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Spatiotemporal Distribution of Linear Microcracks and Diffuse Microdamage Following Daily Bouts of Fatigue Loading of Rat Ulnae
Author(s) -
Liu Xiyu,
Tang Chi,
Zhang Xuhui,
Cai Jing,
Yan Zedong,
Xie Kangning,
Yang Zhiping,
Wang Jing,
Guo X. Edward,
Luo Erping,
Jing Da
Publication year - 2019
Publication title -
journal of orthopaedic research®
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.041
H-Index - 155
eISSN - 1554-527X
pISSN - 0736-0266
DOI - 10.1002/jor.24391
Subject(s) - linear elasticity , bone canaliculus , cortical bone , ultimate tensile strength , resorption , osteocyte , materials science , bone resorption , chemistry , biophysics , composite material , anatomy , medicine , structural engineering , biology , osteoblast , biochemistry , finite element method , engineering , in vitro
Microdamage accumulation contributes to impaired skeletal mechanical integrity. The bone can remove microdamage by initiating targeted bone remodeling. However, the spatiotemporal characteristics of microdamage initiation and propagation and their relationship with bone remodeling in response to fatigue loading, especially for more physiologically relevant daily bouts of compressive loading, remain poorly understood. The right forelimbs of 24 rats were cyclically loaded with a ramp waveform for 1,500 cycles/day, and contralateral ulnae were not loaded as the controls. The rats were divided into four equal groups and loaded for 1, 4, 7, and 10 days, respectively. We demonstrated that linear microcracking accumulation exhibited a non‐linear time‐varying process within 10 days of loading with peaked microcrack density at Day 7. Disrupted canaliculi surrounding linear microcracks showed high similarity with the temporal changes of linear microcracking accumulation. Observable intracortical resorption regions were found on Day 10. We found more linear microcracks accumulated in the tensile cortex, but longer cracks were observed in the compressive sides. Increased accumulation of diffuse microdamage was observed from Day 4, but no obvious peak was observed within the 10‐day loading period. Diffuse damage first initiated in the compressive cortices but extended to tension from Day 7. The diffuse damage exhibited no impacts on the surrounding osteocyte integrity. Together, our findings revealed a time‐dependent, bone remodeling‐mediated varying process of linear microcracking accumulation following daily bouts of fatigue loading (with observable peak at Day 7 under our loading regime). Our study also identified distinct spatial accumulation of linear and diffuse microdamage in rat ulnae with tensile and compressive strains. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:2112–2121, 2019