Reliability of the simulator was tested by placing four different weights in random order on the device and recording voltage from the potentiometer with displacement of the device. Linearity of the potentiometer was determined by measuring electrical resistance with displacement. This recording device within the simulator showed a linear displacement and was used to take all the readings. Displacement in the simulator was measured by fixing a pen to the device and measuring the vertical line produced on paper attached to the wall. These four weights were each placed on a force platform to determine the force they would exert on the simulator. Correlation between calculated force and measured force was used to determine validity of the device.
Reliability was tested using the intraclass correlation coefficient (1.000, 95% CI = 0.997–1.000) and the results were found to be significant (P < 0.001). Using the intraclass correlation coefficient the simulator was found to be valid (0.998, 95% CI = 0.973–1.000) and the results were significant (P < 0.001).
During testing the simulator was found to be reliable and valid; it was felt that changes in the device are needed to allow it to more closely represent resistance of the human thoracic spine. The studies used to determine thoracic resistance were mostly done in vitro and may therefore not represent thoracic stiffness of a thoracic spine in vivo. More studies of thoracic stiffness in vivo are needed to be able to modify the adjusting simulator to more accurately represent the stiffness of the thoracic spine in a living human body.
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