This study quantified and compared the efficacy of in-shoe
orthoses and ankle
braces in stabilizing the hindfoot and medial longitudinal arch in a cadaveric model of acquired
flexible flatfoot deformity. This was addressed by combining measurement of hindfoot and arch kinematics with plantar pressure distribution, produced in response to axial loads simulating quiet standing. Experiments were conducted on six fresh-frozen cadaveric lower limbs. Three conditions were tested: intact-unbraced;
flatfoot-unbraced; and
flatfoot-braced.
Flatfoot deformity was created by sectioning the main support structures of the medial longitudinal arch. Six different
braces were tested including two in-shoe
orthoses, three ankle
braces and one molded ankle-
foot orthosis. Our model of
flexible flatfoot deformity caused the calcaneus to evert, the talus to plantarflex and the height of the talus and medial cuneiform to decrease.
Flexible flatfoot deformity caused a pattern of medial shift in plantar pressure distribution, but minimal change in the location of the center of pressure. Furthermore, in-shoe
orthoses stabilized both the hindfoot and the medial longitudinal arch, while ankle
braces did not. Semi-rigid foot and ankle
orthoses acted to stabilize the medial longitudinal arch. Based on these results, it was concluded that treatment of
flatfoot deformity should at least include use of in-shoe
orthoses to partially restore the arch and stabilize the hindfoot.