Use this URL to cite or link to this record in EThOS: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.755274
Title: Prediction of the strength of human long bone using CT based finite element method
Author: Altai, Zainab
ISNI:       0000 0004 7428 2725
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2018
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Abstract:
Bone fracture is one of the most common injuries during life, both during the early age of childhood and when we get old. The main cause of fractures usually differs with age. For very young children (e.g. infants), fracture of bone is sometimes associated with child abuse as they have limited mobilities (e.g. non-ambulant). On the other hand, fracture of bone in the elderly usually occurs as result of bone disease and degeneration, such as osteoporosis. Hip fracture is the most common fracture at this age, with the percentage increasing in line with the growing risk of falls as one gets older. Fractures for these two age groups are particularly problematic because of the implications on the quality of life. The discrimination of inflicted injury from accidental injury in children is very important to avoid the risk of further abuse, which could significantly affect the mental and physical development of the child. Computed tomography based finite element (CT/FE) models have been widely used to study the biomechanics of human bones. Although this technique has been extensively used in adults there are markedly fewer studies in children, mainly due to the lack of paediatric bone samples. Consequently, the current clinical method used to diagnose the cause of fractures in very young children is based on the clinical judgement and the description of the caretaker, with very little quantitative evidence. For example, until now, the injury tolerance (or bone strength) of a paediatric bone (within a certain age range) has been unclear. Consequently, there is a need for non-invasive tools in order to report on the paediatric bone strength under various loading conditions. Predicting the risk of hip fracture in the elderly has major implications for the prevention of permanent disability, and the associated substantially reduced quality of life (due to reduced or a complete loss of mobility). Experimental investigation has reported that CT/FE models can accurately predict the strength of adult long bone, but the use of these strength predictions to discriminate patients at risk of fracture still needs further investigation, especially in respect to comparing their performance against the clinical gold standard, the bone mineral density (BMD) measurement. In order to enhance our understanding of bone mechanics related to clinical diagnosis, therefore, this thesis investigated bone strength in these two distinct age groups. The work consisted of three studies detailed below. Study I aimed to define the injury tolerance of very young children using a CT/FE model under bending and torsional loads. A range of femora strength of children aged from zero to three years old was reported under bending loads (0.25-27.9 Nm) and, for the first time, under torsional loads (1-31.4 Nm for external rotation and 1-30.7 Nm for internal rotation). These results were found to be in good agreement with the experimental data in the literature. Study II applied the paediatric modelling approach to investigate a special case of reported spontaneous humeral fracture, which is still under debate. Three personalized humerus models were created spanning an age range of four to six months. Simulation results showed that spontaneous humeral fracture is highly unlikely to occur when an infant rolls from a prone to supine position without any external loads. Study III aimed to improve the accuracy of the side fall CT/FE model in classifying fracture and non-fracture cases using a wide range of loading directions, and also attempts to achieve a more accurate prediction of fracture type, using three different boundary conditions: Linear, MPC and Contact model. The study showed that the Contact model achieved the biggest classification power improvement by an increase of 7% compared to BMD as a predictor. The MPC and Contact models were able to predict various hip fractures, including pertrochanteric fracture, which is rarely reported in the literature. In conclusion, the CT/FE model is a valuable tool allowing the non-invasive investigation of bone strengths in a range of ages. In the paediatric application, this thesis reported, for the first time in the literature, a table of injury tolerance (under both bending and torsion) for very young children. It also successfully falsified the spontaneous humerus fracture hypothesis under the current assumptions. In the adult applications, a more refined boundary condition in the side fall FE model was proven to increase the classification accuracy and improve fracture type prediction. This places the FE method one step closer to more accurate predictions in fragile bone fractures.
Supervisor: Li, Xinshan ; Viceconti, Marco Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.755274  DOI: Not available
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