Assessing Socket Fit Effects on Pressure and Shear at a Transtibial Residuum/Socket Interface

Area of Science:

• Biomechanics
• Prosthetics and Orthotics
• Rehabilitation Engineering

Background:

• Lower-limb amputees experience residuum volume fluctuations, altering prosthetic socket fit.
• Current prosthetic sockets struggle to accommodate these fit changes, impacting user comfort and function.
• The biomechanical effects of minor socket fit variations are not well understood.

Purpose of the Study:

• To investigate the real-time biomechanical effects of altered prosthetic socket fit on the residuum/socket interface.
• To quantify changes in interface pressure and shear forces due to modified socket fit.
• To assess the implications of these changes for amputee comfort and tissue health.

Main Methods:

• A transtibial amputee adjusted socket fit using sock layers to simulate looser and tighter conditions.
• Interface pressure and shear sensors were placed at the patellar tendon (PT), popliteal fossa (PF), and anterior-distal (AD) sites.
• Biomechanical data were collected during standing and level walking to analyze interface interactions.

Main Results:

• Slight modifications in socket fit led to observable changes in interface pressure and shear at various anatomical sites.
• Tighter fits reduced pressure at the AD site during early stance and increased pressure at the PT site during terminal stance.
• Significant changes were noted at the AD and PF tissue sites, with shear-to-pressure ratios and time integrals indicating potential impacts on comfort and tissue health.

Conclusions:

• Even minor adjustments in prosthetic socket fit can significantly alter interface biomechanics.
• Combined analysis of pressure, shear, and their ratios provides valuable insights into socket comfort and residuum tissue health.
• This study highlights the importance of considering dynamic fit changes for optimizing prosthetic socket design and amputee care.