Stresses in polyethylene liners in a semiconstrained ankle prosthesis

Area of Science:

• Biomedical Engineering
• Orthopedic Biomechanics
• Finite Element Analysis

Background:

• Semiconstrained ankle implants are used to restore function in patients with ankle arthritis.
• Understanding stress distribution within the polyethylene liner is crucial for predicting implant longevity.
• Previous studies have not fully explored the impact of talar component geometry on stress in ankle implants.

Purpose of the Study:

• To compute stresses in the polyethylene liner of a semiconstrained ankle implant using finite element analysis.
• To compare the biomechanical performance of two different talar component widths.
• To evaluate the effect of increased surface area on stress reduction within the implant.

Main Methods:

• Construction of a finite element model of a semiconstrained ankle implant, including the tibia and fibula.
• Application of proximal boundary conditions derived from an inverse process, simulating a load of five times body weight.
• Analysis of von Mises stresses and contact stresses within the polyethylene liner for two talar component widths.

Main Results:

• Finite element analysis revealed localized yielding and contact stresses comparable to acetabular cup liners.
• A wider talar component, featuring 36% more surface area, significantly reduced stress.
• Contact stress and von Mises stresses at the polyethylene component's center decreased by 17% with the wider component.

Conclusions:

• Increasing the surface area of the talar component in semiconstrained ankle implants can effectively reduce stress concentrations.
• The findings suggest that optimizing talar component geometry is a viable strategy for enhancing the durability of ankle prostheses.
• This study provides valuable biomechanical data for the design and development of next-generation ankle implants.