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

Finite element modeling of the knee joint is increasingly used to estimate subject-specific contact and fluid pressure distributions. Previous linear elastic analyses have suggested that segmentation-induced geometric uncertainties may result in up to 10% differences in maximum contact stress. However, the extent to which image reconstruction-induced geometric discrepancies propagate into nonlinear, time-dependent joint mechanics remains to be fully characterized. The objective of this study was to quantify how operator-dependent differences in MRI reconstruction influence contact mechanics and creep response in a subject-specific, nonlinear poromechanical finite element model of the knee. Two experienced operators independently reconstructed knee geometries from the same 3T MRI data using the same software, while maintaining comparable mesh quality, along with identical material properties and loading conditions. While bony structures exhibited minimal geometric variation (<2% area difference), soft tissues demonstrated substantially larger discrepancies, with up to 30% variation in medial tibial cartilage volume. These geometric differences propagated nonlinearly into finite element simulations. Maximum contact pressure differed by 15% between the models, and average medial contact pressure disagreed by 24%. Notably, maximum contact and fluid pressure regions relocated between medial and lateral compartments despite identical external loading. Location matched comparisons confirmed different contact and fluid pressure distributions. Time-dependent simulations further revealed progressively increasing divergence in maximum contact pressure during creep. Although likely case specific, the present study indicated potential influence of operator-dependent reconstruction variability in predicting load-sharing patterns and time-dependent joint mechanics beyond simple differences in maximum stress.