Ex vivo Comparison of Handheld Myotonometry and Tensile Deformation in Porcine Patellar Tendons

Objectives: Patellar tendon (PT) stiffness is relevant for understanding tendon loading, adaptation, and mechanical changes. However, objective tools for assessing PT stiffness are limited in clinical settings. Myoton PRO is a handheld device used for regional oscillation-based stiffness measurement; however, the association between Myoton PRO and a tensile testing machine for the PT remains unclear. This ex vivo study aimed to examine the association between regional dynamic stiffness measured using the Myoton PRO and structural stiffness measured using tensile testing in porcine PTs. Material and Methods: Twenty-eight fresh porcine knees were included in this ex vivo experimental study. The primary outcome was the correlation between regional dynamic stiffness measured using the Myoton PRO and structural stiffness measured using tensile testing. Dynamic stiffness was measured at the PT proximal (PT-p), central (PT-c), and distal (PT-d) sites using the Myoton PRO. The structural stiffness was measured using a tensile testing machine. The correlations between dynamic and structural stiffness were analyzed using Pearson’s correlation coefficients, and intra-rater reliability was evaluated using the intraclass correlation coefficient (ICC). Results: The dynamic stiffness measured using the Myoton PRO was as follows: 911.3 ± 129.5 N/m at PT-p, 875.9 ± 183.3 N/m at PT-c, and 930.3 ± 136.0 N/m at PT-d. The structural stiffness was 38.2 ± 9.6 N/mm. Dynamic stiffness showed moderate positive correlations with structural stiffness at PT-p (r = 0.46, 95% CI 0.11-0.71, p = 0.013), PT-c (r = 0.57, 95% CI 0.25-0.77, p = 0.002), and PT-d (r = 0.44, 95% CI 0.08-0.70, p = 0.020). The intra- rater reliability was satisfactory at all sites, with ICC (1,3) values ranging from 0.98 to 0.99. Conclusion: Myoton PRO measurements were highly reproducible and moderately correlated with structural stiffness measured using tensile testing under ex vivo conditions. Interpretation is limited by the use of healthy ex vivo porcine specimens, the absence of direct human validation, and the evaluation of structural rather than intrinsic material stiffness. These findings provide preliminary biomechanical evidence supporting further investigation of regional myotonometry in pathological and in vivo tendon models.