In Vivo Measurement and Visualization of Pelvic Position and Orientation and Changes in Soft Tissue Shape and Thickness with Respect to Changes in Seating Surface Shape

.......................................................................................................xv Introduction...................................................................................................1 1.1 Scope of This Thesis................................................................................................2 1.2 Thesis Overview ......................................................................................................3 Pressure Ulcers..............................................................................................5 2.1 Incidence and Prevalence.........................................................................................5 2.2 Etiology....................................................................................................................7 2.3 Physiopathology.......................................................................................................9 2.4 Mortality ................................................................................................................10 2.5 Treatment ...............................................................................................................10 2.6 Prevention ..............................................................................................................11 2.7 Models of Pressure Ulcer Formation .....................................................................12 2.7.1 Impaired Microcirculation ............................................................................13 2.7.2 Reperfusion Injury ........................................................................................14 2.7.3 Interstitial Fluid Loss ....................................................................................14 2.7.4 Impaired Lymphatic Return..........................................................................14 2.7.5 High Strain Rate Injury.................................................................................15 2.7.6 Apparent Contradiction Between Formation Mechanisms and Physiopathology ...........................................................................................................................15 2.8 Experimental Analysis of Proposed Mechanisms for Pressure Ulcer Formation..15 2.8.1 Animal Models .............................................................................................16 2.8.2 Finite Element Models..................................................................................19 2.8.3 Noninvasive External Measurements Indicative of Internal Tissue Shape ..23 The System...................................................................................................27 3.1 Description of Subsystems.....................................................................................29 3.1.1 Motor Subsystem ..........................................................................................31 3.1.2 Pressure And Orientation Subsystem ...........................................................33 3.1.3 Ultrasound Subsystem ..................................................................................39 3.1.4 Position Wand Subsystem ............................................................................41 3.2 Coordinate Systems ...............................................................................................41