Single Case Study of the Effect of a Bi-Motion Orthotic Ankle Joint on Balance Stability Throughout the Gait Cycle in Hemiplegia

Current orthotic treatments in post-stroke tend to focus on blocked ankle motion, allowed sagittal motion, stopped plantar flexion, and assisted dorsiflexion, while human ankles also have anatomical movement. In particular, the subtalar joint, which is located under the ankle joint, plays the main role in maintaining balance. This study aimed to test the hypothesis of imitation human ankle column movement by allowing both sagittal and coronal movement in a proper range of motion affected by gait balance. A bi-motion orthotic ankle joint was designed in SOLIDWORKS, and fabricated by the aluminum alloy Al 7075. Mechanical verification was performed before testing with a human subject. Then, one 37-year-old male was recruited. He presented with hemiplegia post-stroke, a normal passive range of motion, and mild spasticity. Gait detection was performed in the Gait and Motion Laboratory, focused on knee and ankle motion, and center of gravity displacement during a gait cycle, then time up and go (TUG) testing was done to evaluate stability through performance of the test. A sinusoidal center of gravity (COG) pattern was detected from using the ankle foot orthosis with the bi-motion orthotic ankle joint (AFO-BJ) with the least symmetry index between left and right excursion. The ankle foot orthosis with the bi-motion orthotic ankle joint also presented the fastest time spent in the TUG test but could not achieve a minimally detectable change (MDC) in the stroke group.