Reconstruction-induced variability in subject-specific knee joint modeling: Implications for time-dependent contact...

Area of Science:

• Biomechanics
• Medical Imaging Analysis
• Computational Mechanics

Background:

• Finite element modeling (FEM) of knee joints estimates subject-specific contact and fluid pressures.
• Previous studies indicated geometric uncertainties from segmentation cause up to 10% stress differences.
• The impact of image reconstruction variability on nonlinear, time-dependent knee mechanics is not fully understood.

Purpose of the Study:

• To quantify how operator-dependent MRI reconstruction differences affect contact mechanics and creep response.
• To analyze these effects within a subject-specific, nonlinear poromechanical FEM of the knee.

Main Methods:

• Two operators independently reconstructed knee geometries from identical 3T MRI data using the same software.
• Comparable mesh quality, material properties, and loading conditions were maintained.
• Nonlinear, time-dependent poromechanical FEM simulations were performed on the reconstructed geometries.

Main Results:

• Soft tissues showed significant geometric discrepancies (up to 30% variation in medial tibial cartilage volume), unlike bony structures (<2% area difference).
• Maximum contact pressure varied by 15%, and average medial contact pressure by 24% between models.
• Contact and fluid pressure distributions, including peak pressure locations, differed, and diverged progressively during creep simulations.

Conclusions:

• Operator-dependent MRI reconstruction variability can significantly influence subject-specific knee joint contact mechanics and time-dependent behavior.
• These variations may alter predictions of load-sharing patterns beyond simple stress differences.
• Careful attention to reconstruction protocols is crucial for reliable FEM analysis of knee joint mechanics.