soft tissue stiffness using hyper-elastic material properties (D and C values).

Main Results:

• Optimal parameters identified for the volunteer: 12.5 cm tibial length, 45° distal tibial bevelling angle, and 55 kPa soft tissue stiffness, minimizing maximum von Mises stress.
• Predicted normal stress in the fibular head region (0.89 MPa) remained below the pain threshold, suggesting no pain during standing.
• Residual limb morphology significantly influences soft tissue stress distribution.

Conclusions:

• For the specific patient studied, optimal prosthetic parameters include a 15 cm tibial length, 45° tibial bevelling angle, and contracted soft tissue.
• Tailoring socket design based on individual residual limb morphology can enhance amputee comfort and prosthesis function.
• Further research can refine these parameters for broader application in prosthetic fitting.