Compliant buffer layer achieves native-like cartilage stress in talar prosthesis: a finite element analysis study

Area of Science:

• Biomaterials science
• Orthopedic biomechanics
• Medical device engineering

Background:

• Avascular necrosis (AVN) of the talus poses significant clinical challenges with poor treatment outcomes.
• Current 3D-printed talar prostheses face a hard-soft mismatch, leading to increased stress and wear.
• Identifying optimal buffering materials and thicknesses is crucial for improving talar prosthesis performance.

Purpose of the Study:

• To determine the most suitable buffering layer material and thickness for 3D-printed talar prostheses.
• To evaluate the impact of prosthetic material properties and buffering layer thickness on periprosthetic cartilage biomechanics.
• To minimize stress on prosthesis adjacent cartilage (PAC) for enhanced durability and patient outcomes.

Main Methods:

• Dynamic biplane radiography (DBR) integrated with finite element analysis (FEA) was used.
• Nine common prosthetic materials and varying buffering layer thicknesses were tested across five gait phases.
• Statistical analyses, including ANOVA and mixed-effects models, assessed the effects on PAC stress.

Main Results:

• A 3mm polycarbonate urethane (PCU) buffering layer effectively normalized cartilage stress distributions.
• Soft prosthetic materials significantly reduced PAC stress compared to hard materials.
• Specific buffering layer criteria (1.5mm < 43.32 MPa or 3mm < 96.94 MPa) significantly lowered PAC stress.

Conclusions:

• Talar prostheses with a 1.5mm buffering layer (<43.32 MPa) or a 3mm layer (<96.94 MPa) closely replicate native PAC stress.
• A 3mm PCU buffering layer demonstrates potential for improving talar prosthesis design.
• Findings offer insights for optimizing material selection and structural design in total talar replacement (TTR).