Ability of a novel foot and ankle loading device to reproduce loading conditions in the standing position during computed tomography

To describe a loading device, we created for use with current computed tomography (CT) scanners and to evaluate its ability to reproduce loading conditions. Ten feet of five healthy volunteers (three men and two women) with no history of foot or ankle disorders and no foot pain were studied. Subjects lay on the device in the supine position with the legs extended and ankles in a neutral position. An axial load equivalent to their body weight was applied to the soles. A foot scan measured plantar contact area, plantar pressure, and the center of pressure under standing and weight-bearing conditions. Differences between measurements were assessed using the paired t test with a two-sided significance of 5%. No subjects complained of pain or discomfort during loading. Weight-bearing measurements varied from standing measurements as follows: plantar contact area, -4.15 cm²; contact % (forefoot/midfoot/hindfoot), -0.61%/-0.17%/0.79%; plantar pressure, -1.47 N/cm²/-0.49 N/cm²/3.7 N/cm² (6.40 N/cm² overall); and center of pressure location (anterior-posterior/medial-lateral), 0.88%/0.36%. With the numbers available, no significant difference could be detected for any tested items. We were able to produce load distributions and intensities resembling standing conditions. Thus, the standing condition can be well produced on CT images if our device is used. Furthermore, images can be compared with those of healthy individuals to yield useful information for elucidating the pathophysiology and pathology of foot disorders.