| Summary: | A lack of the application of appropriate mechanical stimuli to cells within healing tissue in tendon defects has been proposed as a possible mechanism of incomplete defect healing with scar formation. This suggested that different mechanical environment in a tendon defect with a different geometry may result in different healing outcome. Therefore, the present study adopted a slit injury model in a mouse patellar tendon model and performed macroscopic and microscopic mechanical analysis on tissue regenerated in the central slit defect. Tensile strength and tangent modulus of the tissue in the defect at 3 weeks of healing were lower significantly than that of normal patellar tendon, which recovered to a level still lower than the normal level but without statistical significance at 6 weeks of healing. Micromechanical analysis on local strain field revealed that microscopic tensile strain was not different between normal patellar tendon and healing tissue at 6 weeks. However, microscopic transverse and shear strain was significantly lower in healing tissue than normal tendon tissue. The former may indicate that collagen fibers in healing tissue exhibit no crimp morphology, and the latter demonstrates that collagen fibers were not aligned to the long axis of the tendon. Although healing tissue in the slit defect possessed better strength that that in a rectangular defect examined in our previous study, microscopic strain field was similar between two models, possibly due to that healing tissue in both models was still immature structurally at 6 weeks of healing when compared to the normal patellar tendon.
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