Effect of fatigue loading on impact response of rat ulna

Stress fracture is a common injury among athletes, such as basketball players. The occurrence of stress fracture is a consequence of both fatigue and impact loading of the bone that will potentially threat athletes’ careers. Scientists and engineers have studied the fatigue properties of many engineering materials, and more recently biological materials. Investigating the role of fatigue on impact properties has received much less attention in bone. In this study, cyclic axial compressive loading was applied in vivo on the right ulnae of sixteen rats (Sprague-Dawley, Charles River), and the left served as contralateral control. The animals were divided into two groups: one day of rest before they were sacrificed and the other seven days. Afterwards, the ulnae were harvested and potted in epoxy and then scanned using micro-Computed Tomography (CT). Impact tests were performed using a customized figure where the impact energy was normalized for all specimens and following impact the specimens were re-scanned using micro-CT scans. There was no significant change in bone volume between the control (mean = 7.01 0.61mm3) and loaded (mean = 6.63 0.19mm3) ulnae in the group with one day rest (p = 0.28). However, after seven days of rest, the average bone volume increased by 4.35% among the control ulnae (mean = 7.32 0.49mm3) , and 15.10% among the loaded (mean = 7.63 0.47mm3). The increase in volume was attributed to woven bone formation and was visually confirmed from the micro CT images. The peak impact force was 37.5% higher in the control (mean = 174.96 33.25N) specimens than the loaded (mean = 130.34 22.37N ). Our data is limited to some degree by the sample size and two specimens fractured after the cyclic loading which further decease the sample size. Future work should investigate the effect of different rest times. This study indicated that cyclic fatigue loading had a negative impact on bone’s impact response. Bones that experienced fatigue loading became less stiff and resulted in lower peak forces, and an increased fracture rate when subjected to impact. Rest time was crucial to the recovery of fatigue damage. Seven days rest decreased the fracture rate by 66.67%. If more rest time was given, the peak force could return to the same level as the control or even higher as new bone would possibly mineralize. This study can provide a baseline guidance of the training, competition and rest arrangement to minimize the risk of stress fracture and prolong athletes’ careers.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Mechanical Engineering

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2018

Author dc:creator

• Yan, Chenxi

Contributors dc:contributor

• Kersh, Mariana

• rat ulna, fatigue and impact loading. Image processing.

Statement dc:rights

• Copyright 2018 Chenxi Yan

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/101593

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/101593