Introduction
This application enables you to visually analyze the 3D motion of the humerus and scapula during various single-plane shoulder motions. It decomposes the orientation of the humerus and scapula via commonly utilized methods in shoulder biomechanics research. This allows you to visually compare differences between these methods.
Frame Selection
The slider bar at the top of the page allows you to select the frame in the data capture which you would like to analyze. Notice that as you change the frame number, the orientation of the humerus and scapula in each view is updated. This same functionality can be achieved using the plots on the lower-right quadrant by hovering over a plot-line. Once you have chosen a frame to analyze, click the downward facing arrow next to the slider bar. This same functionality can be achieved by clicking a point on a plot.
The Views
The lower-right view plots the components of the decomposed orientation of the humerus/scapula as specified in the adjustable label in the upper-left corner of this quadrant. Each of the remaining 3 views decompose the humerus or scapula orientation according to the adjustable label shown in the upper-left or upper-right corner of the quadrant. In all views, the elbow is represented by a thin black or blue rectangle attached to the humerus. Axial orientation is illustrated by the angle between the black (starting) and blue (ending) rectangle.
Interactions
Rotate by dragging the left mouse button, zoom using the scroll-wheel, and pan by dragging the right mouse button. To maximize one of the views, double-click on it. Another double-click brings you back to the 4-pane view. The humerus views are linked to each other so as you rotate, pan, or zoom in one view, the same action happens in the other humerus views.
Animations
Once you have selected a frame to decompose (see Frame Selection), the application allows you to animate the sub-rotations associated with each decomposition. The state buttons at bottom of the application allow you to choose which sub-rotation you would like to animate. Once you select a sub-rotation, the play/pause button and slide bar at the bottom of each quadrant provide control of the animation for the selected sub-rotation.
Options
The Open Controls button in the lower-right corner of the page provides various configuration options for the application. Notably, the Humerus Base option allows you to change whether the humerus is decomposed and plotted by measuring its orientation against the Torso or Scapula. The Visualize Angles option allows you to display a simple visualization of the humerus angles as measured by a particular decomposition sequence. The Spherical Area option enables the visualization of the actual path traversed by the distal humerus (blue), and the path assumed by the chosen decomposition sequence (brown). The spherical area between these two trajectories describes the difference between true and apparent axial rotation for the xz'y'' and Swing Twist decompositions.