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University of Illinois – Urbana-Champaign

1. Chennimalai Kumar, Natarajan. Numerical modeling of cortical bone adaptation due to mechanical loading using the finite element method.

Degree: PhD, 0133, 2010, University of Illinois – Urbana-Champaign

It is well known that bone tissue adapts its shape and structure according to its mechanical environment. Bone adaptation occurs on the dense cortical bone and porous trabecular bone. The process of bone adaptation is shown to be dependent on a number of mechanical loading parameters such as magnitude, frequency, number of bouts etc. of applied loading through experimental studies. We propose to develop a numerical framework, which can simulate and predict cortical bone adaptation due to diff erent parameters of loading. In pursuit of the development of the framework, we develop a method to generate fi nite element (FE) models of actual rat ulna from micro computed tomography (micro-CT) images. The external adaptation process is implemented in the model by moving the surface nodes of the FE mesh along the normal direction based on an evolution law characterized by two parameters: one that captures the rate of the adaptation process (referred to as gain); and the other characterizing the threshold value of the mechanical stimulus required for adaptation (referred to as threshold-sensitivity). Cortical bone is firstly modeled as an elastic material. Loading from experiments of Robling et al is applied on the FE model and the elastic boundary value problem is solved. Based on the results of the FE solution, the surface nodes are displaced according to the local strain energy density as the growth stimulus. Using this stimulus, we show that the model can simulate the e ffect of the magnitude of applied loading on the growth response. We calibrate the growth law parameters by comparing the results from our model to the experimental results. A parametric study is carried out to evaluate the e ffect of these two parameters on the adaptation response. We show, following comparison of results from the simulations to the experimental observations, that splitting the loading cycles into di fferent number of bouts a ffects the threshold-sensitivity but not the rate of adaptation. We also show that the threshold-sensitivity parameter can quantify the mechanosensitivity of the osteocytes. The use of strain energy density stimulus and elastic material model cannot simulate the e ect of frequency of applied loading on the cortical bone adaptation response. We model cortical bone as a poroelastic material to account for the interstitial fluid flow. We aim to develop a growth stimulus similar to strain energy density for the poroelastic material model. In order to achieve this goal, we develop the FE model of a rectangular beam subjected to pure bending. This geometric model is chosen for simplicity, as an idealized representation of cortical bone. We then propose the use of the dissipation energy of the poroelastic ow as a mechanical stimulus for bone adaptation, and show that it can predict the eff ect of frequency of the applied load. Surface adaptation in the model depends on the weighted average of the mechanical stimulus in a "zone of influence" near each surface point, in order to incorporate… Advisors/Committee Members: Dantzig, Jonathan A. (advisor), Dantzig, Jonathan A. (Committee Chair), Jasiuk, Iwona M. (committee member), Turner, Charles H. (committee member), Wagoner Johnson, Amy J. (committee member).

Subjects/Keywords: Bone adaptation; Cortical bone; poroelasticity; rat ulna; finite element methods; Biomechanics

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Chennimalai Kumar, N. (2010). Numerical modeling of cortical bone adaptation due to mechanical loading using the finite element method. (Doctoral Dissertation). University of Illinois – Urbana-Champaign. Retrieved from http://hdl.handle.net/2142/16700

Chicago Manual of Style (16th Edition):

Chennimalai Kumar, Natarajan. “Numerical modeling of cortical bone adaptation due to mechanical loading using the finite element method.” 2010. Doctoral Dissertation, University of Illinois – Urbana-Champaign. Accessed August 17, 2019. http://hdl.handle.net/2142/16700.

MLA Handbook (7th Edition):

Chennimalai Kumar, Natarajan. “Numerical modeling of cortical bone adaptation due to mechanical loading using the finite element method.” 2010. Web. 17 Aug 2019.

Vancouver:

Chennimalai Kumar N. Numerical modeling of cortical bone adaptation due to mechanical loading using the finite element method. [Internet] [Doctoral dissertation]. University of Illinois – Urbana-Champaign; 2010. [cited 2019 Aug 17]. Available from: http://hdl.handle.net/2142/16700.

Council of Science Editors:

Chennimalai Kumar N. Numerical modeling of cortical bone adaptation due to mechanical loading using the finite element method. [Doctoral Dissertation]. University of Illinois – Urbana-Champaign; 2010. Available from: http://hdl.handle.net/2142/16700

2. Yan, Chenxi. Effect of fatigue loading on impact response of rat ulna.

Degree: MS, Mechanical Engineering, 2018, University of Illinois – Urbana-Champaign

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. Advisors/Committee Members: Kersh, Mariana (advisor).

Subjects/Keywords: rat ulna; fatigue and impact loading. Image processing.

…parameters at the endosteal surface of rat tibiae. From a methodological perspective, ulna can be… …small changes in the structural properties of the rat ulna increases its fatigue resistance… …15]. Although the fatigue damage of rat ulna has been well studied in both structural… …fatigue fracture models [14]. The current standard method to load rat ulna to fatigue… …impact response of rat ulna. Hypotheses: The first hypothesis of this study is that a single… 

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Yan, C. (2018). Effect of fatigue loading on impact response of rat ulna. (Thesis). University of Illinois – Urbana-Champaign. Retrieved from http://hdl.handle.net/2142/101593

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Yan, Chenxi. “Effect of fatigue loading on impact response of rat ulna.” 2018. Thesis, University of Illinois – Urbana-Champaign. Accessed August 17, 2019. http://hdl.handle.net/2142/101593.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Yan, Chenxi. “Effect of fatigue loading on impact response of rat ulna.” 2018. Web. 17 Aug 2019.

Vancouver:

Yan C. Effect of fatigue loading on impact response of rat ulna. [Internet] [Thesis]. University of Illinois – Urbana-Champaign; 2018. [cited 2019 Aug 17]. Available from: http://hdl.handle.net/2142/101593.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Yan C. Effect of fatigue loading on impact response of rat ulna. [Thesis]. University of Illinois – Urbana-Champaign; 2018. Available from: http://hdl.handle.net/2142/101593

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

.