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Figure 3 | Journal of Foot and Ankle Research

Figure 3

From: The instantaneous helical axis of the subtalar and talocrural joints: a non-invasive in vivo dynamic study

Figure 3

Pictorial representation of the IHA. For the sagittal, coronal, and axial images (left foot) the view is from lateral to medial, anterior to posterior, and distal to proximal, respectively. The maximum DF/PF is shown in the darkest shade of red/green; and the beginning, middle, and end of the PF cycle is highlighted with a thicker line. For clarity the IHA was graphed at 5° increments of tib-foot angle, instead of single degree increments. Since all images are of the same scale (280 mm2), the length of each IHA represents the actual angular velocity, which directly relates to the amount of rotation, at that tib-foot angle. The inclination of the IHA is provided (white dashed lines) for the talocrural and the calcaneal-tibial joints at the mid-range of motion (tib-foot angle = 20° and 25°, respectively).

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