Shape-memory-alloy-based smart knee spacer for total knee arthroplasty: 3D CAD modelling and a computational study

Area of Science:

• Biomedical Engineering
• Materials Science

Background:

• Total knee arthroplasty (TKA) often involves tibial components with spacers that can fracture, loosen, or dislocate.
• Traditional polymethylmethacrylate (PMMA) spacers have limitations in durability and stability.

Purpose of the Study:

• To introduce and analyze a novel shape memory alloy (SMA)-based smart knee spacer for TKA.
• To evaluate the mechanical properties and performance of the SMA spacer compared to conventional PMMA spacers.

Main Methods:

• A 3D CAD model of a smart tibial component using SMA (NiTi) was designed and analyzed using finite element analysis (FEA) in ANSYS Workbench.
• The pseudoelasticity (PE) and shape memory effect (SME) properties of SMA were modeled and investigated.
• FEA was used to compare maximum deformation and stress distribution of the SMA spacer against a PMMA-based spacer across varying body mass index (BMI) subjects.

Main Results:

• The SMA-based smart knee spacer exhibited 96.67% less deformation and 30 times less permanent deformation than the PMMA-based spacer.
• FEA confirmed the effectiveness of the SMA spacer's SME for secure fixation.
• Fatigue analysis indicated superior performance of the SMA spacer under cyclic loading.

Conclusions:

• The SMA-based smart knee spacer offers a significant improvement over PMMA spacers, mitigating issues like fracture, loosening, and dislocation.
• The proposed design leverages SMA's unique properties for enhanced TKA component stability and longevity.