DEVELOPMENT OF A NON-FUSION SCOLIOSIS CORRECTION DEVICE DESIGNING AND TESTING This research is supported by the Dutch Technology Foundation STW, which is part of the Netherlands Organisation for Scientific Research (NWO) and partly funded by the Ministry of Economic Affairs, Agriculture and Innovation (project number 07618) DEVELOPMENT OF A NON-FUSION SCOLIOSIS CORRECTION DEVICE DESIGNING AND TESTING PROEFSCHRIFT ter verkrijging van de graad van doctor aan de universiteit Twente, op gezag van de rector magnificus, prof.dr. H. Brinksma, volgens besluit van het College voor Promoties in het openbaar te verdedigen op donderdag 13 september 2012 om 16:45 uur door Martijn Wessels geboren op 30 juni 1974 te Vriezenveen De promotor prof.dr.ir. G.J. Verkerke en de assistent-promotor dr.ir. J.J. Homminga hebben dit proefschrift goedgekeurd Copyright © 2012 by M. Wessels, Vriezenveen, The Netherlands All rights reserved ISBN: 978-90-365-3377-5 Ter herinnering aan Mart Wessels 4 april 2012 5 april 2012 CONTENTS CHAPTER 1. GENERAL INTRODUCTION ........................................................................................................ 11 1.1. INTRODUCTION ....................................................................................................................................... 11 1.2. SPINAL ANATOMY.................................................................................................................................... 11 1.3. ADOLESCENT IDIOPATHIC SCOLIOSIS (AIS) .................................................................................................... 17 1.4. NON-SURGICAL TREATMENT ...................................................................................................................... 21 1.5. SURGICAL TREATMENT ............................................................................................................................. 22 1.6. PROBLEM ANALYSIS ................................................................................................................................. 29 1.7. REFERENCES ........................................................................................................................................... 31 CHAPTER 2. FRAMEWORK .......................................................................................................................... 41 2.1. INTRODUCTION ....................................................................................................................................... 41 2.2. DESIGN STRATEGY ................................................................................................................................... 41 2.3. SPINE MODELS FOR RESEARCH ................................................................................................................... 46 2.4. CONCLUSIONS ........................................................................................................................................ 48 2.5. REFERENCES ........................................................................................................................................... 48 CHAPTER 3. DESIGN PROCEDURES .............................................................................................................. 53 3.1. INTRODUCTION ....................................................................................................................................... 53 3.2. STAKEHOLDERS ....................................................................................................................................... 53 3.3. REQUIREMENTS ...................................................................................................................................... 54 3.4. DESIRES ................................................................................................................................................ 59 3.5. TECHNICAL SPECIFICATIONS ....................................................................................................................... 60 3.6. SYSTEM FUNCTIONS ................................................................................................................................. 60 3.7. CONCLUSION .......................................................................................................................................... 63 3.8. REFERENCES ........................................................................................................................................... 64 CHAPTER 4. STRUCTURAL DESIGN............................................................................................................... 69 4.1. INTRODUCTION ....................................................................................................................................... 69 4.2. SOLUTIONS FOR SCOLIOSIS CORRECTION....................................................................................................... 69 4.3. GENERATION OF GENERAL CONCEPT ............................................................................................................ 72 4.4. FINAL DESIGN (XS LATOR) ................................................................................................................... 79 4.5. MANUFACTURING PROCEDURES ................................................................................................................. 87 4.6. SURGICAL INSTRUMENTS .......................................................................................................................... 87 4.7. STERILISATION PROCEDURES ...................................................................................................................... 91 4.8. IMPLANTATION PROCEDURES ..................................................................................................................... 91 4.9. FUNCTIONAL PROTOTYPES......................................................................................................................... 91 4.10. REFERENCES ........................................................................................................................................... 96 CHAPTER 5. A NOVEL ANCHORING SYSTEM FOR THE NON-FUSION SCOLIOSIS CORRECTION DEVICE ......... 99 5.1. ABSTRACT .............................................................................................................................................. 99 5.2. INTRODUCTION ..................................................................................................................................... 100 5.1. MATERIALS AND METHODS ..................................................................................................................... 100 5.2. RESULTS .............................................................................................................................................. 104 5.3. DISCUSSION ......................................................................................................................................... 107 5.4. ACKNOWLEDGEMENTS ........................................................................................................................... 110 5.5. REFERENCES ......................................................................................................................................... 110 CHAPTER 6. MECHANICAL BEHAVIOUR OF THE NON-FUSION SCOLIOSIS CORRECTION DEVICE ................ 115 6.1. ABSTRACT ............................................................................................................................................ 115 6.2. INTRODUCTION ..................................................................................................................................... 117 6.3. MATERIALS AND METHODS ..................................................................................................................... 117 6.4. RESULTS .............................................................................................................................................. 122 6.5. DISCUSSION ......................................................................................................................................... 126 6.6. CONCLUSION ........................................................................................................................................ 128 6.7. REFERENCES ......................................................................................................................................... 128 CHAPTER 7. BENDING FATIGUE OF PSEUDO-ELASTIC NITI ROD IMPLANTS ................................................ 133 7.1. ABSTRACT ............................................................................................................................................ 133 7.2. INTRODUCTION ..................................................................................................................................... 135 7.3. MATERIALS AND METHODS ..................................................................................................................... 136 7.4. RESULTS .............................................................................................................................................. 140 7.5. DISCUSSION ......................................................................................................................................... 145 7.6. CONCLUSIONS .....................................................................................................................................