Biomechanical analysis of soft tissue thickness in residual limb: impact on stress distribution and interface pressure in prosthetic fitting

Abstract

The thickness of the residual limb’s soft tissue plays a crucial role in determining the mechanical behavior and stress distribution at the stump–prosthesis interface. Using finite element analysis (FEA), this study investigates the biomechanical effects of different soft tissue thicknesses (30 mm, 50 mm, and 70 mm) on stress distribution. A patient-specific finite element model of the residual limb was developed to simulate realistic anatomical and mechanical conditions. To replicate physiological loading, a static vertical load of 350 N was applied, and the interface between the residual limb and the prosthetic liner was modeled using appropriate contact mechanics. The results revealed that reducing the soft tissue thickness to 3 cm produced higher Von Mises stress concentrations (0.115 MPa) and contact pressure (0.0697 MPa), which may increase discomfort and the risk of tissue damage. Conversely, increasing the thickness to 70 mm reduced stress values (0.016 MPa) and contact pressure (0.0312 MPa) but led to excessive deformations (6.277 mm) that could compromise prosthetic stability. An optimal soft tissue thickness of 5 cm was identified, where Von Mises stress and contact pressure remained at moderate levels, offering a balance between stress distribution and mechanical stability. These findings provide valuable guidance for optimizing prosthetic socket design, as maintaining appropriate soft tissue thickness can enhance comfort, reduce pressure-related injuries, and improve the overall functionality of lower-limb prostheses.