Development of Optimal Total Hip Joint Replacement

Rabbani, Mohammad (2018) Development of Optimal Total Hip Joint Replacement. Doctoral thesis, Birmingham City University.

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Abstract

Total hip replacement (THR) is a surgical process in which the hip joint is replaced by a hip prosthesis. It is one of the most popular and cost effective surgery. In particular in 2014, 83,125 primary procedures were recorded. Some of these operations need to be carried out again for different reasons after sometime. These are called revision (replacement of the prosthesis) procedures. Important studies and statistics suggest that the number of THR procedures is projected to increase by almost 175% by 2030. Aseptic loosening appears to be the most significant cause of failure in THR. Aseptic loosening might lead to revision surgery and in turn can be avoided by enhancing the stability and durability of the hip replacement. Primary stability attained after surgery is a determinant issue for the long-term stability of cementless hip arthroplasty. Primary stability is the level of relative micromotion between the femur and the prosthesis induced via the physiological joint forces following the surgery. The hip prosthesis is also exposed to dynamic loadings and activities of daily living, which can induce the stress distribution on the prosthesis of the hip joint model and affect the durability of the implant. The aim of this study is to develop an optimal total hip replacement (THR) implant with new and improved design features to achieve stability and durability. The micromotion between bone and implant interface and the stress distribution on the prosthesis and femur assembly has been reviewed and investigated. The laboratory testing were carried out on the femur including the compression, torsion and Brinell hardness testing. A compression testing using strain gauge technique done on the hip implant. Finite element analysis software used to simulate all compression and torsion testing assuming the same boundary and loading conditions and subsequently the computational results were compared with the earlier experimental data to verify the experiments and models used. 7 The comparative micromotion studies and findings of other researchers were used beside the clinical follow-up reports on success or failure rates of related hip designs, to justify the best solutions for design factors. In this computational approach researchers usually use finite element methodology to calculate micromotion of elements, sometimes known as migration. The elements exceeding the threshold limit would simulate the migration and subsequently eliminated from the assembly. This procedure recurs until reaching the convergence that derives a stable mechanical equilibrium. One of the restrictions of micromotion analysis was the inability to divide the final results into axial and rotational components. Therefore it would have been inappropriate to eventually conclude the best femoral stem, without considering the sustaining torsional loadings. Another limitation was that the micromotion analysis would not reflect the stress distribution on the hip prosthesis and consequently would ignore the potential high stress concentration that is associated with post operative pain as well as low durability and long-term stability. For these reasons stress analysis was carried out under dynamic loadings of nine different activities to examine the von Mises stress, shear stress and principal stress distribution of a cementless hip implant. In each activity realistic boundary and loading conditions of a complete assembly of femur and hip implant were investigated which includes defining of many variables including different geometry, material properties, boundary conditions, forces and moments of varying magnitude and orientation over specific time intervals. The critical points and areas that were developed in the entire 3D model were evaluated and explained. The finite element analysis which verified by experimental testing and hold the clinical relevance were used to decide the best optimal hip stem design amongst different presented design concepts. This was accompanied and improved with further stress analysis of different design factors to get the final optimal model. High offset stem option is a unique feature that helps tightening the abductor and boosts the hip implant stability with the ability to adjust neck and offset. It gives a surgeon more options to fix the most accurate offset and do the operation more effectively. The final optimal design and its advantages were presented in the last chapter.

Item Type: Thesis (Doctoral)
Additional Information: This project is certainly the most significant academic accomplishment of my life, and without the wonderful people who have supported and believed in me, this thesis would not have been possible. It is with great pleasure that I sincerely thank those who have helped me on this journey. Firstly, I would also like to thank Professor Michal Krzyzanowski, my senior supervisor at the school of engineering and the built environment for his contribution and suggestions that made a difference. I’d like to express my sincere appreciation to Professor Hanifa Shah, my second supervisor. I am very grateful for her guidance, intensive supervision, and trust through my candidature. Her energy and enthusiasm in research have been a major source of motivation to me. I extend my sincere appreciation to Professor Hossein Saidpour through my Ph.D. candidature. His knowledge and advice contributed enormously to my journey through the research world. This thesis would likely not have matured had it not been for his support and inspiration. I have the deepest gratitude to my lovely parents, wonderful brother and also my uncle Dr. Masoud Rabbani, who continue to offer their unwavering support, love and encouragement to keep me moving forward throughout my entire education. I love you all. I dedicate this work to my kind and lovely parents. There’s no doubt in my mind that, without your constant love, endless encouragement and support, I would not have achieved this outcome.
Uncontrolled Keywords: Design, Biomedical Engineering, THR
Subjects: B800 Medical Technology
H900 Others in Engineering
Divisions: REF UoA Output Collections > Doctoral Theses Collection
Depositing User: Kip Darling
Date Deposited: 26 Feb 2019 15:46
Last Modified: 26 Feb 2019 15:46
URI: http://www.open-access.bcu.ac.uk/id/eprint/7132

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