Optimisation of Fixation Methods for Vancouver Type B2 and B3 Periprosthetic Femoral Fracture Treatment Lee William Etchels Submitted in accordance with the requirements for the degree of Doctor of Philosophy The University of Leeds School of Mechanical Engineering October, 2014 ii The candidate confirms that the work submitted is his own and that appropriate credit has been given where reference has been made to the work of others. This copy has been supplied on the understanding that it is copyright material and that no quotation from the thesis may be published without proper acknowledgement. The right of Lee William Etchels to be identified as Author of this work has been asserted by him in accordance with the Copyright, Designs and Patents Act 1988. © 2014 The University of Leeds and Lee William Etchels iii Acknowledgements I would like to thank Ruth Wilcox and Alison Jones for all their support and advice over the years, as well as for reading through this thesis far more times than could ever be fair and, quite frankly, for having enough of a sense of humour to put up with me. Eleftherios Tsiridis for all the phone calls and conversations that made the transition into a biomedical project easier and made the clinical importance much clearer, and also for being utterly tireless during the experimental testing phases. Zhongmin Jin for his help and feedback on all my abstracts and reports, Simon Graham for his help setting up and testing our specimens and Jon and Mehran for all their help over the years, from modelling advice to experimental help, feedback on abstracts, suggestions on interpreting results and just generally for keeping me sane. I’d like to thank the technicians, IT support and admin staff at the University of Leeds Engineering department for fixing every problem that I could invent and everyone at the Institute of Medical and Biological Engineering for making it an interesting and enjoyable place to work. Finally I’d like to thanks everyone who made getting through thesis submission possible. From cooked lunches and cakes to encouraging texts, dances, hugs and the occasional much needed drink, it made an unbelievable difference when I was sat late in the office having to turn the motion sensitive lights back on every 20 minutes. This work is supported by British Orthopaedic Association (BOA) through the Latta Fellowship. In addition, it was partially funded through WELMEC, a Centre of Excellence in Medical Engineering funded by the Wellcome Trust and EPSRC, under grant number WT 088908/Z/09/Z and additionally supported by the NIHR (National Institute for Health Research) as part of a collaboration with the LMBRU (Leeds Musculoskeletal Biomedical Research Unit). Surgical components for the experimental testing were provided by Stryker (Stryker UK Limited, Berkshire). iv Abstract Periprosthetic femoral fractures (PFF) are a complication associated with total hip arthroplasty patients that can be both traumatic and challenging to treat. With the increasing age of the population and increasing prevalence of hip replacement surgery periprosthetic femoral fractures are expected to occur more frequently in the future. The most common type of PFF is the Vancouver Type B fracture that occurs near the tip of the original prosthesis. These fractures can be complicated further by loosening of the primary femoral stem (Type B2 fractures) and poor bone stock (Type B3 fractures). Clinical failures and unclear optimal treatment recommendations for many fractures suggest that further investigation is required. This study mechanically tested experimental specimens representing the cemented long stem revision treatment of a Type B2 PFF at a range of loading orientations to evaluate their biomechanical response. From these specimens the axial stiffness, medial axial strain, distal lateral axial strain, and relative fracture movement were recorded under semi-physiological loading. These experimental results were also used to validate computational, finite element (FE), models of long stem PFF treatment. The computational models were shown to achieve reasonable agreement with the experimental data, such that they could be used to investigate a wider range of clinical scenarios. The FE models were then used to compare the relative effects of different cement mantle geometries, fracture location, fracture bridging distance, fracture angle, revision femoral stem length and osteoporosis. The specific location and angle of the fracture appeared to have an effect on the bending response of the femur and the optimal treatment. Long stem revision treatment however seemed to be suitable for achieving stability around an unstable fracture and it may be possible to counter-act the increased risk of fixation failure in osteoporotic patients by selecting a longer bridging distance. v Table of Contents Acknowledgements ............................................................................................................... iii Abstract ................................................................................................................................. iv Table of Contents ................................................................................................................... v List of Tables......................................................................................................................... ix List of Figures ....................................................................................................................... xi Abbreviations .................................................................................................................... xxiii 1. Introduction and Project Overview ................................................................................ - 1 - 1.1 Introduction ........................................................................................................... - 1 - 1.2 Research Aims and Objectives .............................................................................. - 2 - 1.2.1 Research Aim ............................................................................................... - 2 - 1.2.2 Objectives .................................................................................................... - 2 - 1.3 Project Overview ................................................................................................... - 3 - 1.4 Thesis Structure ..................................................................................................... - 4 - 2. Literature Review and Background Information ........................................................... - 5 - 2.1 Periprosthetic Femoral Fracture ............................................................................ - 5 - 2.1.1 Introduction .................................................................................................. - 5 - 2.1.2 Total Hip Arthroplasty ................................................................................. - 5 - 2.1.3 Definition and Epidemiology of PFF ........................................................... - 7 - 2.1.4 Clinical Management of PFF ....................................................................... - 9 - 2.1.5 Discussion .................................................................................................. - 12 - 2.2 In Vivo Mechanical Environment ....................................................................... - 16 - 2.2.1 Introduction ................................................................................................ - 16 - 2.2.2 Anatomy ..................................................................................................... - 16 - 2.2.3 Joint Kinematics and Kinetics ................................................................... - 24 - vi 2.2.4 Properties of Human Tissues and Fixation Constructs .............................. - 28 - 2.2.5 Fracture Configurations and Fracture Healing .......................................... - 30 - 2.2.6 Discussion .................................................................................................. - 31 - 2.3 Experimental Biomechanical Testing .................................................................. - 33 - 2.3.1 Introduction ................................................................................................ - 33 - 2.3.2 Specimen Selection and Preparation .......................................................... - 33 - 2.3.3 Constraints and Loading ............................................................................ - 35 - 2.3.4 Measurements ............................................................................................ - 38 - 2.3.5 Discussion .................................................................................................. - 40 - 2.4 Computational Biomechanical Testing ............................................................... - 41 - 2.4.1 Introduction ................................................................................................ - 41 - 2.4.2 Constraints and Loading ............................................................................ - 41 - 2.4.3 Discussion .................................................................................................. - 42 - 2.5 Discussion ............................................................................................................ - 43 - 3. Experimental Investigation into Long Stem Fixation .................................................. - 45 -