Having got the tracker positions and orientations from the TCA and the bone position and angle from the BCA, now a relationship must be built between the two.
Pairing each Tracker with a line:
- First, the coordinates of the trackers must be transformed to fit the coordinates of whatever projection was chosen.
- The closest tracker to each line is chosen by calculating the midpoint of the tracker and using a simple shortest-distance algorithm to assign each tracker to a line. The result can be seen in Fig. 20.
Relating the Trackers to the Bones:
- A transformation matrix is needed to place the coordinate frame of the trackers into the coordinate frame of the bone, so the output of the camera will be directly translated into the movement of the bones.
- As can be seen in Fig. 21, This can be done since the tracker orientation and the bone orientation as well as their positions are known.
- After the transformation, the angle between the two lines can be found with simple geometry and can be displayed as can be seen below in Fig. 22.
In the operating room, the camera needs to be directly interfaced with the script in order to get real time bone movement and angle measurements. This will require more testing to ensure the system is robust and efficient for a surgery setting.