Are subject-specific models necessary to predict patellar tendon fatigue life? A finite element modelling study

• Published in: Computer methods in biomechanics and biomedical engineering Vol. 25; no. 7; pp. 729 - 739
• Main Authors: Firminger, Colin R., Haider, Ifaz T., Bruce, Olivia L., Wannop, John W., Stefanyshyn, Darren J., Edwards, W. Brent
• Format: Journal Article
• Language: English
• Published: England Taylor & Francis 19.05.2022; Taylor & Francis Ltd
• Subjects: Athletes; Data collection; Elastic properties; Estimates; Fatigue; Fatigue life; Finite element method; finite element modelling; Geometry; Knee; Magnetic resonance imaging; Material properties; Materials fatigue; Mathematical models; overuse injury; Patellar tendinopathy; Repeated loading; strain; finite element modelling; strain; overuse injury; Patellar tendinopathy
• ISSN: 1025-5842; 1476-8259; 1476-8259
• DOI: 10.1080/10255842.2021.1975683

Patellar tendinopathy is an overuse injury that occurs from repetitive loading of the patellar tendon in a scenario resembling that of mechanical fatigue. As such, fatigue-life estimates provide a quantifiable approach to assess tendinopathy risk and may be tabulated using nominal strain (NS) or finite element (FE) models with varied subject-specificity. We compared patellar tendon fatigue-life estimates from NS and FE models of twenty-nine athletes performing countermovement jumps with subject-specific versus generic geometry and material properties. Subject-specific patellar tendon material properties and geometry were obtained using a data collection protocol of dynamometry, ultrasound, and magnetic resonance imaging. Three FE models were created for each subject, with: subject-specific (hyperelastic) material properties and geometry, subject-specific material properties and generic geometry, and generic material properties and subject-specific geometry. Four NS models were created for each subject, with: subject-specific (linear elastic) material properties and moment arm, generic material properties and subject-specific moment arm, subject-specific material properties and generic moment arm, and generic material properties and moment arm. NS- and FE-modelled fatigue-life estimates with generic material properties were poorly correlated with their subject-specific counterparts (r 2 ≤0.073), while all NS models overestimated fatigue life compared to the subject-specific FE model (r 2 ≤0.223). Furthermore, FE models with generic tendon geometry were unable to accurately represent the heterogeneous strain distributions found in the subject-specific FE models or those with generic material properties. These findings illustrate the importance of incorporating subject-specific material properties and FE-modelled strain distributions into fatigue-life estimations.