Males have Inferior Achilles Tendon Material Properties Compared to Females in a Rodent Model
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The Achilles tendon is the most commonly ruptured tendon in the human body. Numerous studies have reported incidence of these injuries to be upwards of five times as common in men than women. Therefore, the objective of this study was to investigate the sex- and hormone-specific differences between Achilles tendon and muscle between female, ovariectomized female (ovarian hormone deficient), and male rats. Uninjured tissues were collected from all groups for mechanical, structural, and histological analysis. Our results showed that while cross-sectional area and failure load were increased in male tendons, female tendons exhibited superior tendon material properties and decreased muscle fiber size. Specifically, linear and dynamic moduli were increased while viscoelastic properties (e.g., hysteresis, percent relaxation) were decreased in female tendons, suggesting greater resistance to deformation under load and more efficient energy transfer, respectively. No differences were identified in tendon organization, cell shape, cellularity, or proteoglycan content. Additionally, no differences in muscle fiber type distribution were observed between groups. In conclusion, inferior tendon mechanical properties and increased muscle fiber size may explain the increased susceptibility for Achilles tendon injury observed clinically in men compared to women.
KeywordsMechanics Injury Fatigue Gender Ankle Orthopaedics
This study was funded by NIH/NIAMS R01AR064216S1, the NIH/NIAMS supported Penn Center for Musculoskeletal Disorders (P30 AR050950), the NIH/NCATS (TL1TR000138), the NIH/NIAMS T32AR007132, and NSF GRFP. The authors thank Dan Choi and Cori Riggin for their contributions.
All authors were fully involved in the study and preparation of the manuscript. The manuscript has been read and approved by all of the authors.
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