Efficacy of a Novel Thoracopelvic Orthosis in Reducing Lumbar Spine Loading and Muscle Fatigue in Flexion: A Study with Weighted Garments by Daniel D. Johnson A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy (Mechanical Engineering) in the University of Michigan 2012 Doctoral Committee: Professor Albert J. Shih, Co‐Chair Professor James A. Ashton‐Miller, Co‐Chair Professor Thomas J. Armstrong Assistant Professor Paul Park from: Iron Man Vol. 1, No. 300, Jan. 1994 (pp. 39-42) New York: Marvel Comics For my parents and students …Oh, and Sheamus ii Acknowledgements I’d like to thank all those who have supported and assisted me along the way to completing the work for my doctoral program, including: Leah Buechley, Adam Brzezinski, Robert Coury, Alicia Davis (and the orthotists at the University of Michigan Orthotics & Prosthetics Center), Robert Dodde, Toby Donajkowski, Patrick Hughes, Jennifer Keller, Janet Kemp, Anne Kirkpatrick, Achin Masli, Ronald McCarty, Connor Moelmann, Hannah Perner‐ Wilson, Mary Ramirez, Corwin Stout, and Grace Wu…not to mention all of my long‐suffering test subjects. I also owe a special thanks to Massimo Banzi (and the entire team behind the ArduinoTM platform), as well as SparkFun® Electronics: two pioneers of open‐source hardware design. iii Table of Contents Dedication .................................................................................................................................. ii Acknowledgements ................................................................................................................... iii List of Figures ........................................................................................................................... vii List of Tables ............................................................................................................................. ix List of Appendices ...................................................................................................................... x Abstract ..................................................................................................................................... xi Chapter 1. Background and Introduction .......................................................................................... 1 1.1 ANATOMY, INJURY, AND BIOMECHANICS OF THE SPINE ....................................... 1 1.1.1 Overview of the Spine ................................................................................... 1 1.1.2 Motion Segments: Mechanical Sub‐units of the Spine ................................. 2 1.1.3 Back Pain from Injury to the Spine ................................................................ 3 1.1.4 Morphology and Kinematics of the Lumbar Spine ........................................ 3 1.2 MUSCLES OF THE LOWER BACK .............................................................................. 5 1.2.1 Flexors ........................................................................................................... 5 1.2.2 Extensors ....................................................................................................... 6 1.2.3 Lateral Flexors ............................................................................................... 7 1.3 SPINAL OFFLOADING VIA A CORRECTIVE SUPPORT: A THEORETICAL MODEL ....... 8 1.4 WORKING HYPOTHESIS AND THESIS OVERVIEW .................................................. 10 1.5 REFERENCES .......................................................................................................... 11 2. Effect of Lead Use on Back and Shoulder Postural Muscle Activity in Healthy Young Adults ............................................................................................................................. 19 2.1 INTRODUCTION ..................................................................................................... 19 2.2 METHODS .............................................................................................................. 20 2.2.1 Study Design ................................................................................................ 20 2.2.2 Subjects ....................................................................................................... 21 iv 2.2.3 Data Acquisition .......................................................................................... 21 2.2.4 Data Analysis ............................................................................................... 23 2.3 RESULTS ................................................................................................................ 25 2.3.1 Mean RMS SEMG Amplitude and ANOVA, Tests 1 through 4 ..................... 25 2.3.2 Mean RMS SEMG Amplitude, Test 5 ........................................................... 26 2.3.3 Questionnaire Results ................................................................................. 26 2.4 DISCUSSION ........................................................................................................... 27 2.4.1 Conclusions .................................................................................................. 29 2.5 REFERENCES .......................................................................................................... 30 3. Contact Stress Distribution under a Lower Thorax Partial Orthosis Worn by Healthy Young Men: Effects of Distraction Force, Sagittal Plane Moment, Respiration Phase, and Thoracic Cross‐sectional Shape ............................................................................... 37 3.1 INTRODUCTION ..................................................................................................... 37 3.2 METHODS .............................................................................................................. 39 3.2.1 Subjects ....................................................................................................... 39 3.2.2 Data Acquisition .......................................................................................... 39 3.2.3 Data Analysis ............................................................................................... 42 3.3 RESULTS ................................................................................................................ 43 3.3.1 Normalized Applied Distraction Force ........................................................ 43 3.3.2 Normalized Applied Moment ...................................................................... 43 3.3.3 Respiration Phase ........................................................................................ 44 3.3.4 Average Thorax Eccentricity ........................................................................ 44 3.4 DISCUSSION ........................................................................................................... 45 3.4.1 Conclusions .................................................................................................. 48 3.5 REFERENCES .......................................................................................................... 49 4. Design and Preliminary Testing of a Novel Thoracopelvic Orthosis for Reducing Lumbar Spine Loading and Muscle Effort in Trunk Flexion with and without Weighted Garments ....................................................................................................... 59 4.1 INTRODUCTION ..................................................................................................... 59 4.2 METHODS .............................................................................................................. 62 v 4.2.1 Prototype Description ................................................................................. 62 4.2.2 Validation ‐ Data Acquisition ....................................................................... 64 4.2.3 Validation ‐ Data Analysis ............................................................................ 66 4.3 RESULTS ................................................................................................................ 66 4.4 DISCUSSION ........................................................................................................... 67 4.4.1 Conclusions .................................................................................................. 69 4.5 REFERENCES .......................................................................................................... 69 5. General Discussion ........................................................................................................ 74 5.1 PER‐CHAPTER REVIEW .......................................................................................... 74 5.2 LIMITATIONS ......................................................................................................... 76 5.3 OVERALL ANALYSIS ............................................................................................... 76 5.4 REFERENCES .......................................................................................................... 78 6. General Conclusions ...................................................................................................... 80 7. Future Work .................................................................................................................. 82 7.1 INTRODUCTION ..................................................................................................... 82 7.2 DEVICE DESIGN ....................................................................................................