Nanomechanical Testing and Elemental Microanalysis of Human Femoral Heads

Chih-ling Lin (2010). Nanomechanical Testing and Elemental Microanalysis of Human Femoral Heads MPhil Thesis, School of Mechanical and Mining Engineering, The University of Queensland.

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Author Chih-ling Lin
Thesis Title Nanomechanical Testing and Elemental Microanalysis of Human Femoral Heads
School, Centre or Institute School of Mechanical and Mining Engineering
Institution The University of Queensland
Publication date 2010-07
Thesis type MPhil Thesis
Supervisor A/Prof Han Huang
Dr Bronwen Cribb
Dr Anthony Russell
Total pages 146
Total colour pages 26
Total black and white pages 120
Subjects 11 Medical and Health Sciences
Abstract/Summary Osteoporosis is a disorder of bone, which can cause extreme pain and increases vulnerability to bone fracture. This disease has affected the life of millions of people worldwide, has become a major health issue and is extremely costly to our health systems. Osteoporosis is characterized by the compromised bone strength that predisposes patients to an increased risk in fragility fracture. The fractures have been hypothesized to not only be related to a reduction in bone mass, but also to changes in bone quality. The measurement of bone mineral density (BMD) using dual energy x-ray absorptiometry is a conventional method for the prediction and diagnosis of osteoporotic fractures. However, it neglects some factors that are strongly associated with osteoporotic fractures, such as architectural deterioration, material properties and mineral composition of bone tissues. This study focused on the characterization of bone material quality by measuring the mechanical properties and mineral elemental concentrations of human femoral heads at microscale. Advanced analytical methods, including nanoindentation and scanning electron microscopy (SEM) combined with energy dispersive x-ray (EDX) analysis were used to provide extended insight into bone tissues. The microstructures of cortical bones (osteons and interstitial lamellae) and trabecular bones from femoral heads obtained from eleven living donors were investigated. The elastic modulus and hardness of the bone tissues were determined by nanoindentation and the heterogeneous mineralization of bone tissues was visualized using backscattered electron imaging. Additionally, the degree of mineralization, represented by the amount of elemental concentrations (i.e. calcium, phosphorus and magnesium) within bone tissues, was assessed by EDX analysis. The results obtained from this study revealed that the mechanical properties of human femoral heads were significantly influenced by the microstructures of bone tissues. Both the modulus and hardness of interstitial lamellae were significantly higher than those of osteons and trabeculae. The trabeculae had the lowest indentation modulus among the three microstructures. Gender also had an influence on the mechanical properties of human femur heads. Both the modulus and hardness measured on the femur heads from the males were greater than the respective values of the females. However, no distinct correlation was found between the mechanical properties and the donor age. The elemental microanalysis using backscattered electron images demonstrated that the interstitial lamellae had higher Ca and P concentrations (wt%), in comparison with those obtained from osteons and trabeculae. Moreover, the backscattered electron imaging showed that interstitial lamellae had a higher mineral content than other microstructures. The measured concentrations (wt%) of calcium (Ca) and phosphorus (P) were significantly greater for interstitial lamellae, as compared with osteons and trabeculae. The calcium deposit obtained from the microanalysis responded well with the variation in the mechanical properties of the bone tissues measured by nanoindentation. Strong correlations were found between bone mineral density and Ca wt% or Ca/P ratio in interstitial lamellae. This thus suggested that the calcium content in bone might play an important role in bone strength. This study clearly indicated that both the elemental composition and the mechanical properties of bone tissues were important factors that affect bone quality, which might be used in the prediction of osteoporotic fractures.
Keyword Nanoindentation
mechancial properties
Cortical Bone
Trabecular Bone
Mineral Content
Additional Notes 20,25,30-32,47,52-56,59,60,62-70,72,76,103,104

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Created: Thu, 04 Nov 2010, 12:50:14 EST by Ms Chih-ling Lin on behalf of Library - Information Access Service