CatWalk XT Gait Parameters Associated with Mouse Achilles Tendon Injury and Healing

Tendons are connective tissues with limited healing potential which results in perma-nently impaired function. Although direct mechanical testing of tendon remains the gold standard for functional analyses, this assay is terminal and tracking healing over time requires the use of many animals. An alternative method for quantifying tendon function is gait analysis, which is non-terminal and enables longitudinal tracking of the same animal. To date, commercial systems used to analyze gait are mostly applied to study neurobehavior, and applications for tendon research has been limited. Since these systems typically output many parameters, it is challenging to know which parameter is most relevant for a specific injury model. To address this challenge, we used a well-established rodent locomotion system (CatWalk XT) to measure longitudinal gait parameters in sham and Achilles tendon-injured mice (from PREOP to 56 days post-injury) and identified relevant and reproducible parameters specifically associated with Achilles tendon injury and healing. Micro computed tomography (micro-CT) and mechanical testing also confirmed persistent tendon impairment in the same animals at the terminal timepoint. Collectively, our results provide a useful reference and recommendation of CatWalk gait parameters and the control comparisons that both conserve the use of animals while maintaining high reproducibility standards for Achilles tendon injury studies.