Evaluating the validity of lightweight talar replacement designs: rational models and topologically optimized models

Area of Science:

• Biomedical Engineering
• Orthopedic Surgery
• Materials Science

Background:

• Total talar replacement is a standard procedure with generally satisfactory outcomes.
• Existing methods for designing talar implants, including topology optimization (TO), have limitations.
• A novel rational scaffold design is proposed as an alternative to TO for talar implants.

Purpose of the Study:

• To create and evaluate a rational scaffold talus model using topology optimization (TO).
• To compare the mechanical performance of a rational scaffold model against a topologically optimized scaffold model using finite element analysis (FEA).
• To test the hypothesis that the rational scaffold design is more effective for actual talar replacement applications than the TO scaffold.

Main Methods:

• Rational and TO scaffold models were designed and sized using TO and scaffold simplification techniques.
• Worst-case load scenarios were determined by applying plantar and dorsiflexion forces (P10, D5, D10) under a 5340 N load.
• Finite element analysis (FEA) was performed on representative models to assess peak von Mises stress (PVMS) and evaluate model validity.

Main Results:

• The minimum D5 model exhibited the highest PVMS (532.11 MPa) under worst-case conditions.
• FEA showed lower PVMS in the rational scaffold model (218.01 MPa) compared to the TO model (565.35 MPa).
• Rational scaffold application reduced model weight from 1106 g to 965.4 g, demonstrating significant weight reduction.

Conclusions:

• The rational inner-scaffold design is a safer alternative to TO for talar implants, verified by FEA.
• Three rational scaffold types cover all anatomical talus sizes, validating their use in total talar replacement.
• This method enables patient-customized, lightweight, and mechanically stable talar implants without relying on TO.